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Huawei Technologies Co. Ltd.
Product Version ConfidentialityV100R001 For internal use
onlyProduct Name: WCDMA RNP Total pages: 83
WCDMA RNO Access Procedure
Analysis GuidanceFor internal use only
Prepared by URNP-SANA Date 2003-05-24Reviewed by DateReviewed by DateApproved by Date
Huawei Technologies Co., Ltd.All rights reserved
HUAWEIHUAWEI
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Revision Record
Date Revision
Version
Description Author
2003-05-24 1.00 Initial issued Chen Qi
2003-06-03 1.00 Revision based on the review comments Chen Qi
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4.7.2 Parameters to be Analyzed and Adjusted in the Access Procedure ........................................ 485 Analysis of Problems in Access Procedure .............................................................................................. 485.1 UE Failing in Cell Search .................................................................................................................... 485.2 UE Failing in Cell Access or Receiving RRC Connection Rejection ................................................. 485.3 RNC Failing in Receiving the RRC_CONNECTION_REQ Message Transmitted by UE ................ 48
5.4 UE Failing in Receiving the RRC_CONNECTION_SETUP Message Transmitted by RNC ............ 495.5 UE Failing in Receiving ACK Message Indicating RRC Connection Completion ............................ 49
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List of Tables
Table 1 S criteria parameter description .................................................................................................... 9
Table 2 Cell reselection parameter description ......................................................................................... 15Table 3 Description of the parameters of cell reselection in system information broadcasts .......................... 15Table 4 Relation between access subchannel and access slot and SFN ..................................................... 21Table 5 System information block ........................................................................................................... 23Table 6 Parameters to be analyzed and adjusted in the access procedure .................................................. 49
List of Pictures
Figure 1 Number of RACH access slots and interval between them ............................................................. 17Figure 2 Structure of random access transmission ..................................................................................... 18Figure 3 PRACH-AICH timing relation from the view of UE ......................................................................... 19Figure 4 Definition of access slot set (with the example of uplink/downlink access slot fixed differencep-a
7680chips) 22Figure 5 System information structure ...................................................................................................... 23Figure 6 RRC signalling connection setup process .................................................................................... 33Figure 7 RRC CONNECT REQUEST ....................................................................................................... 35Figure 8 RRC CONNECT SETUP (DCCH is mapped on common channel) ................................................. 36Figure 9 MappingInfo of SRB1 and SRB2 of the DCCH mapped to the common channel .............................. 38Figure 10 RRC CONNECT SETUP COMPLETE (DCCH is mapped on the common channel .......................... 39Figure 11 RRC CONNECT SETUP (DCCH is mapped to the dedicated channel ............................................ 40Figure 12 MapingInfo of SRB1 and SRB2 of the DCCH mapped to the DCH .................................................. 42Figure 13 RRC CONNECT SETUP COMPLETE (DCCH is mapped to the DCH) ............................................ 42
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WCDMA RNO Access Procedure Analysis Guidance
Key words: Access procedure, cell search, cell selection and reselection, random accessAbstract: This document analyzes in detail the whole access procedure from the view of access
stratum (AS), discusses access performance indices and influence factors, and
presents the analysis process of access procedure in the actual network planning and
the solutions to the possible problems in the access.
Acronym list: Omitted.
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1 Access Procedure
UE can run in one of these two basic modes: idle mode and connected mode. After the UE is
powered on, it keeps in idle mode and is differentiated through non AS identities, such as IMSI,
TMSI or P-TMSI. The UTRAN does not store the information of the UE in idle mode, but it can
page all UEs which are powered on and camp on the cell one by one, or page all the UEs in idle
mode in an RNC at the same time. Only after the UE finishes the RRC connection setup will it
enter to connected mode (CELL_FACH or CELL_DCH state) from idle mode. When the RRC
connection is released, it will enter idle mode from connected mode.
Viewing from the AS, access procedure is the procedure of a transition from idle mode to
connected mode of the UE. It includes four basic procedures: cell search, cell system information
broadcast receiving, cell selection and reselection, and random access. Once the UE enters
connected mode, it can carry out such non AS activities as PLMN selection and reselection,
location registration, service application and authentication. This document summarizes all the
steps in the UE access procedure, analyzes the signalling and performance of the whole access
procedure, and discusses the analysis methods for the access procedure and the solutions to the
problems in the drive test based on the analysis.
1.1 Cell Search
UE will search cell according to one of the following procedure:
UE is independent of the information of the RF channel of UTRA carrier frequency. In this
case, UE will scan all frequencies in all UTRA bands to locate a suitable cell to camp on in the
selected PLMN. In each carrier frequency, UE only needs to search the best serving cell.
UE has the stored UTRA carrier frequency information and cell parameter information which
obtained from measurement control information received before, such as primary scrambling
code of cell. In this case, UE will attempt to camp on this cell directly. If it fails, it can only scan all
frequencies in all UTRA bands to locate a suitable cell in the selected PLMN.
The procedure of carrying out cell search is as follows (Of course, a frequency locked first):
1.1.1 Step 1: Slot Synchronization
All primary SCH synchronization codes in the UTRAN are identical and are transmitted in the
former 256 chips of each slot. The synchronization codes of each slot are the same. The UE can
achieve slot synchronization easily by using a matched filter or the similar technology.
1.1.2 Step 2: Frame Synchronization and Scrambling Code Group Identification
Frame synchronization is realized by means of secondary SCH synchronization. There are
16 secondary SCH synchronization codes in all, which are different in each slot. They form 64
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groups of code sequences according to different code words in each slot. The 64 groups of code
sequences feature that the result after any cyclic shift is unique. The UE can perform SSC
correlation calculation, FWHT and RS decoding to determine the cell scrambling group and
achieve frame synchronization.
1.1.3 Step 3: Cell Primary Scrambling Code Identification
In the above step the UE got the scrambling code group which contains 8 primary scrambling
codes of the local cell. Then the UE performs correlation calculation based on symbol until it finds
the one with the biggest correlation value, so as to determine the primary scrambling code. After
getting this code word, the UE can read the information of the broadcast channel since both
CPICH and PCCPCH use this scrambling code and their channelization codes are fixed.
1.2 Cell Selection and Cell Reselection
Once the UE is powered on, it will determine whether the current PLMN is suitable or not
according to the system information after it finds a cell. If the PLMN is suitable, it performs cell
measurement and determines whether the current cell is suitable to camp on according to the S
criteria, this is the cell selection procedure. If the current cell cannot meet the S criteria, it will start
the procedure of PLMN selection and cell reselection (It carries out cell reselection in the current
PLMN first. In case of no suitable cell, it carries out PLMN search and goes to another PLMN for
cell reselection and cell selection), and then performs the adjacent cell measurement. Thereafter,
it sequences the cells under measurement according to the R criteria or H criteria, and it then cancamp on the one meeting the S criteria. Of course, cell selection and reselection are not always
carried out during power-on. This procedure will be triggered by other reasons.
1.2.1 Cell Selection
This section introduces the triggering occasions and cell selection procedure, as well as the
criteria for determining Suitable Cell.
1.2.1.1 Triggering occasions:
The UE initiates cell selection in the following cases:
UE power-on
Returning to idle mode from connected mode
cell information lost in connected mode
Failure in finding cell to camp on normally in the cell reselection based on the cell list
provided in the measurement control system information (TS25.133)
1.2.1.2 PLMN selection
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If the UE has obtained the PCCPCH scrambling code from step 3 in Section 1.1, and the
PCCPCH channelization code (SF (ch,256,1)) is known, which is unique in the whole UTRAN, the
UE can read the information of the broadcast channel.
The MIB scheduling information is known, that is, SIB_POS=0 and SIB_REP =8. The UE canread MIB in the radio frame of the SFN in the value range of (0,8,16, ....). How does UE acquire
SFN? If the SYSTEM INFORMATION message is transmitted on BCH (PCCPCH), the first field of
this message is SFNprime whose value is the initial SFN corresponding to this transport block.
The value range is (0, 2, 4, 6, ..., 4094), but it is (0..2047) after the PER encoding. In this case,
one bit can be saved. Why are the SFN values 0, 2, 4, ...? Because the BCH TTI is 20ms,
including two radio frames. Therefore the step length of the SFNprime field can be 2 only.
