09 WCDMA RNO Access Procedure Analysis
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Transcript of 09 WCDMA RNO Access Procedure Analysis
WCDMA Access Procedure
ReviewReview
Access is associated with the call setup success
rate of the network. Mastering the access
procedure can increase this KPI with the access
parameters optimization.
ObjectivesObjectives
� Know the detailed access
procedure in UMTS
� Know how to optimize the
access procedure
Upon completion of this course,you will be able to:
Course ContentsCourse Contents
Random access procedure
RRC setup procedure
RAB setup procedure
Random access procedure Random access procedure
�� Physical channel about accessPhysical channel about access
� Random access procedure
� Parameters optimization
PRACH access slotPRACH access slot
#0 #1 #2 #3 #4 #5 #6 #7 #8 #9 #10 #11 #12 #13 #14
5120 chips
radio frame: 10 ms radio frame: 10 ms
Access slot
Random Access Transmission
Random Access Transmission
Random Access Transmission
Random Access Transmission
UE can start the random-access transmission at the beginning of a access slot
There are 15 access slots per two frames
what access slots are available is given by higher layers
Structure of the random-access transmissionStructure of the random-access transmission
� Each random-access transmission consists of one or several
preambles of length 4096 chips and a message of length 10
ms or 20 ms.
� Each preamble is of length 4096 chips and consists of 256
repetitions of a signature of length 16 chips.
M essa g e p a r tP rea m ble
4 0 9 6 ch ip s1 0 m s (on e ra d io fr a m e)
P rea m ble P rea m ble
M essa g e p a r tP rea m ble
4 0 9 6 ch ip s 2 0 m s (tw o ra d io fr a m es)
P rea m ble P rea m ble
Structure of the random-access transmissionStructure of the random-access transmission
The preamble-to-preamble distance τp-p shall be larger than or
equal to the minimum preamble-to-preamble distance
τp-p,min .
One access slot
τp-a
τp-mτp-p
Pre-amble
Pre-amble Message part
Acq.Ind.
AICH accessslots RX at UE
PRACH accessslots TX at UE
Structure of the random-access transmissionStructure of the random-access transmission
when AICH_Transmission_Timing is set to 0
τp-p,min = 15360 chips (3 access slots)
τp-a = 7680 chips
τp-m = 15360 chips (3 access slots)
when AICH_Transmission_Timing is set to 1, then
τp-p,min = 20480 chips (4 access slots)
τp-a = 12800 chips
τp-m = 20480 chips (4 access slots)
The parameter AICH_Transmission_Timing is
signalled by higher layers.
Random access procedure Random access procedure
�� Physical channel about accessPhysical channel about access
� Random access procedure
� Parameters optimization
Concepts in random access procedureConcepts in random access procedure
� Preamble Signature
� AC (Access Class)
� ASC (Access Service Class)
� RACH sub channels
� Access slot set
Preamble SignaturePreamble Signature
Value of n Preamble
signature 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
P0(n) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
P1(n) 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1 1 -1
P2(n) 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1
P3(n) 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1 1 -1 -1 1
P4(n) 1 1 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1
P5(n) 1 -1 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1
P6(n) 1 1 -1 -1 -1 -1 1 1 1 1 -1 -1 -1 -1 1 1
P7(n) 1 -1 -1 1 -1 1 1 -1 1 -1 -1 1 -1 1 1 -1
P8(n) 1 1 1 1 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1
P9(n) 1 -1 1 -1 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1
P10(n) 1 1 -1 -1 1 1 -1 -1 -1 -1 1 1 -1 -1 1 1
P11(n) 1 -1 -1 1 1 -1 -1 1 -1 1 1 -1 -1 1 1 -1
P12(n) 1 1 1 1 -1 -1 -1 -1 -1 -1 -1 -1 1 1 1 1
P13(n) 1 -1 1 -1 -1 1 -1 1 -1 1 -1 1 1 -1 1 -1
P14(n) 1 1 -1 -1 -1 -1 1 1 -1 -1 1 1 1 1 -1 -1
P15(n) 1 -1 -1 1 -1 1 1 -1 -1 1 1 -1 1 -1 -1 1
The preamble signature corresponding to a signatures consists of 256 repetitions of a length
16 signature Ps(n) shown as the following table. UE gets signature from system info type5.
