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Company Confidential
1 © Nokia Siemens Networks Radio Resource Manager / June2007
Radio Resource Manager Overview
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Contents
• RRM Introduction• Power Control• Load Control• Admission Control• Packet Scheduler• Resource Manager
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RRM Introduction
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Radio Resource Management
Target for RRM is to ensure the RAN offers:
• The planned coverage for each targeted service• High capacity i.e. low blocking (new calls, handovers)• The required Quality of Service (QoS)• Optimize the use of available capacity (priorities)
By continuously monitoring/adjusting how the available resources are used in accordance with user requests
Radio Resource Management (RRM) is responsible for optimalutilisation of the air interface resources
RRM
Link Quality
Cell CoverageCell Capacity
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RRM must be able to:
• Predict the impact on interference (power) of admitting a new user for UL & DL
• Perform appropriate actions (e.g. new call admissions, bitrate increase/decrease etc.) in accordance with prevailing load conditions
• Provide different quality of service for real time (RT) and non-real time (NRT) users
• Take appropriate corrective action when the different cell load thresholds are exceeded in order to maintain cell stability (i.e. load control)
Overload
Load TargetOverload Margin
Po
we
r
Time
Estimated capacity for NRT trafficMeasured load causedby non-controllable load (RT)
RT services must have higher quality assurance than NRT
Radio Resource Management tasks
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RRM Module
• Power Control• Load Control• Admission Control• Packet Scheduling• Handover Control• Resource Manager
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• RRM is made up of a number of closely interdependent functions (i.e. algorithms)
• These functions can be divided into;
• Cell Based• Load control (LC)
• Admission control (AC)
• Packet scheduling (PS)
• Resource manager (RM)
• Connection Based• Handover control (HC)
• Power control (PC)
RRM Functional Split
PC
HC
Connection based functions
LC
AC
Cell based functions
PSRM
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Load Control
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…
BTS Measurements
RRI Period
Radio Resource Indication
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Load Estimation Methods
• Actual prevailing load in the cell depends on multiple factors
• Number of active connections• Properties of the connections
• Bit rate
• Eb/No requirement
• BLER requirement
• Propagation channel conditions (speed, multipath profile etc.)
• SHO condition
• Activity
• Different methods can be applied to measure/estimate prevailing load conditions, e.g.
• Throughput Based Load Estimation• Power Based Load Estimation
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Throughput Based Load Estimation
• The downlink load of the cell can be estimated by using the sum of the downlink allocated bit rates as follows
• The uplink load of the cell can be estimated by using the sum of the load factors of the users connected to this cell.
• Definition of Rmax and loadj requires estimates of Eb/No, little i,
activity, SHO overhead etc.
max
1
R
RN
jj
DL
∑==η
∑=
⋅+=N
jjUL loadi
1
)1(η
Max. allowed throughtput of the cell
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Power Based Load Estimation
• The downlink load of the cell can be estimated by dividing the total downlink transmission power, Ptx_total by the maximum Node B transmission
power Ptx_BTS,max.
