wcdma paging analysis

Course OWJ104101

WCDMA Paging Analysis

ISSUE 1.0

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Table of Contents

Confidential Information of Huawei. No Spreading without Permission

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Table of Contents

Chapter 1 Paging Process Analysis ................................................................................................1 1.1 Paging Initiation .....................................................................................................................1 1.2 Paging Flow ...........................................................................................................................1

1.2.1 Paging Type 1 .............................................................................................................1 1.2.2 Paging Type 2 .............................................................................................................2 1.2.3 Actions of UE Received Paging ..................................................................................3

1.3 DRX Process of UE ...............................................................................................................4 1.3.1 DRX Cycle Length and Paging Occasion ...................................................................4 1.3.2 Association between PICH and SCCPCH ..................................................................5 1.3.3 Paging Channel Selection...........................................................................................6 1.3.4 Example of UE DRX....................................................................................................6

Chapter 2 Paging Signaling Analysis..............................................................................................8 2.1 L3 Signaling Analysis.............................................................................................................8

2.1.1 IU Interface Paging .....................................................................................................8 2.1.2 Paging Type 1 .............................................................................................................9 2.1.3 Paging Type 2 ...........................................................................................................10 2.1.4 Common Transport Channel (CCH) Setup Request of IUB .....................................10 2.1.5 System Information Block Type 1 .............................................................................12 2.1.6 System Information Block Type 5 .............................................................................12

2.2 L2 Signaling Analysis...........................................................................................................13 Chapter 3 Paging Problem Analysis Process ..............................................................................16

3.1 Problem Analysis Flow ........................................................................................................16 3.2 Network Information Collection............................................................................................17

3.2.1 Traffic Statistics .........................................................................................................17 3.2.2 Subscriber Complaints ..............................................................................................19 3.2.3 History Record of Network Planning Optimization ....................................................19 3.2.4 Radio Parameter Configuration.................................................................................20

3.3 Determining Optimization Goal............................................................................................20 3.4 Locating Paging Problems...................................................................................................20

3.4.1 Determining Basic Location Direction .......................................................................20 3.4.2 Direct Causes of Paging Loss...................................................................................21 3.4.3 Further Analysis on Paging Loss Cause...................................................................21 3.4.4 Other Cause Analysis ...............................................................................................22

3.5 Paging Problems Optimization ............................................................................................22 3.6 Optimization Verification ......................................................................................................22

Chapter 4 Typical Paging Problem Analysis ................................................................................23 4.1 Too Large Paging Area Planned .........................................................................................23

4.1.1 Problem Analysis ......................................................................................................23 4.1.2 Optimization Measures .............................................................................................23

4.2 Improper Setting of CN Paging retransmission Times and Interval ....................................23 4.2.1 Problem Analysis ......................................................................................................23 4.2.2 Optimization Measures .............................................................................................24

4.3 Improper Setting of UTRAN Paging Retransmission Times and Interval............................24 4.3.1 Problem Analysis ......................................................................................................24 4.3.2 Optimization Measures .............................................................................................25

4.4 CN Adopts Whole-Network Paging......................................................................................25 4.4.1 Problem Analysis ......................................................................................................25 4.4.2 Optimization Measures .............................................................................................25

4.5 Improper Setting of DRX Paging Cycle Coefficient .............................................................25 4.5.1 Problem Analysis ......................................................................................................25 4.5.2 Optimization Measures .............................................................................................26

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Table of Contents


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4.6 Improper setting of Np value ................................................................................................27 4.6.1 Problem Analysis ......................................................................................................27 4.6.2 Optimization Measures .............................................................................................27

4.7 UE Identifier Utilized by CN Paging.....................................................................................27 4.7.1 Problem Analysis ......................................................................................................27 4.7.2 Optimization Measures .............................................................................................28

4.8 UTRAN Should Activate IMSI ATTACH and DETACH Functions.......................................28 4.8.1 Problem Analysis ......................................................................................................28 4.8.2 Optimization Measures .............................................................................................29

4.9 Too Low Power allocation of Paging Channels ...................................................................29 4.9.1 Problem Analysis ......................................................................................................29 4.9.2 Optimization Measures .............................................................................................29

4.10 Existence of Coverage Dead Zones..................................................................................30 4.10.1 Problem Analysis ....................................................................................................30 4.10.2 Optimization Measures ...........................................................................................30

4.11 UE Performance Problems................................................................................................30 4.11.1 Problem Analysis ....................................................................................................30 4.11.2 Optimization Measures ...........................................................................................30

OWJ104101 WCDMA Paging Procedure ISSUE1.0 List of Tables


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List of Tables

Table 1-1 PI-to- PICH mapping.................................................................................................. 5

Table 3-1 RNC Paging Traffic Statistics Index......................................................................... 17

Table 3-2 UMSC Paging Traffic Statistics Indexes .................................................................. 18

Table 3-3 SGSN Paging Traffic Statistics ................................................................................ 19

Table 3-4 Subscriber complaint information ............................................................................ 19

Table 4-1 IMSI ATTACH and DETACH Identifier ..................................................................... 28

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Chapter 1 Paging Process Analysis


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Chapter 1 Paging Process Analysis

1.1 Paging Initiation

In the paging process, paging massage is transmitted to the UE in the idle, CELL_PCH or URA_PCH state on the paging control channel. The core network (CN) may request paging, to e.g. establish a signaling connection. UTRAN can also initiate paging for UEs in CELL_PCH or URA_PCH state to trigger the cell update procedure. In addition, UTRAN may initiate paging for UEs in idle mode, CELL_PCH and URA_PCH state to trigger reading of updated system information. To be specific, paging are initiated on the network side in the following cases:

For CN originated paging:

In order to request UTRAN connect to UE, CN initiates the paging procedure by transmitting paging message to the UTRAN through Iu interface, and UTRAN transmites the paging message from CN to UE through the paging procedure on.

When the cell system message is updated: When system messages change, the UTRAN will trigger paging process in order to inform UE in the idle, CELL_PCH or URA_PCH state to carry out the system message update, so that the UE can read the updated system message.

UE state transition: In order to trigger UE in the CELL_PCH or URA_PCH state to carry out state transition (for example, transition to the CELL_FACH state), the UTRAN will perform a paging process. Meanwhile, the UE will initiate a cell update or URA update process, as a reply to the paging.

1.2 Paging Flow

1.2.1 Paging Type 1

To setup a call, the CN transmites the paging message to the UTRAN on Iu interface. Then the UTRAN transmites the paging message from CN to UE through the paging procedure on Uu interface, which will have the UE initiate a signaling connection setup process with the CN.

