UMTS and HSPA Static Simulations

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Transcript of UMTS and HSPA Static Simulations
UMTS/HSPA STATIC SIMULATIONS
V 7.0
ALGORITHMS AND OUTPUTS RELATING TO THE
SIMULATOR
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 2
© Copyright 2009 AIRCOM International Ltd
All rights reserved
This document is supplementary to the User Reference Guides, and is protected by copyright and
contains proprietary and confidential information. No part of the contents of this documentation may be
disclosed, used or reproduced in any form, or by any means, without the prior written consent of
AIRCOM International.
Although AIRCOM International has collated this documentation to reflect the features and capabilities
supported in the software products, the company makes no warranty or representation, either expressed
or implied, about this documentation, its quality or fitness for particular customer purpose. Users are
solely responsible for the proper use of ENTERPRISE software and the application of the results
obtained.
AIRCOM International Ltd
Cassini Court
Randalls Research Park
Randalls Way
Leatherhead
Surrey
KT22 7TW
ENGLAND
Telephone: +44 (0) 1932 442000
Support Hotline: +44 (0) 1932 442345
Fax: +44 (0) 1932 442005
Web: http://www.aircominternational.com
VERSION HISTORY
Document Version Date Author Comments 1.0a 22/12/2009 A. Awad Adapted from V6.1 document
with subsequent changes
and description of HSPArelated
changes in V6.2.
1.0 01/02/2010 P. Nahi Approved
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 3
CONTENTS
1 What Is A Snapshot?................................................................................................................... 5 1.1 Randomness in a Cellular Network .................................................................................. 5 1.2 Timeaveraging in Coverage Evaluations......................................................................... 8 1.3 Timeaveraging in Capacity Evaluations .......................................................................... 8 1.4 Why Produce Snapshots? .................................................................................................... 8 1.5 Activity Factors..................................................................................................................... 9 1.6 Bitrates and Processing Gain ............................................................................................ 10 1.7 Resource Types ................................................................................................................... 10
2 Formulae ..................................................................................................................................... 11 2.1 Notation ............................................................................................................................... 11 2.2 List of Principal Symbols .................................................................................................. 11 2.3 Downlink Power and Noise Formulae ............................................................................ 14 2.4 Uplink Power and Noise Formulae ................................................................................. 16 2.5 Link Budget Formulae ....................................................................................................... 17 2.6 Extended HSDPA Analysis Formulae ............................................................................. 21
3 Snapshot Overview................................................................................................................... 24 3.1 Random Terminal Distribution ........................................................................................ 24 3.2 Random Speed Distribution ............................................................................................ 25 3.3 Power Control Modelling ................................................................................................. 25 3.4 Power Iterations ................................................................................................................. 26 3.5 Convergence Test ............................................................................................................... 27 3.6 Gathering Of Results ......................................................................................................... 27
4 Connection Evaluation in a Snapshot ................................................................................... 28 4.1 Connection Scenario Prioritisation .................................................................................. 28 4.2 Production of a Candidate Active Set ............................................................................. 29 4.3 UMTS Uplink Evaluation .................................................................................................. 29 4.4 HSUPA Uplink Evaluation ............................................................................................... 31 4.5 UMTS Downlink Evaluation ............................................................................................ 31 4.6 HSDPA Downlink Evaluation .......................................................................................... 32 4.7 Failure Reasons ................................................................................................................... 34
5 Output Arrays ............................................................................................................................ 34 5.1 Array dependencies ........................................................................................................... 35 5.2 Pathloss Arrays ................................................................................................................... 37 5.3 Pilot Coverage Arrays ....................................................................................................... 37 5.4 Handover Arrays ............................................................................................................... 39 5.5 Uplink Noise Arrays .......................................................................................................... 40 5.6 Downlink Noise Arrays .................................................................................................... 40 5.7 Uplink Coverage Arrays ................................................................................................... 41 5.8 Downlink Coverage Arrays .............................................................................................. 42 5.9 Coverage Balance ............................................................................................................... 43 5.10 Soft Blocking Arrays .......................................................................................................... 43 5.11 Hard Blocking Arrays ........................................................................................................ 43 5.12 HSDPA Arrays ................................................................................................................... 44 5.13 HSUPA Arrays ................................................................................................................... 46
6 Coverage Array Calculations .................................................................................................. 48 6.1 Notation ............................................................................................................................... 48 6.2 Fades in the Simulation Snapshots .................................................................................. 49 6.3 Fades in Arrays for Mean Values ..................................................................................... 49 6.4 Fades in Arrays for Soft/Hard Blocking ......................................................................... 49 6.5 Fades in Coverage Array Calculations ............................................................................ 50 6.6 Conditional Expectation for Correlated Fades ............................................................... 54
7 Blocking Array Calculations ................................................................................................... 55 7.1 Uplink Soft Blocking Probability Array .......................................................................... 56 7.2 Downlink Soft Blocking Probability Array ..................................................................... 58
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 4
7.3 Hard Blocking Probability Arrays (Resource Blocking) ............................................... 60 8 Blocking Probability and Failure Rate .................................................................................. 61
8.1 Calculation of Blocking Probability in the Blocking Report ......................................... 61 8.2 Failure Rate ......................................................................................................................... 61
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 5
1 WHAT IS A SNAPSHOT?
1.1 RANDOMNESS IN A CELLULAR NETWORK
In a simulation of a cellular network there are two main types of randomness that one needs to
consider.
Spatial randomness in the location of terminals.
Temporal randomness in the activity of terminals.
We shall consider the spatial domain to be discrete and consisting of a large number of pixels (bins)
some of which will contain terminals. Each possible pattern of terminal locations has an associated
probability of occurrence. We can label these spatial patterns X1, X2, etc and represent the
corresponding probabilities of occurrence by P(X1), P(X2), etc. An example of two spatial patterns X1
and X2 are shown below.
X1 X2
Each spatial pattern has many possible configurations of transmitting and nontransmitting terminals.
Two such configurations for the spatial patterns X1 and X2 are shown below, with 1 representing a
transmitting terminal, and 0 a nontransmitting terminal.
(X1,T1) (X2,T1)
(X1,T2) (X2,T2)
X X
X
X
X
X X X
X
X
X
X
X
1 1
0
0
0
1 1 0
1
0
1
0
1
1 0
1
0
0
1 0 1
0
1
0
0
0
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 6
We call each of these patterns a spatiotemporal pattern to highlight the fact that we have specified
spatial locations of terminals and also their temporal state (transmitting/nontransmitting). We can
label the spatiotemporal patterns for spatial pattern X1 as follows (X1,T1), (X1,T2), etc and their
probabilites of occurrence P(X1,T1), P(X1,T2), etc. Note that the probability of occurrence of a spatio
temporal pattern (Xi,Tj) is proportional to the probability of occurrence of the spatial pattern Xi:
P(Xi,Tj)= P(Xi) P(Tj  Xi).
One can think of a spatiotemporal pattern as being a picture of a real network at a random instant in
time. This is what most people have in mind when one mentions a simulation “snapshot”, but a
snapshot in our simulator represents something slightly different, as explained below.
The ideal static simulation would calculate an average quantity (e.g. the average noise rise on a cell) by
performing a weighted sum over the set of all possible spatiotemporal patterns (Xi,Tj), with the weight
for a pattern being its probability of occurrence. So the average of some quantity F would be given by
ji TX
jiji TXPTXFF
,
),(),( . (a)
We can split this into separate spatial and temporal sums:
i jX
ij
T
jii XTPTXFXPF )(),()( . (b)
The summations in (a) and in (b) are over every conceivable pattern of terminal locations and activities,
including the unlikely ones, so clearly some simplifications are necessary in any practical static
simulator.
Simplification 1: Model spatial randomness explicitly by sampling.
This simplification is the most common one made in static simulations, and it is used universally.
Instead of considering all spatial patterns, we consider a set of N sample spatial patterns drawn from
the distribution of all spatial patterns. The first weighted sum in (b) can then be approximated by a
simple average over the set of N sample spatial patterns:
i jX
ij
T
ji XTPTXFN
F )(),(1
.
Spatial randomness is therefore handled explicitly by considering a set of sample spatial patterns that
have been selected in a random and unbiased way. There is still the issue of how to handle the
different temporal states for each sample spatial pattern. There are two main approaches we can use:
Model temporal randomness explicitly by sampling. (Simplification 2).
Model temporal randomness implicitly with timeaverages. (Simplification 3).
Simplification 2: Model temporal randomness explicitly by sampling.
This simplification is fairly common but has some drawbacks as explained below. Firstly, as in the
previous simplification, one selects a sample spatial pattern from the set of all possible spatial patterns,
making sure that the selection is made in a random and unbiased way. One then assigns a random
“activity flag” (1 or 0) to each terminal in the pattern, to indicate if the terminal is transmitting or not.
The probability of assigning a “1” to a terminal is just the service activity factor for that terminal. This
ensures that activity flags are assigned in a random and unbiased way. The weighted sum over the set
of all spatiotemporal patterns in (a) can be approximated by a simple average over the set of N
sample spatiotemporal patterns:
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 7
ji TX
ji TXFN
F
,
),(1
.
If we called a spatiotemporal pattern a “snapshot” then the above formula simply says that we can
approximate F by performing a simple average over the snapshots. This simple average works
because the sample spatiotemporal patterns are selected in a random and unbiased way. Also note that
this averaging explicitly accounts for spatial randomness and explicitly accounts for temporal
randomness.
There are problems with assigning “activity flags” to terminals however.
For low activity services, the user can do 100s of snapshots and never set an activity flag, and
therefore certain outputs may not have any results. For example, a simulation report may say
that many users are served on a cell but that there is no throughput on the cell. Forcing the
user to run 1000s of snapshots is unacceptable in a commercial tool, so we either have to
remove the problem outputs or calculate them some other way.
Activity flags are set when the terminals are created. For multirate packetswitched (PS)
services, different bearers can have different activity factors. Since we do not know which
bearer a multirate terminal will ultimately use, we have to define a set of activity flags, one
flag for every bearer that the terminal may use. This is conceptually horrible, and can lead to
convergence issues during iterations.
For the above reasons, we do not use Simplification 2 and use the following simplification instead.
Simplification 3: Model temporal randomness implicitly with timeaverages.
As before, one selects a sample spatial pattern from the set of all possible spatial patterns, but now we
completely remove the activity flags from the randomly scattered terminals. Each terminal is therefore
neither instantaneously active nor instantaneously inactive, but rather represents a sort of “time
averaged” entity. Essentially, this means that when we examine the interference that the terminal
produces, or the resources it consumes, we use the timeaverages for these quantities, and we calculate
these timeaverages implicitly by using activity factors to scale things.
So in our simulator, a “snapshot” does not represent a random instant in time for a random distribution
of terminals, but rather “the average instant in time for a random distribution of terminals”. The
snapshot represents the average instant because all the measures of system load (i.e. UL interference,
DL interference, resource usage, and throughput) are timeaverages.
It is still valid to perform simple averages of quantities over our snapshots. However, averaging over
the snapshots now explicitly accounts for spatial randomness only. The temporal randomness is now
handled implicitly within each snapshot through the use of timeaverages in our calculations. Time
averages feature in the evaluation of both coverage and capacity as described below.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 8
1.2 TIMEAVERAGING IN COVERAGE EVALUATIONS
All our link budgets (in SI units, not dB) are essentially of the form
E = ( P / L ) / N,
where
E = signal to interference ratio for the link in a period of activity,
P = TX power in a period of activity,
L = linkloss,
N = timeaverage RX interference on the link.
To check for coverage, we set P to the maximum allowed link power and check that E meets
requirements. In other words we examine the link assuming it is active. The timeaveraging affects the
coverage evaluation only because we use the timeaverage interference N in the linkbudget.
1.3 TIMEAVERAGING IN CAPACITY EVALUATIONS
When evaluating capacity, we only use timeaverage quantities.
In the UL, the capacity constraint is that the timeaverage noise rise at the cell must not exceed the
noise rise limit.
In the DL, the capacity constraint is that the timeaverage power of the cell must not exceed the
maximum cell power.
For resources, the capacity constraint is that the timeaverage number of resources consumed must not
exceed the userspecified limits.
For HSDPA, the capacity constraint is that the timeaverage HSDPA power of the cell must not exceed
the HSDPA link power. This is equivalent to saying that the sum of the activity factors of served
HSDPA users must not exceed 100%.
Timeaverages are calculated by scaling quantities (i.e. powers transmitted and resources consumed) by
activity factors. (Note that the activity factor for a CS resource is always 100%, regardless of the
service activity factor.)
One should remember that our snapshot contains no information about the instants of time at which
links are active. Only two things are known about each link:
The power and resources required to service the link in a period of activity.
The timeaverage interference and timeaverage resource consumption that the link produces
in the system.
1.4 WHY PRODUCE SNAPSHOTS?
The coverage in a CDMA system depends on system load. This effect is often called cellbreathing.
One cannot perform a coverage analysis for a CDMA system without knowing the extent to which the
system is loaded. The main purpose of a snapshot is to provide us with measures of system load. In
particular, each snapshot tells us:
The total DL transmission power of each cell.
The total UL interference power (incell noise & outcell noise) on each cell.
The total UL and DL throughput on each cell.
The resources consumed on each cell.
By running many snapshots, we obtain values for these quantities for different spatial distributions of
terminals, and can then proceed to analyse UL and DL coverage for the system.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 9
1.5 ACTIVITY FACTORS
As explained in previous sections, activity factors are used to calculate implicit timeaverages for
bearers in a simulation snapshot. There are two areas where timeaveraging is important and these
have separate activity factors. We call these the poweractivity factor and the resourceactivity factor.
The poweractivity factor is used to calculate the timeaverage power and timeaverage
throughput for a link.
Timeaverage Power = Power Activity x Power when Active.
Timeaverage Throughput = Power Activity x User Bitrate.
The resourceactivity factor is used to calculate the timeaverage resource consumption for a
link.
Timeaverage Resources = Resource Activity x Resources when Active.
The poweractivity factor and resourceactivity factor for a bearer are not necessarily the same.