After reading MIB, the UE can determine whether the current PLMN is the one wanted,
because the MIB contains the PLMN identity field. If this is the case, the UE will find other SIBsand acquire their contents according to the schedulding information of other SIBs in the MIB.
Otherwise, the UE must find another frequency and start this procedure from the beginning,
namely, cell search.
1.2.1.3 Determing Criteria (S criteria)
If the current PLMN is the one wanted, the UE will read SIB3 to acquire Cell selection and
re-selection info, and read Qqualmin , Qrxlevmin and Maximum allowed UL TX power
(UE_TXPWR_MAX_RACH ) in the IE of Cell selection and re-selection info for SIB3/4 , and
then determine whether the current cell is suitable to camp on according to S criteria.
S criteria:
Srxlev > 0 AND Squal > 0
Where:
Squal = Q qualmeas Qqualmin
Srxlev = Qrxlevmeas
- Qrxlevmin - Pcompensation
Table 1 S criteria parameter description
Parameters Description
Squal It is the quality evaluation value for cell selection, in dBs. It is not suitable for
the TDD and GSM mode. Squal is only used for the FDD cell with the CPICH
Ec/Io as the measurement value.
Srxlev It is the cell selection RX level value, in the unit of dBm.
Qqualmeas It is the cell quality measurement value. The quality of the received signal is
represented by CPICH Ec/Io. This parameter is used for the FDD mode only.
Q rxlevmeas It is the measurement value of cell receiving level, in the unit of dBm. This
parameter is suitable for CPICH RSCP of the FDD cell, the P-CCPCH RSCP
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in the TDD cell and the TXLEV of GSM.
Qqualmin It refers to the minimum quality requirement for cell, in dBs. It is not suitable
for TDD or GSM.
Qrxlevmin It refers to the minimum requirement for cell receiving level, in the unit of
dBm.Pcompensation It is the max value of (UE_TXPWR_MAX_RACH P_MAX, 0), in the unit of
dBm.
UE_TXPWR_MAX_RACH It refers to the maximum transmit power of the UE in the RACH of the cell, in
the unit of dBm.
P_MAX It refers to the maximum output power of the UE, indicating the capability of
the UE, in the unit of dBm.
If a cell meets the S criteria, the UE will take this cell as a suitable cell and camp on it, and
then read other system information required. Hereafter, the UE initiates the location registration
procedure.
If the cell does not meet the S criteria, the UE will read SIB11, Measurement control system
information, Intra-frequency measurement system information, Intra-frequency cell info list, cell
info, Primary CPICH info, Reference time difference to cell and Cell Selection and Re-selection
info for SIB11/12. In CPICH info, the UE can get the primary scrambling code. Since the channel
code of CPICH is unique in the whole UTRAN, the UE can measure Qqualmeas and Q rxlevmeas of the
adjacent cell easily (but it requires slot synchronization and frame synchronization) based on the
primary scrambling code and the reference time difference to cell. Moreover, in the IE of Cell
Selection and Re-selection info for SIB11/12 , the UE can know the Maximum allowed UL TX
power , Qqualmin and Qrxlevmin of the adjacent cell, so that it can calculate the Squal and
Srxlev of the adjacent cell to determine whether the adjacent cell meets the above selection
criteria or not.
The UE can also read Inter-frequency measurement system information, Inter-frequency cell
info list, frequency info and cell info, and the Cell info is the same as above. The Frequency info
contains UARFCN uplink (Nu) and UARFCN downlink (Nd) . Based on all the above information,
the UE can work out Squal and Srxlev of the adjacent cell and determine whether it meets the S
criteria or not.
If the UE cannot find any cell meeting the S criteria, it will consider there is no coverage and
go on with the PLMN selection and reselection procedure.
In idle mode, the UE needs to monitor the signal quality of the current cell and adjacent cell
all the time to select the best serving cell to acquire the service. This is the cell reselection
procedure.
If the UE finds an adjacent cell meeting the selection criteria, it will camp on this cell and read
other system information required. Then the UE will start the random access and initiate the
location registration procedure.
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1.2.2 Cell Reselection
The UE will fulfill the following tasks when it is in normal residence state in the UTRAN:
Monitoring PCH and PICH according to indication of system information;
Monitoring relevant system information;
Carrying out cell measurement procedure to provide data for the cell reselection evaluation
procedure;
The following is the introduction to the triggering occasions and measurement rules of cell
reselection, as well as the criteria for cell reselection evaluation.
1.2.2.1 Triggering occasions
The UE initiates cell reselection in the following cases:
Time triggering in idle mode (with the quality measurement value of the current service cell
being smaller than intra-frequency measurement threshold)
When the UE in idle mode cannot find any service cell meeting the S criteria within Nserv
DRXs (in spite of the setting in system information)
When the UE detects that it is in a non -service area
1.2.2.2 Measurement rules
Measurement rules for non Hierarchical Cell Structure (HCS) cells
If the cell broadcast system information indicates that the HCS is not adopted, the UE
decides to perform the corresponding measurement according to the following rules: (Note: in the
CPICH Ec/Io measurement status, Squal corresponds to Sx , in the CPICH RSCP measurement
status, Srxlev corresponds to Sx )
Intra-frequency measurement
If Sx>S intrasearch, UE does not need to perform intra-frequency measurement.
If SxS intrasearch, UE does not need to perform inter-frequency measurement.
If Sx
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If system information does not contain S intrasearch , UE need to perform inter-frequency
measurement in all cases.
Inter-system measurement
If Sx>Ssearch RATm , UE does not need to measure system m.
If Sx
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IF (Srxlev s
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R s = Q meas ,s + Qhyst s
R n = Q meas ,n - Qoffset s,n - TO n * (1 L n)
Where:
TOn = TEMP_OFFSETn * W(PENALTY_TIMEn Tn)
Ln = 0 if HCS_PRIOn = HCS_PRIOsLn = 1 if HCS_PRIOn HCS_PRIOs
W(x) = 0 for x < 0W(x) = 1 for x >= 0
The parameter TEMP_OFFSET n , defined for the H criteria and R criteria, is the offset of the
adjacent cells within the PENALTY_TIME n . The two parameters of TEMP_OFFSET n and
PENALTY_TIME n are suitable for the HCS cells only (which are designated in the system
information).
Each adjacent cell is assigned with a timer T n, which will be reset when the following
conditions are met:
If HCS_PRIO n HCS_PRIO and Q meas_LEV ,n > Qhcs n
Or
If HCS_PRIO n = HCS_PRIO and
if the measurement value is set to CPICH RSCP for the FDD cell and the adjacent cells,
Qmap,n > Q map ,s + Qoffset1 s,n
if the measurement value is set to CPICH Ec/No for the FDD cell and the adjacent cell
Qmeas_LEV,n > Q meas_LEV ,s + Qoffset2 s,n
for other types of cells:
Qmap,n > Q map ,s + Qoffset1 s,n
If the above conditions are not met, Tn should stop counting immediately. TQn is valid only
when Tn is counting; otherwise, it should be set to 0.
The cell reselection procedure and Tn are still valid after the UE selects a new cell, unless the
above conditions are not met or the cell is not the adjacent cell of the selected cell any more.
However, the system information of the new system after the new cell is selected should be used
to evaluate the above criteria.
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Table 2 Cell reselection parameter description
Parameters Description
Sn The cell selection value of adjacent cells (db)
Qmap,s It is the quality mapping value of the service cell, including the CPICH RSCP
and CPICH Ec/No in the FDD mode, CPICH P-CCPCH RSCP in the TDD
mode and the RXLEV of the GSM. The parameters of the mapping functions
are provided by thecell_selection_and_cell_quality_measure section of the
system information.
Qmap,n It is the quality mapping value of the service cell, including the CPICH RSCP
and CPICH Ec/No in the FDD mode, CPICH P-CCPCH RSCP in the TDD
mode and the RXLEV of the GSM. The parameters of the mapping functions
are provided by thecell_selection_and_cell_quality_measure section of the
system information.
Qmeas_lev It is the quality value of the signal received provided in the
cell_selection_and_cell_quality_measure section of the system information.
It is represented by in CPICH RSCP the FDD mode, and P-CCPCH RSCP in
the TDD mode and RXLEV in the GSM.