Access ClassAccess Class
The SIMs/USIMs of all the UEs are allocated with one of Access Class 0~9. In addition,
one or more special access classes (Access Class 11~15) might be allocated to the
SIM/USIM storage information of the UEs with high priority, as shown below:
� Access Class 15 --- PLMN Staff;
� Access Class 14 --- Emergency Services;
� Access Class 13 --- Public Utilities;
� Access Class 12 --- Security Services;
� Access Class 11 --- For PLMN Use.
Different from Access Class 0~9 and 11~15, the control information of
Access Class 10 is sent to UEs by means of air interface signalling,
indicating whether the UEs belonging to Access Class 0~9 or without IMSI
can be accessed to the network in case of emergency calls. For the UEs
with Access Class 11~15, they cannot initiate the emergency calls when
Access Class 10 and Access Class 11~15 are all barred.
Access Service ClassAccess Service Class
� The PRACH resources (access timeslots and preamble signatures in FDD
mode) can be classified into several ASCs. One ASC defines a partition of
certain PRACH resources.
� The ASCs are numbered within the range 0<= i <=7, and the maximum
number of ASCs is 8. "0" indicates the highest priority and "7" indicates the
lowest priority.
� AC to ASC mapping. In case the UE is member of several ACs it shall
select the ASC for the highest AC number.
AC 0 – 9 10 11 12 13 14 15
ASC 1st IE 2nd IE 3rd IE 4th IE 5th IE 6th IE 7th IE
Access Slot SetAccess Slot Set
Access slot set 1 contains PRACH slots 0 – 7 and starts τp-a chips before
the downlink P-CCPCH frame for which SFN mod 2 = 0. Access slot set 2
contains PRACH slots 8 - 14 and starts (τp-a –2560) chips before the
downlink P-CCPCH frame for which SFN mod 2 = 1.
AICH accessslots
10 ms
#0 #1 #2 #3 #14#13#12#11#10#9#8#7#6#5#4τp-a
#0 #1 #2 #3 #14#13#12#11#10#9#8#7#6#5#4
PRACHaccess slots
SFN mod 2 = 0 SFN mod 2 = 1
10 ms
Access slot set 1 Access slot set 2
RACH sub channelsRACH sub channels
1413121110987
210765436
1413121110985
543210764
8141312111093
765432102
1110981413121
765432100
11109876543210
Sub-channel numberSFN modulo 8 of corresponding P-
CCPCH frame
A RACH sub-channel defines a sub-set of the total set of uplink access
slots. There are a total of 12 RACH sub-channels.
Random access procedureRandom access procedure
Random access procedureRandom access procedure
Before random-access procedure, Layer 1 shall receive the
following information from the RRC layers:
� The preamble scrambling code.
� The message length in time, either 10 or 20 ms.
� The AICH_Transmission_Timing parameter [0 or 1].
� The set of available signatures and the set of available RACH sub-channels
for each ASC.
� The power-ramping factor Power Ramp Step.
� The parameter Preamble Retrans Max.
� Preamble_Initial_Power.
� The Power offset P p-m = Pmessage-control – Ppreamble.
� The set of Transport Format parameters, This includes the power offset
between the data part and the control part of the random-access message for
each Transport Format.
Random access procedureRandom access procedure
Layer 1 shall also receive the following information from the
MAC layers :
� The Transport Format to be used for the PRACH message
part.
� The ASC of the PRACH transmission.
� The data to be transmitted .
Random access stepsRandom access steps
1. Derive the available uplink access slots in the next full
access slot set and Randomly select one access slot .
2. Randomly select a signature from the set of available
signatures within the given ASC .
3. Set the Preamble Retransmission Counter to Preamble
Retrans Max.
4. Set the parameter Commanded Preamble Power to
Preamble_Initial_Power.
Random access stepsRandom access steps
5. Transmit a preamble using the selected uplink access slot,
signature, and preamble transmission power.
6. Check the corresponding AI, if received positive AI, send the
message part and set L1 status “RACH message transmitted”.