For circuitswitched (CS) services, resources are consumed even during periods of inactivity.
Therefore CS services always have a resourceactivity factor of 100%, regardless of the poweractivity
factor.
For packet switched (PS) services, resources are only consumed during periods of activity. So one
could expect the poweractivity factor and resourceactivity factor for a bearer to be equal, and this is
the default behaviour in the tool. However, there are cases when the user may wish to consider the
resourceactivity factor to be larger than the poweractivity factor. For example, once a PS link has
ceased being active, resources may not be released immediately due to a release timeout. The user is
therefore given the option of editing the power and resource activities for PS services directly.
PS Activity Factor Calculation
For a PS service, the tool can automatically calculate the poweractivity factor from the PS parameters
in the service definition:
airR Air interface bitrate (bps).
bytesN Number of bytes per packet.
packetsN Number of packets per packet call.
callsN Number of packet calls per session.
readT Reading time (s).
interT Interarrival time between packets (s).
BLER1
BLERr Retransmission factor ( 10 r ) in terms of BLER.
Active time: aircallspacketsbytesactive /)1(8 RrNNNT
Inactive time: )1()1(1)( interpacketscallsreadcallsinactive rTNNTNT
Session time: inactiveactivesession TTT
Activity factor: session
active
T
T
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 10
1.6 BITRATES AND PROCESSING GAIN
Air Interface Bitrate and Processing Gain
The Air Interface Bitrate is used to calculate the processing gain ( kk GG , ) in the bearer linkbudget
equations (2932). The quantities ( kk GG , ) are always calculated by dividing the system chiprate (W )
by the air interface bitrate.
For HSDPA bearers, the airinterface bitrate is automatically calculated to give the correct processing
gain after demodulation as follows:
Chip rate / Symbol rate = 16.
Bits per symbol = M = 2 or 4 (for QPSK & 16QAM respectively).
For a HSDPA bearer using N codes, the net gain after demodulation = )(/16 NM .
Therefore the air interface bitrate is set to 16
NMW, as this gives
NMGk
16.
User Bitrates
The User Bitrate is used to calculate data throughput on a cell, and it also affects certain outputs in the
Extended HSDPA Analysis.
1.7 RESOURCE TYPES
The user can define up to 6 different resource types in the tool and these can be pooled at various
locations in the network (i.e. site, sitecarrier, or cell). A resource pooled at the site level is shared
between all the cells on that site. Similarly a resource pooled at the sitecarrier level, is shared between
all the cells on a site that use that carrier.
“Air Interface” Resources
Any resource type that is flagged as being of type “airinterface” can only be pooled at the cell level.
In other words, these resources cannot be shared between cells. Also, “airinteface” resources are not
consumed in the uplink on handover cells.
HSDPA Resource
The user can choose precisely one of the 6 resource types in the tool to represent a HSDPA resource
(i.e. HSDPA codes). A cell must be allocated some HSDPA resources in order to support HSDPA
users. HSDPA resources are downlink resources. (Please notice that HSUPA can be supported without
the need to specify any recources although any of the nonHSUPA resource types can be optionally
used to model HSUPA resources).
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 11
2 FORMULAE
2.1 NOTATION
Symbols in subsequent sections use the following notation.
A lowercase Greek subscript always indexes a carrier.
indicates a sum over all carriers.
An uppercase Roman subscript always indexes a cell.
J
indicates a sum over all cells.
A lowercase Roman subscript always indexes a terminal.
k
indicates a sum over all terminals.
Jk
indicates a sum over all terminals in cell J.
A superscript arrow ),( indicates if a quantity is uplink or downlink.
Unless stated otherwise, all quantities and formulae are in standard SI units, not in dB.
As an example, the quantity JkE represents the uplink Eb/No for the link between terminal k and cell
J using carrier .
2.2 LIST OF PRINCIPAL SYMBOLS
AA , UL (DL) adjacent carrier inteference ratio. This is the power leakage from
carrier to carrier . By definition 1AA .
k Interference cancellation efficiency of terminal k.
k Chip equalisation efficiency of terminal k.
JkE UL traffic channel Eb/No when UL is active.
JkE DL traffic channel Eb/No when DL is active.
pilotJkE Pilot channel Ec/Io.
SIRJkE Pilot channel SIR.
HSDPA
kJE HSDPA Eb/No.
HSUPA
kJE HSUPA Eb/No.
SCCHHS
kJE HSSCCH Ec/Nt
SINR HS
JkE HSDPA SINR.
kk GG , UL,DL processing gain.
antennaJG Cell attenna gain.
antennakG Terminal antenna gain.
mhaJG Mast head amplifier UL gain.
k Boltzmann constant. mhaJL Mast head amplifier (MHA) DL insertion loss.
JkJk LL , UL,DL linkloss between cell and terminal.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 12
pathlossJkL Pathloss between cell and terminal.
antennaJkL Antenna masking loss.
feederJL Feeder loss, including feeder connector loss.
bodykL Terminal body loss.
splitterJL Cell DL splitter loss.
thermalkN Thermal noise at terminal.
thermalJN Thermal noise at cell.
Max MSkP Power allocated to terminal k.
kP UL traffic channel TX power when UL is active.
Max BSJP Power allocated to cell J.
pilotJP Pilot channel TX power.
CCPCHPJP PCCPCH TX power.
CCPCHSJP SCCPCH TX power.
SCHPJP PSCH TX power.
SCHSJP SSCH TX power.
AICHJP AICH TX power.
PICHJP PICH TX power.
AGCHE
JP EAGCH TX power.
HICHE
JP EHICH TX power.
RGCHE
JP ERGCH TX power.
commonJP Timeaverage common channel TX power.
HSDPAJP Timeaverage total HSDPA TX power.
SCCHHS
JP Timeaverage total HSSCCH TX power.
PDSCHHS
JP Timeaverage total HSPDSCH TX power.
HSUPA
JP Timeaverage total HSUPA Downlink TX power.
HSUPA
JP Timeaverage total HSUPA Uplink TX power.
syncJP Timeaverage synchronisation channel TX power.
JkP DL traffic channel TX power when DL is active.
maxJP Maximum DL power for an active (nonHSDPA) link.
minJP Minimum DL power for an active (nonHSDPA) link.
linkHSDPA
JkP HSDPA link power (i.e. the HSDPA TX power for an active link).
maxHSDPA JP Maximum HSDPA link power (specified in the cell parameters).
HSUPA
kP Timeaverage HSUPA UL TX Power.
link SCCHHS
JkP HSSCCH link power (i.e. the HSDPA control TX power for an active link).
link SPDSCHHS
JkP HSPDSCH link power (i.e. the HSDPA data TX power for an active link).
k SCCHHS
JP Timeaverage total HSSCCH power for the other HSDPA links other than k.
totalJP Timeaverage total DL TX power.
UMTSJP Timeaverage total UMTS DL TX power.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 13
UMTS
JP Timeaverage total UMTS UL TX power.
k
JPUMTS Timeaverage interfering UMTS DL TX power for link to terminal k.
cellinJR Timeaverage total UL “incell” noise.
celloutJR Timeaverage total UL “outcell” noise.
totalkR Timeaverage total DL noise at terminal.
totalJR Timeaverage total UL noise at cell.
T Temperature in Kelvin (for thermal noise calculation).
W Chip rate (bps). CCPCHP
J PCCPCH activity factor.
CCPCHSJ SCCPCH activity factor.
SCHPJ PSCH activity factor.
SCHSJ SSCH activity factor.
AICHJ AICH activity factor.
PICHJ PICH activity factor.
AGCHE
J EAGCH activity factor.
HICHE
J EHICH activity factor.
RGCHE
J ERGCH activity factor.
kk , UL,DL traffic channel activity factor.
kk , UL,DL traffic channel controloverhead factor
J Cell orthogonality factor.
k Terminal noise figure.
J Base station noise figure.
mhaJ Mast head amplifier noise figure.
feederJ Feeder noise figure ( =
feederJL ).
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 14
2.3 DOWNLINK POWER AND NOISE FORMULAE
DL Loss
splittermha
antennaantenna
feederbodyantennapathloss
JJ
Jk
JkJkJkJk LL
GG
LLLLL . (1)
The first part of the above expression ( ) is read from the prediction file.
Timeaverage Common Channel TX Power
AGCHEAGCHEPICHPICHAICHAICHCCPCHSCCPCHSCCPCHPCCPCHPcommon
JaJaJJJJJJJJJ PaPPPPP .
(2)
This is calculated by scaling the TX powers of the PCCPCH, SCCPCH, AICH and PICH by their
activity factors.
Timeaverage Synchronisation Channel TX Power
SCHSSCHSSCHPSCHPsync
JJJJJ PPP . (3)
This is calculated by scaling the TX powers of the PSCH and SSCH by their activity factors.
Timeaverage UMTS TX Power
UMTSk
Jkk
UMTSk
JkkJ PPPUMTS . (4)
The sums are over the UMTS terminals that are served by the cell. The first sum is the timeaverage
TX power for the traffic channels. The second sum is the total control overhead TX power for those
channels.
Timeaverage Interfering UMTS TX Power
JqqqJq
J PPP )(UMTSUMTS. (5)
The quantity q
JPUMTS is only relevant to UMTS terminals. It is similar to
UMTSJP except it excludes
the timeaverage TX power for the terminal q. The only purpose for defining this quantity is to
simplify the UMTS DL link budget equation.
Total HSDPA Links TX Power (for all simultaneously codemultiplexed active links)
DPA using if),(min
DPA usingnot if
UMTSHSUPA commonsyncpilotMax BSmaxHSDPA
maxHSDPA linkHSDPA
JJJJJJJ
JJ
PPPPPPP
PP
(6)
This refers to the total links power for an active link (i.e. HSDSCH + HSSCCH). When using
Dynamic Power Allocation (DPA), the total links power is the smaller of the available (nonHSDPA)
power on the cell and the HSDPA Link Power specified on the cell. When not using DPA, the total
antennapathlossJkJk LL
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 15
links power is the HSDPA Link Power specified on the cell. This power can be shared by a number of
simultaneous users in the case of code multiplexing.
HSDPA Single Link TX Power
There are 2 components to the link power (link SCCHHS
kJP and link PDSCHHS
kJP ).
The instantaneous HSSCCH power for the link (link SCCHHS
kJP ) is calculated first. (Fixed or Dynamic)
The instantaneous HSPDSCH power for the link (link PDSCHHS
kJP ) is then given by:
ngmultiplexi codewith )(15
ngmultiplexi code nowith
kSCCHHSlink SCCHHSlinkHSDPA
link SCCHHSlinkHSDPA
link PDSCHHS
JkkJJkk
kJJk
kJPPP
N
PP
P
(7)
where kN is the number of codes used by the link.
The quantitykSCCHHS
JkP is the timeaverage total HSSCCH power for the other HSDPA links, and is
given by:
link SCCHHSSCCHHSkSCCHHS
JkkJJk PPP (8)
Timeaverage Total HSSCCH TX Power
HSDPAk
kJkJ PP link SCCHHSSCCHHS . (9)
Timeaverage Total HSPDSCH TX Power
HSDPAk
kJkJ PP link PDSCHHSPDSCHHS . (10)
Timeaverage HSDPA TX Power
PDSCHHSSCCHHSHSDPA
JJJ PPP . (11)
This is the timeaverage HSDPA power transmitted by the cell. The sum is over the HSDPA terminals
that are served by the cell.
HSUPA Dedicated DL Channel TX Power
RGCHERGCHEHICHEHICHEHSUPA
JJJJJ PPP . (12)
Timeaverage DL TX Power
SCCHHSPDSCHHSUMTSHSUPA commonsyncpilottotal
JJJJJJJJ PPPPPPPP . (13)
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 16
DL Thermal Noise
kk WTkN thermal. (14)
Timeaverage Total DL Noise Power
J Jk
Jkk
L
PANR
totalthermaltotal . (15)
Timeaverage DL “outcell” Interference
kJ
J
C kC
C
kJL
P
L
PAI
totaltotal
out . (16)
2.4 UPLINK POWER AND NOISE FORMULAE
UL Loss
mhaantennaantenna
feederbodyantennapathloss 1
JJk
JkJkJkJk
GGG
LLLLL . (17)
The first part of the above expression (antennapathlossJkJk LL ) is read from the prediction file.
UL Thermal Noise at Cell
feedermhamha
feedermha
feeder
mhathermal
/
11
JJ
J
J
JJ
J
JJ
LGGL
GWTkN . (18)
The first pair of brackets contains the net UL gain between the receiving antenna and the BS. The
second pair of brackets contains the net UL noise figure between the receiving antenna and the BS.
Timeaverage Total UL “incell” Noise
Jk kJ
kkk
Jk kJ
kkk
JL
P
L
PR
HSUPAUMTS
cellin)1()(
. (19)
This is the total RX power from “incell” terminals. The sum is over terminals that have cell J as their
primary cell.
Timeaverage Total UL “outcell” Noise
Jk Jk kJ
kkk
kJ
kkk
JL
P
L
PAR
HSUPAUMTS
cellout)1()(
. (20)
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 17
This is the total RX power from “outcell” terminals. The sum is over terminals that do not have cell J
as their primary cell.
Timeaverage Total UL Noise Power
celloutcellinthermaltotal
JJJJ RRNR . (21)
This is the UL thermal noise plus the total RX power from all terminals.
UL Noise Rise
thermal
total
Rise) (NoiseJ
JJ
N
R. (22)
The UL noise rise is expressed in dB in the simulation report.
UL Load
JJ
Rise) (Noise
11Load) (UL . (23)
The UL Load is expressed as a percentage in the simulation reports.
UL Frequency Reuse Efficiency
celloutcellin
cellin
FREJJ
JJ
RR
R. (24)
UL FRE is the total RX power from “incell” terminals divided by the total RX power from all
terminals. It is expressed as a percentage in the simulation reports.
2.5 LINK BUDGET FORMULAE
The following formulae are all expressions for signal to noise ratios, and are used to determine the
power required to successfully service a link. The basic relations below ignore handover gains, power
control headroom, power rise gain, and maximal ratio combining. The influence of these effects is
described in the section describing Connection Evaluation. Note that all denominators in our link
budgets contain timeaveraged quantities.