The UE sequences these cells meeting the S criteria according to the R criteria:
The cells with the highest HCS_PRIO meeting the H criteria, that is, H is greater than or
equal to 0. This is not for the case when the UE is in the fast moving mode.
If HCS is not considered, or no cell meets the H criteria, the UE will sequence all cells.
In all the cases, a cell will be selected only when it meets all the criteria above within the time
of Treselect .
Table 3 Description of the parameters of cell reselection in system information broadcasts
Parameters Description
Qoffset1s,n It is the offset between two cells, used for the CPICH RSCP in the TDD, GSM
and FDD mode.
Qoffset2s,n It is the offset between two cells, used for the CPICH Ec/No in the TDD, GSM
and FDD mode.
Qhyst1s It is the hysteresis value, used for the CPICH RSCP in the TDD, GSM and
FDD mode.
Qhyst2 It is the hysteresis value, used for the CPICH Ec/No in the TDD, GSM and
FDD mode.
HCS_PRIOs, HCS_PRIO It is the priority assigned to service cell and adjacent cell, in the value range of
(0-7).
Qhcss, Qhcsn It is the quality threshold of the service cell and adjacent cell in the cell
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reselection in HCS.
Qqualmin It is the minimum quality standard designated to the cell, in the unit of db. It is
used for CPICH Ec/No of FDD only.
Qrxlevmin It is the minimum receiving level, in the unit of dBm, TEMPORARY_OFFSET1n
PENALTY_TIMEn It refers the time duration for which the TEMPORARY_OFFSETn is applied for
a neighbouring cell.
TEMPORARY_OFFSET1n It is the offset of applying the H and R criteria within the penaltiy time, used for
the CPICH RSCP in the TDD, GSM and FDD mode.
TEMPORARY_OFFSET2n It is the offset of applying the H and R criteria within the penalty time, used for
the CPICH Ec/No in the FDD mode.
TCRmax It indicates the maximum time spent for cell reselection.
NCR It is the maximum times of cell reselection
TCRmaxHyst It refers to the hysteresis time for the UE resumes to the normal mode from the
high-speed moving mode.
Treselections It indicates the value of the cell reselection counter (for designating the
hysteresis time for cell reselection)
SsearchHCS It specifies the threshold for the UE to perform measurement on the adjacent
cell when HCS is adopted.
SsearchRAT 1 - SsearchRAT k It specifies the threshold for the startup of the measurement on the system
RATm.
SHCS,RATm It specifies the threshold for the UE to perform inter-system measurement on
the adjacent cell when HCS is adopted.
Sintrasearch It specifies the threshold for intra-frequency measurement. It is used in the
HCS measurement criteria.
Sintersearch It specifies the threshold for inter-frequency measurement. It is used in the
HCS measurement criteria.
Slimit,SearchRATm It indicates the measurement criteria for cell reselection in HCS. It is used to
designate the time when the UE starts up the inter-system measurement
(RATm) on the adjacent cell.
1.3 Random Access
Random access procedure is the procedure when an MS requests access to the system,
receives the response of the system and is allocated with dedicated channel. (Note: If the RRC
connection is set up on the common control channel (CCCH), the system does not need to
allocate DCCH. If the RRC connection is set up on the dedicated control channel (DCCH), the
system needs to allocate DCCH). This procedure is attached once the MS is powered on, and will
be detached when the MS is powered off, location area update, routing area update, and
signalling connection setup process for executing any service. The 3GPP 25.211 protocol defines
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the random access channel (RACH) and physical random access channel (PRACH), as well as
the frame structure of the access channel and physical-layer timing relation. The 3GPP 25.213
defines the spread spectrum demodulation of the domudulation and message parts (data and
control) of the access channel preamble code, as well as the preamble code, scrambling code
and spread code. The 3GPP 25.214 protocol defines the access procedure. The following are the
further description of these contents.
1.3.1 Random Access Channel
RACH, an uplink common transport channel, maps to PRACH, which is an uplink physical
common channel. RACH is always received by NodeB in the whole cell. It features collision and
adopting open loop power control.
The RACH transmission is based on a Slotted ALOHA approach with fast acquisition
indication (AI). The MS can start the transmission at a pre-defined time offset, which is
represented by an access slot. Two 10-ms radio frames constitute a 20ms access frame, which
are divided into 15 access slots, with an interval of 5120 chips (with the time of 1.332ms). Figure 1
shows the timing information and AI on the access slot, as well as the number of access slots and
the interval between them. The high-layer signalling indicates the access slot whose information
is available in the current cell.
Figure 1 Number of RACH access slots and interval between them
The user can initiate random access transmission at the start time of each access slot. Figure
2 shows the structure of the random access transmission, which is composed of one or more
message parts of 10ms or 20ms in length.
#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
ccess slot
Random Access Transmission
Random Access Transmission
Random Access Transmission
Random Access Transmission
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Figure 2 Structure of random access transmission
The preamble of the random access is 4096 chips, including 256 repetitions of a 16-chip
signature. There are 16 different signatures in all.
The 10-ms message of random access is divided into 15 slots, each of which is 2560 chips in
length. Each slot includes two parts, one is data part, which the RACH transport channel maps to;the other is the control part, which is used to transport the L1 control information. The data and
control parts are transmitted simultaneously in code multiplexing mode. A 10-ms message part is
composed of one radio frame, and a 20-ms message part is composed of two continuous 10-ms
radio frames. The length of the message part can be determined by the signature and/or access
slot used. This is configured by the high layer.
The data part includes 10*2 k bits, where, k=0, 1, 2, 3. The data part of the message
corresponds to the spread factors of 256, 128, 64 and 32.
The control part includes eight known pilot bits (used for supporting the channel estimation
for correlation detection) and two TFCI bits. For the message control part, this corresponds to the
spread factor of 256. For the pilot bit pattern, refer to the 3GPP TS 25.211 protocol. The total
number of TFCI bits in the access message is 15 2, that is 30. The TFCI value corresponds to
the transport format of the current random access message. When the PRACH message part is
20ms in length, the TFCI will repeat in the second radio frame.
The downlink AICH is divided into downlink access slots, each of which is 5120 chips in
length. The downlink access slot is aligned with the PCCPCH in terms of time. The uplink PRACH
is divided into uplink access slots, each of which is 5120 chips. The nth uplink access slot are
transported the p-a chips before the UE receives the nth downlink access slot (where n=0,
1, 14). The downlink AI is transmitted at the beginning of the downlink access slot. Similarly, the
preamble and message part of the uplink RACH are transmitted at the beginning of the uplink
access slot. Figure 3 shows the PRACH/AICH timing relation.
Message partPreamble
4096 chips10 ms (one radio frame)
Preamble Preamble
Message partPreamble
4096 chips 20 ms (two radio frames)
Preamble Preamble
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Figure 3 PRACH-AICH timing relation from the view of UE
The preamble-preamble code distance p-p should be greater than or equal to the minimum
preamble-preamble code distance p-p,min , that is p-p p-p,min .
The distance from the preamble to the AI p-a , and the distance from the preamble to the
message p-m are as shown below:
When AICH_Transmission_Timing is set to 0, then
p-p,min = 15360 chips (3 access slots)
p-a = 7680 chips
p-m = 15360 chips (3 access slots)
When AICH_Transmission_Timing is set to 1, then
p-p,min = 20480 chips (4 access slots)
p-a = 12800 chips
p-m = 20480 chips (4 access slots)
The parameter AICH_Transmission_Timing is provided through the signalling mode.
1.3.2 Random Access Procedure
After the physical layer of the UE receives the PHY-DATA-REQ primitive request of the MAC
sublayer, the UE will start the physical random access procedure. Refer to the 3GPP TS 25.321
protocol.
Before the physical random access procedure is initiated, the layer 1 (physical layer) of the
UE should be able to receive the following system information from the high layer of the UE (RRC
layer):
Scrambling code of the preamble part
Length of the message part, 10ms or 20ms
One access slot
p-a
p-mp-p
Pre-amble
Pre-amble Message part
Acq.Ind. AICH access
slots RX at UE
PRACH accessslots TX at UE
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The value of AICH_Transmission Timing (0 or 1)
The signature set and RACH access subchannel group set assigned for the SN of each ASC
(access subchannel)
The parameter of Power_Ramp_Step (integer > 0)
The parameter of Preamble_Retrans_Max (integer > 0)
The parameter of Preamble_Initial_Power
The power used for the last preamble transmission and the offset of the transmission power
of the control part in the random access message P p-m = P message-control P preamble , in the unit
of dB.