The PAGING message is transmitted on Iu interface in the connectionless message mode. After RNC receives paging message from the CN, if the information element (IE) of Non Searching Indication in the PAGING message is set to “non-searching” [1] (that is not to check whether the UE is in the connection state or not), or set to “searching”, but the UTRAN cannot find SRNTI (indicating the UE is in the idle state). The RNC delivers the PAGING TYPE 1 message through the PCCH channel. If the PAGING message at the Iu interface carries LAI or RAI, the RNC will deliver the PAGING TYPE 1 message to all the cells within the location areas or routing areas. If there is no LAI or RAI, the RNC will deliver PAGING TYPE 1 message to all the cells of this RNC. In addition, the UTRAN will deliver the PAGING TYPE 2 message through the DCCH channel, which is called collaboration paging.

As shown in Figure 1-1, the CN initiates paging in a location area (LA), which is covered by two RNCs. After receiving a paging message, the RNC searches all the cells



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corresponding to the LAI, and then calculates the paging time, at which it will send the PAGING TYPE 1 message to these cells through the PCCH.

CN RNC1 RNC2 NODEB1.1 NODEB2.1 UE

RANAPRANAP

RANAP RANAP

PCCH: PAGING TYPE 1

PAGING

PAGING

PCCH: PAGING TYPE 1

Figure 1-1 PAGING TYPE 1

The UTRAN can initiate PAGING TYPE 1 directly without the CN. When the UE is in the CELL_PCH or URA_PCH state, if the UTRAN needs to exchange information (including signaling and data, as described in Section 2.1) with the UE, it is necessary to send PAGING TYPE 1 message through the PCCH channel to notify the UE to transit to the CELL_FACH state from the URA_PCH or URA_PCH state. Then the state of the UE is transited by means of the cell updating process.

1.2.2 Paging Type 2

As shown in Figure 2, if the UTRAN determines it is a collaboration paging, indicating the UE is in the CELL_DCH or CELL_FACH state, the UTRAN will immediately transmite PAGING TYPE 2 message to the paged UE on DCCH channel.

If UE is in CELL_PCH or URA_PCH state, the UTRAN transmits the paging information in PAGING TYPE 1 message to UE. After received paging message, UE performs a cell update procedure to transit state to CELL_FACH.

In conclusion, if the UE is in CELL_FACH or CELL_DCH state, PAGING TYPE 2 message is delivered on the network side; otherwise, PAGING TYPE 1 message is delivered.



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CN SRNC UE

RANAPRANAP

PAGING

RRCRRCDCCH: PAGING TYPE 2

Figure 1-2 PAGING TYPE 2

1.2.3 Actions of UE Received Paging

UTRAN may page several UEs in the same paging occasion by including one IE “Paging record” for each UE in the PAGING TYPE 1 message. When the UE receives a PAGING TYPE 1 message. it shall perform the actions as specified below.

If the UE is in the idle state, for each occurrence of the IE “Paging record” included in the message the UE shall: ! If the IE “Used paging identity paging originator” is a CN identity:

! compare the IE “UE identity” with all of its allocated CN UE identities: ! If one match is found, indicate reception of paging; and forward the IE of

“CN domain identity”, the IE“UE identity" and the IE "Paging cause" to the upper layers;

! 2 Otherwise, UE ignores this paging record. If the UE is in connection mode, for each occurrence of the IE “Paging record” included in the message the UE shall: 1) If the IE “Used paging identity” is a UTRAN identity and if this U-RNTI is with the

same as the U-RNTI allocated to the UE: ! f the optional IE “CN originated page to connected mode UE” is included,

indicate reception of paging; and forward the IE “CN domain identity", the IE "Paging cause" and the IE "Paging record type identifier" to the upper layers.

! If the optional IE “CN originated page to connected mode UE” is not included, the UE performs a cell update procedure with cause “Paging record” as response.

2) If the IE “Used paging identity” is not UTRAN, the UE ignores this paging record. If the IE "BCCH modification info" is included, any UE in idle mode, CELL_PCH or URA_PCH state shall re-read the system message, ignoring the contents of "Paging record".



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1.3 DRX Process of UE

1.3.1 DRX Cycle Length and Paging Occasion

In idle mode, the UE can monitor the paging in two modes: one is to decode SCCPCH directly every 10ms, the other is to decode the PICH periodically. Only when the Page Indicator (PI) exists will the associated SCCPCH information be decoded, that is the Discontinuous Reception (DRX), which can reduce the power consumption.

Calculation formula [1] for the DRX paging cycle length when the UE is in idle state:

DRX cycle length = 2K x PBP frames

Where: K represents the IE of “CN domain specific DRX cycle length coefficient”, which is broadcast in the system information. At present, the K value of CS and that of PS are 8. PBP, the paging block periodicity, is 1 for the FDD mode.

Then the formula is simplified as:

DRX cycle length =2K (1)

The value of the Paging Occasion is determined as follows:

Paging Occasion(CELL SFN) = {(IMSI mod M) mod (DRX cycle length div PBP)} * PBP + n * DRX cycle length + Frame Offset

When n=0,1,2……. As long as SFN is below its maximum value 4096, for FDD, Frame Offset = 0. M represents the number of the SCCPCHs bearing PCH, which is 1 in generally cases.

The above formula is simplified as:

SFN = IMSI mod 2K + n*2K (2)

The UE needs to monitor the PI on these PICH frames only. As shown in Figure 1-3, the UE needs to monitor the frames (paging occasions) indicated by the red dots, and then decodes the qth PI of this frame. The formula for the value of q is formula (3).

��

0

2^K-1

0 4095

��

P I P I P I P I��

0 1 q NP-1

One DRX cycle

Figure 1-3 Schematic diagram of UE paging occasion



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1.3.2 Association between PICH and SCCPCH

The Page Indication Channel (PICH) is a fixed rate (SF=256) physical channel used to carry the paging indicators. The PICH is always associated with an S-CCPCH to which a PCH transport channel is mapped

Figure 1-4 illustrates the frame structure of the PICH. One PICH radio frame of length 10 ms consists of 300 bits (b0, b1, …, b299). Of these, 288 bits (b0, b1, …, b287) are used to carry paging indicators. The remaining 12 bits are not formally part of the PICH and shall not be transmitted. The part of the frame with no transmission is reserved for possible future use [1].

b1b0

288 bits for paging indication12 bits (transmission

off)

One radio frame (10 ms)

��

��

��

b287 b288 b299

Figure 1-4 Structure of Paging Indicator Channel (PICH)

Each PICH frame carries NP PIs. NP (the number of paging indications per frame) defines the maximum number of PIs supported by each frame on the PICH channel. The UE obtains the value of NP in the cell system message, including 18, 36, 72 and 144, that means to divide the 288 bit by NP, with each part constituting a PI. The mapping from {PI0, .., PIN-1} to PICH bits {b0,..,b287} are according to Table 1:

Table 1-1 PI-to- PICH mapping

Number of PI per frame (NP) PIp = 1 PIp = 0 NP=18 {b16p, .. b16p+15} ={1,1,..,1} {b16p, .. b16p+15} = {0,0,..,0} NP=36 {b8p, .. b8p+7} = {1,1,..,1} {b8p, .. b8p+7} = {0,0,..,0} NP=72 {b4p, .. b4p+3} = {1, 1,1,1} {b4p, .. b4p+3} = {0, 0,0,0} NP=144 {b2p, b2p+1} = {1,1} {b2p, b2p+1} = {0,0}

The UE determines to associate the qth part of bits by calculating the suffix p of its IP.

