WCDMA RNP Paging Area Planning Guidance

Huawei Technologies Co. Ltd.

Product version Confidentiality level

V100R001 For internal use only

Product name: WCDMA

RNP Total pages: 27

WCDMA Paging Area Planning

Guidance

For internal use only

Prepared by: URNP-SANA Date: 2003-02-28

Reviewed by: Date:

Reviewed by: Date:

Approved by: Date:

Huawei Technologies Co., Ltd.

All rights reserved

WCDMA Paging Area Planning Guidance For internal use only

10-4-30 Confidential , Total 25

Revision Record

Date Revision version

Description Author

2003-02-28 0.90 Initial transmittal Miao Jiashu

2003-03-28 1.00 Revision based on the review comments Miao Jiashu



Table of Contents

1 Introduction to Paging Area ..................................................................................................... 6

2 WCDMA Paging Mechanism ................................................................................................... 6

2.1 Paging Cause ..................................................................................................................... 7

2.1.1 Paging Type 1 .............................................................................................................. 8

2.1.2 Paging Type 2 .............................................................................................................. 8

2.2 Structure of Paging Channel .............................................................................................. 8

3 WCDMA Paging Channel Capacity Calculation .................................................................... 11

3.1 CN_ID IMSI Paging .......................................................................................................... 11

3.2 CN_ID TMSI Paging ......................................................................................................... 11

3.3 UTRAN_ID Paging ........................................................................................................... 12

4 Analysis on Location Area Size for Mixture Service .............................................................. 12

4.1 Analysis on Calculation Method ....................................................................................... 12

4.2 Key Value Recommendations .......................................................................................... 16

5 Instance of Paging Area Cell Size in Typical Environment ................................................... 16

6 Precautions in the Paging Area Planning .............................................................................. 22

6.1 Paging Area Size Restriction ........................................................................................... 22

6.2 Geographic Distribution of Paging Area .......................................................................... 23

6.3 Paging Area Crossing MSCs and RNCs ......................................................................... 24

7 Summary of Pending Problems ............................................................................................. 25



List of Tables

Table 1 SRB parameters of PCCH channel .............................................................................. 8

Table 2 Corresponding relations between the bits and different IEs in PCCH ......................... 9

Table 3 Values of the four assumption conditions for paging area dimensioning .................. 20

Table 4 Location area dimemsion for paging based on CN ID of IMSI .................................. 21

Table 5 Location area dimemsion for paging based on CN ID of TMSI ................................. 21

List of Figures

Figure 1 CS service reference model ....................................................................................... 17

Figure 2 PS service reference model ....................................................................................... 17

Figure 3 Assumption conditions for the dimensioning of the dense urban area ...................... 20

Figure 4 Diagram of paging area dimensioning for paging based on CN ID of IMSI .............. 21

Figure 5 Diagram of paging area dimensioning for paging based on CN ID of TMSI ............. 22

Figure 6 Schematic diagram of location area division .............................................................. 24

Figure 7 Motorola test result ..................................................................................................... 26



WCDMA Paging Area Planning Guidance

Key words: LA, RA, URA, Paging

Abstract: This article briefs some concepts related to paging area in WCDMA, and then depicts

how to plan the paging area in the WCDMA network with the equipment. It also

provides the analysis methods and calculation formulas, with instances. It finally lists

some pending problems occurred in the analysis.

List of abbreviations:

LA Location Area

RA Routing Area

URA UTRAN registration area



1 Introduction to Paging Area

In the WCDMA system, there are many types of area concepts, such as BSC

area, RNC area, location area (LA), routing area (RA), MSC area, VLR area, SGSN

area, Zones for Regional Subscription (RSA), service area, group call area, UTRAN

registration area (URA), cell area and etc. Among which four area concepts are

mainly related to paging area: Location Area and Routing Area (corresponding to the

CN side), and Registration Area and Cell areas (corresponding to the UTRAN side),.

When the UE is in the RRC-IDLE state, for the CS domain service, the CN

identifies and pages the UE with the location area. In the protocol, location area

refers to an area that the mobile terminal can freely move without updating the VLR.

One location area can cover one or more cells. Therefore, when several MSCs

share one VLR, the location area can cross MSC areas. But in practice, one MSC is

bound with one VLR in most cases, so the LA can cross RNC areas instead of MSC

areas. That is, one LA can be controlled by one CN serving node (UMSC or

3G_MSC/VLR) only. Therefore one MSC area can contain one or more LAs.