Pilot Ec/Io
Jkk
JJk
LR
PE
total
pilotpilot
. (25)
HSSCCH Ec/Nt
outinthermal
link SCCHHS
SCCHHS
)1(
/
kJkkJk
kJkJ
kJIIN
LPE . (26)
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 18
where in
kJI is the timeaverage incell interference. There are 2 cases for this:
No codemultiplexing: In this case there is no interference between HSDPA users on a cell.
kJ
JJJJJJkJ
L
PPPPPI
))(1( UMTSHSUPA commonpilotsync
in
Codemultiplexing:
kJ
JJJJJJJJkJ
L
PPPPPPPI
))(1( kSCCHHSkPDSCHHSUMTSHSUPA commonpilotsync
in
Pilot SIR
outinthermal
pilot
SIR
)1(
/
kJkkJk
kJJkJ
IIN
LPE . (27)
where k is the interference cancellation efficiency of the terminal, and in
kJI is the timeaverage in
cell interference:
kJ
JJJJJJJkJ
L
PPPPPPI
))(1( SCCHHSPDSCHHSUMTSHSUPA commonsync
in .
Own pilot is not considered as interference. Owncell interference from common channels, UMTS,
and HSDPA channels is reduced because of orthogonality.
HSPDSCH SINR
outinthermal
link PDSCHHS
SINR HS
)1(
/16
kJkkJk
kJkJ
kJIIN
LPE . (28)
where in
kJI is the timeaverage incell interference. There are 2 cases for this:
No codemultiplexing: In this case there is no interference between HSDPA users on a cell
kJ
JJJJJJkJ
L
PPPPPI
))(1( UMTSHSUPA commonpilotsync
in
Codemultiplexing:
In this case we calculate a worst case SINR by assuming we have interference from the other ( kN15 )
HSDPA codes that are not used by the user. So if the user’s data power is link PDSCHHS
kJP , the
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 19
interfering HSPDSCH power is link PDSCHHS)
15( kJ
k
k PN
N. This is reduced by the chip equalisation
efficiency k of the terminal.
kJ
kJk
kkJJJJJJJ
kJL
PN
NPPPPPP
I
))15
)(1()(1( link PDSCHHSkSCCHHSUMTSHSUPA commonpilotsync
in
Owncell HSDPA power is not considered as interference. Owncell interference from pilot, common,
and UMTS traffic channels is reduced because of orthogonality.
HSPDSCH Eb/No
SINR HSPDSCHHS
16kJ
k
kJ EG
E (29)
The above formula gives the Eb/No for the HSPDSCH. See section 1.6 for the calculation of kG for
a HSDPA bearer.
HSUPA Eb/No
HSUPAtotal
HSUPAHSUPA
HSUPA
)1( kkkkJJ
kk
JkPLR
PGE (30)
UMTS UL Eb/No
kkkJkJ
kkJk
PLR
PGE
)(total. (31)
Own link power is not considered as interference. See section 1.6 for the calculation of kG for a
bearer.
UMTS DL Eb/No
outinthermal )1(
/
kJkkJk
kJkJk
kJIIN
LPGE . (32)
where in
kJI is the timeaverage incell interference.
kJ
JJJJJJJJ
kJL
PPPPPPPI
))(1( SCCHHSPDSCHHSkUMTSHSUPA commonpilotsync
in
The quantitykUMTS
JP is the timeaverage total UMTS power for the other links, and is given by:
kJkkJJ PPP )(UMTSkUMTS
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 20
Own link power is not considered as interference. Owncell interference from other UMTS and
HSDPA channels is reduced because of orthogonality. See section 1.6 for the calculation of kG for a
bearer.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 21
2.6 EXTENDED HSDPA ANALYSIS FORMULAE
The calculations that make up the Extended HSDPA Analysis are performed after the snapshots have
been run. All outputs are related to the Achievable HSDPA Bearer plot. The achievable HSDPA
bearer at each pixel provides us with:
An achievable userbitrate for the service in the pixel.
An activity factor for the service in the pixel. This is just the poweractivity factor of the
Achievable HSDPA Bearer.
A cell that “owns” the pixel. The cell that supports the Achievable HSDPA Bearer and
provides the strongest pilot “owns” the pixel.
Offered HSDPA Pixel Load
This is the mean number of service M terminals in pixel k, weighted by activity factor.
powerkMkMkM N . (33)
kM = Offered load from service M terminals in pixel k.
kMN = Mean number of offered service M terminals in pixel k (read from the traffic density array).
powerkM = Poweractivity factor of service M terminals in pixel k. This is the activity factor of the
Achievable HSDPA Bearer for the service M terminal in pixel k.
Offered HSDPA Cell Load
Offered HSDPA cell loads are calculated by summing individual pixel loads. Each pixel load is
assigned to one of the cells that cover the pixel. The cell that “owns” the pixel receives the load. In the
following formula, the first summation indicates that the HSDPA load for cell J is found by summing
individual pixel loads. The second summation is over the services that support HSDPA.
Jk M
kMJ
HSDPAsupports
. (34)
J = Offered load on Cell J.
kM = Load from service M terminals on pixel k.
Effective Service Rate (Unloaded)
The effective service rate at a pixel is found by calculating the Achievable HSDPA Bearer at the pixel.
The effective service bitrate is the userbitrate of the bearer, multiplied by the activity factor of the
bearer.
kMkM
kM
M
kM CT
X powerunloaded . (35)
powerkM = Power activity factor of service M in pixel k.
kMC = Achievable DL HSDPA userrate for service M in pixel k.
MX = Total data (in bits) for service M (calculated from the PS parameters of the service).
kMT = Unloaded session time in seconds, i.e. the session time when there is no queuing delay.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 22
Effective Service Rate (Loaded)
A high cell load ( J ) increases the session time and so decreases the effective service rate at a pixel.
unloaded
power
loaded
)1(1
1kM
kMJ
JkM . (36)
If 1J then 0loadedkM .
Effective Cell Service Rate (Unloaded)
This is the effective bitrate for a service M user on cell J when there is no queuing delay.
JMJM TX /unloaded . (37)
MX = Total data (in bits) for service M (calculated from the PS parameters of the service).
JT = Mean service time for a user in cell J (defined later).
If the cell load ( J ) is zero, then both JT and unloadedJM are undefined, and this is indicated by
assigning an effective cell service rate of 1.
Effectice Cell Service Rate (Loaded)
This is the effective bitrate for a service M user on cell J when there is queuing delay. A high cell load
( J ) decreases the effective cell service rate.
)1(unloadedloadedJJMJM . (38)
If 1J then 0loadedJM .
If the cell load ( J ) is zero, then both unloadedJM and
loadedJM are undefined, and this is indicated by
assigning an effective cell service rate of 1.
Mean Service Time in Pixel
The mean service time ( kMS ) for a user of service M in pixel k is the time spent transmitting data, and
is related to the unloaded session time ( kMT ) as follows
kMMkMkMkM CXTS /power
. (39)
powerkM = Power activity factor of service M in pixel k.
MX = Total data (in bits) for service M (calculated from the PS parameters of the service).
kMC = Achievable DL HSDPA userrate for service M in pixel k.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 23
Mean Service Time in Cell
The mean service time for a user in cell J is given by
Jk M kM
kM
Jk M
kM
J
S
T . (40)
In other words, it is a weighted harmonic mean of the mean service times at pixels, weighted by offered
pixel loads. If the offered load on a cell is zero, then both the numerator and denominator in the above
expression are zero, and so JT is undefined. This means that the Effective Cell Service Rate
(Unloaded) and the Effective Cell Service Rate (Loaded) will both be undefined.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 24
3 SNAPSHOT OVERVIEW
The key purpose of a snapshot is to provide us with measures of system load for a particular
distribution of terminals. To obtain these measures of system load, we must calculate uplink and
downlink transmission powers for all the links in the system. A snapshot involves the following stages:
Creating a random terminal distribution.
Setting random terminal parameters (speeds, shadow fades, power control errors).
Calculating link powers using power iterations.
Gathering results.
3.1 RANDOM TERMINAL DISTRIBUTION
The first stage of a snapshot involves creating a random distribution of terminals representing the
offered traffic in the network. The spatial distribution of terminals must be random, but more
importantly it must be unbiased. In other words, it must be reasonable compared to the terminal
density array provided by the user. To see how this can be achieved, we need only consider a single
pixel (bin) in the simulation.
Consider a pixel that has a terminal density of D terminal/km2 and an area of A km
2, so that the average
number of terminals in the pixel is DA. We note that:
Terminal occurrences within the pixel are independent of each other, and are spatially uniform
within the pixel. In other words, a terminal is just as likely to be located at one point within
the pixel as any other point within the pixel.
The probability that two or more terminals are located at exactly the same point within a pixel
is zero. This is simply because there are an infinite number of locations within the pixel.
These imply that terminal occurrence is a spatial Poisson process within the pixel. Therefore the total
number of terminals in the pixel satisfies the Poisson distribution:
!
)() terminals (
k
eDAkP
DAk
.
We choose the number of terminals to assign to the pixel by drawing a number from this Poisson
distribution. Doing this at each pixel ensures our terminal distribution is unbiased. Since the sum of
many Poisson distributions is also a Poisson distribution, the total number of terminals in the snapshot
will also be Poisson distributed.
One may note that if the average number of terminals at a pixel is small (DA << 1), then working to
first order in DA,
.) terminal1 (
,)1() terminal0 (
DAP
DAP
So one is effectively making a binary decision about whether a terminal should be placed at the pixel.
After creating the random terminal distribution, the terminals are randomly sequenced. This
determines the order in which they will be considered during the power iterations.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 25
3.2 RANDOM SPEED DISTRIBUTION
Each randomly scattered terminal in a simulation is given a random speed according to its terminal type
and the clutter type in which it resides. For each combination of terminal type and clutter type, the
user specifies 4 parameters that determine the speed distribution. These are:
speed Mean speed.
speed Standard deviation of the speed distribution.
mins Minimum speed.
maxs Maximum speed.
A random speed is then given by
)),max(,min( speedspeedminmax Xsss .
where X is a random number drawn from a normal distribution of zero mean and unit variance.
Terminals are randomly assigned as being indoor or outdoor, according to their terminal type and the
clutter type in which they reside. Indoor terminals are all given a speed of zero.
When defining a bearer, the user specifies how speed affects the Eb/No requirement and handover
gains for that bearer. The user enters values at speeds of (in SI units) 3 km/h, 50 km/h, 120 km/h.
Values at other speeds are obtained by linear interpolation. Values are not extrapolated to speeds
higher than 120 km/h or lower than 3 km/h, which explains the labels (03 km/h & >= 120km/h).
Therefore stationary terminals will always use the values corresponding to 03km/h, and there is no
difference between a stationary terminal and one travelling at 3 km/h. The output arrays for the
simulation are available at 3 different speeds (03 km/h, 50 km/h, 120 km/h) so the user can more
clearly see how coverage changes with speed.
3.3 POWER CONTROL MODELLING
Power control in a real network
In a real network, link powers are modified by stepping up or down by a power step size, so
the set of possible link TX powers is discrete. A step size of 0 dB is meaningless since powers
could never change.
Power control is dynamic and imperfect. Hence served terminals will sometimes
underachieve Eb/No requirements and sometimes overachieve them.
Power control in a snapshot
Link powers in a snapshot are modified but not by stepping up or down. It is computationally
more efficient to calculate a required link power and set it directly, rather than trying to
achieve the power via several steps up or down. Therefore there is no reason to restrict link
TX powers to a discrete set, although the user can still do this by entering a nonzero Power
Step Size in the terminal definition. A Power Step Size of 0 dB simply implies that a
continuum of link powers is available.
A snapshot is not dynamic, in the sense that there is no concept of the network changing with
respect to time. It is possible to produce a snapshot where all links exactly satisfy their Eb/No
requirements, which is something that would never be observed in reality. In reality, the
errors between achieved and required Eb/No values follow a lognormal distribution. The
user can randomise the “perfect” set of link powers produced by a snapshot using the Power
Control Std Dev parameter in the simulation wizard. This takes the “perfect” link powers of
served terminals and adds random (lognormal) errors to them so that the served terminals
underachieve and overachieve their Eb/No requirements.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 26
It is recommended that users set the Power Step Size parameter to 0 dB and the Power Control Std Dev
parameter to 0 dB for the following reasons:
Their effects are insignificant compared to the input sources of error to the simulation (i.e. the
pathloss predictions and terminal density array supplied by the user).
Given that the snapshot spends a great deal of time trying to accurately calculate link powers,
it is wasteful to then throw away this work by quantising or randomising the results.
3.4 POWER ITERATIONS
The main task in a snapshot is to assign a set of link powers satisfying the Eb/No requirements of the
randomly spread terminals. Before commencing the power iterations, the system is placed in the state
of an unloaded network by setting all link powers to zero, and making all resources available at the
cells. The link powers in the system are then calculated iteratively by repeatedly cycling through the
list of randomly spread terminals and applying the following logic to each terminal.
If the terminal is already “connected”, then “disconnect” it as follows:
o Zero the UL & DL powers for the terminal.
o Zero the cell resources used by the terminal.
o Recalculate the UL interference on all cells (because the UL power for the terminal
has been zeroed).
o Recalculate the total DL power on all cells (because the DL powers for the terminal
have been zeroed).
o Recalculate resources available on all cells (because the terminal has released
resources).
Try and “connect” the terminal to the network in the most favourable way possible. Note that
this may be different to the way it was previously “connected”. For example, it may be
preferable to use a different carrier if interference has increased since the last time the terminal
was evaluated. The procedure for finding the most favourable method of connection is
described in the section on Connection Evaluation.
If a connection is possible, then “connect” the terminal as follows:
o Set the UL and DL powers for the terminal.
o Set the cell resources used by the terminal.
o Recalculate the UL interference on all cells (because the UL power for the terminal
has been set).
o Recalculate the total DL power on all cells (because the DL powers for the terminal
have been set).
o Recalculate resources available on all cells (because the terminal has consumed
resources).