( )( )( ) NpNpSFNSFNSFNSFNPIq mod144

144mod512/64/8/18

×+++×+= (3)

Where, PI = DRX index mod NP = (IMSI div 8192) mod NP

SFN is the paging time of the UE, it is the SFN of the PCCPCH once the PICH appears.

Based on formula (3), the UE can get the suffix of itself. Thus, the UE can monitor the bits associated with itself in the PICH. Once they are assigned to 1, the UE knows that it is paged. Then it starts to receive the paging message from the 7680th chip after the radio frame of this PICH ends, and then resolves the paging message. The time sequence relation between PICH and SCCPCH is shown in Figure 1-5. The end part of the radio frame of PICH is 7680 chips ahead of the associated SCCPCH.



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τPICH

Associated S-CCPCH frame

PICH frame containing paging indicator

Figure 1-5 Time sequence relation between PICH and SCCPCH

1.3.3 Paging Channel Selection

The system information block type 5 (SIB5) defines commom channel to be employed in the idle mode. In a cell, a single or several PCHs may be established. Each SCCPCH indicated to the UE in system information may carry up to one PCH. Thus, for each defined PCH there is one uniquely associated PICHalso indicated.

If case that more than a single PCH and associated PICH are defined in the SIB5, the UE shall perform a selection according to the following rule:

! The UE shall select a SCCPCH from the ones listed in SIB5 based on IMSI as follows:

Index of selected SCCPCH = (IMSI div (( “DRX cycle length”div PBP)*Np*NPICH)) mod K,

Where K is equal to the number of listed SCCPCHs which carry a PCH (e.g.SCCPCHs carrying FACH only shall not counted). These SCCPCH shall be indexed in the order of their occurrence in SIB5 from 0 to k-1.

“Index of selected SCCPCH” identifies the selected SCCPCH with the PCH and the uniquely associated PICH to be used by the UE.

At present, Huawei realizes the scheme of one cell being configured with one PICH and one SCCPCH, with the SCCPCH carry two FACHs and one PCH.

1.3.4 Example of UE DRX

After a cell is set up, the parameters of paging in the broadcast system information are set as follows:

! IE “CN domain specific DRX cycle length coefficient”: 7 ! IE “Number of PI per frame”: 36

After receiving this information, the UE calculates the paging time, the PI and the p value of itself.

For example, a user whose IMSI is 448835805669362, the calculation is as follows:

DRX cycle length = 28 = 256

Cell SFN 448835805669362 mod 28+ n*28 = 242 + 256*n (n = 0,1,2,...)

PI = (448835805669362 div 8192) mod 36 = 14

q = (14 + [((18*(242 + [242/8] + [242/64] + [242/512])) mod 144) *0.25]) mod 36 = 27

It can be learnt from the above data that the PICH of this cell carries 36 PIs in each frame, with each PI composed of 288/36 bits, that is 8 bits. The UE needs to monitor bit



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216 (27x8)–bit223 of each PICH radio frame. If these 8 bits is changed to 1, the UE learns that it is paged, and needs to receive the paging message at the SCCPCH.

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Chapter 2 Paging Signaling Analysis


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Chapter 2 Paging Signaling Analysis

2.1 L3 Signaling Analysis

The signaling related to paging include paging IU, paging type 1, paging type 2, as well as the common transport channel setup request (IUB) for configuring the PCH and PICH parameters, system information 1 and system information 5.

2.1.1 IU Interface Paging

If the CN needs to set up signaling connection with the UE, it shall initiate the paging procedure at Iu interface. The signaling resolution is shown in Figure 2-1

The CN initiates the procedure by sending a PAGING message, this message shall contain information necessary for RNC to be able to page the UE,like:

! The CN Domain Indicator IE shall be used by the RNC to identify from which CN domain the PAGING message originates.

! The Permanent NAS UE Identity IE (i.e. IMSI) shall be used by the UTRAN paging co-ordination function to check if a signaling connection towards the other CN domain already exists for this UE. In that case, the radio interface paging message shall be sent via that connection instead of using the paging broadcast channel.

! DRX Cycle Length Coefficient: Represented by K, for calculating the DRX period (2K*PBP) of the UE. If this IE contains UTRAN, the K value will be transferred to the UE transparently. The UE may probably receives the K values configured by the CS, PS or the UTRAN, and will take the smallest one. This IE is optional.

! The Temporary UE Identity IE (e.g. TMSI) is the temporary identity of the user (allocated by that CN Domain) which can be used in a radio interface paging message. If the Temporary UE Identity IE is not included in the PAGING message, the RNC shall use the Permanent NAS UE Identity instead – if no signaling connection exists.

! The Paging Area IE shall be used by the RNC to identify the area in which the radio interface paging message shall be broadcast in case no signalling connection, as described above, already exists for the UE. If the Paging Area IE is not included in the PAGING message, the whole RNC area shall be used as Paging Area – if no signaling connection exists for that UE

! The Paging Cause IE shall indicate to the RNC the reason for sending the PAGING message. The paging cause is transferred transparently to the UE.

! .The Non Searching Indication IE shall, if present, be used by the RNC to decide whether the UTRAN paging co-ordination function needs to be



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activated or not. In the absence of this IE, UTRAN paging co-ordination shall be performed.

Figure 2-1 IU interface paging signaling resolution

2.1.2 Paging Type 1

The UTRAN can page several UEs in one PAGING TYPE 1 message through the paging packet. Figure 2-2 illustrates the signaling resolution of paging type 1.

Paging type 1 contains the following IEs:

Paging record list: It is specified in the protocol that a maximum of 8 UEs, corresponding to 8 paging records containing the paging resource, can be paged at the same paging occasion. If the CN initiates paging, the information such as domain ID of the CN, the NAS layer ID of the UE and the paging cause should be specified. If the UTRAN initiates paging, the UE ID of the AS layer, URNTI, should be specified.

BCCH modification info: Identifies the system information changes with the value tag. If this IE exists, the UE will read the system information, ignoring the Paging record list.