When the UE is in the RRC-IDLE state, for the PS domain service, the CN

identifies and pages the UE with the routing area. RA refers to an area that the

mobile terminal can freely move without updating the SGSN under the specific

operation mode. One RA can contain one or more cells. The relation between the

routing area and the location area the same as the GSM, that is, a routine area can

equal to a location area in size, or can be a subset of a location area. Therefore, RA

is always contained in an LA. In addition, RA can cross RNC areas instead of SGSN

areas. That is, one RA can be controlled by one CN serving node (UMSC or

3G_SGSN) only.

When the UE is in the RRC-CONNECTED state, the UE is paged with the

internal area of the UTRAN, which have the UE state be transited to CELL_FACH. In

the RRC-CONNECTED mode, the location of the UE can be learnt at the cell level or

URA level. After the RRC connection mode is set up, the UTRAN will assign the UE

with a temporary ID RNTI used in the UTRAN. The internal area updating process is

a radio network process, whose structure is invisible outside the UTRAN.

URA is a set of a group of cells, and one cell can belong to multiple URAs, so

URAs and cells are in multiple-to-multiple relation. URA and LA do not have fixed

relation, nor do the URA and RA.

2 WCDMA Paging Mechanism



2.1 Paging Cause

The 3GPP protocol specifies two paging types: PAGING TYPE 1 and PAGING

TYPE 2

Viewing from the paging cause, paging is to be initiated in the following cases:

Traffic modeling dependent paging, including the following cases:

1. The UE is called in the idle state (PS/CS) to set up communication

2. The UE is called in the connection state or it needs to receive downlink

data (caused by a PS service)

Traffic modeling independent paging, including the following cases:

1. System information updating when the UE is in the idle or connection

state, or URA and cell updating when the UE is in the connection state1

2. Periodical paging initiated at the network side when the location service

is supported

3. Paging initiated when the CN side starts the security mode (including

encryption at the CN side or completeness protection parameters)

4.

As the analysis on the traffic modeling independent paging will be complicated

with many uncertain factors, this article only discusses the influences on the paging

capacity caused by the traffic modeling dependent paging.

To increase the UE paging success rate, the UTRAN sometimes transmits a

paging message for several times. It is realized at the equipment side as follows:

CN Side: Before receiving the paging response of the UE, the CN is allowed to

initiate 5 times of paging to each UE (it is fixed in the program, which cannot be

modified). If the UE is assigned with a TMSI, the paging of the former two times will

be transmitted in the TMSI format, and the latter three paging will be transmitted in

the IMSI format. For the paging interval, it is (t-1) s 2 for the former four times, and t

s for the last time. The upper limit of paging interval is 5s, and it is 3s by default.

UTRAN side – The UTRAN supports paging message re-transmission at the air

interface. The re-transmission times is once by default, but can be modified to 0..k (k

is the upper limit 2, that is, the paging can be transmitted for three times at the

maximum) with the MML command. Please note that the re-transmission times is

1 Example: When the UE needs to transit the state of the UE from URA_PCH or CELL_PCH to CELL_FACH; or

the network side expects to release the RRC connection, it needs to initiate paging to transit the state of the UE from URA_PCH or CELL_PCH to CELL_FACH, and then release the RRC connection. 2 This parameter should be set with care. It must be greater than the interval required for the paging response of

the UE in the normal case. Especially when NodeB is in the asynchronous work mode, the value of this parameter should be greater.



dependent of the value of parameter k instead of the response of the UE. It

means the potential paging volume at the air interface is k+1 times more.

Recommendation: As the CN re-transmits paging message, we can set the

paging re-transmission times at the CN side only but not at the UTRAN side for a

higher paging efficiency.

2.1.1 Paging Type 1

For the UEs in the idle, CELL_PCH or URA_PCH state, the UTRAN transmits

PAGING TYPE 1 message through the PCCH channel to start the paging process.

Then these UEs will monitor the corresponding paging channel according to the

instruction of the PICH and DRX requirement.

As the PAGING TYPE 1 message is sent through the PCCH channel, and it is

specified in the protocol that each SCCPCH can contain only one PCH channel,

which corresponds to one PICH channel (The UE selects the suitable PICH channel

according to the algorithm specified in the protocol 25.304). Therefore, the paging

capability of the network will be restricted by the paging area size. On the other hand,

the paging area planning is mainly for reasonable dimensioning of LA, RA and URA

for PAGING TYPE 1.