Several cycles through the list of terminals must be performed before a stable set of link powers
emerge. The following diagram illustrates how a snapshot converges with successive cycles through
the terminal list. The histograms show how “connected” terminals underachieve their Eb/No
requirements.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 27
After the first cycle through the terminal list, the majority of “connected” terminals underachieve their
Eb/No requirements. This is because terminals connected at the beginning of the first cycle see little or
no interference and so have their link powers set to low values. By the end of the first cycle, the
interference in the system is higher. Therefore terminals evaluated at the beginning of the cycle no
longer achieve their Eb/No requirements by the end of the cycle. Successive cycles through the
terminal list produce increasingly accurate pictures of network interference. After a few cycles,
practically all the “connected” terminals have link powers that achieve the Eb/No requirements, and the
system interference no longer changes significantly. The power iterations have converged to produce a
plausible picture of served and failed terminals in the network.
3.5 CONVERGENCE TEST
A good practical measure of convergence is to examine how the interference changes between cycles.
This is considerably faster than measuring the distribution of achieved Eb/No values described above.
Asset3g now uses a much stronger convergence criterion for simulation snapshots than previous
versions of the tool (Version 5.0 and earlier), since both the UL and DL are checked. The user only
needs to enter a single parameter, namely a percentage power change. After each cycle through the
terminal list, the percentage changes in total UL RX power and total DL TX power are noted. If these
both fall within the user specified limit for 15 consecutive iterations, then the snapshot is considered to
be converged. So the percentage changes in UL and DL noise must not only become small but must
remain small also. Note that the user no longer enters a maximum number of iterations parameter (i.e.
maximum number of cycles) as in older versions of the tool, and power iterations will now run until the
snapshot has converged, so there is no possibility of producing nonconverged snapshots.
3.6 GATHERING OF RESULTS
The final stage of a snapshot involves gathering results. The information gathered includes cell
information (e.g. resource and power usage), information about the states of “connected” terminals, and
the reasons for failure of terminals which failed to be served.
End of 3
cycles
8 6 4 2 0 2
Error (dB)
End of 1
cycle
8 6 4 2 0 2
Error (dB)
End of 7
cycles
8 6 4 2 0 2
Error (dB)
End of 5
cycles
8 6 4 2 0 2
Error (dB)
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 28
4 CONNECTION EVALUATION IN A SNAPSHOT
4.1 CONNECTION SCENARIO PRIORITISATION
A connection scenario describes how a terminal “connects” to the network and consists of the
following set of parameters:
The carrier used for connection.
Carrier load status (overloaded/underloaded). If any covering cell with the carrier exceeds its
“load balance threshold”, then the carrier load status is “overloaded”, otherwise it is
“underloaded”.
The primary cell for the connection (this is where the primary resources are consumed)
The Ec/Io of the primary cell.
The DL bearer used.
The UL bearer used.
Typically, several connection scenarios are available to each terminal. Our snapshot attempts to
connect the randomly spread terminals to the network in the most favourable way possible, so some
logic is required for ranking the different scenarios that each terminal may use.
The rules for ranking scenarios during connection evaluation are (in order of decreasing importance):
Prefer underloaded carriers to overloaded carriers.
Prefer higher priority carriers to lower priority carriers.
Prefer cells with higher Ec/Io levels to cells with lower Ec/Io levels.
Prefer higher priority DL bearers to lower priority DL bearers.
Prefer higher priority UL bearers to lower priority UL bearers
As an example, the scenarios available to a terminal may be (from most to least favoured):
Cell_X Carrier_1 Ec/Io = 10 DL=24 kbps UL = 12 kbps
Cell_X Carrier_1 Ec/Io = 10 DL=12 kbps UL = 12 kbps
Cell_Y Carrier_1 Ec/Io = 12 DL=24 kbps UL = 12 kbps
Cell_Y Carrier_1 Ec/Io = 12 DL=12 kbps UL = 12 kbps
Cell_Z Carrier_1 Ec/Io = 14 DL=24 kbps UL = 12 kbps
Cell_Z Carrier_1 Ec/Io = 14 DL=12 kbps UL = 12 kbps
Cell_A Carrier_2 Ec/Io = 8 DL=24 kbps UL = 12 kbps
Cell_A Carrier_2 Ec/Io = 8 DL=12 kbps UL = 12 kbps
Cell_B Carrier_2 Ec/Io = 9 DL=24 kbps UL = 12 kbps
Cell_B Carrier_2 Ec/Io = 9 DL=12 kbps UL = 12 kbps
In this example, the user has specified Carrier_1 to be of higher priority than Carrier_2, so cells with
Carrier_1 are preferred even though there are better Ec/Io levels on Carrier_2. Cell_X is the most
preferred cell since it has the highest Ec/Io of the Carrier_1 cells. The 24 kbps DL bearer has been
given a higher priority than the 12 kbps bearer, so it is the preferred DL bearer on every cell.
The connection scenarios for each terminal are evaluated in turn (from most to least favoured) until one
that permits a network connection is found. The scenario employed by a terminal may change each
time it is evaluated in the power iterations, and this flexibility provides us with link adaptation.
There are 3 stages to evaluating a connection scenario to see if a connection is possible:
Production of a candidate active set for the terminal.
Uplink evaluation.
Downlink evaluation.
We now describe each stage in turn.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 29
4.2 PRODUCTION OF A CANDIDATE ACTIVE SET
In order for a cell to be in the candidate active set of a terminal, it must have an adequate number of
resources available, and the pilot levels (SIR, Ec/Io, RSCP) for the cell must also be acceptable. It is
necessary to produce a candidate active set before the uplink and downlink can be evaluated. A
candidate active set is produced by the following procedure.
Check primary resource availability & pilot levels (SIR, Ec/Io, RSCP) of primary cell.
Check handover resource availability & pilot Ec/Io levels of other cells.
The connection scenario being examined sets the candidate primary cell. This cell is checked to see if
it has a sufficient number of primary resources available, and to see if it provides an adequate pilot for
the terminal. If these conditions are met, the cell is flagged as the primary cell of the candidate active
set.
The remaining covering cells are evaluated to see if they can be handover cells. Cells with the best
pilot levels are checked before cells with weaker pilots. A handover cell must have a sufficient number
of handover resources available, and provide a pilot Ec/Io level of adequate strength (i.e. within the
handover margin of the Ec/Io level of the primary cell). Each cell that satisfies these requirements is
flagged as a handover cell unless the active set size limit specified on the primary cell has been
reached.
4.3 UMTS UPLINK EVALUATION
This is the process of determining the terminal transmit power required to meet the uplink Eb/No
requirement. It is necessary to consider several effects here, such as handover gains, power control
headroom, and noise rise limits on cells. Before describing the uplink evaluation procedure, we
describe each of these effects in turn.
Terminal Power Reduction (TXP Gain)
The Terminal Power Reduction (reductionpower
kG ) is a gain that reduces the required transmit power of a
terminal in soft handover. It is equivalent to a reduction in the uplink Eb/No requirement.
Average Power Rise
The Average Power Rise (risepower
kP ) effect is due to fast power control. Fast power control can
compensate for fading in a channel and keep the uplink received power from a terminal fairly constant
in the cell providing the power control. However this compensation for fades causes peaks in the
terminal transmission power. This results in a rise in the average interference experienced in other
cells. This is modelled in the simulator by adding an average transmit power rise to the terminal
transmit power when calculating the uplink interference caused to other cells. When calculating the
interference a terminal causes to its own cell, the average power rise is not added.
Power Control Headroom
The Power Control Headroom (PCHkH ) is an overhead on the transmit power a terminal requires to
make the uplink. It is a function of terminal speed, and the overhead is largest for slow moving
terminals. The overhead ensures that the uplink power control is able to compensate for deep fades at a
cell edge.
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Soft Handover Gain against Average Power Rise (PR Gain)
The Soft Handover Gain against Average Power Rise ( risepower kG ) reduces the average power rise for
soft handover cells. For nonhandover cells, 1risepower
kG .
Soft Handover Gain against Power Control Headroom (PCH Gain)
The Soft Handover Gain against Power Control Headroom (PCHkG ) reduces the power control
headroom when a terminal is in soft handover.
UPLINK TX POWER CALCULATION
For each cell in the active set, use the link budget equation (31) to calculate the uplink traffic
channel TX power needed to meet the uplink Eb/No requirement. Call the smallest of these
powers best
kP .
Assuming the terminal transmits at full power, calculate the difference in dB between the two
best uplink Eb/No’s. Call this difference Eb/Nok .
Get the values of reductionpower
kG ,risepower
kP ,PCHkH ,
risepower kG ,
PCHkG based on
Eb/Nok and the
speed of the terminal. If the service does not support soft handover then
1PCHrisepower PCHrisepower reductionpower kkkkk GGHPG .
The uplink traffic channel TX power in an active period is given by reductionpower best / kkk GPP .
The uplink control overhead TX power in both active and inactive periods is kk P , where
k is the control overhead factor of the uplink bearer.
Therefore, the total uplink TX power in an active period is kk P)1( .
UPLINK COVERAGE CHECK
The uplink is covered if
PCH
PCHMax MS)1(
k
kkkk
H
GPP ,
where Max MS
kP is the maximum power of the mobile.
UPLINK SOFT CAPACITY CHECK
The timeaverage uplink interference that the terminal would produce on its own cell (J) is
Jk
kkk
L
P)(,
where k is the bearer activity factor and JkL is the UL loss.
The timeaverage uplink interference that the terminal would produce on another cell (Q) is
risepower
risepower )(
k
k
Qk
kkk
G
P
L
P.
The terminal will not be connected to the network if doing so would cause the total uplink
interference on any cell to increase to a level that breaks the cell’s noise rise limit.
UMTS/HSPA Static Simulations – V 7.0
© Copyright 2009 AIRCOM International Ltd. 31
4.4 HSUPA UPLINK EVALUATION
The HSUPA link evaluation is the same as the UMTS Uplink one with the exception that when a
terminal tries to connect to a cell, the simulator should check if both the terminal and cell support
HSUPA as well as if the TTI duration, Min SF and Max Number of Codes used by the bearer are
supported by both the terminal and cell.
4.5 UMTS DOWNLINK EVALUATION
This is the process of determining the cell transmit powers required to meet the downlink Eb/No
requirement at the terminal.
Downlink Eb/No Target Reduction
The Downlink Eb/No Target Reduction (reductionpower
kG ) is a gain that reduces the downlink Eb/No
requirement of a terminal in soft handover.
DOWNLINK COVERAGE CHECK
For each cell J in the active set, set the downlink traffic channel TX power to
k
JJ
PP
1
max
,
where max
JP is the maximum allowed power for a downlink, and k is the control overhead
factor of the downlink bearer. The downlink control overhead power is kJP and so the
total link power in an active period is max
)1( JJk PP .
For each link in the active set, use the downlink link budget equation (32) to calculate the
achieved Eb/No for the traffic channel in an active period. The total downlink Eb/No after
maximal ratio combining (totalkE ) is the sum of the Eb/No values for the individual links (in
normal units, not dB).
Calculate the difference in dB between the two best pilot Ec/Io levels in the active set. Call
this difference Ec/Iok .
Get the value of reductionpower
kG based on Ec/Iok and the speed of the terminal. If the service
does not support soft handover then 1reductionpower
kG .
The downlink is covered if reductionpower requiredtotal / kkk GEE ,
where requiredkE is the downlink Eb/No requirement of the traffic channel in a period of
activity.
DOWNLINK TX POWER CALCULATION & DOWNLINK SOFT CAPACITY CHECK
For the link with the primary cell, use the downlink link budget equation (32) to calculate the
downlink traffic channel TX power ( T ) needed to meet the DL Eb/No requirement in an active
period.
We find the downlink traffic channel powers for cells in the active set by iterating over the
value T as follows:
o For each cell J in the active set, set the DL traffic channel TX power to
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kk
J
k
J
k
J TPPP
1,
1max,
1,
1min
minmaxavailable
,
where min
JP is the minimum allowed power for a downlink and the timeaverage
power available on the cell is given by totalMax BSavailableJJJ PPP .
In other words, try to set all link powers to T but make sure links do not transmit
more power than is available.
o For each link in the active set, use the downlink link budget equation (32) to calculate
the achieved Eb/No for the traffic channel in an active period. The total downlink
Eb/No after maximal ratio combining (totalkE ) is the sum of the Eb/No values for the
individual links (in normal units, not dB).
o Modify T as follows
total
reductionpower required/
k
kk
E
GETT .
This reduces to TT if the Eb/No requirement is satisfied exactly.
o Repeat the previous 3 steps until totalkE has converged to some value
finalkE .
If reductionpower requiredfinal / kkk GEE then we have enough power on the cells to serve the user,
and the traffic channel TX power for cell J in an active period is
kk
J
k
J
k
JJ
TPPPP
1,
1max,
1,
1min
minmaxavailable
.
Since the control overhead power is Jk P , the total link power in an active period is given
by Jk P)1( and satisfies
)),max(,,min()1(minmaxavailable TPPPP JJJJk .
If reductionpower requiredfinal / kkk GEE then we do not have enough power on the cells to serve
the user, so the terminal will not be connected to the network.
4.6 HSDPA DOWNLINK EVALUATION
HSDPA DOWNLINK TX POWER CALCULATION
Each HSDPA link is transmitted in two parts: Control Channel link SCCHHS
kJP
and data channel
link PDSCHHS
kJP . The calculation of the control channel depends on the HSSCCH dynamic power setting
of the cell, while the calculation of the data channel depends on the codemultiplexing setting of the
cell as given by equation (7).
HSDPA DOWNLINK COVERAGE CHECK
Use the HSDPA link budget equations (26) and (29) to calculate the HSSCCH Ec/Nt (SCCHHS
JkE ) and the HSPDSCH Eb/No at the terminal (
PDSCHHS
JkE ).