TFS parameters, including the power offset of the data part and control part of the random
access message for every transmission format.
Please note that the above parameters may be updated by the high layer before the physical
random access procedure is initiated every time.
In addition, before the physical random access procedure is initiated, layer 1 should be able
to receive the following information from the MAC layer:
The transmission format used for the PRACH message part
ASC transmitted by PRACH
Data to be transmitted (TBS)
When initiating the physical random access, the UE needs to operate according to the
following procedure:
Step 1: It determines the available RACH access subchannel set according to the
designated ASC and the available uplink access slot set in the next complete access slot set
(SFN mod 2 = 0 and SFN mod 2 = 1, where the former one is called access slot set 1, and the
latter one is called access slot set 2), and then selects one uplink access slot randomly. The rule
for random selection is equal probability selection. If no access slot set is available currently, it
selects one in the next access slot set at random.
Step 2: It selects the signature randomly from the signature set according to the designated
ASC. The rules for random selection are equal probability selection.
Step 3: It sets the initial value of the preamble retransmission counter to
Preamble_Retrans_Max .
Step 4: It sets the parameter Commanded Preamble Power to Preamble_Initial_Power.
Step 5: If the value of Commanded Preamble Power exceeds the largest allowed value, it
will set the transmission power of the preamble to the maximum allowed transmission power. If
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the value of Commanded Preamble Power is less than the minimum value required (specified in
the 3GPP TS 25.101 protocol), it will set the transmission power of the preamble to the current
calculation value (which may be greater than, less than or equal to the Commanded Preamble
Power ). Otherwise, it sets the transmission power of preamble to Commanded Preamble Power .
It transmits the preamble by using the selected uplink access slot, signature and preamble
transmission power.
Step 6: It waits for the NodeB to return an acknowledgement for the used signature. If the UE
cannot detect the AI of +1 or -1 on the downlink access slot with the same number as the uplink
access slot used for transmitting preamble, it will select an available uplink access slot at random.
Then it adds Commanded Preamble Power according to the power ramp step P p-m =
P message-control P preamble , and then subtract the preamble reset counter by 1. If Commanded
Preamble Power is greater than the maximum power threshold 6dB, the UE will report the status
of layer 1 (No ack on AICH) to the MAC layer, and then exit the physical random access
procedure. Thereafter, if the value of the retransmission counter is greater than 0, repeat Step 6;
otherwise, report the status of layer 1 (No ack on AICH) to the MAC layer, and exit the physical
random access procedure
Step 7: If the received value of AI for UE is -1, it will report the status of layer 1 (No ack on
AICH) to the MAC layer, and then exit the physical random access procedure.
Step 8: If the received value of AI for UE is +1, it will transmit the random access message
part three or four uplink access slots after the last time of preamble transmission according to thevalue of AICH_Transmission_Timing . The transmission power of the control part of the random
access message should be P p-m higher than the power for the last preamble transmission. For
that of the data part, refer to the protocol.
From the view of the operation flow of the random access procedure, the UE needs to
transmit preamble before initiating an access, and then waits for the acknowledgement from
NodeB. Then the NodeB detects the preamble transmitted by the UE in each uplink slot. It will
return an AI through the AICH channel if it finds a preamble. The UE detects AI in a specific
downlink access slot after transmitting the preamble. If it receives a permission AI, it continues to
transmit the message part, so as to complete a physical random access. If it does not receive any
AI, the UE will r epeat the handshake process of transmit preambledetect AI for N times (preset),
and start transmitting the message part, to complete a physical random access. If the UE receives
a rejection AI, it will exit this random access procedure, and then report the status. The message
of the random access message part includes the flag information of the UE, the service type
requested, and so on.
The following shows the access subchannels and the definitions of access slot sets, with the
following example:
Table 4 Relation between access subchannel and access slot and SFN
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SFN modulo 8 of
corresponding P-CCPCH
frame
Subchannel number
0 1 2 3 4 5 6 7 8 9 10 11
0 0 1 2 3 4 5 6 7
1 12 13 14 8 9 10 112 0 1 2 3 4 5 6 7
3 9 10 11 12 13 14 8
4 6 7 0 1 2 3 4 5
5 8 9 10 11 12 13 14
6 3 4 5 6 7 0 1 2
7 8 9 10 11 12 13 14
AICH access
slots
10 ms
#0 #1 #2 #3 #14#13#12#11#10#9#8#7#6#5#4p-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
Figure 4 Definition of access slot set (with the example of uplink/downlink access slot fixed differencep-a 7680chips)
2 Signalling Messages of Access Procedure
Before the access procedure, the UE needs to receive the cell system information broadcast
message of the UTRAN. The following is the introduction to the meanings and applications of
these signalling messages and information elements (IE).
2.1 System Information Broadcast2.1.1 System Information Structure
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Figure 5 System information structure
System IEs are broadcast in system information block (SIB). The system IEs with the same
character are combined to an SIB. Different SIBs may have different characters, for example, the
periodical repetition rate and the requirement on SIB re-read of the UE.
The system information is organized as a tree, as shown in Figure 5. As the reference of
large numbers of SIBs in a cell, the primary information block contains the sequence of these
SIBs. The upper level SIB functions the same on the blocks of the lower level. The referenced SIBmust have the same function range and update mechanism with the SIBs of the upper level.
Some SIBs may be present for several times with different contents. In this case, the
sequence for each present of the SIBs must be provided. At presently, this is only suitable for the
SIB type 16.
The following table shows the description of each system information block.
Table 5 System information block
SIB RRC Protocol
State
Description Size
[TTI]
1 Idle mode Contains the NAS information and the information of the timers and
counters of the UE in idle mode and connected mode
1
2 Connected mode Contains the URA identity and the periodical cell updating and URA
updating information
1
3 Idle mode Contains the parameters of cell selection and reselection read by the UE
in idle mode
1
4 Connected mode Contains the parameters of cell selection and reselection read by the UE
in connected mode
(1)
5 Idle mode Contains the configuration parameters of the common channel read bythe UE in idle mode
3
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SIB RRC Protocol
State
Description Size
[TTI]
6 Connected mode Contains the configuration parameters of the common channel and
common physical channel read by the UE in connected mode
(3)
7 Idle modeConnected mode
Contains the parameters of fast variance (UL-Interference and dynamicpersistence level)
0.5
8 Connected mode
(FDD only)
Contains the static CPCH information 1.5
9 Connected mode
(FDD only)
Contains the CPCH information 0.5
10 CELL_DCH
(FDD only)
Contains the Dynamic Resource Allocation Control (DRAC)
procedure information
-
11 Idle mode Contains the adjacent cell list and measurement control information read
by the UE in idle mode
1-10
12 Connected mode Contains the adjacent cell list and measurement control information read
by the UE in connected mode
(1-10)
13 Idle mode
Connected mode
Contains the ANSI-41 information 1
13-1 Idle mode
Connected mode
Contains the ANSI-41 RAND information 0.5
13-2 Idle mode
Connected mode
Contains ANSI-41 user zone ID 0.5
13-3 Idle mode
Connected mode
Contains the ANSI-41 private neighbour list 0.5
13-4 Idle mode
Connected mode
Contains ANSI-41 service redirect information 0.5
14 Idle mode
Connected mode
(TDD only)
Contains the uplink outloop function control information read by the UE in
the idle and connected mode
-
15 Idle mode
Connected mode
Contains the LCS information supported 1
16 Idle mode
Connected mode
Contains the RB used for handover and the parameters of the transport
channel and physical channel read and stored by the UE in the idle andconnected modes.
3
18 Idle mode
Connected mode
Contains the PLMN ID of the Neighboring cell
2.1.2 System Information Broadcast Procedure
According to the protocol, the system information message transmits the SIB on the BCCH,
and BCCH can be mapped to the BCH or FACH, so the size of the system information message
should be in accord with the size of the BCH or FACH. The RRC layer is responsible for the
cascading (when the size of the SIB is less than that of the transport block of the BCH or FACH)
and segmentation of the SIB (when the size of the SIB is greater than that of the transport block of
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the combination of IB adding, reducing and content updating) for the first time according to the
value of the SFN set by this IE. Otherwise, NodeB will update the scheduling information on the
BCCH as much as possible. Refer to the message analysis in Section 5.