2.1.2 Paging Type 2

For the UEs in the CELL_DCH or CELL_FACH state, the UTRAN transmits the

PAGING TYPE 2 message through the DCCH channel to start the paging process.

In the CELL_DCH and CELL_FACH connection modes, as the paging is

transmitted through the DCCH channel, the paging capability of the air interface is

not affected. Therefore, in the paging area planning, it is mainly to analyze the

influence on the paging area planning caused by the paging capacity when the UE is

in the idle, CELL_PCH or URA_PCH state.

2.2 Structure of Paging Channel

The logical channel for paging is PCCH, whose parameters are as follows

(Refer to 34.108 V340):

Table 1 SRB parameters of PCCH channel

Higher layer RAB/signalling RB SRB

User of Radio Bearer RRC

RLC Logical channel type PCCH

RLC mode TM

Payload sizes, bit 240 (alt. 80)

Max data rate, bps 24000 (alt. 8000)

TrD PDU header, bit 0



The above table shows that PCCH has two formats of 240bit/10ms TTI and

80bit/10ms TTI. Obviously, the paging capability of the former one is much greater

than the latter one. At present, Huawei can configure only one PCH paging channel

for each cell, and support the format of 240bit/10ms TTI only3.

According to the specification of the 25.331 protocol, the PCH paging channel

transfers three types of information only: paging list, BCCH modified information 4

and Extension mechanism for non-release99 information5. Where, only the paging

list is for storing universal paging message. After the above three types of

information are mapped to the 240bit of the PCCH, the sequence and the number of

occupied bits are specified definitely. The actual situation of the RNC is as follows:

Table 2 Corresponding relations between the bits and different IEs in PCCH

Name Number of bits

Description

PCCH-MessageType 1 Indicates paging type 1 is selected

OPTIONAL(PagingRecordList) 1 Optional ID

OPTIONAL(BCCH-ModificationInfo) 1 Optional ID

OPTIONAL(Extension mechanism for non- release99 information)

1 Optional ID

PagingRecordList Index 3 PagingRecordList ::=SEQUENCE(SIZE(1..MaxPage1))OF

PagingRecord, here, MaxPage1= 8；

PagingRecord Choice 1 Chooses the bit between CN-Identity and

UTRAN-Identity6

cn-Identity part (used when

PagingRecord Choice is selected)

PagingCause 3

Enumerated(Terminating Conversational Call,Terminating Streaming Call,Terminating Interactive Call,Terminating Background Call, Terminating High Priority Signalling,

Terminating Low Priority Signalling, Terminating – cause unknown)

CN-DomainIdentity 1 CN-DomainIdentity::= ENUMERATED {

cs-domain, ps-domain }

3It is known that NOKIA uses alt 80bit/10ms TTI in Hutchison’s network in Hongkong.

4 BHCA-SIBchange. This is a paging request caused by system information update. For example, system

information block 7 has a parameter requiring fast update, that is, uplink interference. This parameter is used to calculate the initial transmission power of the random access channel in the case of random access. The requirement of this aspect depends on the update frequency of the uplink interference value. The update requirement of other information block is less (including the dynamic parameter configuration at the background and the dynamic parameter update by the RRM in the communication process). The paging requirement caused by the system information update is defined to BHCA-SIBchange. 5 At present, this part is not processed in the practice, so the influence of this part is not necessary to be

considered. 6 CN ID is used when the CN initiates paging to the UE in the idle mode; UTRAN ID is used when the UTRAN

actively initiates paging or when the CN initiates paging to the UE in the connection (CELL_PCH or URA_PCH) state.



cn-pagedUE-Identity Choice 3

IMSI-GSM-MAP, TMSI-GSM-MAP,

P-TMSI-GSM-MAP, IMSI-DS-41, TMSI-DS-41

cn-pagedUE-Identity

4＋60＝64

IMSI-GSM-MAP ::= SEQUENCE (SIZE (6..15)) OF Digit. Where, Digit ::= INTEGER (0..9). That is each Digit

occupies four bits. As the length of the IMSI is

changeable, when this item is selected, four bits (0000－1001) are to be added, indicating the length adopted.

32 TMSI-GSM-MAP ::= BIT STRING (SIZE (32))

32 P-TMSI-GSM-MAP ::= BIT STRING (SIZE (32))

5–7 IMSI-DS-41 ::= OCTET STRING (SIZE (5..7)). It is not

used at present.