If received negative AI, set L1 status “Nack on AICH received”.
7. If no AI received, select the next access slot, signature and
decrease the preamble retransmission counter by one,
increase the preamble power by power ramp step. Check if the
counter more than 0 and the preamble power less than the
maximum allowed. If true, send a preamble again. Otherwise,
set L1 status “No ack on AICH” .
Random access procedure Random access procedure
�� Physical channel about accessPhysical channel about access
� Random access procedure
� Parameters optimization
ConstantValueConstantValue
� Preamble_Initial_Power = DL_Path_Loss + UL_interference +
Constant_Value. This parameter is used for the UE to estimate
the initial PRACH transmission power according to the open
loop power.
� Influence on the network performance: If this parameter is set
too big, the initial transmission power will be too big, but the
access process will become shorter; if it is set too small, the
access power will satisfy the requirements, but the preamble
requires multiple ramps, which will lengthen the access
process.
PRACH Power Ramp Step PRACH Power Ramp Step
� PRACH PowerRampStep is the ramp step of the preamble
power by the UE before it receives the NodeB capture
indication.
� Influence on the network performance: If this value is set too
big, the access process will be shortened, but the probability of
wasting power will be bigger; if it is set too small, the access
process will be lengthened, but some power will be saved. It is
a value to be weighed.
Maximum Preamble Retransmit Times Maximum Preamble Retransmit Times
� PreambleRetransMax is the maximum preamble
retransmission times of the UE within a preamble ramp cycle.
� Influence on the network performance: If this value is set too
big, the access process will be shortened, but the probability of
wasting power will be bigger; if it is set too small, the access
process will be lengthened, but some power will be saved. It is
a value to be weighed.
Maximum Preamble Cycle TimesMaximum Preamble Cycle Times
� Mmax defines the maximum times of the random access
preamble cycle. When the UE transmits a preamble and has
reached the maximum retransmit times
(PreambleRetransMax), if the UE has not received the capture
indication yet, it will repeat the access attempt after the
specified waiting time; but the maximum cycle times cannot
exceed Mmax.
� Influence on the network performance: If this parameter is set
too small, the UE access success rate will be influenced; if it is
set too big, the UE will probably try access attempt repeatedly
within a long time, which will increase the uplink interference.
Course ContentsCourse Contents
Random access procedure
RRC setup procedure
RAB setup procedure
RRC Setup ProcedureRRC Setup Procedure
Parameters optimizationParameters optimization
� T300 and N300
� DPDCH Power Control Preamble Length (PCPreamble)
� Successive Synchronization Indication Times (NInSyncInd)
� Successive Out-of-sync Indication Times (NOutSyncInd)
� Radio Link Failure Timer Duration (TRLFailure)
� N312 and T312
� N313, N315, T313
T300 and N300T300 and N300
� After the UE transmits RRC CONNECTION REQUEST message, the T300
timer will be started, and the timer will be stopped after the UE receives RRC
CONNECTION SETUP message. Once the timer times out, if RRC
CONNECTION REQUEST message is retransmitted less than the number of
times specified by the constant N300, the UE repeats RRC CONNECTION
REQUEST; otherwise it will be in the idle mode.
� Influence on the network performance : The T300 setting should be
considered together with the UE, UTRAN processing delay and the
propagation delay. The bigger T300 is, the longer time the UE T300 will wait
for. The bigger N300 is, the higher success probability of the RRC connection
setup will be, and the longer RRC setup time will probably be. It will likely be
that a UE repeats the access attempt and the connection setup request
transmission, and consequently other users will be influenced seriously.
PCPreamblePCPreamble
� PCPreamble defines the lasting time of DPCCH transmission by the UE
before the UE transmits DPDCH.
� Influence on the network performance : At first, this parameter has been
originally used in the uplink and downlink power control convergence to
prevent the uncontrollable power of the UE at the beginning. Later, it was
considered in some proposals that NodeB needs some time to find the uplink
signal after the UE starts DPCCH transmission. This delay depends on the
searching process and the propagation delay. It makes no sense to start the
uplink DPDCH transmission process before the end of this process, because
the data cannot be received normally at this time, and data loss will occur; or,
if it is the confirmation mode, the retransmission may cause more serious data
delay. If this parameter is set improperly, it will lead to data loss and
retransmission delay, which will consequently influence the service rate and
the transmission delay.