• The uplink load can be estimated with Prx_noise, the background and
receiver noise and Prx_total, the total received power, according to this
formula:
• Measures the load in actual conditions
max,_
_
BTStx
totaltxDL P
P=η
NRP
P
totalrx
noiserxUL
111
_
_ −=−=η
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• The BTS measures the total received power (PrxTotal) and the total transmitted power (PtxTotal) on cell basis
• The BTS reports PrxTo ta l and PtxTo ta l of each cell to the RNC by sending RADIO RESOURCE INDICATION message periodically (RRIndicationPeriod)
• LC updates cell load status for each cell based on RADIO RESOURCE INDICATION
• LC updates non-controllable UL (PrxNC) and DL (PtxNC) load in cell
• AC and PS algorithms work on the current cell load status provided by LC
• Denying call admission (AC) and throttling back NRT traffic (PS) are the overload actions
• After scheduling PS provides LC with PrxNRT, PtxNRT & LNRT estimates
• After admitting RT RAB, AC provides LC with NC load increase estimate
Radio interface load
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UL power based load measurement
PRx_Own
PRxTotal = PRx_Own + PRx_Other + PNoise
= PRx_NRT + PRx_RT + PRx_Other + PNoise
= PRx_NRT + PRx_NC
PRx_Other
iUL = PRx_Other / PRx_Own
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DL power based load measurement
PTx_Own
PTxTotal = PTx_Own
= PTx_NRT + PTx_RT + PTx_Common
= PTx_NRT + PTx_NC
PTx_Common
Common Channels
PRx_Own_DL
PRx_Other_DL
iDL = PRx_Other_DL / PRx_Own_DL
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UL Preventive & Overload Thresholds
Prx Target [dB]
PrxTarget [dB] + PrxOffset [dB]
load factor η
Range [0..1]
tota
l rec
eive
d po
wer
Prx T
otal
[dB
m] Overloaded Area
Marginal Load Area
Feasible Load Area
Range Prx Total [Prx noise ... inf]
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Uplink preventive threshold
Preventive threshold = PrxTargetPrx Target is relative to the system noise, it gives an upper threshold for the noise rise
Target threshold defines the optimal operating point of the cell load, up to which PS & AC can operate normally
If cell load exceeds these limits then AC & PS move to PREVENTIVE STATE function
New RT RABs are blocked, and PS can't schedule more NRT bit rates in the cell
PrxTarget range: 0...30 dB, step 0.1 dBdefault: 4 dB
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Overload threshold = PrxTarget + PrxOffset
• Overload Threshold defines the limit when the cell is considered to be overloaded• If load in the cell exceeds these limits then AC & PS move to OVERLOAD STATE
function• New calls are blocked, and PS starts to decrease NRT bit rates in the cell
PrxOffset range: 0...6 dB, step 0.1 dBdefault: 1 dB
Uplink overload threshold
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DL Preventive & Overload Thresholds
Ptx Target [dBm]
Ptx Target [dBm] + PtxOffset [dB]
load factorη
tota
l tra
nsm
itte
d po
wer
Ptx T
otal
[dB
m]
Overloaded Area
Marginal Load Area
Feasible Load Area
Cell Maximum
Range Ptx Total [0… Ptx BS total]
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Preventive threshold = PtxTarget
• Target threshold defines the optimal operating point of the cell load, up to which PS & AC can operate normally
• If cell load exceeds these limits then AC & PS move to PREVENTIVE STATE function
• New RT RABs are blocked, and PS can't schedule more NRT bit rates in the cell
PtxTargetrange: -10...50 dBm, step 0.1 dBdefault: 40 dBm
• Default value depends on the cell max TX power: in case the cell max power is 43 dBm, the PtxTarget should be 40 dBm (3 dB below max)
Downlink Preventive threshold
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Overload threshold = PtxTarget + PtxOffset
• Overload Threshold defines the limit when the cell is considered to be overloaded• If load in the cell exceeds these limits then AC & PS move to OVERLOAD STATE
function• New calls are blocked, and PS starts to decrease NRT bit rates in the cell
PtxOffset range: 0...6 dB, step 0.1 dBdefault: 1 dB
Downlink overload threshold
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Admission Control
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• Maximises capacity whilst maintaining stability
• Decides if new RAB request is admitted into RAN
• AC decision procedure set according to whether;
• Request is for RRC connection and RT or NRT RAB Setup• RAB setup can be for call setup or handover
• Admission control for RAB setup is different for RT and NRT
• For RT RAB admission requests AC;
• estimates the non-controllable power (load) increase that would result from admitting the new RAB
• checks if the new non-controllable load is below a certain threshold
• Bearer is not admitted if the predicted load exceeds defined thresholds in UL or DL
• AC is also responsible for determining quality requirements of the RB including;
• setting RLC and TrCH parameters• BLER & Eb/No targets
• initial SIR target (used in Outer Loop PC) & upper and lower limits for the uplink SIR target
• AC determines the power allocation for the requesting UEs (initial, minimum and maximum transmission power)
LCLC
AC
Network based functions
PSPSRMRM
RNCAdmission Control Functional Overview
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RAB Establishment
6
RAB attributes (HLR);• SDU error ratio• traffic class• max bit rate
NokiaRNC
Core NetworkRAB ASSIGNMENT
REQUESTNRT PS call
ACRAB admitted
RAB request denied
Queue RAB
Radio Access Bearer Service Request
1Quality Requirements
of Radio Bearer2
RB attributes (RNC);• target BLER• target Eb/No• initial SIRtarget
Admission Decision
4
RT CS call
Power Increase Estimates
3
UL/DL Load Change Report to LC
5
RRC Connection Establishment
0
NRT Admission Decision Process
(PS)
Admission Control Functional Overview
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Load Based Admission Decision Process
• To maintain stability, UL and DL loads at each cell must be maintained below defined thresholds.