2–12 TMSI-DS-41 ::= OCTET STRING (SIZE (2..12)). It is not

used at present.

utran-Identity part( used when PagingRecord Choice is selected)

Optional 1 Indicates whether the information of cn-OriginatedPage-connectedMode-UE (used by the CN to initiate paging in the connection state)

U-RNTI

SRNC-Identity 12 SRNC-Identity ::= BIT STRING (SIZE (12))

S-RNTI 20 S-RNTI ::=BIT STRING (SIZE (20))

cn-OriginatedPage-connectedMode-UE

PagingCause 3

Enumerated(Terminating Conversational Call, Terminating Streaming Call,Terminating Interactive Call,Terminating Background Call, Terminating High

Priority Signalling,Terminating Low Priority Signalling,Terminating – cause unknown)

CN-DomainIdentity 1 CN-DomainIdentity ::= ENUMERATED {

cs-domain, ps-domain }

pagingRecordTypeID 2 PagingRecordTypeID ::= ENUMERATED { imsi-GSM-MAP, tmsi-GSM-MAP-P-TMSI,

imsi-DS-41, tmsi-DS-41 }

BCCH-ModificationInfo

MIB-ValueTag 3 MIB-ValueTag ::= INTEGER (1..8)

BCCH-ModificationTime 9 BCCH-ModificationTime ::= INTEGER (0..511)

nonCriticalExtensions

None This item is not processed in practice.

The IEs appear in the sequence specified in the table above. Consulting to the

protocol, we can learn that all the IEs corresponding to the OP item or expansion

item in the protocol will reserve a bit for identification, indicating this item is selected



or not. The details of this OP item or expansion item will be displayed only when this

item is selected.

3 WCDMA Paging Channel Capacity Calculation

Table 2 shows that the paging based on different ID items generate different

paging overheads. For example:

One case for paging based on CN_ID: The CN_ID is selected when the CN

initiates paging, and the paged UE is in the connectionless state.

Two cases for paging based on UTRAN_ID:

The cn-OriginatedPage-connectedMode-UE of the UTRAN_ID is not

selected when the UTRAN initiates paging.

The cn-OriginatedPage-connectedMode-UE is selected when the CN

initiates paging but the paged UE is in the connection state.

Based on the above analysis and Table 2, we can respectively calculate

the paging volume that can be supported by one PCCH channel when

CN_ID and UTRAN_ID are used.

3.1 CN_ID IMSI Paging

As specified in the 3GPP protocol, IMSI is divided into IMSI-GSM-MAP and

IMSI-DS-41. IMSI-DS-41 is an IS-95 concept, which is not described here. The

length of IMSI-GSM-MAP is variable in the decimal mode. At present, China adopts

the IMSI of 15 digits, while some counties adopt the IMSI less than 15 digits.

With the decimal IMSI-GSM-MAP of 15 digits, the calculation is as follows:

Suppose M1=1+3+1+3+(15*4+4)=72. When BCCH modified information7 is not

considered, with the equation of 1+1+1+1+3+M1*X1=240, the maximum number of

IMSI paging X1 that can be supported will be 3.23. Therefore, in the case of paging

based on the decimal IMSI-GSM-MAP of 15 digits, a maximum of three

IMSI-GSM-MAP paging can be supported by each 10ms TTI.

When the IMSI-GSM-MAP varies, the paging capacity can be calculated in the

same method as above, with the numeral of 15 in the equation changed to the

corresponding length value. This is not detailed here.

3.2 CN_ID TMSI Paging

7 It is shown in table 2 that BCCH modified information has 12 bits only, occupying 5% information bits in the

whole 240-bit 10ms TTI.



As specified in the 3GPP protocol, TMSI is divided into TMSI-GSM-MAP,

P-TMSI-GSM-MAP and TMSI-DS-41. TMSI-DS-41 is an IS-95 concept, which is not

described here.

With the 32-bit TMSI-GSM-MAP, the calculation is as follows:

Suppose M2=1+3+1+3+(32)=40. When BCCH modified information is not

considered, with the equation of 1+1+1+1+3+M2*X2=240, the maximum number of

TMSI-GSM-MAP paging X2 that can be supported will be 5.83. Therefore, in the

case of paging based on the 32-bit TMSI-GSM-MAP, a maximum of five

TMSI-GSM-MAP paging can be supported by each 10ms TTI.

The P-TMSI-GSM-MAP is the same as TMSI-GSM-MAP in length, so the

calculation result will be the same.