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Figure 2-2 Paging Type 1 Signaling Resolution

2.1.3 Paging Type 2

For the UE in CELL_DCH or CELL_FACH state, the UTRAN sends the PAGING TYPE 2 message with AM RLC on DCCH channel to initiate the paging procedure. The UTRAN may send the PAGING TYPE 2 message in other processes, without influence on the state in that process, unless otherwise specified.

UTRAN should set the IE "Paging cause" to the cause for paging received from upper layers. If no cause for paging is received from upper layers, UTRAN should set the value "Terminating – cause unknown".

2.1.4 Common Transport Channel (CCH) Setup Request of IUB

The RNC notifies the NODEB PCH transport channel parameters and the relevant parameters of PICH through the Iub interface signaling of “Common Transport Channel Setup Request”. In Figure 2-3, we can see that the two transport block formats of the PCH (0x240 and 1x240), whose power is 2 dB greater than that PCPICH; the NP value of PICH is 36, whose power is 3 dB smaller than PCPICH.



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Figure 2-3 CCH setup request signaling resolution



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2.1.5 System Information Block Type 1

Figure 2-4 System message 1 signaling resolution

The UTRAN notifies UE DRX cycle coefficient with the system information block type 1. As shown in Figure 2-4, the cycle coefficients of CS and PS are 8.

2.1.6 System Information Block Type 5

The UE gets the PCH transport format and the NP value of the PICH by reading the system information block type 5.



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2.2 L2 Signaling Analysis

MACC

FACH

FP

FACH

FP

RAC

H FP

RAC

H FP

FACH

FP

FACH

FP

PCH FP

SCCPCH SCCPCH PRACH PRACH

��

PCCHCCCH CCCH

RLC RLC

MACD MACD

AAL2

(DL) (DL)CCCH(UL)

(UM) (UM)

Figure 2-5 CCH layer structure

Figure 2-5 shows the mapping relation among PCCH, MACC, PCH FP and SCCPCH. The PCCH adopts the TM mode at the RLC layer. The MACC schedule the paging packets. The relevant features of the PCH are represented in the PCHFP frame.

The PCH data frames include the PI information and paging message. To page an UE, two continuous PCH data frames are sent with continuous CFNs: the first frame contains the PI information, and the other contains the paging message.

For NODEB, except NP that is obtained by means of CCH setup, other parameters are present in the PCH FP frame delivered from the upper layer. The PI is contained in the PI bitmap; DRX Cycle length is determined by the time interval of the PCH FP with the same PI; paging time can be worked out based on the CFN in the PCH FP. The frame structure of the PCH FP frame is shown below:



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Header CRC

CFN

First TB

Header

Payload

FT

First TB

Pad

7 0

Payload CRC

Payload CRC (cont)

Last TB

Last TB

Pad

CFN (cont)

TFI

Not Used

PI-bitmap

PI-bitmap

Pad

PI

Spare Extension

Spare

Figure 2-6 PCH FP frame structure

The units in the data frame are described as follows:

Header CRC: The polynomial of cyclic redundancy is calculated according to the header of a data frame by means of the polynomial of (X^7+X^6+X^2+1). The calculation of the CRC should include all the bits in the header, that is, from bit 0 in the first byte (FT field) to the end of the header. The field is 7 bits in length, with the value range of (0–127).

Frame type: Indicates it is a data frame or control frame, 0 for data frame and 1 for control frame. It is 1 bit in length.

Connection frame number (CFN): Indicates the radio frame of which the first data to be received in the uplink or to be sent at the downlink. The value range and length depends on the transport channel used by the CFN. In the case of PCH, the value range is (0-4095), and the length (PCH) is 12 bits. In the case of other channels, the value range is (0-255).

Transport format indicator (TFI): It is the indicator of the transport format used to transport a TTI. It is 5 bits in length, ranging from 0 to 31.

Transport block: It is a data block to be transported or that has been received through the radio interface. The transport format indicated by the TFI describes the transport block length and the transport block set size.

Pay load CRC: The polynomial of cyclic redundancy is calculated according to the payload of a data frame by means of the polynomial of (X^16+X^15+X^2+1). The



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calculation of the CRC should include all the bits in the payload, that is, from bit 7 in the first byte to the byte before the payload CRC. It is 16 bits in length.

Page instruction (PI): Describes whether the PI Bitmap is present in the payload, with 0 for no and 1 for yes. It is 1 bit in length.

PI-bitmap: Bit map of PI0..PIN-1. Bit 7 of the first byte contains PI0, and Bit 6 of the first byte contains PI1,,…, Bit 7 of the send byte contains PI8, and so on. The value range is 18, 36, 72 or 144 PIs). It is 3, 5, 9 or 18 in length. If PI-bitmap is 1, it indicates the UE at the PI monitored is paged.

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Chapter 3 Paging Problem Analysis Process


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Chapter 3 Paging Problem Analysis Process

3.1 Problem Analysis Flow

The paging problem analysis flow is as shown in Figure 3-1. Similar to the general analysis methods of network problems, there are four steps of paging problem analysis, which are detailed as follows:

Network information collection: Collect traffic statistics information related to network and paging, alarm information, complaints of subscribers, network planning information, optimization records and configuration of network parameters;

Determination of optimization goal: Determine KPI of paging problem optimization;

Paging problems location: Locate causes of paging problems

Paging problems optimization: Take corresponding optimizing and adjusting measures according to location results;

Optimization verification: Verify whether the KPI meets the requirements and whether other information about paging is normal after optimization.

Figure 3-1 Paging Problem Analysis Flow



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3.2 Network Information Collection

Network information collection is the first step of paging problem analysis. The optimization personnel should obtain the paging-related information to-be-optimized, such as traffic statistics, subscriber complaints, optimization history record of network planning and radio parameters configuration, so as to prepare for the subsequent analysis.

3.2.1 Traffic Statistics

The paging-related traffic statistics can be observed respectively on the traffic statistics console of RNC, UMSC and SGSN according to different paging areas. RNC traffic statistics corresponds to a RNC area, UMSC traffic statistics corresponds to a location area and SGSN traffic statistics corresponds to a RA. In the actual traffic statistics analysis process, the traffic statistics of CN is mainly analyzed, with combination of the traffic statistics data of RNC and CN. If there is no paging-related traffic statistics on the traffic statistics console, it is necessary for equipment users to establish the paging traffic statistics tasks. The paging-related traffic statistics of RNC, UMSC and SGSN are discussed below based on the paging traffic statistics of our company.