2.1.3 System Information UpdateThe UE and the UTRAN may use different mechanisms for SIB update. If the SIB contains a
value tag, the UTRAN should indicate the time to change an IE. This time is determined by means
of changing the value tag. Even though the value tag is not changed, the UE should consider that
the SIB will become invalid six hours after it is received. In addition, such SIBs exist, in which the
IEs are changed too frequently to indicate the change with the value tag. Such SIBs are not
related to the value tag in the primary information block or the value tag of the upper-level SIB.
The stored SIB should be taken as invalid after the UE is powered off.
Modifying SIB with value tag
When the system information is changed, the UTRAN should execute the following
operations to indicate the UE of these system information changes.
1. It updates the system information in the SIB
2. It updates the upper- level SIB with the value tag in the updated SIB if the updated SIB
is connected to the upper-level SIB
3. It updates the primary information block with th e value tag in the updated SIB or the
upper-level SIB, and changing the value tag in the primary information block
4. It transmits the new primary information block on the BCH mapped by the BCCH, and
then the updated SIB
5. It transmits the new primary information block on the FACH mapped by the BCCH, so
that all the UEs in the CALL_FACH state can get the information. The UTRAN can
retransmit the new primary information block on the FACH so as to increase the correct
receiving rate of this information.
6. It transmits the PAGING TYPE 1 message on the PCCH, so that the UEs in the idle or
connected (CELL_PCH or URA_PCH) mode can get the information. In the IE of BCCH
Modifacation Information in the PAGING TYPE 1 message, the UTRAN should indicate
the new value tag for the primary information block. The PAGING TYPE 1 message
should be transmitted in all paging occasions. For the BCCH Modification Information
on the PCH, the system information should not be changed to frequently, but should
coordinate with the maximum DRX cycle supported by the UTRAN.
7. After receiving the PAGING TYPE 1 message, the UE should check the value tag of
the primary information block indicated in the IE of BCCH Modification Information. If it
is different from the value stored in the VALUE_TAG, and then read the new primary
information block according to the present sequence information.8. After the UE receives the new primary information block on the BCH or FACH mapped
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by the BCCH, it should store the new value tag (transmitted in the VALUE_TA G
variable in the primary information block, and then check the IE of value tag of all SIBs
used by the UE. If there is change, the UE should read this SIB. After receiving the
modified SIB, the UE executes the operations specified in Section 8.1.1.5 of the 25.331
protocol.
Modifying system information without value tag
When the UE knows that the SIB contains no value tag, it should start up a timer, whose
value equals to the repetition cycle of the SIB (SIB_REP). When the timer expires, the information
transmitted by this SIB should be taken as invalid. Before using the value contained in the system
IE, the UE should get the new SIB. After receiving the modified SIB, the UE executes the
operations specified in Section 8.1.1.5 of the 25.331 protocol.
Time critical modification of SIB
For the modification of some system IEs (for example, re-configuration of the channel), it is
essential to know the time of the modification. In this case, the UTRAN executes the following
operations to notify the UE of these changes:
1. It transmits the PAGING TYPE 1 message on the PCCH, so that the UE in the CELL_PCH
and URA_PCH state can acquire the information. In the BCCH Modification Information, the
UTRAN should indicate the change time and the new value tag suitable for the primary
information block after the change. The PAGING TYPE 1 message should be transmitted in
all paging occasions (it is the continuous 256 frames at present (with the paging cycle of 2^8 ).
(The PIs of the CN will be discarded in this case).2. It transmits the SYSTEM INFORMATION CHANGE INDICATION message on the FACH
mapped by the BCCH, so that all the UEs in the CELL_FACH state can acquire the
information. In the IE of BCCH Modification Information , the UTRAN should indicate
change time and the new value tag suitable for the primary information block after the change.
The UTRAN can repeat transmitting the SYSTEM INFORMATION CHANGE INDICATION
message on the FACH so as to increase the correct receiving rate of this information.
3. The UE updates the system inf ormation, and changes the value tag in the corresponding
SIB.4. If the updated SIB is connected to the upper-level SIB, the UE updates the upper-level SIB
with the value tag in the updated SIB.
5. It updates the new information block with the value tag in the updated SIB or the upper-level
SIB, and changes the value tag of the primary information block.
6. When the designated time comes, it transmits the new primary information block on the BCH
mapped by the BCCH, and then transmits the updated SIB on the BCCH.
7. After receiving the PAGING TYPE 1 or SYSTEM INFORMATION CHANGE INDICATION
message, the UE should wait until the time indicated by the IE BCCH Modification
Information comes, and then read the new primary information block.
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8. When receiving the new prima ry information block, the UE should store the value tag of the
new primary information block, and check the IE of value tag of all SIBs used by the UE. If it
is different from the value stored in the VALUE_TAG , the UE will read corresponding SIB.
After receiving the modified SIB, the UE executes the operations specified in Section 8.1.1.5
of the 25.331 protocol.
9. If the UE cannot find the primary information block, it considers that the physical
re-configuration has happened, and then carries out new cell searching.
2.1.4 Description of IEs of SIBs
Here only provides the description of the IEs of the SIBs realized by RNC V1.2.
2.1.4.1 MIB:
By comparing the latest MIB tag, the UE can determine whether to update the MIBinformation stored previously.
MIB contains some basic information of the access network, such as PLMN information,
MNC and MCC.
It contains the scheduling information of other SIBs (SB1, SB2 and SIB1). Where, the
scheduling information of SB1 and SB2 must be put in the MIB, and that of others can be put
in SB1 and SB2.
2.1.4.2 SIB1:NAS information
CN DOMAIN information:
T3212: CS domain periodical location update, once every 1/10 hour;
T3312: SGSN MM periodical route update;
NMO: no GS information between SGSN and MSC/VLR, with NMO being 1;
DRX: it is equal to 2^K * PBP, with K being the DRX cycle length coefficient of the CN domain,
and PBP being the number of paging block cycles, and FDD being 1.
The timer and counter constants of the UE in connected mode: the timer constant used for
the UE capability information (T304), the timer constant used for RRC connection release
completion (T308), the timer constant used for cell reselection in connected mode (T309), the
timer constant used for transmitting the PUSCH capability request (T310), the timer constant
used for selecting PUSCH allocation hangup in the physical common shared channel
allocation (T311), the timer constant used for out-of-sync. Indication in connected mode
(T313), the timer constant used for indicating radio link failure (T314 and T315).
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Various timer constants of the UE in idle mode: The timer constant used for RRC connection
setup (T300) and the synchronization indication timer constant used for creating dedicated
channel (T312).
Note: [1] In this version of protocol, the UE does not use T301 or N301. The UE starts thetimer T302 after transmitting CELL UPT/URA UPT, and stops this timer after the receiving
CONFIRM. Once the timer expires, and if V302
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[10] The UE starts the timer T313 after tdetecting N313 (the maximum number of continuous
out-of-sync indications received from L1) continuous out-of-sync indications, and stops this timer
after detecting N315 (the maximum number of continuous in-sync indications received from L1
during the timing period of T313) continuous synchronization indications. Once the timer expires,
the radio link will be disconnected.
[11] The UE starts T314 only when the radio link failure criteria are met and the radio bearer
associated with the T314 timer exists, and stops this timer when the cell updating procedure is
completed. For the case of timeout, refer to Section 8.3.1.13 of the 25.331 protocol. According to
the protocol, when the cell updating procedure is initiated for RRC connection re-setup, and if
either T314 or T315 expires, and T302 is not running, it is necessary to release the RAB related to
T314/T315. However, RR does not support the crossing flow for the cell updating and RAB
configuration releasing, so T314/T315 should be set to 0 or a value greater than T302 N302.
[12] The timer T316 is initiated when the UE in the URA_PCH/CELL_PCH detects it is out of
the service area, and this timer is stopped when the UE detects it enters the service area again. If
the UE is in the service area, it initiates the cell updating procedure, and the timer T317 is initiated.
When the UE detects the state is transited to CELL_FACH after entering the service area and
initiates the cell updating procedure, the UE will enter idle mode once T317 expires.