3.3 UTRAN_ID Paging

When the UE is in the connection state (CELL_PCH or URA_PCH), the

UTRAN_ID will be used for paging. The bit length of UTRAN ID is SRNC-Identity +

S-RNTI, that is 12+20=32.

When cn-OriginatedPage-connectedMode-UE is not selected: Suppose

M3=1+1+(32)=34. When BCCH modified information is not considered, with the

equation 1+1+1+1+3+ M3*X3=240, the maximum number of UTRAN ID paging X3

that can be supported will be 6.85. Therefore, in the case of paging with the 32-bit

UTRAN ID, a maximum of six UTRAN ID paging can be supported by each 10ms

TTI.

When cn-OriginatedPage-connectedMode-UE is selected: Suppose

M4=1+1+(32)+3+1+2=40. When BCCH modified information is not considered, with

the equation 1+1+1+1+3+ M4*X4=240, the maximum number of UTRAN ID paging

X4 that can be supported will be 5.82. Therefore, in this case, a maximum of five

UTRAN ID paging can be supported by each 10ms TTI.

4 Analysis on Location Area Size for Mixture Service

4.1 Analysis on Calculation Method

In Chapter 3, only the paging of single CN ID or single UTRAN ID is considered.

But in the actual network, the users are in different status. On the other hand, the

paging capacity will be mapped to the number of users supported or the

number of corresponding carriers, which can be the reference for the location

area planning. Therefore, the analysis on the influence of the traffic modeling on the

paging capacity is necessary.



In the analysis, for the service that may occupy paging channel, we suppose as

follows:

1. Suppose the ratio of service callers to callees is A:B (which may vary with

different services).

2. Suppose (1-C) percent of the MSs give response at the first time of paging,

and C percent of the MSs give response at the second time of paging. The

MSs giving response at the third time of paging or later are ignored.

3. Suppose the ratio of the paged UEs in the idle state in the PS to those in

the CELL_PCH &URA_PCH state is D:E. The UEs in the CELL_FACH and

CELL_DCH state of the CS and PS is ignored.8.

4. Suppose the ratio of the paging initiated by the UTRAN actively to the

paging initiated by the CN to the UEs in the connection state is F:G.

We can work out the number of busy hour paging requests generated when the

UEs using a certain type of CS service: Equation Section 4

jPaging CS % _i i iBHCA Penetration User Contribution i

i i

B_Num_ =(k+1)（ 1+C%)

A +B (4.1)

Where, Paging_Num_CSj refers to the paging requests generated by the UEs

using a certain type of CS service, Penetrationi% is the penetration rate of different

levels of UEs using this type of service. User_Contributioni refers to the distribution

ratio of different levels of UEs using this type of service.

With the same analysis method as the CS service, we can get the number of

busy hour paging requests generated when the UEs using a certain type of CS

service.

jPaging PS _ % _i i iBHPC Num Penetration User Contribution i

i i

B_Num_ =(k+1)（ 1+C%)

A +B(4.2)

Where, Paging_Num_PSj refers to the paging requests generated by the UEs

using a certain type of PS service. BHPC_Numi is the Busy Hour Packet Call

Number in the traffic modeling parameter. User_Contributioni refers to the

distribution ratio of different levels of UEs using this type of service.

Suppose: _ _j

a Paging Num CS _ _j

b Paging Num PS (4.3)

Suppose the number of carrier waves/sectors supported by the RA is NRA, and

that supported by the LA is NLA. The equation will be:

8 This is the worst case, with the maximum occupation the paging channel.



_ _ celluser LA celluser RAPCCH Paging Capacity a N N b N N (4.4)

Where, Ncelluser is the number of cell users obtained by means of dimensioning

under a certain condition, and PCCH_Paging_Capacity is the maximum paging load

allowed in a single PCCH channel.

As specified in the protocol, RA is a subset of LA. In a certain typical

environment with even user distribution, the number of carrier waves/sectors

supported by LA is NLA=n*NRA (n is a positive integer).

In the case of paging based on the CN ID of IMSI:

Under the traffic model condition, Mmix is the number of users supported by the

paging channel within 10ms:

mix

240 (1 1 1 1 3)M =

1 ( ) ( 3 4 )a n b D b E F G

M M Mb a n b a n D E b a n D E F G F G

(4.5)

The UE selects the proper terminating time (V350) according to the

discontinuous reception (DRX) algorithm specified in the 3GPP 25.304

specifications.