The DL is covered if
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requiredSCCHt HSSCCHHS
JkJk EE AND
required PDSCHPDSCHHS
JkJk EE
where required SCCHHS
JkE and
required PDSCHHS
JkE is the HSSCCH Ec/Nt requirement of the
terminal and the DL Eb/No requirement of the HSDPA bearer, respectively.
HSDPA DOWNLINK SOFT CAPACITY CHECK
We must ensure that connecting the terminal will not cause the timeaverage HSDPA power on
the cell (HSDPAJP ) to exceed
linkHSDPA JP . This condition is equivalent to saying that the sum of
the activity factors of served HSDPA users must not exceed 100%.
We must ensure that connecting the terminal will not cause the timeaverage cell power (totalJP
) to exceed Max BS
JP . The same rule applies to nonHSDPA links.
ON THE USE OF CQI TABLES
When evaluating a connection to a terminal demanding a service set up to use HSDPA CQI tables the
evaluation follows the same procedure described earlier with the exception that the simulation will first
need to decide which list of bearers (i.e. which CQI table) to consider for the set of produced scenarios.
This is achieved by checking the HSDPA terminal category (selected by the user) and the serving cell’s
HSDPA capability. Based on both ends’ capabilities the simulation will choose one or more CQI table
bearers to evaluate using the following table.
Table 1 Applicability of CQI mapping tables
Category
Used CQI mapping table
64QAM/MIMO not configured
64QAM configured MIMO configured
16 A N/A
7 and 8 B N/A
9 C N/A
10 D N/A
11 and 12 E N/A
13 C F N/A
14 D G N/A
15 C N/A H
16 D N/A I
17 C F H
18 D G I
As can be seen from the table, some terminal categories may support multiple tables depending on
whether 64QAM and/or MIMO are supported by the cell. The simulation will still create scenarios for
all the terminalsupported tables as the simulation may need to evaluate multiple covering cells –with
different capabilities before finding a suitable connection scenario.
A final note on the usage of CQI tables is regarding the order in which CQI table entries are evaluated.
When the user sets up a service to use HSDPA CQI tables they may notice that all entries of all CQI
tables (A to I) are listed in an ascending order as supported bearers. To clear any confusion over this
display it should be stated that the ascending order is being used only for display clarity. When creating
the connection scenarios CQI table entries are sorted in a descending order starting with the highest
index (e.g. A30 to A1). Also, the reason why all tables are displayed is because the service will not
know which CQI tables are to be used until both the terminal category and the cell are identified.
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4.7 FAILURE REASONS
A connection scenario can fail for one or more of the following reasons:
Low Pilot.
This means that one or more of the pilot requirements specified on the terminal type (i.e.
Ec/Io, SIR, RSCP) are not satisfied.
No UL/DL Resources.
This means that the primary cell has too few resources to serve the UL/DL bearer.
No UL/DL Primary Resources.
This means that the primary cell had too few primary resources to serve the UL/DL bearer.
UL Eb/No (Range).
This means the terminal cannot meet the Eb/No requirement of the UL bearer, even if the
terminal transmits at maximum power. More precisely, the scenario fails the UPLINK
COVERAGE CHECK described in section 4.3.
UL Noise Rise.
This means that the connection would break the noise rise limit on the cell. More precisely,
the scenario fails the UPLINK SOFT CAPACITY CHECK described in section 4.3.
DL Eb/No (Range).
This means the cells in the active set cannot meet the Eb/No requirement of the DL bearer,
even if all links are transmitted at maximum power. More precisely, the scenario fails the
DOWNLINK COVERAGE CHECK described in section 4.4 (and section 4.5 for HSDPA
bearers).
DL Eb/No (Capacity).
This means the cells in the active set have insufficient available power to meet the Eb/No
requirement of the DL bearer. More precisely, the scenario fails the DOWNLINK SOFT
CAPACITY CHECK described in section 4.4 (and section 4.5 for HSDPA bearers).
If all of the connection scenarios available to a terminal fail to produce a connection, then the terminal
is classed as a failure. Note that each scenario in the list can fail for multiple reasons. Also, different
scenarios in the list can fail for different sets of reasons. All of this makes failure reporting
problematic. For example, consider a terminal with the following scenario list containing only 2
scenarios:
Cell Name Carrier Ec/Io (dB) DL Bearer UL Bearer Problems
Cell_X 1 18 24 kbps 12 kbps Noise rise, Low Pilot.
Cell_Y 2 16 24 kbps 12 kbps DL Eb/No Range.
In this example, Carrier 1 has a higher priority than Carrier 2, and so Cell_X is the top scenario even
though it has a worse Ec/Io than Cell_Y. What is the correct reason for failure to assign to the
terminal? There is no correct way of doing this. The tool only records the failure reasons of the top
scenario, as in most cases this provides the most useful information as to why a terminal fails. So in
the above example, the terminal would be deemed to have failed because of problems with Noise Rise
and Low Pilot on Cell_X. The terminal would only contribute to the failure statistics for Cell_X, not
Cell_Y, and it would not affect the failure statistics for DL Eb/No (Range).
5 OUTPUT ARRAYS
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5.1 ARRAY DEPENDENCIES
All arrays are produced on a per carrier basis.
Most arrays have a dependency on terminaltype because body loss and terminal antenna gain are
always included in the linkloss.
Many arrays depend on whether the terminal is taken to be indoor or outdoor. Indoor arrays use the in
building parameters for the clutter type at each pixel (i.e. indoor loss and indoor shadowfading
standard deviation). Indoor terminals are always taken to be slow moving.
Coverage arrays can be drawn even if no snapshots have been run, but the user should note that the
arrays then refer to coverage in an unloaded system. To obtain coverage arrays for a loaded system the
user must run some snapshots. Remember that the key purpose of running snapshots is to provide
measures of system load.
Arrays for coverage tend to have a weak dependence on the number of snapshots run, and the arrays
change little after a relatively small number of snapshots have been performed (10s of snapshots in
most cases). This is because only a small number of snapshots are needed to get an idea of the average
noise rise and average DL traffic power on each cell.
Arrays for hard or soft blocking probabilities have a strong dependence on the number of snapshots
run. This is because blocking is evaluated by reporting the proportion of snapshots that would block
further connections. For example, if the user has run 1 snapshot then all blocking probabilities will be
either 0% or 100%. If 5 snapshots have been run then all blocking probabilities will belong to the set
{0%, 20%, 40%, 60%, 80%, 100%}.
The following table lists the types of array that are available in the simulator, and shows some of their
dependencies. Most terms (e.g. Indoor) should be self explanatory.
“Fading” means the array depends on the standard deviation of shadow fading for the clutter type.
“Reliability level” means the array depends on the coverage reliability threshold in the array settings
dialog. The user can change this parameter and then redraw the array without running any more
snapshots.
“Snapshots done” means the accuracy of the array has a strong dependence on the number of snapshots
done, so the array will require 1000s of snapshots to give accurate results instead of 10s of snapshots.
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C=Carrier T=Terminal, S=Service U=UL Bearer, D=DL Bearer
V=Velocity I=Indoor F=Fading R=Reliability level n=Snapshots done
C T S U D V I F R n
DL Loss X X X
Nth DL Loss X X X
Best DL Cell by RSCP X
Best RSCP X X X
Nth Best RSCP X X X
RSCP Coverage Probability X X X X
RSCP Coverage OK X X X X X
Number of RSCP OK X X X X X
Pilot Ec/Io X X X
Nth Best Pilot Ec/Io X X X
Pilot Ec/Io Coverage Probability X X X X
Pilot Ec/Io Coverage OK X X X X X
Number of Pilot Ec/Io OK X X X X X
Pilot SIR X X X
Pilot SIR Coverage Probability X X X X
Pilot SIR Coverage OK X X X X X
Number of Pilot SIR OK X X X X X
Available Soft/Softer Cells X X X
Available Soft Cells X X X
Available Softer Cells X X X
Active Set Size X X X
Pilot Polluters X X X
UL Load X
UL FRE X
DL Io X X
DL Iother / Iown X
DL FRE X
Best UL Cell X
UL Eb/No Margin X X X X X X
UL Req TX Power X X X X X X
UL Coverage Probability X X X X X X X
UL Coverage Probability OK X X X X X X X X
Achievable UL Bearer X X X X X X X
Best DL Cell X
DL Eb/No Margin X X X X X X
DL Coverage Probability X X X X X X X
DL Coverage Probability OK X X X X X X X X
Achievable DL Bearer X X X X X X X
Coverage Balance X X X X X X X
UL Soft Blocking Probability X X X X X X X
DL Soft Blocking Probability X X X X X X X
Hard Blocking Probability X X X X X X X X
Hard Blocking Probability – Primary X X X X X X X X
HSDPA  Best DL Cell by SINR X
HSDPA SINR X X X
HSDPA  DL Eb/No Margin X X X X X X
HSDPA  DL Coverage Probability X X X X X X X
HSDPA  DL Coverage Probability OK X X X X X X X X
HSDPA  Achievable DL Bearer X X X X X X X
HSDPA  Cell for Achievable DL Bearer X X X X X X X
HSDPA  Achievable Data Rate (kbps) X X X X X X X
HSDPA  Offered Load X X X
HSDPA  Effective Service Rate (Unloaded) X X X X X X X
HSDPA  Effective Service Rate (Loaded) X X X X X X X
HSDPA  Effective Cell Service Rate (Unloaded) X X X X
HSDPA  Effective Cell Service Rate (Loaded) X X X X
HSUPA  Best UL Cell X
HSUPA  UL Eb/No Margin X X X X X X
HSUPA  UL TX Power X X X X X X
HSUPA  UL Coverage Probability X X X X X X X
HSUPA  UL Coverage Probability OK X X X X X X X X
HSUPA  Achievable UL Bearer X X X X X X X
HSUPA  Cell for Achievable UL Bearer X X X X X X X
HSUPA  Achievable Data Rate (kbps) X X X X X X X
C T S U D V I F R n
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5.2 PATHLOSS ARRAYS
DL Loss & Nth DL Loss
Dependencies: Terminal, Carrier, Indoor
These are the lowest (and Nth lowest) downlink losses. They represent average values and are
therefore calculated with fades of 0 dB.
5.3 PILOT COVERAGE ARRAYS
These arrays all provide information on pilot levels and coverage probabilities. There are 3 types of
quantity relating to the pilot (RSCP, Ec/Io, SIR) and there are arrays for all of these.
Best DL Cell by RSCP
Dependencies: Carrier
This is the cell that provides the highest RSCP for the terminal.
Best RSCP & Nth Best RSCP
Dependencies: Terminal, Carrier, Indoor
These are the highest (and Nth highest) RSCP levels. They represent average values and are therefore
calculated with fades of 0 dB.
RSCP Coverage Probability
Dependencies: Terminal, Carrier, Indoor
This is the probability that the Best DL Cell (by RSCP) satisfies the RSCP requirement specified on the
terminal type. This probability depends on the standard deviation of shadow fading for the clutter type
at the pixel. If this standard deviation has been set to zero, then there are only three possible coverage
probabilities: 0% if the requirement is not satisfied, 50% if the requirement is satisfied exactly, and
100% if the requirement is exceeded.
RSCP Coverage OK
Dependencies: Terminal, Carrier, Indoor
This is a thresholded version of the RSCP Coverage Probability array and has just two values
(Yes/No). It has the advantage of being quicker to calculate than the RSCP Coverage Probability
array. A value of “Yes” means that the RSCP coverage probability meets the coverage reliability level
specified in Array Settings Sim Display Settings.
Number of RSCP OK Dependencies: Terminal, Carrier, Indoor
This is the number of covering cells with a satisfactory RSCP. A cell is counted as having a
satisfactory RSCP if its RSCP coverage probability meets the coverage reliability level specified in
Array Settings Sim Display Settings.
Pilot Ec/Io & Nth Best Pilot Ec/Io
Dependencies: Terminal, Carrier, Indoor
These are the highest (and Nth highest) Ec/Io values. They represent average values and are therefore
calculated with fades of 0 dB.
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Pilot Ec/Io Coverage Probability
Dependencies: Terminal, Carrier, Indoor
This is the probability that the Best DL Cell (by RSCP) satisfies the Ec/Io requirement specified on the
terminal type. This probability depends on the standard deviation of shadow fading for the clutter type
at the pixel. If this standard deviation has been set to zero, then there are only three possible coverage
probabilities: 0% if the requirement is not satisfied, 50% if the requirement is satisfied exactly, and
100% if the requirement is exceeded.
Pilot Ec/Io Coverage OK
Dependencies: Terminal, Carrier, Indoor
This is a thresholded version of the Pilot Ec/Io Coverage Probability array and has just two values
(Yes/No). It has the advantage of being quicker to calculate than the Pilot Ec/Io Coverage Probability
array. A value of “Yes” means that the pilot Ec/Io coverage probability meets the coverage reliability
level specified in Array Settings Sim Display Settings.
Number of Pilot Ec/Io OK
Dependencies: Terminal, Carrier, Indoor
This is the number of covering cells with a satisfactory pilot Ec/Io. A cell is counted as having a
satisfactory pilot Ec/Io if its pilot Ec/Io coverage probability meets the coverage reliability level
specified in Array Settings Sim Display Settings.
Pilot SIR
Dependencies: Terminal, Carrier, Indoor
This is the best Pilot SIR value. It represents an average value and is therefore calculated with fades of
0 dB.
Pilot SIR Coverage Probability Dependencies: Terminal, Carrier, Indoor
This is the probability that the Best DL Cell (by RSCP) satisfies the pilot SIR requirement specified on
the terminal type. This probability depends on the standard deviation of shadow fading for the clutter
type at the pixel. If this standard deviation has been set to zero, then there are only three possible
coverage probabilities: 0% if the requirement is not satisfied, 50% if the requirement is satisfied
exactly, and 100% if the requirement is exceeded.
Pilot SIR Coverage OK
Dependencies: Terminal, Carrier, Indoor
This is a thresholded version of the Pilot SIR Coverage Probability array and has just two values
(Yes/No). It has the advantage of being quicker to calculate than the Pilot SIR Coverage Probability
array. A value of “Yes” means that the pilot SIR coverage probability meets the coverage reliability
level specified in Array Settings Sim Display Settings.