• Admission decision takes into account 3 main issues;
• The measured power quantities (current load status of the cell)
• Average total wideband UL received power
• Average total DL transmit power
• Non-controllable UL power
• Non-controllable DL power
• Non-controllable power increase estimation associated with new admissions
• Comparison against admission criteria thresholds
totalrxP _
NRTrxtotalrxNCrx PPP ___ −=
totaltxP _
NRTtxtotaltxNCtx PPP ___ −=
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UL Admission Procedure Summary
BTS sends periodically the received UL power to the RNCBTS sends periodically the received UL power to the RNC
Fractional load[0..1]
OVERLOADAREA
MARGINALLOADAREA
FEASIBLELOADAREA
0
Load curve in UL
PrxTotal[dBm]
PrxNoise [dBm]
PrxTarget [dB]
PrxTarget [dB]+PrxOffset [dB]
1
Noise RiseNR [dB]
XX [dB]
RNC compares the measured received power levels against the set thresholdsRNC compares the measured received power levels against the set thresholds
If measured UL (PrxTotal) load exceeds target thresholds (PrxTarget) The NRT RAB bitrate can not be increased and remains at the same level as after previous scheduling period
If measured UL (PrxTotal) load exceeds overload thresholds (PrxTarget+PrxOffset) no RABs can be admitted and NRT bitrates are reduced until PrxTotal reaches again PrxTarget
Over Load
MarginalLoad
FeasibleLoad
In feasible load area the admission decision is based on the power rise estimate of the new RT bearer
If the resulting power is still below PrxTraget the RAB is admitted
rx_targetrx_ncrx_nc PPP ≥∆+In case the RAB can not be admitted it is put into the queueIn case the RAB can not be admitted it is put into the queue
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BTS sends periodically the total transmitted DL power to the RNCBTS sends periodically the total transmitted DL power to the RNC
RNC compares the measured transmitted power levels against the thresholdsRNC compares the measured transmitted power levels against the thresholds
If measured DL (PtxTotal) transmitted power exceeds target thresholds (PtxTarget) ,The NRT RAB bitrates can not be increased and they remain at the same level as after previous scheduling period
If measured DL (PTxTotal) transmitted power exceeds overload thresholds (PtxTarget+PtxOffset) no RABs can be admitted and NRT bitrates are reduced until PtxTotal reaches again PtxTarget
Over Load
MarginalLoad
FeasibleLoad
In feasible load area the admission decision is based on the power rise estimate of the new RT bearer
If the resulting power is still below PtxTraget the RAB is admitted
In case the RAB can not be admitted it is putinto the queueIn case the RAB can not be admitted it is putinto the queue
OVERLOAD AREA
MARGINALLOADAREA
FEASIBLELOADAREA
Load curve in DL
PtxTotal[dBm]
PtxTarget [dBm]
PtxTarget [dBm]+PtxOffset [dB]
Cell maximum [dBm]
Load[0...1]
0 1
tx_targettxtx_total PPP ≥∆+
DL Admission Procedure Summary
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NRTNRT
RRC connection setupRRC connection setup RAB setupRAB setup
RRC connection request is not rejected either for received wide band power or transmitted power reasons
RT over NRT and pre-emption procedure can be applied
RRC connection request is not rejected either for received wide band power or transmitted power reasons
RT over NRT and pre-emption procedure can be applied
Admitted if non-controllable load is below target threshold
RT over NRT pre-emption procedure can be applied
Admitted if non-controllable load is below target threshold
RT over NRT pre-emption procedure can be applied
Emergency call
Emergency call
RTRT
Admitted if non-controllable load is below target threshold
Admitted if non-controllable load is below target threshold
Admitted if non-controllable load added by estimated change is below target
If non-controllable load added by estimated change is above target, RT RAB pre-emption procedure can be applied
In case of congestion, RT over NRT procedure can be applied
Admitted if non-controllable load added by estimated change is below target
If non-controllable load added by estimated change is above target, RT RAB pre-emption procedure can be applied
In case of congestion, RT over NRT procedure can be applied
Admitted always at 0 bit rate, capacity requests scheduled by PS
Admitted always at 0 bit rate, capacity requests scheduled by PS
Admission Control for RT and NRT
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Packet Scheduler
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• It is characteristic for RT traffic that it’s load cannot be controlled in efficient way. Load caused by RT traffic, interference from other cell users and noise together is called non-controllable load.