Paging Occasion={(IMSI div K) mod (DRX cycle length div PBP)} * PBP + n *

DRX cycle length + Frame Offset;

Where n = 0,1,2… as long as SFN is below its maximum value.

The DRX cycle length shall be MAX(2k, PBP) frames.

PBP: Paging Block Periodicity, it is 10ms TTI at present.

The RNC maps the paging message to different CFNs according to the same

algorithm. We can learn from the equation that the location of the paging message is

the corresponding paging block position that the IMSI of the UE modulo the DRX

cycle length. Therefore, a UE can occupy only one paging block within a DRX cycle.

On the other hand, the paging messages of different UEs will be arranged to the

same paging block as long as the IMSI modulo results are identical. In this case, for

a specific paging block, when the number of paging message exceeds Mmix, the

paging block will suffer from blocking. At present, the RNC discards the excessive

paging messages instead of buffering them, and then transmits the paging message

within the next DRX cycle or waits for the CN re-transmits it according to the

re-transmission parameters of the UTRAN.



For the point of time of a certain CFN, the paging message termination rate is

distributed based on poission distribution. For a specific paging block, when the

number of messages messageperTTIN exceeds the value of Mmix, the excessive ones

will be discarded. The blocking formula is as follows:

( )outage messageperTTI mixP P N M (4.6)

then 0

( )1

!

mixM H k

outage

k

e HP

k

(4.7)

With the formula above, we can work out the value of H , which indicates

the traffic supported by a specific paging block within a DRX cycle.

Based on the traffic model, the traffic generated by the UE within a DRX cycle is

as follows:

2( ) (2 0.01)

3600

RA

RA

RA

kPerDRXCycleLengthInN

PerDRXCycleLengthInN


a n bErlang

(4.8)

Then, we can work out NRA as follows:

%

2RA

RAcelluser

PerDRXCycleLengthInN k

H LN

NErlang

(4.9)

Where, L% is the paging margin reserved for the future development of network.

For the definitions and values of M1, M2, M3 and M4, refer to Chapter 3.

In the case of paging based on the CN ID of TMSI:

With the same analysis method, we can work out Mmix, the number of users

supported by the paging channel within 10ms:

mix

240 (1 1 1 1 3)M =

2 ( ) ( 3 4 )a n b D b E F G

M M Mb a n b a n D E b a n D E F G F G

(4.10)

Then 0

( )1

!

mixM H k

outage

k

e HP

k

(4.11)

Based on the traffic model, the traffic generated by the UE within a DRX cycle is

as follows:

2( ) (2 0.01)

3600

RA

RA

RA

kPerDRXCycleLengthInN



a n bErlang

(4.12)

Then, we can work out NRA as follows:



%

2RA

RAcelluser

PerDRXCycleLengthInN k

H LN

NErlang

(4.13)

4.2 Key Value Recommendations

K parameter: k+1 represents the number of paging re-transmission at the

UTRAN side. The air interface must transmits the paging for k+1 times no matter the

UE gives response to the paging or not. As the CN side re-transmits paging, the

recommended value of k is 1 for a higher paging efficiency.

L parameter: (1-L)% is the paging margin reserved for the future development

of the network. Since the RNC supports modifying the paging area of the existing

cells by means of dynamic data configuration, the value of L mainly depends on the

special network construction requirement of the carrier. Generally speaking, to avoid

the paging area IDs of other existing cells are to be modified caused by the capacity

expansion of partial areas or individual sites, so we recommend the value of L is 80,

corresponding 20% of the paging margin.

Poutage parameter: Poutage is the blocking rate of the paging block. If it is

supposed that 99 percent of UEs can be paged within two continuous DRX cycles,

the value of Portage will be 1%.

DRX parameter: It is the k parameter is The DRX cycle length shall be MAX(2k,

PBP) frames. Its value is 8 at present.

n parameter: It is the n in the NLA=n*NRA (where n is a positive integer). The

bigger the n, the less the paging cells that can be supported by RA, and the more

paging cells supported by LA when the capacity of the paging channel keeps

unchanged. Generally, the paging requests of PS services are more than those of

CS services. To prevent the PS from occupying too much paging channel resources,

n can be set to a value greater than 1, depending on the value of a (for CS services)

or b (for PS services), for example, mixM = 0.5b

na

. To avoid the location

update flow caused by a too-small NRA, it is recommended that when NRA is less

than 50, the value of n can be decreased properly to make its value greater than 50.