[13] The UE starts the timer after transmitting RRC REQ, and stops this timer after receiving
RRC CON SETUP. Once the timer expires, and if V300
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2. Cell selection and reselection. When all the above three IEs are in the NOT_XXX state,
this cell can be selected in the cell selection and reselection in the connection and idle mode.
When the cell is in the not barred or not reserved for operator use or reserved for SoLSA state,
the UE that does not support SoLSA cannot access this cell. When the cell is in the state of not
barred or reserved for operator use, the users with the AC level of 11 to 15 in the home PLMN can
access this cell. The users with the AC level of 0 to 10 cannot access this cell. When the cell is in
the barred state, the UE cannot select this cell, but it provides emergency call service in general
cases, unless this cell in the IE of Access class barred list indicates this cell prohibited emergency
call. The UE ignores the IE of Cell Reserved for SoLSA. The UE can select other cells according
to the following rules:
[1] If the IE of Intra-frequency cell re-selection indicator in the Cell Access Restrict
section is ALLOWED , and if the cell reselection condition is met, the UE can select another
intra-frequency cell.
[2] If this UE camps on other cells, it will delete this cell from the neighboring cell set within
the time of Tarred . The parameter of Tarred and the cell state are provided in the system
information of Cell Access Restriction.
[3] If the UE does not select other cells and this cell is still the best serving cell, the UE will
check the state of this cell within the time of Tarred .
[4] If the IE of Intra-frequency cell re-selection indicator in the Cell Access Restrict
section is not allowed , even if the cell reselection condition is met, the UE cannot select the best
serving cell with the same frequency with the barred cell. The emergency call is the exception,
that is, the emergency call service ignores this IE.
[5] If this cell is still the besting service cell, the UE checks the state of this cell within the
Tarred time.
3. Access control. The UEs that camp on this cell will not detect the access level or the
related cell access restriction information. That is, the UE will not discard the cell that it camps on,
as it bars other UEs of all levels from accessing. Therefore, the change of the access restrictioncondition will not trigger the cell reselection procedure of the UE. Before transmitting the RRC
CONNECTION REQUEST message to the cell, the UE will detect the access level and the related
cell access restriction information. For the UE starting the initial cell access when it selects
UTRAN for inter-system measurement on other cells (it enters connected mode) and the UEs in
connected mode, the access level and cell restrict condition information will be ignored.
4. Emergency call. Generally, all the cells in the not barred state will provide the emergency
service, in spite of the restriction condition and reserving condition. If necessary, the restriction on
the emergency calls will be indicated in the IE of Access class barred list. For the details of the IEof Access class barred list, refer to TS 22.201.
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2.1.4.5 SIB5:
PICH-PowerOffset
AICH-PowerOffset
PrimaryCCPCH-Info: tx-DiversityIndicator for FDD
PRACH-SystemInformationList:
SCCPCH-SystemInformationList:
CBS-DRX-Level1Information
Note:
1. The SIB5 contains the configuration information of the common channel, such as
information received by paging. To fast calculate the paging time during cell reselection, it ishelpful to shorten the repetition cycle of SIB5.
2. The paging and SCCPCH in idle mode. If one or more PCHs are set up in a cell, each
SCCPCH bears one PCH, and each PCH has one PICH respectively, more than one PCH and
PICH will be defined in SIB5, and the UE will select one SCCPCH in the IMSI-based list of SIB5
according to this rule: the selected SCCPCH index= IMSI mod K, where K is the number of
SCCPCHs for bearing PCH in the cell (that is the number of SCCPCHs for bearing FACH is not
included). The relevant information of SCCPCH is sequenced from 0 to k-1 in the system
information. The index of SCCPCH uniquely identifies the PCH borne by the SCCPCH in this cell
as well as the relevant PICH. When the UE has no IMSI, for emergency call for example, the IMSI
is regarded as 0.
3. SCCPCH selection in connected mode. If the UE enters connected mode from idle
mode by transmitting the RRC CONNECTION REQUEST message, it will select the SCCPCH
bearing FACH in SIB5 based on the Initial UE identity according to the following rules to receive
the RRC CONNECTION SETUP message: the selected SCCPCH index= Initial UE Identity
mod K. where K is the number of SCCPCHs for bearing FACH in the cell (that is the number of
SCCPCHs for bearing PCH is not included). The relevant information of SCCPCH is sequenced
from 0 to k-1 in the system information. The initial UE identity is obtained by the UE by
transmitting the IE in RRC CONNECTION REQUEST. Refer to Section 8.2 of the 25.304 protocol,
and SIB5 in the 25.331 protocol.
4. Discontinuous connection. The UE in idle mode can use the discontinuous receiving
method (DRX) to lower the power consumption. When DRX is used, the UE only needs to monitor
the PI within each DRX period. The length of the paging period is MAX(2 K,PBP) frames, where K
is an integer, and PBP is the paging block period. The PBP is only used for TDD, and it is equal to
the receiving period of PICH. For FDD, PBP=1. The CBS-DRX of SIB5 is only for the
discontinuous receiving for CTCH, and this will be realized in V1.3.
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2.1.4.6 SIB7:
UL-Interference: Uplink interference information (-110 to -70)
prach-Information-SIB5-List
prach-Information-SIB6-List, optional
expirationTimeFactor: expirationtimer=MAX ([320ms], SIB_REP expirationTimeFactor),
indicating update period, with expirationTimeFactor:: 1 8.
Note: SIB7 includes the parameters requiring constant changes transmitted on the RACH
uplink, such as uplink interference, and it is not updated with the value tag of MIB. It must be read
from the BCCH before the usage of these parameters and the transmission in short repeated
cycle.
2.1.4.7 SIB11:
FACH measurement occasion info
Measurement control system information
Note: The size of the SIB11 depends on the number of adjacent cells and the volume of
measurement control information contained. When it is supposed that only one cell exists and
there is other measurement control information, this information block will have no segmentation
in a TTI. When there is 32 adjacent cells (including 12 intra-frequency cells, 12 inter-frequency
cells and 8 GSM cells for example), SIB11 will use 10 TTIs. All these are suitable for SIB12 in
connected mode.
2.1.4.8 SIB18:
Idle mode PLMN identities
Connected mode PLMN identities
2.2 RRC Connection
UE UTRAN
RRC CONNECTION REQUEST
RRC CONNECTION SETUP
RRC CONNECTION SETUP COMPLETE
Figure 6 RRC signalling connection setup process
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To access network service, the UE must set up RRC connection at the AS and UTRAN,
namely the RRC CONN REQ for setting up channel allocated by UTRAN, shown in Figure 6, and
then it uses this AS connection for the signalling exchange with the CN. As UTRAN can decide
the initial connected state, CELL_FACH or CELL_DCH, of the UE requesting to access, that is,
different common transport channels mapped by the DCCH corresponds to different RRC flows.
2.2.1 RRC_CONNECTION_REQUEST
Figure 7 shows IEs of this message.
UE information elements
Initial UE identity: Indicates whether a UE has available TMSI, PTMSI, IMSI and IMEI
information, based on the priority of the UE.
Establishment cause: It refers to the RRC connection setup cause, including: OriginatingConversational Call, Originating Streaming Call, Originating Interactive Call, Originating
Background Call, Originating Subscribed traffic Call, Terminating Conversational Call,
Terminating Streaming Call, Terminating Interactive Call, Terminating Background Call,
Emergency Call, Inter-RAT cell re-selection, Inter-RAT cell change order, Registration,
Detach, Originating High Priority Signalling, Originating Low Priority Signalling, Call
re-establishment, Terminating High Priority Signalling, Terminating Low Priority Signalling,
Terminating - cause unknown.
Protocol error indicator: It is the protocol error indicator, including the options of No error,
ASN.1 violation or encoding error, Message type non-existent or not implemented, Message
not compatible with receiver state, Information element value not comprehended, Information
element missing, Message extension not comprehended.
Measurement information elements
Measured results on RACH: It reports the measured results on RACH of the intra-frequency
cell (monitoring set) designated in SIB11, including the qualities of the primary scrambling
code and pilot Ec/No of the cell.