• The available capacity, which is not used by non-controllable load, can be used for NRT radio bearers on best effort basis. To fill the whole load budget and achieve the maximum capacity, the allocation of non-GBR traffic needs to be fast.
• The Packet scheduler is a general feature, which takes care of scheduling radio resources for NRT radio bearers for both uplink and downlink directions; Packet scheduling happens periodically and is implemented for both dedicated (DCH) and common control transport channels (RACH/FACH).
• Scheduled capacity depends on the UE capabilities, Node B capabilities, current load of the cell as well as the availability of the physical radio resources.
Why Packet Scheduling ?
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• Packet Scheduler switches between common channels (FACH/RACH = low capacity) and dedicated channels (DCH = higher bit rates)
• Packet Scheduler allocates to RABs temporarily dedicated channels with a set of maximum bit rates
• For instance within an allocation for 384kbit/s, the instantaneous bit rate can be {0, 8, 16, 32, 64, 128, 384} kbit/s
• Packet Scheduler allocates DCH based on Capacity Requests• A Ca pa c ity Re q ue s t (Nokia term) is triggered based on traffic volume
measurement info: the sender (UE or RNC) has data in buffer and no sufficient dedicated channel
• Packet Scheduler releases DCH upon inactivity• Packet Scheduler re-schedules continuously DCH to serve all requests
equally, and take into account changes in non-controllable load
Packet Scheduling Principles
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Power/ Load
time
non-controllable loadi.e. RT Traffic
controllable loadi.e. non RT Traffic
PtxTotal (variable) PrxTotal
PtxNrt PrxNrt
PtxTarget PrxTarget
PtxOffset PrxOffset
PtxTargetBTS PrxTargetBTS
overload
De s iredPrx /PtxVa lue sPtxRt PrxRt
Packet Scheduling
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Packet Scheduler as part of RRM
• The packet scheduler (PS) co-operates with other radio resource management functions like handover control (HC), load control (LC), admission control (AC) and the resource manager (RM)
• HC provides active set information• LC provides periodical load information to PS on a cell basis• PS informs AC and LC of the load caused by non-real time radio bearers
• AC informs PS when new non-real time radio bearers are admitted, reconfigured or released
• RM allocates the RNC internal resources, downlink spreading codes and takes care of allocating radio links using the base station application protocol (NBAP)
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Packet Scheduler functions
• Packet Scheduler consists of multiple different functions which can be categorised based on the scope of the function
• UE-specific part• Functions working based on single radio link/bearer status, measurements and conditions
• Cell-specific part• Functions working based on cell level measurements and conditions
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Minimum bit rate
Packet Scheduler actions during call – Loaded cell
Max. bit rate
Initial bit rate
Allocated bit rate
Actual throughput
Load Margin
Normal load
Overload
AC
PS1
PS2
PS3
PS4
PS5
PBS FLXU EOLC FLXU
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URA_PCH
CELL_DCH CELL_FACH
CELL_PCH
UTRA RRC Connected Mode
Idle Mode
URA_PCH
CELL_DCH CELL_FACH
CELL_PCH
Cell selectionCell re-selection
Dedicated resourcesallocated (DCH)Tx and Rx mode
Common resourcesallocated (RACH-FACH)
Tx and Rx mode
UE in DRX modediscontinous receiption
UE in DRX modediscontinous reception
RRC State Machine
Cell Update, UL Tx
UL/DL activation timer
Traffic volumeRACH load
Inactivity TimerOverload
UL Tx
Frequent cell updates
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Power Control
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UL Outer LoopPower Control
Open Loop Power Control(Initial Access)
(Fast) Closed Loop Power Control
RNC
BS
MS
DL Outer LoopPower Control
Power Control types
BLER target
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• Purpose: To set the initial transmitted power of PRACH & DPCCH in the UL.• UE determines the uplink preamble power of PRACH
• UE PRACH First Preamble Power =
Transmission power of CPICH (Broadcast on BCH, SIB 5)) - Downlink RSCP measurement from active cell on CPICH (Measured by UE) +Total received wideband interference power at WCDMA BTS (Broadcast on BCH, SIB 7) +Required received C/I at the WCDMA BTS (Broadcast on BCH, SIB 5)
• Open loop PC is a part of the random access procedure for PRACH channel
Path loss calculationsPath loss
calculations
Additional Power
required
Additional Power
required
Example:PtxCPICH=33dBm (Parameter per Node-B)
DL RSCP = -80dBm (Measured by UE)UL_IF = –100 dBm
UL_Required_C/I = -25 dB (Parameter per Node-B)
UE PRACH First Preamble Power = 33 dBm – (-80 dBm) + (-100 dBm) + (-25 dB) = -12 dBm
Open Loop Power Control
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tp-mtp-p
Message part
PRACHaccessslots TX atUE
One access slot
tp-a
Acq.Ind.