NInSyncIndNInSyncInd
� This parameter defines the successive synchronization indication times
required for the NodeB to trigger the radio link recovery process. The radio link
set remains in the initial state until it receives NInsyncInd successive
synchronization indications from L1, then NodeB triggers the radio link
recovery process, which indicates that the radio link set has been
synchronized. Once the radio link recovery process is triggered, the radio link
set is considered to be in the synchronized state.
� Influence on the network performance : The bigger this parameter is, the
stricter the synchronization process will be, and the more difficult the sync will
be; the smaller it is, the easier the synchronization will be. However, if the link
quality is bad, a simple synchronization requirement will lead to the waste of
the UE power and the increase of uplink interference; in the radio link
maintenance process, this parameter is used together with the successive out-
of-sync indication counter.
NOutSyncIndNOutSyncInd
� NOutSyncInd defines the successive out-of-sync indication times that are
required to receive to start the timer TRlFailure. When the radio link set is in
synchronized state, the NodeB will start the timer TRlFailure after it receives
NOutsyncInd successive out-of-sync indications. The NodeB should stop and
reset the timer TRlFailure after receiving NInsyncInd successive sync
indications. If the timer TRlFailure times out, the NodeB will trigger the radio
link failure process, and indicate the radio link set that is out-of-sync.
� Influence on the network performance : If this parameter is set too small, the
link out-of-sync decision will be likely to occur; if it is set too big, out-of-sync
will not be likely to occur, but, if the link quality is bad, it will result in waste of
the UE power and increased uplink interference. In the radio link maintenance
process, this parameter is adopted together with the successive
synchronization indication counter.
TRLFailureTRLFailure
� This value defines the timer TRlFailure duration. When the radio link set is in
synchronized state, NodeB should start the timer TRlFailure after it receives
NOutsyncInd successive out-of-sync indications; and NodeB should stop and
reset the timer TRlFailure after receiving NInsyncInd successive sync
indications. If the timer TRlFailure times out, NodeB will trigger the radio link
failure process, and indicate the radio link set that is out-of-sync.
� Influence on the network performance : If the timer is set too short, there will
few chances for link synchronization; if it is set too long, the radio link failure
process will probably be delayed, and the downlink interference will be
increased.
N312 and T312N312 and T312
� When the UE starts to set up the dedicated channel, it starts the T312 timer,
and after the UE detects N312 synchronization indications from L1, it will stop
the T312 timer. Once the timer times out, it means that the physical channel
setup has failed.
� Influence on the network performance : The bigger N312 is, the more
difficult the dedicated channel synchronization will be; the longer T312 is, the
bigger the synchronization probability will be, but the longer the
synchronization time will be.
N313, N315, T313N313, N315, T313
� After the UE detects N313 successive out-of-sync indications from L1, it will
start the T313 timer. And after the UE detects N315 successive sync
indications from L1, it will stop the T313 timer. Once the timer times out, the
radio link fails.
� Influence on the network performance : The bigger N313 is, the more
difficult it will be to start T313, which will reduce the out-of-sync probability; the
smaller N315 is, the longer T313 will be, and the bigger the link recovery
probability will be. These three parameters should be used together.