Number of Pilot SIR OK
Dependencies: Terminal, Carrier, Indoor
This is the number of covering cells with a satisfactory pilot SIR. A cell is counted as having a
satisfactory pilot SIR if its pilot SIR coverage probability meets the coverage reliability level specified
in Array Settings Sim Display Settings.
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5.4 HANDOVER ARRAYS
The aim of the following arrays is to provide the planner with an idea of potential handover areas, and
to indicate areas of pilot pollution. All arrays are based on mean Pilot Ec/Io levels calculated with
fades of 0 dB.
Available Soft/Softer Cells
Dependencies: Terminal, Carrier, Indoor
This is the number of suitable handover candidates for the Best DL Cell (by RSCP). If the Ec/Io level
of the best DL cell is below the Ec/Io requirement on the terminal type then no result is given.
Otherwise all the other cells are checked to see if their pilot Ec/Io levels make them suitable handover
candidates. Note that the primary cell is not counted as a handover cell, so an area where 3way
handoff is possible will report Available Soft/Softer Cells=2.
Available Soft Cells
Dependencies: Terminal, Carrier, Indoor
This is the number of suitable soft handover candidates for the Best DL Cell (by RSCP). If the Ec/Io
level of the best DL cell is below the Ec/Io requirement on the terminal type then no result is given.
Otherwise all the other cells (on different sites to the best cell) are checked to see if their pilot Ec/Io
levels make them suitable handover candidates.
Available Softer Cells
Dependencies: Terminal, Carrier, Indoor
This is the number of suitable softer handover candidates for the Best DL Cell (by RSCP). If the Ec/Io
level of the best DL cell is below the Ec/Io requirement on the terminal type then no result is given.
Otherwise all the other cells (on the same site as the best cell) are checked to see if their pilot Ec/Io
levels make them suitable handover candidates.
Active Set Size
Dependencies: Terminal, Carrier, Indoor
This is the potential size of the active set. It is related the Available Soft/Softer Cells array (see above)
by
Active Set Size = min (1 + Available Soft/Softer Cells , Max Active Set Size).
Pilot Polluters
Dependencies: Terminal, Carrier, Indoor
If the Pilot Pollution Threshold specified by the user in the Simulation Wizard is X dB then:
For UMTS: The number of pilot polluters at a location is the number of cells that are not in the active
set, but provide an Ec/Io level within X dB of the best Ec/Io in the active set. Therefore the pilot
pollution threshold in UMTS is a relative quantity. A typical value is 5 dB.
For CDMA2000: The number of pilot polluters at a location is the number of cells that are not in the
active set, but provide an Ec/Io level higher than X dB. Therefore the pilot pollution threshold in
CDMA2000 is an absolute quantity. A typical value is 16 dB.
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5.5 UPLINK NOISE ARRAYS
UL Load
Dependencies: Carrier
This is the uplink cell load of the Best DL Cell (by RSCP). Note that for OTSR cells, there can be a
different uplink load on each antenna used by the cell (just as in the uplink simulation reports for OTSR
cells).
UL FRE
Dependencies: Carrier
This is the uplink frequency reuse efficiency of the Best DL Cell (by RSCP). Note that for OTSR
cells, there can be a different uplink FRE on each antenna used by the cell (just as in the uplink
simulation reports for OTSR cells).
5.6 DOWNLINK NOISE ARRAYS
DL Io
Dependencies: Terminal, Carrier, Indoor
This is the total downlink power spectral density. It represents an average value and is therefore
calculated with fades of 0 dB.
DL Iother/Iown
Dependencies: Carrier
This is the ratio of downlink power received from other cells to downlink power received from own
cell, where “own cell” is the Best DL Cell (by RSCP).
DL FRE
Dependencies: Carrier
This is the downlink frequency reuse efficiency at a pixel and it is related to DL Iother/Iown as
follows.
DL FRE = 1 / ( 1 + Iother / Iown ).
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5.7 UPLINK COVERAGE ARRAYS
Uplink coverage arrays are available for each bearer at different speeds.
Best UL Cell
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the cell requiring the minimum uplink transmit power. For UMTS bearers, the only real
dependence is on the carrier used. However for CDMA2000 bearers, the Best UL Cell must have an
RC type that is supported by the terminal type.
UL Eb/No Margin
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is how much we exceed the uplink Eb/No requirement by on the Best UL Cell, assuming the
terminal transmits at full power.
UL Req TX Power
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the required UL TX power of the terminal. It is equal to the maximum output power of the
terminal type (dBm) minus the UL Eb/No margin (dB).
UL Coverage Probability
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the probability of satisfying the uplink bearer Eb/No requirement on the Best UL Cell, assuming
the terminal transmits at full power. This probability depends on the standard deviation of shadow
fading for the clutter type at the pixel. If this standard deviation has been set to zero, then there are
only three possible coverage probabilities: 0% if the requirement is not satisfied, 50% if the
requirement is satisfied exactly, and 100% if the requirement is exceeded.
UL Coverage Probability OK
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is a thresholded version of the UL Coverage Probability array and has just two values (Yes/No).
It has the advantage of being quicker to calculate than the UL Coverage Probability array. A value of
“Yes” means that the uplink coverage probability meets the coverage reliability level specified in Array
Settings Sim Display Settings.
Achievable UL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
The purpose of this array is to provide a combined coverage plot for the uplink bearers of a service.
The array shows the highest priority uplink bearer with acceptable uplink coverage, i.e. with UL
Coverage Probability meeting the coverage reliability level specified in Array Settings Sim Display
Settings.
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5.8 DOWNLINK COVERAGE ARRAYS
Downlink coverage arrays are available for each bearer at different speeds.
Best DL Cell
Dependencies: Terminal, Carrier, Indoor, Service, DL Bearer, Speed
This is the cell requiring the minimum downlink transmit power. For UMTS bearers, the only real
dependence is on the carrier used, and so this array is exactly the same as the Best DL cell by RSCP.
However for CDMA2000 bearers, the Best DL Cell must have an RC type that is supported by the
terminal type.
DL Eb/No Margin
Dependencies: Terminal, Carrier, Indoor, Service, DL Bearer, Speed
This is how much we exceed the downlink Eb/No requirement by, assuming that the link powers of
cells in the active set are at maximum allowed levels.
DL Coverage Probability
Dependencies: Terminal, Carrier, Indoor, Service, DL Bearer, Speed
This is the probability of satisfying the downlink bearer Eb/No requirement, assuming that the link
powers of cells in the active set are at maximum allowed levels. This probability depends on the
standard deviation of shadow fading for the clutter type at the pixel. If this standard deviation has been
set to zero, then there are only three possible coverage probabilities: 0% if the requirement is not
satisfied, 50% if the requirement is satisfied exactly, and 100% if the requirement is exceeded.
DL Coverage Probability OK
Dependencies: Terminal, Carrier, Indoor, Service, DL Bearer, Speed
This is a thresholded version of the DL Coverage Probability array and has just two values (Yes/No).
It has the advantage of being quicker to calculate than the DL Coverage Probability array. A value of
“Yes” means that the downlink coverage probability meets the coverage reliability level specified in
Array Settings Sim Display Settings.
Achievable DL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
The purpose of this array is to provide a combined coverage plot for the downlink bearers of a service.
The array shows the highest priority downlink bearer with acceptable downlink coverage, i.e. with DL
Coverage Probability meeting the coverage reliability level specified in Array Settings Sim Display
Settings.
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5.9 COVERAGE BALANCE
Coverage Balance
Dependencies: Terminal, Carrier, Indoor, Service, Speed
The purpose of this array is to provide a composite uplink/downlink coverage plot for a service. The
uplink is deemed to have coverage if any of the uplink bearers on the service have UL Coverage
Probability meeting the coverage reliability level specified in Array Settings Sim Display Settings.
Similarly, the downlink is deemed to have coverage if any of the downlink bearers on the service have
DL Coverage Probability meeting the coverage reliability level specified in Array Settings Sim
Display Settings.
5.10 SOFT BLOCKING ARRAYS
UL Soft Blocking Probability
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the probability of uplink soft blocking on the Best UL Cell. Uplink soft blocking occurs if an
additional connection with the uplink bearer would cause the noise rise limit to be exceeded. The
uplink soft blocking probability is determined by examining the proportion of snapshots that would
block a connection with the uplink bearer in this way. Note that for OTSR cells, the noise rise is
measured on a per antenna basis (as in the simulation reports), so the soft blocking probability depends
on the antenna that covers the pixel.
DL Soft Blocking Probability
Dependencies: Terminal, Carrier, Indoor, Service, DL Bearer, Speed
This is the probability of downlink soft blocking on the Best DL Cell. Downlink soft blocking occurs if
an additional connection with the downlink bearer requires more power than is available on the cell.
The downlink soft blocking probability is determined by examining the proportion of snapshots that
would block a connection with the downlink bearer in this way.
5.11 HARD BLOCKING ARRAYS
There a two types of hard blocking arrays for each uplink and downlink resource type. The exception
is the HSDPA resource type used to represent HSDPA codes. This does not have a “primary” blocking
array because there are no “primary” limits for HSDPA codes.
Hard Blocking Probability
Dependencies: Terminal, Carrier, Indoor, Service, Bearer, Speed
This is the probability of hard blocking on the Best DL Cell because of lack of resources. This sort of
blocking occurs if an additional connection with the bearer requires more resources than are available.
The blocking probability is determined by examining the proportion of snapshots that would block a
connection with the bearer in this way.
Hard Blocking Probability – Primary
Dependencies: Terminal, Carrier, Indoor, Service, Bearer, Speed
This is the probability of hard blocking on the Best DL Cell because of lack of primary resources. This
sort of blocking occurs if an additional connection with the bearer requires more primary resources
than are available. The blocking probability is determined by examining the proportion of snapshots
that would block a connection with the bearer in this way.
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5.12 HSDPA ARRAYS
HSDPA  Best DL Cell by SINR
Dependencies: Carrier
This is the cell that provides the highest SINR level for the terminal.
HSDPA SINR
Dependencies: Terminal, Carrier, Indoor
This is the highest SINR level. It represents an average value and is therefore calculated with fades of
0 dB.
HSDPA  DL Eb/No Margin
Dependencies: Terminal, Carrier, Indoor, Service, HSDPA Bearer, Speed
This is the extent to which the Eb/No requirement of the HSDPA bearer is exceeded. The cell of
interest is chosen by examining the SINR levels of cells that support the HSDPA bearer, and choosing
the cell with the largest level.
HSDPA  DL Coverage Probability
Dependencies: Terminal, Carrier, Indoor, Service, HSDPA Bearer, Speed
This is the probability of satisfying the Eb/No requirement of the HSDPA bearer. The cell of interest is
chosen by examining the SINR levels of cells that support the HSDPA bearer, and choosing the cell
with the largest level. The probability depends on the standard deviation of shadow fading for the
clutter type at the pixel. If this standard deviation has been set to zero, then there are only three
possible coverage probabilities: 0% if the requirement is not satisfied, 50% if the requirement is
satisfied exactly, and 100% if the requirement is exceeded.
HSDPA  DL Coverage Probability OK
Dependencies: Terminal, Carrier, Indoor, Service, HSDPA Bearer, Speed
This is a thresholded version of the HSDPA  DL Coverage Probability array and has just two values
(Yes/No). It has the advantage of being quicker to calculate than the HSDPA  DL Coverage
Probability array. A value of “Yes” means that the coverage probability meets the coverage reliability
level specified in Array Settings Sim Display Settings.
HSDPA Achievable DL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
The purpose of this array is to provide a combined coverage plot for the HSDPA bearers of a service.
The array shows the highest priority HSDPA bearer with acceptable coverage. i.e. with HSDPA  DL
Coverage Probability meeting the coverage reliability level specified in Array Settings Sim Display
Settings.
HSDPA –Cell for Achievable DL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the cell that provides the best achievable HSDPA DL bearer for a terminal (The achievable
HSDPA DL bearer is given by the previous array).
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HSDPA –Achievable Data Rate (kbps)
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the user rate of the best achievable HSDPA DL bearer for a terminal. The HSDPA bearer’s user
rate is modified to reflect any Spatial Multiplexing rate gains if MIMO is supported by both the cell
and the terminal.
HSDPA  Offered Load
Dependencies: Carrier,
This is the offered HSDPA load on the Best DL Cell by RSCP. Note that the offered load is calculated
for each HSDPA resource pool in the network. Therefore, if the HSDPA resources have been pooled
on a site, all HSDPA cells on that site will show the same offered load. The offered load is expressed
as a percentage value between 0% and 100%. See section 2.6 of this document for a more detailed
description of the offered load calculation.
HSDPA  Effective Service Rate (Unloaded)
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the bitrate that the user experiences at a location when there is no queuing delay on the cell. It
is calculated by multiplying the bitrate of the HSDPA – Achievable DL Bearer by its activity factor.
See section 2.6 of this document for a more detailed description of the effective service rate
calculations.
HSDPA  Effective Service Rate (Loaded)
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the bitrate that the user experiences at a location when there is queuing delay on the cell. The
rate drops to zero as the HSDPA load on the cell approaches 100%. See section 2.6 of this document
for a more detailed description of the effective service rate calculations.
HSDPA  Effective Cell Service Rate (Unloaded)
Dependencies: Carrier, Service
This is the total amount of data in a service session (bits) divided by the mean service time per user on
the cell (seconds) assuming there is no queuing delay. If the offered HSDPA load is zero, then the
Effective Cell Service Rate is undefined, and this is indicated by assigning the rate a value of 1 in the
view. See section 2.6 of this document for a more detailed description of the effective cell service rate
calculations.
HSDPA  Effective Cell Service Rate (Loaded)
Dependencies: Carrier, Service
This is like the previous array except that the mean service time per user on the cell is increased
because of queuing delay. As the offered HSDPA load on the cell approaches 100%, the queuing delay
approach infinity and the Effective Cell Service Rate (Loaded) drops to zero. If the offered HSDPA
load is zero, then the Effective Cell Service Rate is undefined, and this is indicated by assigning the rate
a value of 1 in the view. See section 2.6 of this document for a more detailed description of the
effective cell service rate calculations.