The traffic statistics of RNC is shown in Table 3-1. Attention should be paid to CN_PAGE_IDLE_UE_SUCC_RATE (paging success rate of UE in idle state initiated by CN) and UTRAN_PAGE1_SUCC_RATE (The success rate of Paging Type 1 initiated by UTRAN). These two indexes indicate the page success rate of the corresponding paging area of RNC. CN_PAGE_IDLE_UE_SUCC_RATE indicates the page success rate from the aspect of CN, while UTRAN_PAGE1_SUCC_RATE includes not only CN paging, but also UTRAN system information update and UE state migration (the paging information of UE is cell updating). The two indexes can be used to analyze the paging performance of an RNC area which includes one or more location areas.

Table 3-1 RNC Paging Traffic Statistics Index

Name Description Standard measuring point

CN_PAGE_REQ Count paging times at IU interface

Receive the PAGING messages initiated by CN

CN_PAGE_IDLE_UE_REQ

Count paging times at IU interface of idle subscribers

Receive the PAGING messages initiated by CN when UE is in idle status

CN_PAGE_IDLE_UE_SUCC

Count paging success times of idle subscribers

Receive RRC connection request message of UE and the reason belongs to the called type, such as “Terminating Conversational Call”

UTRAN_PAGE1_REQ

Count times of initiating PAGING TYPE 1 initiated from UTRAN side

PAGING TYPE 1 message initiated from UTRAN side

UTRAN_PAGE1_SUCC

Count PAGING TYPE 1 message initiated from UTRAN side and the times of UE success receive response received

UE paging response message received at UTRAN side .

CN_PAGE_IDLE_UE_SUCC_RATE

Count paging success rate of idle UE initiated by CN

The calculation index, obtained by the formula of [CN_PAGE_IDLE_UE_SUCC]/ [CN_PAGE_IDLE_UE_REQ]

UTRAN_PAGE1_SUCC_R Count the paging The calculation index, obtained by



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ATE success rate of Page Type 1 initiated by UTRAN

the formula of [UTRAN_PAGE1_SUCC]/[UTRAN_PAGE1_REQ]

The relevant traffic statistics of UMSC paging are all based on a location area, as shown in Table 3-2. Generally, the location area will not be configured cross RNC and BSC, so we can carry out statistics on the paging success rate, the first paging success rate and non-first paging success rate of a location area. The location area paging success rate focuses on the paging status of a location area, not on paging repeat times, while first paging success rate and non-first paging success rate focus on the influence of paging repeat times on paging success rate.

ion times transmisspagingFirst messages response-no delivered ofnumber ion times transmisspagingFirst rate success pagingLA =

ion times transmisspagingFirst timesresponse pagingFirst rate success pagingFirst =

timesresponse repitetion paging Interface timesrepitetion paging Interfacerate success pagingfirst -Non =

Table 3-2 UMSC Paging Traffic Statistics Indexes

Name Description Standard measure point The first paging times

The first sending times of Paging Req by MSC

Carry out statistics when MSC sends PAGING message to RNC/BSC

The first paging response times

Successfully receiving response times after the first sending of Paging message by MSC

Carry out statistics when MSC receives PAGING RESPONSE after the first sending of Paging message

Interface paging repeat times

The non-first paging times of MSC

Carry out statistics when MSC sends PAGING message to RNC/BSC

Interface paging repeat response times

Successfully receiving response times after the non-first sending of Paging message by MSC

Carry out statistics when MSC receives PAGING RESPONSE after the non-first sending Paging message

The first paging times of Iu interface

The first sending Paging times of Iu interface

Carry out statistics when MSC sends PAGING message to RNC

Lu interface paging repeat times

The non-first sending Paging times of Iu interface

Carry out statistics when MSC sends PAGING message to RNC not at the first time

Delivery paging no-response times

Times of having no paging response messages received Paging timer stay-over statistics

The relevant traffic statistics indexes of SGSN paging are all based on a RA, as shown in Table 3-3, the paging success rate of a certain RA can be obtained.

questTimesingRAGroupPagTimesingFailureRAGroupPagquesTimesingRAGroupPagccessRateRAPagingSu

ReRe



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Table 3-3 SGSN Paging Traffic Statistics

Name Description Standard measure point

Group paging request times of each RA

It provides delivery group paging request times in the specific RA, not including retransmission messages

SGSN sends Iu interface paging request message (PAGING), and its CN Domain is PS.

Group paging failure times of each RA

It provides group paging failure times in the specific RA

Paging retransmission message times reach maximum.

During traffic statistics analysis, attention should be paid to “location area paging success rate” and “ RA paging success rate”, which are KPI measuring paging performance. The RNC paging traffic statistics CN_PAGE_IDLE_UE_SUCC_RATE and UTRAN_PAGE1_SUCC_RATE can be taken as reference analysis.

3.2.2 Subscriber Complaints

If paging messages are lost, UE will not be called. The calling party will hear the system prompt tone “the subscriber you dialed is out of service”. We can learn about the subscriber complaints from 1860 Customer Service Center of pilot office or learn about the cases of “out of service” by contacting with the complainer directly. Attention should be paid to the cases of UE called failure, and information to be collected is shown in Table 3-4, but not limited to it:

Table 3-4 Subscriber complaint information

Time Name (complainer)

UE No. (complainer)

UE No. (the called)

UE type (the called) Place Whether it

is often Description

Sort out complaint information, seek for rules and observe whether the information belongs to the following cases:

! Whether complaints occurs when paging is busy in the daytime and idle at night; if paging failure occurs at the peak traffic, paging congestion analysis should be emphasized on; if not at the peak traffic, other factors should be analyzed.

! Whether types of the called UE are the same. Problems probably exist in UE itself.

! Whether the complaint place is centralized; it is possibly because of signal coverage;

Find the rules and solve problems more quickly.

3.2.3 History Record of Network Planning Optimization

Obtain the network planning report, and pay attention to the division of the paging area (location area and RA). Obtain network planning report: If it is the optimization before network is put into service, the planning report can be obtained from the planning manager responsible for the project; if it is the optimization after network is put into service, the planning report can be obtained from the client. The planning report mentioned above should include planning reports after each network capacity expansion.



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For the network that has been put into service, it may have experienced several optimization processes before this optimization. Then we should obtain the history optimization records and learn about the network adjusting process and outstanding problems. Emphasis should be put on optimization records about coverage absence, system overload, paging loss and low paging channel power allocation.

3.2.4 Radio Parameter Configuration

Parameters related to paging are as follows, which should be collected before optimization:

! CN paging retransmission times and paging interval; ! UTRAN paging retransmission times and paging interval; ! DRX paging cycle coefficient k (DRX paging cycle = 2k); ! Paging indication quantity NP included in a PICH frame; ! Channel power allocation of PICH and PCH; ! Whether CN adopts global paging; ! UE ID used by CN paging (IMSI,TMSI or PTMSI)

3.3 Determining Optimization Goal

Two KPI of “location area paging success rate” and “RA paging success rate” should meet the optimization requirements. The paging success rate is recommended to be over 86%.