Course ContentsCourse Contents
Random access procedure
RRC setup procedure
RAB setup procedure
RAB Setup ProcedureRAB Setup Procedure
Appendix: MOC signaling processAppendix: MOC signaling process
D o w nlink S y nch ro nisa t io n
U E N o d e BS e rving R N S
S e rvingR N C
D C H -FPD C H -FP
R R CR R C C C C H : R R C C o nne c t io n R e q ues t
N B A P R a d io L ink S e tup R esp o nse
N B A P
N B A P R a d io L ink S e tup R e q ue st
C C C H : R R C C o nne c t io n S e tup
S ta rt R X
S ta rt T X
R R C
R L C
R R CD C C H : R R C C o nne c t io n S e tup C o m p le te
D C H -FPD C H -FPU p link S y nch ro nisa t io n
N B A P
Q .A A L 2Q .A A L 2
Q .A A L 2 E sta blish R e q ue st
E sta blish C o nf irm
Inita l D irec t T ra nsfe r
C N
D C C H :R R C
R L C
R R C
R R C
R R C
Q .A A L 2
D C C H : R R C C o nnec t io n S e tup C o m p le te a c k
In ita l D irec t T ra nsfe r
Appendix: MOC signaling processAppendix: MOC signaling process
Inital Direct Transfer
RRC
RANAPRANAP
UE Node BServing RNS
ServingRNC CN
Initial UE Message
RANAPRANAP
DCCH
Direct Transfer
RANAPRANAP Direct Transfer
:
Direct Transfer DCCH ::
Direct Transfer DCCH ::
RRCDownlink
RRC
RRC
Uplink
RRC
RRC
RRC
(CM Service Request)
(CM Service Accept)
(Setup)
DCCH :
DCCH : Downlink
Uplink
Direct Transfer
Direct Transfer RRCRRC
RRC
RRC
RRC
RANAPRANAP Direct Transfer
(Call Proceeding)
Inital Direct Transfer
Appendix: MOC signaling processAppendix: MOC signaling process
UE Node BServing RNS
ServingRNC CN
DCCH :
DCCH :Downlink
Uplink
Direct Transfer
Direct Transfer
RRCRRC
RRC
RRC
RRC
RAB Assignment RequestRANAPRANAP
Establishment( )
Q.AAL2Q.AAL2
Q.AAL2 Establish Request
Establish Confirm
Q.AAL2
NBAPPrepare
NBAPRadio Link Reconfiguration
NBAPRadio Link ReconfigurationNBAPReady
Appendix: MOC signaling processAppendix: MOC signaling process
UENode B
Serving RNS ServingRNC
CN
DCCH : Radio Bearer Setup
DCCH : Radio Bearer Setup Complete
Q.AAL2Q.AAL2
Q.AAL2 Establish Request
Establish Confirm
Q.AAL2
Downlink Synchronisation
Uplink Synchronisation
Radio Link Reconfiguration
NBAP
NBAP
NBAP
NBAP
NBAP
NBAP
Apply new transport format set
RRC
RRC
RRC
RRC
RAB Assignment ResponseRANAP RANAPEstablishment( )
Commit
DCCH : Radio Bearer Setup Complete ackRLCRLC
Appendix: MOC signaling processAppendix: MOC signaling process
UENode B
Serving RNS ServingRNC
CN
RRC
RANAPRANAP Direct Transfer
RRC
RANAPRANAP Direct Transfer
(Alerting)
(Connect)
RRC
RRC
RANAPRANAP Direct Transfer
(Connect Acknowledge)
RRC
RANAPRANAP Direct Transfer
(Rlease Complete)
RANAPRANAP Direct Transfer
(Release)
RANAPRANAP Direct Transfer (Disconnect)
RRC
DCCH ::
DCCH ::
Downlink
Uplink
Direct Transfer
Direct Transfer
RRC
RRC
DCCH :: Downlink
DCCH :: Downlink
Direct Transfer RRC
DCCH :: UplinkRRC Direct Transfer
Direct Transfer RRC
DCCH :: Uplink Direct Transfer RRC
Appendix: MOC signaling processAppendix: MOC signaling process
UENode B
Serving RNS ServingRNC
CN
RANAPRANAP
RANAPRANAP
Iu Release Command
Iu Release Complete
Q.AAL2Q.AAL2
Q.AAL2Q.AAL2 Release Request
Release Complete
Q.AAL2Q.AAL2
Q.AAL2Q.AAL2 Release Request
Release Complete
DCCH : RRC Connection
DCCH : RRC Connection
Release
ReleaseComplete
NBAP Radio Link Deletion
NBAP Radio Link Deletion
NBAP
NBAPComplete
SummarySummary
� Random access procedure: physical channels, detailed
random access procedure, access parameters optimization.
� RRC setup procedure and parameters optimization.
� RAB setup procedure and the whole UE outgoing call
procedure.