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Figure 7 RRC CONNECT REQUEST
2.2.2 RRC_CONNECTION_SETUP & RRC_CONNECTION_SETUP_COMPLETEWhen the DCCH is mapped to the common channel (RACH/FACH), the RRC connection
(SRB) does not need to set up a radio link. But during the service setup (TRB), as the DTCH is
mapped to the DCH, a radio link is to be set up, and the RRC connection will be re-set up on the
dedicated channel. When the DDCH is mapped to the DCH, the RRC connection (SRB) needs to
set up a radio link. During the service setup, as DTCH also needs to be mapped to the DCH, the
number of DCHs will be increased, which will lead to repeated configuration of radio links. In
these two cases, the RRC connection request messages initiated by the UE are identical. The
following is the description of the IEs in the RRC connection setup messages in these two cases.Figure 8, Figure 10, Figure 11 and Figure 13 are two groups of the corresponding flow messages.
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2.2.2.1 UE in the CELL_FACH state after the RRC connection setup
Figure 8 RRC CONNECT SETUP (DCCH is mapped on common channel)
Figure 8 shows the IEs of the RRC CONNECTION SETUP message.
UE Information Elements: When the UE is receiving this message, it will check whether the
ID in this IE is consistent with that of itself. If not so, it will discard this message; if so, it will
read the indication of UE in connected mode from the rrc StateIndication of the UTRAN. If
frequency information is contained, it will select a cell for camping on according to the cell
reselection rule in connected mode. Then it will select PRACH (refer to Section 8.5.17 in the
25.331 protocol) and SCCPCH (refer to Section 8.5.19 in the 25.331 protocol), ignoring the
IE of UTRAN DRX cycle length coefficient, without using DRX. The UE has performed
common channel synchronization before transmitting RRC CONN REQ, so this step is
omitted there.
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RB Information Elements: Figure 8 displays four singling RB IEs. At present, SRB1 is used
to transmit the message in the unacknowledgement mode (RLC UM), such as RRC CONN
REL, URA UPDATE CONFIRM, CELL UPDATE CONFIRM and PHYSICAL SHARED
CHANNEL ALLOCATION (Node: the RRC CONN REQ and RRC CONN SETUP messages
are transmitted on the CCCH borne by SRB0). SRB2 is used to transmit the message in the
acknowledgement mode (RLC AM). At present, most messages (except the directly
transmitted messages of the NAS layer) are transmitted on the DCCH of this bearer. SRB3
and SRB4 are used to transmit the directly transmitted messages in the RCL AM mode on
the NAS layer. Each SRB contains the parameters of the RLC layer of the QoS guaranteed in
this bearer, as shown in Figure 9.
TrCH Information Elements (ul AddReconfTransChInfoList and dl
AddReconfTransChInfoList): This message content is invalid in Figure 8, as RACH and
FACH have been set up when the cell is created. DCH 6 filled in is only for message
alignment, which will not be adopted but reserved by the UE. This useless DCH will be
deleted from ul/dl DeletedTransChInfoList during RB SETUP.
maxAllowed UL TX Power: It is the maximum transmit power of the UE, and is set to 24dBm,
as shown in the figure.
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Figure 9 MappingInfo of SRB1 and SRB2 of the DCCH mapped to the common channel
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Figure 10 RRC CONNECT SETUP COMPLETE (DCCH is mapped on the common channel
Figure 10 shows the IEs of RRC CONNECTION SETUP COMPLETE message:
UE Information Elements: It contains values of STARTCS or STARTPS for triggering the
encryption and integrality protection.
Other information elements: It contains the radio access capability information of the UE,
including PDCP capability (indicating whether the PDCP supports lossless transition), RLC
capability (sizes of all RCL AM BUFFERs and the maximum RLC window), transport channel
capability (including maximum transmission and receiving Bit, conversion bit, TB, TF, TFC,
and so on), radio frequency capability (including transmit capability of the UE and the
uplink/downlink frequency interval), physical channel capability (such as maximum transmit
Bit), inter-system access capability, encryption and integrality protection algorithm supporting
capability, measurement capability (for example, whether the uplink/downlink supports
compressed mode measurement. Huaweis UE supports downlink compressed mode
measurement only).
2.2.2.2 UE in CELL_DCH state after RRC connection setup
Figure 11 shows the IEs of the RRC CONNECTION SETUP message:
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Figure 11 RRC CONNECT SETUP (DCCH is mapped to the dedicated channel
UE Information Elements: When the UE is receiving this message, it will check whether the
ID in this IE is consistent with that of itself. If not so, it will discard this message; if so, it will
read the indication of UE in connected mode from the rrc StateIndication of the UTRAN. If
the UE is in the CELL_DCH state, it will enter the synchronization procedure introduced in the
25.214 protocol. Because when the UE receives this message, NodeB has created the
downlink radio link, so the two stages of downlink synchronization specified in Section 4.3.1.2
of the 25.214 protocol: Stage 1, the physical layer does not report the Out of sync message
within 160ms after the DCH is set up initially, but it will judge the in-sync state with this
criterion: the physical layer estimates the quality of the downlink DPCCH of the former 40ms,
if this quality is always better than the threshold of Qin , it will report the In sync message to
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the high layer. However, before the 40-ms DPCCH quality measurement is completed, this
criterion cannot be realized. Stage 2, 160ms after the DCH is set up, the physical layer will
report the Out of sync and In sync messages according to the actual detection result. Refer to
the protocol for the criterion for judging Out of sync. The out-of-sync timer (T313/N313) of
downlink radio link and the in-sync timer (T315), refer to the description of SIB1 in the
previous part. After the downlink synchronization and the UE transmits pc preamble (the
number of frames in ul DPCH Info ) frames on the UL DPCCH channel, the UL DPDCH starts
data transmission. The signalling on SRB is transmitted on the UL DPDCH only after SRB
Delay (the number of frames specified in ul DPCH Info ) frames. The uplink is judged by
NODE-B, requiring the detection of the synchronization mode of all the radio link sets of the
uplink in each radio frame. Each radio link set has only one synchronization mode. In NODEB,
each radio link set will be tranfered to one of the following three states: initial state,
out-of-sync state and in-sync state. The protocol does not specify the judging criteria directly,
it just recommends to judge based on the DPCCH quality estimation or CRC check. For the
realization mode, refer to the downlink judging mode mentioned above.
RB Information Elements : Refer to 2.2.2.1 for details. The difference from 2.2.2.1 is the
logical channel in RB MappingInfo is mapped to DCH.
TrCH Information Elements (ul CommonTransChInfo, ul AddReconfTransChInfoList, dl
CommonTransChInfo, dl AddReconfTransChInfoList): including the information of TFC, TF
and dl DCH Bler.PhyCH information elements (frequencyInfo): Uplink/downlink frequency information, for
the UE in connected mode to perform cell reselection in the intra-frequency cell.
maxAllowed UL TX Power: The maximum transmit power of the UE, it is 19dBm as shown in
the figure.
Uplink radio resources (ul DPCH Info): It contains the pc preamble, SRB delay and the
uplink power control algorithm, the power offset of the UL DPCCH, scrambling code, spread
factor, TFCI and punching limit used for UL DPCCH synchronization.
Downlink radio resources (dl CommonInfomation and dl Information PerRl List): It
contains the power control mode of the DL DPCH, TFCI, DTX insertion method
(positionFixedorFlexible, it is Fixed at present, which is used for downlink compressed mode
with the punching method), primary scrambling code and channelization code.
Figure 13 shows the IEs of the RRC CONNECTION SETUP COMPLETE message. Refer to
Section 2.2.2.1 for details.
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Figure 12 MapingInfo of SRB1 and SRB2 of the DCCH mapped to the DCH
Figure 13 RRC CONNECT SETUP COMPLETE (DCCH is mapped to the DCH)
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3 Access Procedure Performance Analysis
3.1 Performance Indices of Access Procedure
For network planning, the performance indices for evaluating the access procedure are the
access success rate and connection delay. These two indices directly reflect the access
performance of the RAN (access network) and UE (mobile phone). They are related to the
coverage and capacity of the network. The access success rate refers to success rate of the
active access caused by call initiating of the NAS layer of the UE or the passive access caused by
paging receiving. Connection delay refers to the time from access to service connection setup.