AICHaccessslots RX atUE
P0
Pp-m
Pre-amblePre-
amble
DL
UL
Random Access Procedure
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• UE transmits the first preamble with the power determined by UL open loop PC• If the UE does not detect any acquisition indicator in AICH, it increases the preamble Tx
power by a specified offset Po
• If the UE detects the positive indicator in AICH, it transmits the random access message, 3 or 4 access slots after the UL access slot of the last transmitted preamble
• The Tx power of the control part of random access message should be Pp-m higher than the last transmitted preamble power
• The required power offset values for random access procedure• PowerOffsetLastPreamblePRACHmessage in PRACH(Pp-m)
• PowerRampStepPRACHpreamble (Power Ramp Step)(Po)
Random Access Procedure (1/3)
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• The power ramp-up process will continue until 1) A positive AI is received from the network
2) A negative AI is received from the network
3) RACH_preamble_retrans value is exhausted
4) UE reaches UEtxPowerMaxPRACH value
• When the RACH_preamble_retrans value is exhausted, PRACH preamble power will be re-set to the initial value of the cycle and a new power ramp-up cycle initiated. The preamble power ramp-up cycle will be repeated RACH_tx_Max times. At this stage the UE will send a RACH failure message to the network.
• The maximum allowed UE transmit power for the PRACH procedure is defined by UEtxPowerMaxPRACH. Layer 1 of the UE controls the UE transmit power during the PRACH procedure using the ‘commanded transmit power’. If the commanded transmit power exceeds the maximum allowed transmit power then the UE transmits the maximum allowed transmit power.
• If the commanded transmit power exceeds the maximum allowed transmit power by 6 dB then layer 1 of the UE is able to inform higher layers and exit the PRACH procedure. If the step size is 1 dB then this corresponds to transmitting 6 preambles at maximum power.
Random Access Procedure (2/3)
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Downlink / BSDownlink / BS
Uplink / UEUplink / UEPreamble 1 Message part
…. ….