Other parameters: The values are set according to the actual network

construction objective and traffic model together with the opinions of the carrier.

5 Instance of Paging Area Cell Size in Typical Environment



Here we take a typical traffic modeling of the dense urban area in the radio

network calculation tool as the example to dimension the paging area based on the

result in Chapter 4.

CS traffic modeling

Service type Penetrance BHCA AHT (s) Active factor

Average bitrate kbit/s

Busy hour

traffic / user (Erl)

Busy hour

thruput / user (kbit)

Busy hour

thruput rate / user (kbit)

AMR Voice 100 % 1 90 0.5 8 0.025 360 100

VideoPhone 100 % 0.1 54 1 64 0.0015 345.6 96

Figure 1 CS service reference model

PS traffic modeling

Service type

Economical users Normal users VIP users

Penetrance

BH

SA

Busy hour

packet call Num

Busy hour


Penetrance

BH

SA

Busy hour

packet call Num

Busy hour


Penetrance

BH

SA

Busy hour

packet call Num

Busy hour


Email 10 % 0.10 0.20 24.576 20 % 0.20 0.40 49.152 30 % 0.30 0.60 73.728

WWW 30 % 0.18 0.90 86.4 30 % 0.24 1.20 115.2 20 % 0.30 1.50 144

Game, ICQ

25 % 0.10 0.20 2.304 15 % 0.20 0.40 4.608 5 % 0.30 0.60 6.912

Content DL, FTP

25 % 0.10 0.20 47.616 15 % 0.20 0.40 95.232 10 % 0.30 0.60 142.848

Video Stream

0 % 0.00 0.00 0 10 % 0.10 0.10 320.4 20 % 0.20 0.20 640.8

SMS 50 % 0.50 0.50 0.64 100 % 0.80 0.80 1.024 100 % 0.60 0.60 0.768

EMS / MMS

50 % 0.50 1.00 122.88 100 % 0.80 1.60 196.608 100 % 0.60 1.20 147.456

User contribution

Mophology Economical Normal VIP Total

Dense Urban

60 % 25 % 15 % 100 %

Figure 2 PS service reference model

In the above data service reference model, only the three services of Email9,

SMS and MMS will occupy the paging channel, other data services do not involve

paging process, as the user initiates and terminates service actively.

9 At present, the realization mode is to notify the users with SM every time the network receives an email.



Based on this traffic modeling, we suppose other conditions for the

dimensioning:

Tx power config

Max power of Tx 20 W

Tx power usage

threshold80 %

Common channel

power allocation26.78 %

Noise parameter

UE noise figure 7.0 dB

Margin for background

noise4.0 dB

Coverage Info.

Mophology 1

Channel type 2

Site type 2

Antenna height of UE 1.5 m

Antenna height of BS 30 m

Uplink Frequency 1950 MHz

Downlink Frequency 2140 MHz

Max path loss of Uplink 137.00 dB

Dense Urban

TU3(3km/h)

3 Sectors



UL service info.

Service type Bear type

Bear

proportion

%

BH thruput /

user (kbit)Eb/N0 (dB) BLER

Length of

session

(byte)

Reading

time in

session (s)

Voice 1 100.0 % 360.00 5.4 0.01 - -

VideoPhone 3 100.0 % 345.60 2.7 0.10 - -

Email 3 50.0 % 7.25 2.7 0.10 30,720 320

Email 7 50.0 % 7.25 2.4 0.10 30,720 320

WWW 7 70.0 % 28.51 2.4 0.10 60,000 1648

WWW 8 28.0 % 28.51 1.9 0.10 60,000 1648

WWW 9 2.0 % 28.51 1.6 0.10 60,000 1648

Video Stream 3 75.0 % 8.71 2.7 0.10 128,160 0

Video Stream 4 25.0 % 8.71 2.3 0.10 128,160 0

Content DL, FTP 7 75.0 % 12.86 2.4 0.10 59,520 5

Content DL, FTP 8 25.0 % 12.86 1.9 0.10 59,520 5

Location 3 100.0 % 0.57 2.7 0.10 2,880 8

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

2.3 0.10

AMR12.2

LCD64

LCD64

UDD64

UDD64

UDD144

UDD384

LCD64

LCD144

UDD64

UDD144

LCD64



DL service info.