However, the statistics points of these two indices are in the core network (CN), which cannot
reflect the access state well in the network optimization. In this document the access performance
index of the RAN (that is the RRC connection setup success rate, namely the times of successfulsetup of RRC connection) are evaluated from the statistics points of the AS. This index can be
obtained with the OMC statistics tool by referring to Section 2.1.6 in Reference [3]. For the
detailed traffic statistics, refer to Reference [7]. This consideration is for network coverage in the
pre-planning and network optimization phases, and measuring the cell pilot signals through UE of
drive test equipment, observing whether the UE performs cell searching, selection, reselection,
initiates random access, attaching, location registration/updating, and accepts the services of the
network normally, so as to perform site adjustment (distance between sites, azimuth, downtilt and
so on).
In addition to the success rate of the RRC connection setup, the cell searching and selection
time, the random access rate, the transmit power of the UE can act as the performance indices for
evaluating network coverage. But the main problem is these indices do not have precise statistics
values.
The speed of random access depends on the initial synchronization time (including code
synchronization and frame synchronization in the random access channel). The number of
random access channels depends on the expected access load. All these will affect the
information transmitted in the random access procedure. Moreover, if the UE uses an over-large
transmit power, it will lower the system capacity. Therefore, it is very essential to lower the
transmit power of the UE in the random access procedure, which cannot be controlled by the fast
closed loop power control in the random access procedure. It seems inconsistent that high
transmit power lead to fast synchronization, but cause interference to other users, while lower
transmit power lead to slow synchronization, kept in the finite repetition times, which drives up the
transmit power step by step. Therefore, the accurate open loop power control can have the UE
use a proper initial transmit power, which will be greatly helpful to the performance of random
access.
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3.2 Relevant Factors Affecting Access Procedure Performance
3.2.1 Incorrect Setting of T cell Affecting Cell Searching Speed
Tcell is used to define the transmit start time and the BFN relative delay of the downlink
scrambling codes of the SCH and CPICH of a cell. Its main purpose is to avoid overlap of the
secondary synchronization channels (SSCH) between different cells in the same NodeB. If this
cannot be avoided, it will affect the frame synchronization and scrambling code group
identification during cell searching. The resolution of the cell T cell is 256 chips, the value range of
Tcell is 0 9 256 chips. Please ensure the T cells of intra-frequency Neighboring cell are
inconsistent. Refer to Reference [4]
3.2.2 Unreasonable Neighboring cell List Affecting Cell Selection
The RRC CONNECTION REQUEST message contains the pilot measurement information ofthis cell and the Neighboring cell attached by the UE. These pilot measurements are performed
during cell selection of the UE. If there are many Neighboring cells of the primary cell in the
system information broadcast, the UE needs to take a long time to measure the qualities of the
pilot signals of all the neighboring cells. Thus the user access speed will be lowered. So an
important task for network optimization is to reasonably plan the neighboring cell list of each
primary cell defined in the planning phase, and delete some useless neighboring cells with the
traffic statistics tool in a specific pre-commercial application. For example, two cells are
neighbours to each other, with handover area. But they does not have or have little inter-cellhandover due to the geographic obstructions such as river. Therefore, these two cells should not
be neighboring cells. These factors cannot be considered in the pre-planning phase due to the
factors of map and dimensioning. So this must be optimized.
3.2.3 Doppler Frequency Shift Affecting Access Performance of UE
The frequency shift of BS and UE are related to the radio instruments directly. The frequency
shift of the BS is 0.05PPM (uncertain). The precision of radio instruments have been considered
in the design, which have been defined before delivery, and must be changed if it is too poor.
For UMTS, the Doppler frequency shift is represented as slow shading of the channel, which
will affect the access of the UE in the mobile process. As the performance decrease when the UE
is traveling at the speed below 20km/h can be compensated by the power control of the system,
and the deep shading when the UE is traveling at the speed above 60km/h can be remedied by
means of interleaving. This is represented by the requirement on Eb/No (Refer to Chapter 15 in
Reference [5]). The performance degradation includes access performance degradation of the
UE. For this slow shading, the performance of the UE can be kept in high quality by means of
network planning. (As the network planning software does not support dynamic simulation, it is
described as a problem here.)
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Please note that, the signings such as RRC (borne by SBR) has higher requirement on the
Eb/No than data (borne by TRB). The access procedure is mainly for signalling exchange, so it
requires BLER be 0%. That is, once an error occurs, the signalling must be retransmitted (whose
QoS are guaranteed by RLC).
3.2.4 Traffic Distribution in Cell Effect on Acquisition Probability
We can view from the message contents listed above that the system realized presently has
not considered the division of the ASC like emergency call service. But in the actual
commercialization process, it is necessary to specify the corresponding ASC strategies to ensure
the number of specific user group like emergency call user group. Especially for the case of high
user density, it is likely to encounter access difficulty (For the scenarios like squares. It may have
few people generally, but may have parties in some specific occasion, during which the access
may be difficult due to large numbers of users. For example, the popularization of short messagebrings unexpected pressure to the RAN directly. For the RAN itself, the short message service,
call service and Internet access service are the same, even though short message is a non
real-time service, but it may bring pressure to the services requiring high call success rate, such
as call service and Internet access service. But this will not be represented on traffic model).
These difficulties suffer random access, that is, the user acquisition rate is lowered by collision.
This influence is represented by the random access parameter, namely the maximum
retransmission times of the random access preamble. If the maximum retransmission times is
exceeded, it may cause access failure. This parameter directly maps the collision of the systemon the random access.
The UE may estimate the UL Interference incorrectly due to environment change or different
distance to the BS, because the users at the cell border and those at the cell center use the same
UL Interference (namely the RSSI of NodeB, which is received by the UE in SIB7. This value is
updated once every 1s, and broadcast once every 100ms repeatedly on the BCH. Note that 1s is
the period timer realized by the program, which cannot be modified. The RNC can set the time
interval for repeated broadcast. When the coverage range of the cell is large, this inaccuracy will
affect the initial transmit power of the random access preamble. In addition, it will affect theparameter of Ramp step between preambles will be affected as a specific acquisition rate should
be guaranteed. Considering large traffic of short message service, the ramp step (2 dB at present)
will influence the uplink capacity and the access acquisition rate (This influence degree needs to
be estimated by the whole system simulation. Huawei has not studied to the depth for the
moment).
3.2.5 Different Clutters Affecting Open Loop Power Control
During network planning, different clutters will be covered. Refer to Reference [6]. Different
clutters may lead to different path losses, and this will directly influence the open loop power
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control of the initial transmission power of the random access channel preamble. The parameter
representing the compensation to the uplink/downlink path loss is Constant Value (-25dB at
present). The formula for calculating the initial transmission power is as follows:
Preamble_Initial_Power = Primary CPICH TX power CPICH_RSCP + UL interference +Constant Value
According to the recent analysis, -25dB is a small value for Constant Value , which should be
set to -20dB or larger, so that the access threshold value can be larger. The value of Pp_m can
be set to a small value, so as to keep the coverage, UL interference at an optimal level.
However, in the actual environment, even though the UE estimates the open loop power
accurately, the actual effect of signal transmitted after the estimation of open loop power arriving
NodeB varies due to different distances between the UE and the BS and different clutter
scenarios. For example, In NodeB, the Ec/No of the static channel and that of the case3 channel
are -21.5, but the acquisition probability in the static channel is about 90%, and that in the case3
channel is less than 70%. Therefore, to improve the random access performance, it is necessary
to consider the influence of the propagation environment on the open loop power control, but also
consider increasing the acquisition probability.
4 Analysis Procedure for Access Procedure
Access procedure analysis can be performed after network pre-planning and cell planningand development, so as to provide reference for cell planning optimization and network
performance optimization. The following are the analysis steps:
4.1 Step 1: Knowing System Performance
It is mainly to know the operation mode of the network (that is, whether Gs interface exists
between MSC and SGSN). The relevant algorithms of RNC (such as access, call permission,
uplink outer loop power control, load control, etc.) and the algorithm switch setting, as well as the
basic configuration parameters of NodeB, and basic configuration parameters of UE.
4.2 Step 2: Ensuring a Stable System
It is to ensure stable UTRAN and CN, that is to ensure the equipment of RNC and NodeB run
normally, and the transmission between them are stable, and ensure the equipment of MSC,
SGSN, GGSN, HLR and VLR are stable with correct subscriber registration information.
4.3 Step 3: Determining Neighboring cell Distribution
It is to provide PLMN, SA, RA, URA and Neighboring cell list
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