UEtxPo we rMaxPRACH
Preamble n
PRACH_ p re am ble _ re tra ns : The maximum number of
preambles allowed in one preamble ramping cycle
RACH_ tx _ Max : # of preamble power ramping cycles that can be done before RACH transmission
failure is reported,
Random Access Procedure (3/3)
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• PowerOffsetLastPreamblePRACHmessage in PRACH(Pp-m)
• The power offset between the last transmitted preamble and the control part of the PRACH message (added to the preamble power to receive the power of the message control part)
• range: -5 ... 10 dB, step 1 dB default: 2 dB
• The power offset between last preamble and and message part should ensure decoding the RACH message at BS with high probability. Still, it should be mimised to reduce UL interference
• PowerRampStepPRACHpreamble (Power Ramp Step)(Po)
• The power ramp step on PRACH preamble when no acquisition indicator (AI) is detected by the UE
• range: 1 ... 8 dB, step 1 dB default: 2 dB
• If the "power ramp step" is too low then the RACH preamble ramping takes a too long time. If it is too high, then it may cause high noise rise at BS
Random Access Procedure Parameters
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• RACH_preamble_retrans
• The parameter describes the number of PRACH preamble retransmissions in a preamble power ramping-up cycle
• range: -1 ... 64, step 1 default: 8
• Note: As the 3GPP requires almost certain detection of PRACH preamble at -19.5dB. The default of 8 retransmissions with 2dB power step, starting from -25dB should be sufficient
• RACH_tx_Max• Maximum number of RACH preamble cycles defines how many times the PRACH pre-amble
power ramping-up procedure can be repeated before UE MAC reports a failure on RACH transmission to higher layers
• range: 1,2...32 default: 8
Random Access Procedure Parameters
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Outer Loop Power Control
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4
BS RNC
Outer Loop Power Control
• Outer PC loop is performed to adjust the TARGET SIR in BS/UE, according to the needs of individual radio link:
• UE speed• Changes in the propagation conditions• Available multipath diversity• UE power control dynamics (close to peak power)• SHO branches (Macro Diversity Combining)
• SIR is constantly adjusted in order to maintain a constant QUALITY, usually defined as a certain target BLER
Outer Loop Power Control
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UL OuterLoop PC
Entity #N
UL OuterLoop PC
Entity #1
UL Outer Loop PCController
RNC
BTS 1
UL Fast Closed
Loop PC
BTS 2
UL Fast Closed
Loop PC
UL Outer Loop PC
Uplink Outer Loop Power Control Entities
• In the RNC the functionality of the UL outer loop PC is divided into two parts:
⇒UL outer loop PC Controller, one for each RRC connection
⇒UL outer loop PC Entities, one for each transport channel
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• An UL Outer Loop PC Controller controls all UL OLPC Entities under the same RRC connection.
• The UL OLPC Controller sets the parameters for each UL OL PC Entities at the RAB Setup/Modification.
• The UL OLPC Controller also combines SIR Target changes from the UL OLPC Entities and sends the result to the UL OLPC Entity, which is selected to transmit it to the WCDMA BTS.
UL OuterLoop PC
Entity #N
UL OuterLoop PC
Entity #1
UL Outer Loop PCController
RNC
BTS 1
UL Fast Closed
Loop PC
BTS 2
UL Fast Closed
Loop PC
UL Outer Loop PC
Uplink Outer Loop Power Control Controller
• There is one UL outer loop PC Entity for each transport channel in the RNC.
• This UL OLPC Entity calculates the required change in SIR Target according to UL quality estimates (CRC).
• One of UL OLPC Entities under the same radio link is selected to transmit the New SIR Target to the WCDMA BTS.
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1. RAB Setup:Initial SIR Target
UL Outer Loop PC Entity #n
UL Outer Loop PC Controller
2. - PC Parameters - Initial SIR target
8. Collection of the SIR target changes and calculation of new SIR Target3. Setting of the UL Outer Loop PC Entities
2. PC Parameters at RAB setup
9. New SIR Target
BTS1. SIR Target
1. UL fast closed loop PC
Admission Control
- Entity selected to transmit new SIR target- Activity reporting period
4. - PC parameters
6. Calculation of SIR Target change
Overload info Load Control
(not used in RAN1)
4. Parameters 7. SIR Target modification command
5. Quality info: BER, BLER
5. L1 FP: UL quality info
10. New SIR Target
10. L1 FP: SIR Target
10. Transmission of new SIR Target value to MDC
MDC
Uplink Outer Loop Power Control Algorithm
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• This function is implemented in the UE in order to set the SIR target on each CCTrCH used for the DL closed loop PC.
• This SIR value is adjusted according to an autonomous function of the UE in order to achieve the same measured quality as the quality target set by the RNC.
• In order to control the downlink outer loop PC quality target in UE, Admission Control (AC) determines the value of the DL BLER target for each DCH mapped on a DPCH.
• After Admission Control functionality has determined the DL BLER target for each transport channel, the RNC sends these values to the UE.