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5.13 HSUPA ARRAYS
HSUPA  Best UL Cell
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the HSUPAsupporting cell requiring the minimum uplink transmit power. For HSUPA
bearers, the bearer (in terms of spreading factor, modulation and number of codes) has to be supported
by the cell before that cell is considered as a server.
HSUPA  UL Eb/No Margin
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is how much we exceed the HSUPA Eb/No requirement by on the Best HSUPA Cell, assuming the
terminal transmits at full power.
HSUPA  UL TX Power
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the required UL HSUPA TX power of the terminal. It is equal to the maximum output power of
the terminal type (dBm) minus the HSUPA Eb/No margin (dB).
HSUPA  UL Coverage Probability
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is the probability of satisfying the HSUPA uplink bearer Eb/No requirement on the Best HSUPA
Cell, assuming the terminal transmits at full power. This probability depends on the standard deviation
of shadow fading for the clutter type at the pixel. If this standard deviation has been set to zero, then
there are only three possible coverage probabilities: 0% if the requirement is not satisfied, 50% if the
requirement is satisfied exactly, and 100% if the requirement is exceeded.
HSUPA  UL Coverage Probability OK
Dependencies: Terminal, Carrier, Indoor, Service, UL Bearer, Speed
This is a thresholded version of the HSUPA  UL Coverage Probability array and has just two values
(Yes/No). It has the advantage of being quicker to calculate than the UL Coverage Probability array.
A value of “Yes” means that the uplink coverage probability meets the coverage reliability level
specified in Array Settings Sim Display Settings.
HSUPA  Achievable UL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
The purpose of this array is to provide a combined coverage plot for the HSUPA uplink bearers of a
service. The array shows the highest priority HSUPA bearer with acceptable uplink coverage, i.e. with
HSUPA UL Coverage Probability meeting the coverage reliability level specified in Array Settings
Sim Display Settings.
HSUPA –Cell for Achievable UL Bearer
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the cell that provides the best achievable HSUPA UL bearer for a terminal (The achievable
HSUPA UL bearer is given by the previous array).
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HSUPA –Achievable Data Rate (kbps)
Dependencies: Terminal, Carrier, Indoor, Service, Speed
This is the user rate of the best achievable HSUPA UL bearer for a terminal.
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6 COVERAGE ARRAY CALCULATIONS
Coverage arrays are calculated in a different way to Version 5.0 simulations. The key differences are
The term coverage is used in the classical sense. It looks at the problem of a received signal
being of sufficient strength/quality given that it has been transmitted through a lossy channel
with shadow fading.
In Version 5.0, the Coverage Probability array represents an overall connection probability. It
examines both coverage and capacity constraints, which makes it hard to perform a pure
coverage analysis.
Separate coverage arrays are available for the pilot channel, uplink bearers, and downlink
bearers. Each probability is well defined in that it refers to a particular cell, namely the Best
UL Cell or Best DL Cell.
In Version 5.0, separate coverage arrays are not available. The probability reported at a pixel
is a mixture of results involving different cells, bearers, and terminals.
Coverage probabilities are calculated analytically. This means that coverage plots can be
obtained after running a very small number of snapshots (typically 10s) and plots converge
very quickly. If no snapshots have been run, then coverage plots are still available but they
give the coverage probabilities in an unloaded system.
In Version 5.0, the probabilities are not calculated analytically but by sampling. The accuracy
of the probability reported at a pixel depends strongly on the number of samples (i.e.
connection attempts) at the pixel. This typically means that a large number of snapshots are
required to produce an accurate result. The sampling process also makes the simulation
memoryhungry. If no snapshots have been run, then there are no samples, and so no coverage
plot is available.
We will examine the different ways in which shadow fading affects our calculations. There are
essentially 4 cases to consider.
How fading is handled in the simulation snapshots.
How fading is handled when calculating mean values of quantities.
How fading is handled when calculating soft/hard blocking probabilities.
How fading is handled when calculating coverage probabilities.
6.1 NOTATION
We introduce the following notation to represent the probability density function for a normally
distributed random variable with mean and standard deviation .
2
2
2 2
)(exp
2
1),;(
xxN
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6.2 FADES IN THE SIMULATION SNAPSHOTS
Shadow fading is modelled in a snapshot by randomising the pathlosses experienced by the randomly
scattered terminals. Shadow fades are lognormally distributed, and the user specifies the shadow
fading standard deviation for indoor and outdoor terminals in each clutter type. In reality, the fades
between a terminal and the cells that cover it will exhibit a degree of correlation. In particular, a
terminal is likely to have similar fades to cells that are located on the same site. To account for this, the
user specifies two parameters in the Monte Carlo Wizard:
The normalised intersite correlation coefficient ( terinc ). This is the correlation between
fades to cells on different sites.
The normalised intrasite correlation coefficient ( trainc ). This is the correlation between
fades to cells on the same site.
These two parameters must satisfy the constraints 10 trainterin cc . For each randomly scattered
terminal in a snapshot, a set of correlated fades to the covering cells is generated using the following
procedure. All the random numbers mentioned below are independent and normally distributed with
zero mean and unit variance, and is the standard deviation of the shadow fading at the pixel in dB.
Generate a random number X .
For each site I, generate a random number IY .
For each cell J, generate a random number JZ .
The fade (in dB) to cell J on site I is then set to
JI ZcYccXc trainterintrainterin 1 .
The above procedure is performed for each of the randomly scattered terminals at the beginning of a
snapshot. Fades for different terminals are uncorrelated even if they are located in the same pixel.
6.3 FADES IN ARRAYS FOR MEAN VALUES
Arrays showing the mean level of a quantity (e.g. DL linkloss, RSCP, Ec/Io, etc) are calculated with all
fades set to 0 dB.
6.4 FADES IN ARRAYS FOR SOFT/HARD BLOCKING
The main factor affecting blocking probability is the free capacity at the cell rather than the fading in
the channel, so arrays for soft & hard blocking are calculated with all fades set to 0 dB.
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6.5 FADES IN COVERAGE ARRAY CALCULATIONS
Pilot RSCP Coverage Probability
In the absence of fading, let the pilot RSCP (in Watts) for cell J be represented by
pilotJR .
If cell J has a fade of JF dB, then the pilot RSCP is given by
)10(10/pilot
JJF
R .
We can calculate a coverage probability for the pilot RSCP as follows:
Find the fade JF that causes the pilot RSCP to exactly satisfy the RSCP requirement specified
on the terminal type. Call this fade *F . Note that
*F may be positive or negative. Any fade
bigger than *F will give an inadequate RSCP.
Since JF is normallydistributed with a mean of 0 dB and standard deviation of dB, the
probability that *FFJ is given by
*
),0;()( *
F
JJJ dFFNFFP .
This is the probability that the pilot RSCP meets the requirement.
Pilot Ec/Io Coverage Probability
Although slowfading has a lognormal distribution, one cannot always assume that signalto
interference ratios (such as pilot Ec/Io) also have lognormal distributions. For example, consider a
single isolated cell where the DL Io is dominated by owncell interference and the thermal component
of DL Io is negligible. If the terminal experiences a fade, the signal and interference both decrease by
the same factor, so Ec/Io is effectively unchanged. Because of this, care must be taken in calculating
coverage probabilities for quantities such as Ec/Io.
Consider the situation when there are several cells. In the absence of fading, we can write the pilot
Ec/Io for cell J in terms of mean received cell powers as follows:
JK
KJ
JJoc
RRN
RIE
totaltotalthermal
pilot
.
When we have fades to the cells, the Ec/Io is given by:
JK
FK
FJ
FJ
JocKJ
J
RRN
RIE
)10()10(
)10(10/total10/totalthermal
10/pilot
.
There are two ways of dealing with the random fades in the above expression to arrive at a coverage
probability.
The first way is to use an experimental approach that involves sampling the fading distribution. In
other words, we examine the value of Ec/Io for many different sets of random fades. This is the way
output arrays are calculated in the Version 5.0 simulator. The advantage of this method is that it can
handle complex sets of correlated fades, but it has the drawback of requiring a large amount of time to
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evaluate an adequate number of samples. This makes it an impractical approach for calculating
coverage probabilities.
The second way is to use an approximation that makes an analytic calculation of coverage probability
possible. This is what is done to create the coverage arrays in the current simulator. The idea is to use
an approximation for Ec/Io that involves a single random variable, namely the fade for the cell of
interest ( JF ), and to replace the other fades ( KF ) by their expected values conditioned on JF . In
other words, we make the substitution:
)( JKK FFEF .
As shown in section 6.6, correlated fades in the simulation are produced by a method that leads to the
result:
JJKJK FcFFE )(
where JKc is the correlation coefficient between fades to cells J and K. So if the fade to cell K is
perfectly correlated with the fade to cell J, we give cell K a fade of JF dB. If the fade to cell K is
completely uncorrelated with the fade to cell J, we give cell K a fade of 0 dB, since that is the expected
value of the fade given no other information. So we obtain the following approximation for Ec/Io:
JK
FcK
FJ
FJ
JocJJKJ
J
RRN
RIE
)10()10(
)10(10/total10/totalthermal
10/pilot
.
Although the resulting expression for Ec/Io is not lognormal, it depends on a single normally
distributed random variable ( JF ). We can calculate a coverage probability for the pilot Ec/Io as
follows:
Find the fade JF that causes the pilot Ec/Io to exactly satisfy the pilot Ec/Io requirement
specified on the terminal type. Call this fade *F . Note that
*F may be positive or negative.
Any fade bigger than *F will give an inadequate pilot Ec/Io.
Since JF is normallydistributed with a mean of 0 dB and standard deviation of dB, the
probability that *FFJ is given by
*
),0;()( *
F
JJJ dFFNFFP .
This is the probability that the pilot Ec/Io meets the requirement.
Notice that the twostep procedure for obtaining a coverage probability for Ec/Io is identical to the
procedure used to obtain a coverage probability for pilot strength. The only difference is that the fade
JF influences the Ec/Io formula in a more complex way than the pilot strength formula. In the case of
the pilot strength formula, finding *F is trivial. Finding
*F for the pilot Ec/Io formula cannot be
done analytically in general, and so a numerical method (repeated bisection) is used to determine *F
in this case.
Pilot SIR Coverage Probability
This uses the same method of approximation used in the pilot Ec/Io calculation. Namely the fade to
cell K is replaced by its expected value conditioned on the fade to cell J. The only difference is that the
formula for pilot SIR is used instead of the formula for Ec/Io.
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Uplink Bearer Coverage Probability
We calculate the uplink coverage probability for the Best UL Cell of a terminal. The analysis examines
if a terminal is in a soft handover region, and modifies the link budget accordingly. See section 4.3 for
descriptions of the various handover gains in the uplink.
Assuming all shadow fades are 0 dB, use the link budget equation (29) to calculate the uplink
traffic channel TX power needed to meet the uplink Eb/No requirement on each covering cell.
The cell that requires the lowest power is the Best UL Cell.
Determine which cells are handover cells for the Best UL Cell. The cells with the best Ec/Io
levels enter the active set, providing they have an Ec/Io of sufficient quality (relative to the
Best UL Cell) and that the active set size limit has not been reached.
Assuming the terminal transmits at full power, calculate the difference in dB between the two
best uplink Eb/No’s in the active set. Call this difference Eb/Nok .
Get the values of , , based on Eb/Nok and the speed of the
terminal. If the service does not support soft handover then
1PCHPCHreductionpower kkk GHG .
Set the uplink traffic channel TX power in an active period to its maximum possible value,
remembering to account for control overhead and any handover gains:
PCH
PCHMax MS
)1( k
k
k
kk
H
GPP .
Use the link budget equation (31) to calculate JkE on the Best UL Cell. This is the uplink
Eb/No in the absence of fading.
If cell J has a fade of JF dB, then the uplink Eb/No is given by )10(10/JF
JkE . Find the fade
that causes )10(10/JF
JkE to exactly satisfy the Eb/No requirement of the uplink bearer (
requiredkE ). This fade
*F is given by
reductionpower required10/ /)10(*
kkF
Jk GEE .
Note that *F may be positive or negative. Any fade bigger than
*F will give an inadequate
uplink Eb/No.
Since JF is normallydistributed with a mean of 0 dB and standard deviation of dB, the
probability that *FFJ is given by
*
),0;()( *
F
JJJ dFFNFFP .
This is the probability that the uplink servicebearer meets the Eb/No requirement.
reductionpower kG
PCHkH PCH
kG
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Downlink Bearer Coverage Probability (nonHSDPA)
This uses the same method of approximation used to calculate the pilot Ec/Io coverage probability. We
take the main random variable in the link budget to be the fade ( JF ) to the Best DL Cell and replace all
other fades by their expected values conditioned on JF .
Assuming there is no shadow fading, find the cell that provides the highest Ec/Io and supports
the bearer. This is the Best DL Cell.
Determine which cells are handover cells for the Best DL Cell. The cells with the best Ec/Io
levels enter the active set, providing they have an Ec/Io of sufficient quality (relative to the
Best DL Cell) and that the active set size limit has not been reached.
Calculate the difference in dB between the two best pilot Ec/Io levels in the active set. Call
this difference Ec/Iok .
Get the value of reductionpower
kG based on Ec/Iok and the speed of the terminal. If the service
does not support soft handover then 1reductionpower
kG .
For each cell J in the active set, set the downlink traffic channel TX power to
k
JJ
PP
1
max
where max
JP is the maximum allowed power for a downlink on cell J, and k is the control
overhead factor of the downlink bearer.
Find the fade JF that causes the DL Eb/No to be satisfied exactly. In practice we need to find this
value numerically by repeated bisection. To test a particular value of JF , we do the following:
Set the fade for the Best DL Cell to JF dB. For each other cell K, set the fade to JJK Fc dB
where JKc is the correlation coefficient between fades to cells J and K.