3.4 Locating Paging Problems

3.4.1 Determining Basic Location Direction

Paging problem optimization is intended to guarantee the paging KPI. Whether UE can respond successfully is directly related to the paging KPI. From this aspect, paging problems can be generally divided into three parts:

! Paging message is not delivered at the air interface at all. If paging message is not delivered at the air interface at all, it is most likely that paging is lost. Paging loss is a frequently-seen problem during paging process and it is the emphasis of analysis in this document. For detailed paging loss analysis, please refer to Section 2.4.2 and Section 2.4.3. However, the reason why paging has not been sent out is probably the transmission faults of IUB interface or faults of other equipments, which can be seen through viewing the alarm information.

! Paging message has been delivered, but UE does not receive the message or receives the wrong message. According to the specific subscriber complaints, if problems exist on called UE only (prompt tone “the subscriber you dialed is out of service”), because the reason is probably that the power allocation of PICH and PCH is too low or there are problems with UE performance; if problems exist in calling and



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called UE, the reason is probably that signal coverage dead zones exist in the area.

! UE fails in responding after receiving paging messages. As shown in Figure 1,The problem is related to access failure, for solutions, please refer to WCDMA RNP Access Process Problem Analysis Guidance.

During paging problem location, problems can be located by analyzing paging traffic statistics, alarms and subscriber complaints. Paging loss generally occurs in the period when traffic is heavy. Check “location area paging success rate” and “RA paging success rate” of CN traffic statistics, if these two indexes are low (lower than 86%) when traffic is heavy, and subscriber complaints are centralized in this period, paging loss is serious and attention should be paid to analyzing it. Meanwhile, check whether RNC overload alarm or RNC flow control alarm occurs in CN. If these alarms exist, the probability of paging loss is big.

If events that two indexes are low are evenly distributed on the time, and subscriber complaints are regional, check other reasons except “paging loss”: paging channel power allocation, signal coverage and UE performance.

It is necessary to make dialing test analysis on the site for further analysis on paging problems. Select the period when traffic is heavy and the area where subscriber complaints are centralized, trace paging message delivery and UE paging response process on the CN and RNC maintenance consoles during the dialing test process.

3.4.2 Direct Causes of Paging Loss

Paging will be lost in the following cases: 1) System is in paging flow control state. Because paging message is sent frequently

and System flow-controls paging. If System detects that CPU occupation or message queuing occupation reaches the preset threshold, paging flow control will be triggered and paging message will be lost unconditionally.

2) PCH capacity restriction; Based on the current PCH coding mode, one TTI can only transmit 240bits. If IMSI paging is utilized, only three UEs can be paged at the same paging period; and if TMSI and PTMSI paging are utilized, only five UEs can be paged at the same paging period. If the quantity of UEs paged at the same paging period is beyond the system processing capability, paging loss will occur.

3) Other causes: Transmission faults of IUB interface and equipments faults. Probability of those faults is small and can be viewed from the alarm console.

3.4.3 Further Analysis on Paging Loss Cause

The direct causes of paging loss are system overload and paging channel overload, after further analysis of its causes, it is found that CN and RNC have adopted inappropriate paging strategies, for detailed analysis, please refer to hyperlinks as follows:

! Too large paging area planned ! Improper setting of CN paging retransmission times and interval ! Improper setting of UTRAN paging retransmission times and interval ! CN adopts whole-network paging ! Improper setting of DRX paging cycle coefficient ! Improper setting of Np value ! CN adopts improper UE identifier



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3.4.4 Other Cause Analysis

! Too low power allocation of paging channels ! Existence of coverage dead zones ! UE performance problems

3.5 Paging Problems Optimization

The paging problem optimization methods are described in detail in Section 3.

3.6 Optimization Verification

After network is optimized and adjusted, the optimization results should be verified. The frequently-used verifying methods are available as follows: have it run and check relevant paging traffic statistics, check whether there are paging alarms, collect subscriber complaint information, and carry out UE called dialing test on site.

! Traffic statistics: Check mainly whether “location area paging success rate” and “RA paging success rate” achieve the optimization goal 86% specified in advance;

! Subscriber complaint: Whether there is any subscriber complaint in a certain period;

! Dialing test: Test UE called success rate when traffic is at the peak and in the place where subscriber complaint occurs. During dialing test, it is unnecessary to through-connect UE, just listen to ring back tone and prompt tone.

OWJ104101 WCDMA Paging Procedure ISSUE1.0 Chapter 4 Typical Paging Problem Analysis


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Chapter 4 Typical Paging Problem Analysis

4.1 Too Large Paging Area Planned

4.1.1 Problem Analysis

In general, CN pages target UE in one paging area (location area or RA), which is called intra-office paging. For CS domain service, CN identifies and pages UE with location area. In protocols, location area is defined as the area where mobile terminals can move freely without updating VLR. A location area may contain one or more cells. For PS domain service, CN identifies and pages UE with routing area. RA is defined as the area where mobile terminals can move freely without updating SGSN in a specified operation mode. A RA may contain one or more cells. The relationship between location area and RA is specified in GSM, namely, RA can be equal to location area in size, or only the subset of a certain location area.

If paging area is planned too large, the same paging message of a network paging mobile station may be sent in multi cells, which will overload the paging channel as well as increasing signaling flow at the Iub interface. If the paging channel of a cell is overloaded in a certain period, the paging message sent to UE in the cell will be caused lost and the power-on subscriber within the service area can not be paged (The subscriber is out of service).

On the contrary, if paging area is planned too small, subscribers will update locations frequently while moving, which will increase signaling flow of the system. When network is just put into service, PS paging traffic is not heavy, RA may be planned larger, it can be planned as per n=1. With the development of network, the demands for PS paging traffic are increasing, in this case RA can be planned smaller consequently. However, too small RA may cause more paging area update events of subscribers while moving, and that signaling overhead on network side becomes larger. Moreover, frequent location update will influence the standby time of UEs.

The paging area maximum value is determined by the paging channel capacity.

4.1.2 Optimization Measures

Divide location areas where network capacity or paging traffic is bigger than a specified threshold, which can reduce paging message flow efficiently.

4.2 Improper Setting of CN Paging retransmission Times and Interval


In order to guarantee the paging success rate, CN will retransmission paging message at the IU interface. CN paging retransmission times and interval can be configured. Because paging is initiated specific to location area, paging retransmission will increase paging traffic. Especially in case of public downlink channel congestion at the



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air interface, paging traffic will double due to paging repeat, which will waste downlink channel resources seriously. CN paging retransmission configuration should be in accordance with UTRAN.