Downlink Outer Loop Power Control
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Close Loop Power Control
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UL Outer LoopPower Control
(Fast) Closed Loop Power Control
RNC
BS
MS
DL Outer LoopPower Control
Closed Loop Power Control
BLER target
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MS sets the power on UL DPCCHand UL DPDCH on following way:TPC = '1' --> increase power by 1 dBTPC = '0' --> decrease power by 1 dB
UL DPCCH
MS
Measure received SIR on UL DPCCH Pilot
Compare measured SIR withSIR target value received from
UL outer loop PC
Measured SIR < SIR target --> TPC bit = '1'Measured SIR => SIR target --> TPC bit = '0'
BS
Send TPC bit on DL DPCCH
Changed power on UL DPCCH
UL Closed loop power control
• UL fast closed loop PC shall be active as soon as the frame synchronization has been established in the dedicated physical channels.
• PC frequency 1500 Hz• PC step 1dB• PC delay approx. one slot
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DL Fast Loop PC: UTRAN behaviourMS
Measured SIR < SIR target --> TPC command is "1"Measured SIR => SIR target --> TPC command is "0"
Compare measured SIR with SIR target value received from DL outer loop PC
Measure received SIR on DL DPCCH
WCDMA BTS
BS sets the power on DL DPCCH andDL DPDCH following way:
TPC command = "1" --> increase power by 1 dBTPC command = "0" --> decrease power by 1 dB
DL DPCCH + DPDCHs
Send TPC command on UL DPCCH
Changed power on DL DPCCH + DPDCHs
• Upon receiving the TPC commands BS adjusts its downlink DPCCH/DPDCH power accordingly.
• UTRAN shall estimate the transmitted TPC command TPCest
to be 0 or 1, and shall update the power every slot.
• After estimating the k:th TPC command, UTRAN shall adjust the current downlink power P(k-1) [dB] to a new power P(k) [dB] according to the following formula:
P(k) = P(k - 1) + PTPC(k)
where PTPC(k) is the k:th
power adjustment due to the inner loop power control
DownlinkInnerLoopPCStepSize
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Resource Manager
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Resource Manager
• The main function of RM is to allocate logical radio resources of BS according to the channel request by the RRC layer for each radio connection
• The RM is located in the RNC and it works in close co-operation with AC and PS
• The actual input for resource allocation comes from AC/PS and RM informs the PS about the resource situation
• The RM is able to switch codes and code types for different reasons such as soft handover and defragmentation of code tree
• Manages the BS logical resources• BS reports the available logical HW resources
• Requests for other resources such as ATM• Transport resource manager
• RNC HW manager (L1/L2)
• Maintains the code tree• Allocates the DL spreading (=channelization) codes, UL scrambling code, UL spreading (=channelisation) code type
• Prevents fragmentation, may cause extra HO's
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Spreading Code Allocation
The codes are layered from 0 to 11 according to the Spreading Factor (SF)
• Cm(n) : The code order, m, and the code number, n, designates each and every code in the layered orthogonal code sequences
• In DL code order 2 to 8 (SF 4 to 512) are available (Nokia RAN does not support SF = 512)
• In UL code order 2 to 7 (SF 4 to 256) are available
C 0 (0)=(1)
C 1 (0)=(1,1)
C1 (1)=(1,-1)
C 2 (0)=(1,1,1,1)
C 2 (1)=(1,1,-1,-1)
C 2 (2)=(1,-1,1,-1)
C 2 (3)=(1,-1,-1,1)
C 3 (0)=(…)
C 3 (1)=(…)
C 3 (2)=(…)
C 3 (3)=(…)
C 3 (4)=(…)
C 3 (5)=(…)
C 3 (6)=(…)
C 3 (7)=(…)
Code Order 0 (SF 1)
Code Order 1 (SF 2)
Code Order 2 (SF 4)
Code Order 3 (SF 8)
• Code Allocation Algorithm chooses the correct spreading code depending on the TFC type
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Spreading Code Allocation
• A code is always allocated from the optimum location in the code tree. It makes the allocated code and the codes in the branches below and above the allocated code unavailable
• Code tree will fragment quickly if releases is not re-arranged
• Re-arrangements in the code tree is done by reallocating the codes in better locations
• The above code tree has 4 codes of equal order. The best locations are in the same branch and very close to one another. The badly located codes are released and optimally reallocated allowing the use of upper layer codes
• Codes are only reallocated when there is a benefit at two code tree layers above the code being reallocated