For each cell in the active set, use the link budget equation (32) to calculate the achieved Eb/No
for the traffic channel in an active period. The total downlink Eb/No after maximal ratio
combining (totalkE ) is the sum of the Eb/No values for the individual links (in normal units, not
dB).
The downlink Eb/No requirement is satisfied exactly if requiredreductionpower totalkkk EGE ,
where requiredkE is the downlink Eb/No requirement.
HSDPA Bearer Coverage Probability
This is identical to the above procedure for downlink nonHSDPA bearers but with the following
simplifications:
The Best DL Cell is determined by examining the cells that support the HSDPA bearer, and
choosing the one that provides the best Ec/Io.
There is no handover for HSDPA, and so there is no handover gain ( 1reductionpower
kG ).
The downlink power for a HSDPA link is linkHSDPA
JP (not max
JP ).
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6.6 CONDITIONAL EXPECTATION FOR CORRELATED FADES
We now derive the expected value of the fade to cell K ( KF ), given that we know the fade to cell J (
JF ) and the correlation coefficient between the two fades ( JKc ). The correlated fades in a snapshot
are produced by weighted sums of independent zeromean normallydistributed (ZMND) random
variables (RVs) of unit variance, so that the fade to cell J on site I is given by
JI ZcYccXc trainterintrainterin 1 .
The number of RVs involved is large since we generate a RV for every terminal ( X ), every site ( IY ),
and every cell ( JZ ). However, for the analysis that follows here, we only ever need to consider a
single pair of correlated fades, and the above procedure can be reduced to a simpler construction using
only 3 independent ZMND RVs of unit variance RQP ,, as follows:
QcPcF JKJKJ 1 ,
RcPcF JKJKK 1 .
We can further reduce the number of independent RVs to 2, by using the ZMND RVs U and V
defined by
QcPcU JKJK 1
Rc
Qc
cP
c
ccV
JKJK
JK
JK
JKJK
1
1
11
22
It is easy to show that 1)()( 22 VEUE and 0)(UVE , so U and V have unit variance and are
uncorrelated. Expressed in terms of U and V , the fades become
UFJ ,
VcUcF JKJKK2
1 .
This gives the result
JJKJKJKJKKJK FcUcUVEcUUEcUFEFFE )0()(1)()()(2 .
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7 BLOCKING ARRAY CALCULATIONS
Blocking arrays are calculated in a different way to Version 5.0 simulations. The key differences are:
The blocking arrays have different names to those in Version 5.0. For example a Noise Rise
Failure in Version 5.0 is now described as Uplink Soft Blocking. A DL Eb/No Capacity
Failure in Version 5.0 now corresponds to a situation of Downlink Soft Blocking.
Separate blocking arrays are now available for the different uplink and downlink bearers. The
blocking probabilities are well defined in the sense that they refer to either the Best UL Cell or
Best DL Cell.
In Version 5.0, separate blocking arrays were not available. The probability reported at a pixel
is a mixture of results involving different cells, bearers, and terminals.
The coverage probability arrays are calculated analytically. An analytic calculation is possible because
the dominant random variables affecting coverage are the shadow fades to cells, and these have a
known probability distribution specified by the user. The same cannot be said for blocking
probabilities. The main random variables affecting blocking on a cell relate to availability of particular
“resources”. For downlink soft blocking, the “resource” of interest is the downlink power of the cell.
For uplink soft blocking, the “resource” of interest is the noise rise on the cell. Unlike shadow fading,
we do not know the probability distribution for noise rise on a cell, or downlink power on a cell, so an
analytic calculation of blocking probabilities is not possible. We must therefore calculate blocking
probabilities by sampling. In other words, we must find the proportion of snapshots that block further
connections. The accuracy of the result obtained will depend strongly on the number of samples taken
(i.e. snapshots performed).
In all blocking calculations, it is assumed that the dominant factor is not the shadow fading (which is
taken to be 0 dB) but rather the probability distribution of the quantity that limits capacity. For
example, for uplink soft blocking on a cell, we must consider the probability distribution of uplink
noise rise. In particular, we will want to know the probability that the noise rise on the cell is so large
that it cannot accommodate an extra user.
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7.1 UPLINK SOFT BLOCKING PROBABILITY ARRAY
All arrays dealing with uplink capacity analysis (UL Load, UL FRE, UL Soft Blocking Probability)
refer to the Best UL Cell. This is the cell that gives the lowest mobile UL power requirement.
The uplink soft blocking analysis does not use exactly the same logic as the randomly scattered
terminals in the simulator. The simulator prevents a terminal from connecting if it will cause any cell
to break its UL noise rise limit. This is necessary to ensure that no noise rise limits are exceeded when
producing a snapshot of the network. The UL Soft Blocking Probability array considers only the Best
UL Cell.
The soft blocking probability array is calculated independently of any coverage analysis. Therefore it
is assumed that there are no coverage problems, and even pixels with poor coverage can have a result.
Remember the aim of the soft blocking probability array is to highlight cells where uplink capacity is a
problem, rather than locations where uplink capacity is a problem.
The uplink soft blocking probability calculation:
Estimates the probability that an additional connection will be blocked by examining the noise
rises attained in the snapshots, and seeing how often an overloaded situation occurs. The
probability is therefore not calculated analytically but by sampling.
The blocking probability is not an ErlangB or ErlangC blocking probability, and in fact most
closely resembles an LCH blocking probability (ErlangA).
Assumes no soft handover (therefore no soft HO gains, and no power rise effects).
Uses a modified Eb/No requirement depending on terminal speed and cell TX/RX diversity.
Considers the sectorised uplink for an OTSR cell. In other words, two antennas (sectors) on
the cell may have differing noise rises and hence differing soft blocking probabilities.
The uplink noise power (in Watts) on the Best UL Cell is a random variable ( totalN ) that depends on
the number of terminals in the network, their locations, and levels of activity. If we perform M
snapshots, then we will have a set of M sample values for totalN .
Consider the uplink budget that must be satisfied when connecting an additional terminal to a cell:
G
NLEP
total
,
where
P is the required traffic channel TX power in a period of activity.
E is the traffic channel Eb/No requirement in a period of activity,
L is the UL loss,
G is the processing gain,
We know all the quantities on the righthandside of the above link budget, and so can calculate P .
The timeaverage interference power ( linkN ) that the link will produce at the cell is given by
GNELPN /)(/)( totallink,
where
is the activity factor,
is the control overhead factor for the bearer.
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The total UL noise power on the cell has a maximum allowed level ( limitN ) determined by the user
specified noise rise limit for the cell. The additional connection will be blocked if
limitlinktotal NNN .
This inequality can be rewritten as
GE
NN
/)(1
limittotal
.
All the quantities on the RHS of this expression are known, so we can obtain a measure of the soft
blocking probability by finding the proportion of snapshots where totalN satisfies the above inequality.
The accuracy of the result depends on the number of snapshots performed. For example, if only 2
snapshots have been performed then blocking probabilities are reported as either 0% or 100%.
Typically, planners will be interested in seeing low blocking probabilities (of the order of a few of
percent) and so many hundreds of snapshots are required to obtain sufficient accuracy in the reported
blocking probabilities. Consequently, it is advised that planners perform their uplink capacity analysis
by looking at quantities that converge more quickly. For example the uplink noise rise and uplink load
on a cell.
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7.2 DOWNLINK SOFT BLOCKING PROBABILITY ARRAY
The quantity that limits (soft) capacity in the uplink is the noise rise limit of the cell. In the downlink,
the quantity that limits (soft) capacity is the total cell power. However, soft capacity in the downlink is
not well defined in general, because downlink MRC permits a terminal to be served even when cells in
the active set have insufficient power to serve the terminal on their own. So capacity in the downlink
generally depends on the available power on a set of cells rather than the available power on an
individual cell.
Since we aim to highlight capacity problems on individual cells, we perform a simplified analysis of
soft blocking in the tool. Our array for DL Soft Blocking Probability refers to blocking on the Best DL
Cell. This is the cell with the best RSCP (and for a CDMA2000 system the cell must also have an RC
that supports the terminal type). We perform the analysis by seeing if the cell can serve an additional
terminal that is not in handover.
For an additional link on cell J, the timeaverage DL TX power is given by
GLENP J /)(totalJ
linkJ ,
where
totalJN is the total DL interference power at the pixel when for a link to cell J,
E is the Eb/No requirement for the traffic channel in a period of activity,
is the activity factor,
is the control overhead factor for the bearer,
G is the processing gain,
JL is the DL loss for cell J.
The total DL interference can be split into thermal, incell, and outcell parts
celloutcellinthermaltotal
JJJ NNNN .
The incell interference is given by
J
JJJ
L
PPN
synctotalcellin )1(
,
where is the DL orthogonality factor, and the total cell power is given by
HSDPAUMTSsynccommonpilottotal
JJJJJJ PPPPPP .
We have DL soft blocking if the total power after connection exceeds the cell power (max
JP ), i.e. if
maxlinktotal
JJJ PPP .
After some substitution, we find we can write this condition as
G
E
L
PNN
G
LEP
PJ
JJ
JJ
J )()1(1
)(sync
celloutthermalmax
total.
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We assume that the dominant factor influencing blocking is the total DL power on the cell (total
JP ) and
we treat this as the only random variable in our expression, and replace the other random variables ( JL
, celloutN ) on the RHS by their mean values
JJ LL ,
JK K
KJJ
L
PNN
totalcelloutcellout
,
where
JL is the linkloss to cell J with no shadow fading,
total
KP is the mean total downlink power of cell K.
So the inequality for DL soft blocking becomes
G
E
L
P
L
PN
G
LEP
PJ
J
JK K
KJJ
J )()1(1
)(synctotal
thermalmax
total.
Note that there is a minimum allowed DL traffic power on each cell, and we must have at least this
power available to serve another user, so we also get DL soft blocking when
powerlink min maxtotal
JJJ PPP .
So the overall expression is
G
E
L
P
L
PN
G
LEP
PPPJ
J
JK K
KJJ
JJJ )()1(1
)(
,min
synctotalthermalmax
powerlink min maxtotal .
The quantity on the RHS is known at every pixel, and we obtain the blocking probability for that pixel
by examining the proportion of snapshots where total
JP exceeded the quantity on the RHS.
As in the case of UL soft blocking probability, the accuracy of the result depends on the number of
snapshots performed, and since planners will be interested in seeing low blocking probabilities (of the
order of a few percent), many hundreds of snapshots need to be performed to get confidence in the
reported blocking probabilities. Consequently, it is advised that planners perform their downlink
capacity analysis by looking at quantities that converge more quickly. For example, the total downlink
traffic power in the simulation reports.
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7.3 HARD BLOCKING PROBABILITY ARRAYS (RESOURCE BLOCKING)
The hard blocking probability refers to the Best DL Cell. This is the cell that supports the bearer and
provides the highest pilot Ec/Io. The hard blocking probability for a bearer is calculated by finding the
proportion of snapshots where the Best DL Cell had sufficient resources available to serve an additional
terminal with that bearer. For example, if the timeaverage number of resources required by a bearer is
M, then the blocking probability is the proportion of snapshots where the timeaverage number of
available resources on the Best DL Cell is greater than or equal to M. Since the blocking probability is
being estimated by sampling, the accuracy of the result depends on the number of snapshots performed.
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8 BLOCKING PROBABILITY AND FAILURE RATE
8.1 CALCULATION OF BLOCKING PROBABILITY IN THE BLOCKING REPORT
The blocking probabilities for cells (shown in the blocking report) cannot be found by simply
averaging the blocking probabilities at pixels in the 2dview for the following reasons:
Pixels with high traffic should have more influence on cell blocking probability than pixels
with low traffic.
Pixels in coverage holes should not influence cell blocking probability, even if they contain
high traffic.
A service may use some bearers more frequently than others. Frequently used bearers should
have more influence on the blocking probability than infrequently used bearers.
Several cells may serve the traffic at a pixel.
We need a measure of blocking probability that is sensibly weighted with respect to all the above
factors. We can find such a measure by selective passivescanning at the end of a snapshot. This is
different to the usual (global) passivescanning used to produce coverage arrays. Global passive
scanning tests all pixels, whereas selective passivescanning only tests a subset of pixels and scenarios
at the end of each snapshot. To determine which pixels and scenarios to check, we take the
successfully served terminals from the previous snapshot and use them to check for blocking at the end
of the current snapshot. Each terminal is placed at the location it had in the previous snapshot, and
checked to see if it can connect to the cell that previously served it, using the previous uplink and
downlink bearer. By doing this, we automatically make sure that the cell blocking probability is
correctly weighted, since the most likely terminal locations and connection scenarios are checked.
8.2 FAILURE RATE
The blocking probability measured in the tool is more similar to a Lost Call Held blocking probability
than a Lost Call Cleared (ErlangB) blocking probability. This is a consequence of the way the
simulator works. The simulator simply tries to serve as much of the offered traffic as possible. The
following formulae show how these probabilities are related in a simple situation. Note that these
formulae are not used to explicitly calculate blocking probabilities in the tool, since the probabilities in
the tool are all found by sampling snapshots.
Take a system with fixed capacity C , and Poisson traffic with arrival rate users per second and
mean holding time seconds. The mean offered traffic is uA .
The probability that exactly C users are offered is given by:
!CAeS CA
The probability that more than C users are offered is given by:
1
!Ck
kA kAeS
The probability that less than C users are offered is given by:
1
0
!C
k
kA kAeS
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Lost Call Cleared: In an LCC system, blocked users do not try again.
C
k
k
C
LCC
kA
CA
SS
SCAP
0
!/
!/),(
Lost Call Held: In an LCH system, blocked users immediately retry.
Ck
kA
LCH kAeSSCAP !),(
It is easy to show that ),(),( CAPCAP LCCLCH . The two probabilities are most similar to each
other for low blocking probabilities.
Note that the “Failure Rate” ( F ) in the failure report is the proportion of offered terminals that fail.
A
kAeCk
F Ck
kA
1
!)(
)E(attempts
)E(failures
This is not a blocking probability and it should never be treated as one. The failure rate can be an order
of magnitude lower than both the LCC and LCH blocking probabilities.