CN paging retransmission is the retransmission paging in case that UE has not responded at the first time, which can increase paging success rate and connection rate. But from data in GSM network, paging retransmission success rate is low, especially at the second time or even more, which contributes a little to paging success rate and connection rate. Experience data indicates that: Generally, the success rate of the first paging is approaching to 86%, and the retransmission paging rate is 1.8%. Herein, retransmission paging success is mainly the second paging success, while success rate of the third paging is estimated less than 0.2% calculated by the decreasing pattern, and the third paging (the second repeat) has little influence on paging success rate. The paging mode of WCDMA is similar with that of GSM, from online statistics, frequent CN paging contributes little to the paging success rate; contrarily, it increases the system load.

It is no good for CN paging interval to be too short. CN sends paging messages to RNC through the IU interface, and RNC calculates the paging time according to IMSI attached by the paging message and arranges a delivery at the corresponding paging time of the nearest paging cycle. Currently, RNC of our company also adopts the paging retransmission mode, the default is repeating once and the retransmission interval is a paging cycle. From analysis above, the maximum interval between the time that RNC receives CN paging and the time that message is delivered to the air interface is a paging cycle. If RNC retransmits once, CN paging interval should be longer than two paging cycles. The paging cycle realized by our company is 2.56s. If CN paging interval is bigger than 2.56s and less than 5.12, when CN retransmitted paging reaches, and RNC has not finished repeat paging, RNC will arrange paging in the following paging cycle, Thus only three paging messages are sent in fact, not four expected, which causes paging message loss


CN paging retransmission configuration should be in accordance with UTRAN. When UTRAN retransmits paging once, it is suggested for CN configuration to retransmit once (totally twice) at the interval longer than two paging cycles. If the paging cycle is 2.56s, it is suggested that CN paging retransmission interval be 5s and configuration be 5s with the consideration of paging loss during Iu/Iub flow control. Reduce paging repeat times and increase paging interval, keep the time of no paging responses unchanged, interval of reporting prompt tones when there is no paging response will not be influenced.

CN paging interval and repeat times can be configured through software parameters.

4.3 Improper Setting of UTRAN Paging Retransmission Times and Interval


In order to reduce paging message flow at the Iu interface and increase the probability that UE receives paging message, UTRAN can retransmit paging messages. UTRAN paging retransmission configuration should be in accordance with CN paging retransmission.



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Paging is delivered at the fixed time (a paging cycle), and UTRAN paging interval is the integer multiple of a paging cycle, one paging cycle in general. Therefore, we can adjust the UTRAN paging repeat interval by adjusting DRX paging cycle coefficient k.

UTRAN paging repeat times should not be too many; otherwise, adding paging repeats at Iu interface, the paging channel load at UU interface will increase rapidly. In addition, UTRAN is realized on MACC layer, and MACC does not identify the specific PRC message, MACC will go on repeating paging even if UE replies paging response message. Too many UTRAN paging repeat times will cause the unnecessary system overhead and message flow at UU interface.


It is reasonable for paging retransmission times to keep the current default configuration. It is also reasonable to adjust paging retransmission times on RNC maintenance console using MML command SET WFMRCFGDATA.

4.4 CN Adopts Whole-Network Paging


Considering improving call connection rate, CN side can be configured with whole-network paging, which bears the characteristics that paging has overridden the concept of location area, and is initiated specific to all UTRANs suspended under whole CN. In this case, paging traffic becomes larger, especially when multiple location areas are suspended under CN, the location areas with smaller capacity will be overloaded, and can not recover for a long time.


Global paging should be avoided in CN. From experiences on GSM network, the whole-network paging of CN is the important cause of overload of location area with smaller capacity; meanwhile, CN global paging contributes little to the improvement of connection rate of long-distance incoming call.

CN global paging is useful only when UE location area is recorded as failure by HLR, which hardly occurs, however, once it occurs, it means serious fault occurs; even more CN global paging does not work.

4.5 Improper Setting of DRX Paging Cycle Coefficient


When UE is in IDLE and PCH state, UE will utilize the discontinuous reception technology “Discontinuous Reception (DRX)” to reduce power overhead. According to Protocol TS25.304, paging cycle length (DRX cycle length) = MAX (2K PBP). where, K refers to DRX cycle length coefficient, PBP refers to Paging Block Periodicity which is applied only in TDD mode, for FDD, PBP=1, so, DRX cycle length = 2K.

DRX paging cycle coefficient of UE has three sources: system message, CN paging message and UU interface signaling of UTRAN, while the processing way of CS and PS is different.



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For PS domain, DRX paging cycle coefficient is obtained by the negotiation between UE and SGSN through NAS layer message (attach process), and the negotiation data is adopted as standard whether UE is in IDLE or connection state, however, paging coefficient of CS domain is adopted if negotiation fails.

For CS domain, the minimum values of system message and CN paging message are taken as DRX paging cycle coefficient if UE is in IDLE state. And the minimum values of system message, CN paging message and signaling at UU interface of UTRAN are taken as DRX paging cycle coefficient if UE is in connection state.

Settings of DRX paging cycle coefficient K should be considered with the following factors: 1) DRX paging cycle coefficient K determines the DRX cycle length, the larger the

value of K is, the longer the DRX cycle is. Meanwhile, UE power consumption will be lower, however, the value of K makes UE paging cycle longer. Namely, UE paging response time becomes longer. If K is set too small, paging cycle will become smaller, and UE processing paging overhead and power consumption will increase. In the protocol, the value is within the range of 2 ~12, the current value of our company is 8, and the paging cycle is 2.56 seconds.

2) According to the current coding mode of PCH, a TTI can transmit only 240 bits, if IMSI paging is utilized, only 3 UEs can be paged at the same paging moment; if TMSI paging is utilized, only 5 can be paged at the same paging moment. And if the number of UE paging at the same paging moment exceeds the processing capacity of system, it will cause paging loss and call loss. If K is set too small, the paging cycle will become shorter, the probability of the same calculated UE paging moment will increase, consequently, the probability of paging loss will increase.

3) Because UTRAN paging retransmission interval is a paging cycle, when setting DRX paging cycle coefficient K, we should consider the retransmission interval of UTRAN paging, and the K value should be set in coordination with CN paging retransmission.


The lower limit of value K should be set with the consideration of saving UE power consumption and reducing the probability of the same UE paging moment, and the upper limit of value K should be set with the consideration of the repeat interval of UTRAN paging. During the actual setting process, the value K should be a value within 2 ~12, i.e., 5, 6, 7 and 8, and the corresponding paging cycles are 320ms, 640ms, 1280ms and 2560ms. Suppose that the CN paging repeat time is 1 (totally broadcasting 2 times), and the interval is 2s, so how should the UTRAN repeat times and the intervals be set? Generally, the following rules should be followed: 1) If the UTRAN retransmission time is 0 (no retransmission of UTRAN), the DRX

cycle of UTRAN shall be smaller than CN retransmission interval (2s) ,namely, the value K at this time should be set to 7 or 8 (1.28s,2.56s), the setting to be 8 is considered with the paging loss during lu/luB paging flow control;

2) If the UTRAN retransmission time is 1, the DRX cycle of UTRAN shall be smaller than half of the CN retransmission interval (1s) , namely, the value K at this time should be set to 6 or 7 (0.64,1.28s), the setting to be 7 is considered with the paging loss during lu/luB paging flow control; (Configuration recommended)



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4.6 Improper setting of Np value


Np refers to PI paging indication number delivered in a certain frame by paging indication channel PICH, the value of which is within the range of (18, 36, 72, 144), which is indicated by Number of PI per frame in System Message 5. UE will receive PICH frame at the specified paging time and find the corresponding PI indicator bit (the qth PI). Only when the corresponding PI indicator bit is effective, UE demodulates the corresponding S-CCPCH frame.

( )( )( ) NpNpSFNSFNSFNSFNPIq mod144

144mod512/64/8/18

×+++×+=

Where, PI = DRX index mod NP = (IMSI div 8192) mod NP, SFN refers to UE

paging moment.

Significance of Np in the actual network: IMSI is divided into Np groups by this parameter, and all IMSIs in each group adopt the same PI. Influences of Np value on network: If Np value is too small, the corresponding UE number in each group will be larger. For each IMSI, if the probability that PI indication occurs increases, times that IMSI is waken up will increase, which is no good in saving UE power. If Np value is too large, the corresponding IMSI number in each group will be smaller. For each IMSI, if the probability that PI indication occurs decreases, times that IMSI is waken up will decrease. However, if Np is larger, the bit number of each PI will decrease and PICH demodulation performance of UE will be required higher.


Np value is within the range of (18, 36, 72, 144), which should be determined according to the current network subscriber quantity (subscriber traffic). Generally, the value should be larger when subscribers are of large amount, and the value should be smaller when there are fewer subscribers. In the actual network, the intermediate 36 or 72 can be selected.

4.7 UE Identifier Utilized by CN Paging


Network can page multi UEs at the air interface at the same paging time using paging type 1 message. Because of PCH capacity restriction, UE quantity is closely related to UE identifiers used in paging messages, namely, UE identifier influences the paging channel capacity. Compared with CN paging, the probability that UTRAN initiate paging is much smaller. Only the case that CN initiates paging is considered:

When UE is in IDLE state, CN can only page three UEs at the same paging time using IMSI;

When UE is in IDLE state, CN can only page five UEs at the same paging time using TMSI or PTMSI;



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When UE is in CELL_PCH or URA_PCH state, no matter what paging identifier CN uses, UTRAN transfers UE identifier to U-RNTI and pages, it can only page five UEs at the same paging time.

From analysis above, CN can increase PCH capacity using UE temporary identifiers “TMSI and PTMSI”.


CN optimization pages by using UE temporary identifier TMSI and PTMSI, and it can be adjusted with software parameters.

4.8 UTRAN Should Activate IMSI ATTACH and DETACH Functions


After UE is powered on and registered successfully, MSC/VLR will set the subscriber state as ATTACH state. IMSI DETACH means that after mobile subscribers power off, MS initiates a DETACH flow and MSC/VLR sets the subscriber state as IMSI detach. Generally, HLR will not be informed by this flow. In DETACH state, if the MS is called, CN will directly inform the calling party that the MS is powered off, which skips of the process of sending useless paging messages to UE.

As shown in Figure 4-1, UE determines whether IMSI ATTACH and DETACH processes can be adopted through receiving the system message 1. Gsm MAP IE consists of two octets, one is T3212, and bit1 of the other octet is ATT identifier. “0” means that the network does not allow UE to adopt IMSI ATTACH and DETACH processes. In Figure 4-1, “0a 01” means that T3212 is 60 minutes, UE is admitted to adopt IMSI ATTACH and DETACH processes.

During actual network operation, UTRAN should activate IMSI ATTACH and DETACH functions.

Table 4-1 IMSI ATTACH and DETACH Identifier

8 7 6 5 4 3 2 1 T3212 octet 1 Spare ATT octet 2



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Figure 4-1 System Message 1 Resolution


Check and modify IMSI attachment and detachment admission indication by using the Command “LST CNDOMAIN and MOD CNDOMAIN” on RNC maintenance console.

4.9 Too Low Power allocation of Paging Channels


Phenomenon: Subscriber complaints are centralized in some certain areas, when UE is called, the prompt tone “the subscriber is out of service” will occur, while UE can work normally while calling; the print message of paging decoding failure can be seen at the UE daemon, which is the problem of the over-low paging channel power allocation.

Paging channels include PICH and PCH. Too low PICH power will lead to UE resolution PI indication error. Resolution of PI value from “0” to “1” will cause false alarm and UE power waste; resolution of P1 value from “1” to “0” will cause paging miss and loss. If PCH power is too low, UE will fail in decoding the paging messages.

The current baseline power allocation: PICH is -3dB and PCH is -2dB, which are both relative to pilot channels power.


Improve the power allocation between PICH and PCH properly. Check and modify PICH power by using MML Command LST CHPWROFFSET and MOD PICHPWROFFSET on RNC maintenance console, check and modify PCH power by using Command LST SCCPCH and MOD SCCPCH.



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4.10 Existence of Coverage Dead Zones


Phenomenon: Subscriber complaints are centralized in a certain area, UE fails both in calling and being called, the signal strength shown in UE panel is low, and RSCP and EC/IO of pilot signals tested with the drive test equipment are lower than indexes required for UE normal access, by which coverage dead zone is identified in this area.


Carry out coverage optimization, for specific optimization measures, please refer to relevant Guidance.

4.11 UE Performance Problems


UEs of different subscribers may be made by different manufacturers, the receiving performance and demodulation performance of different UEs are also different. From GSM network experiences, some paging problems are located in UEs themselves.

Sort out and analyze subscriber complaint materials. If the called UE is of the same type, problem may exist in UEs.


Take a called verification test on UEs from different manufacturers, if conditions permit, compare UE receiving performance parameters and demodulation performance parameters, including testing RSCP and EC/IO of pilot signals received at the same place and learn about the service demodulation thresholds of UEs.

wcdma paging analysis

Documents

paging type

paging flow

paging process analysis

paging occasion

paging initiation

paging channel selection

iu interface paging

problem analysis flow