Service type Bear type

Bear

proportion

%

BH thruput /

user (kbit)Eb/N0 (dB) BLER

Length of

session

(byte)

Reading

time in

session (s)

Voice 1 100.0 % 360.00 7.79 0.01 - -

VideoPhone 3 100.0 % 345.60 5.90 0.10 - -

Email 3 50.0 % 7.25 5.90 0.10 30,720 320

Email 7 50.0 % 7.25 4.60 0.10 30,720 320

WWW 7 70.0 % 28.51 4.60 0.10 60,000 1648

WWW 8 28.0 % 28.51 3.80 0.10 60,000 1648

WWW 9 2.0 % 28.51 4.40 0.10 60,000 1648

Video Stream 3 75.0 % 8.71 5.90 0.10 128,160 0

Video Stream 4 25.0 % 8.71 5.00 0.10 128,160 0

Content DL, FTP 7 75.0 % 12.86 4.60 0.10 59,520 5

Content DL, FTP 8 25.0 % 12.86 3.80 0.10 59,520 5

Location 3 100.0 % 0.57 5.90 0.10 2,880 8

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

5.00 0.10

AMR12.2

LCD64

LCD64

UDD64

UDD64

UDD144

UDD384

LCD64

LCD144

UDD64

UDD144

LCD64

Channel Duty cycle

SCH 0.10

Primary CCPCH 0.90

SCCPCH (PCH) 0.25

SCCPCH (FACH) 0.25

CPICH 1.00

AICH 1.00

PICH 1.00

Common channel power allocation ( with one SCCPCH )

Common channel power allocation ( with two SCCPCH )

24.80 %

26.78 %

1.99 %

10.00 %

3.16 %

5.01 %

Power allocation

1.00 %

2.85 %

0.79 %

Common channel power allocation

-13

Power relative to MAX BS Tx

power [dB]

-10

-15

-15

-11

-10

-15

Figure 3 Assumption conditions for the dimensioning of the dense urban area

In the conditions mentioned above, the configurations of sector 3 can be

obtained with the dimensioning tool10

. The number of all kinds of users supported by

each carrier/sector is 1030.

Here are the values of the four assumption conditions required for paging area

dimensioning:

Table 3 Values of the four assumption conditions for paging area dimensioning

A B C D E F G

M1(bit) 72

AMR Voice 60% 40% 25 M2(bit) 40

10

The version of the dimensioning tool is V1.2.



VideoPhone 50% 50% 25 M3(bit) 34

Email 50% 50% 25 50% 50% 50% 50% M4(bit) 40

SMS 50% 50% 25 50% 50% 50% 50% Ncelluser 1030

EMS/MMS 50% 50% 25 50% 50% 50% 50% k 0

… … … … … … … … L 80

… … … … … … … … Poutage 0.1

… … … … … … … … DRX parameter 8

Based on the assumption condition above and the formula deducted in Chapter

4, the calculation result is as follows:

Table 4 Location area dimemsion for paging based on CN ID of IMSI

n Mmix

RA LA

1 3 1.738624042 0.002592996 133 133

2 3 1.741614489 0.003616996 95 190

3 3 1.74665366 0.004640996 74 222

4 3 1.744911078 0.005664996 61 244

5 3 1.745096566 0.006688996 51 255

6 3 1.745372494 0.007712996 44 264

7 3 1.745680526 0.008736996 39 273

8 3 1.745680526 0.009760996 35 280

9 3 1.746014764 0.010784996 32 288

10 3 1.746024614 0.011808996 29 290

0

50

100

150

200

250

300

350

1 2 3 4 5 6 7 8 9 10

RA

LA

Figure 4 Diagram of paging area dimensioning for paging based on CN ID of IMSI

Table 5 Location area dimemsion for paging based on CN ID of TMSI

H RAPerDRXCycleLengthInNErlang



n Mmix

RA LA

1 5 3.156601287 0.002592996 242 242

2 5 3.156601287 0.003616996 173 346

3 5 3.156601287 0.004640996 135 405

4 5 3.156601287 0.005664996 110 440

5 5 3.156601287 0.006688996 93 465

6 5 3.156601287 0.007712996 81 486

7 5 3.156601287 0.008736996 71 497

8 5 3.156601287 0.009760996 64 512

9 5 3.156601287 0.010784996 58 522

10 5 3.156601287 0.011808996 53 530

0

100

200

300

400

500

600

1 2 3 4 5 6 7 8 9 10

RA

LA

Figure 5 Diagram of paging area dimensioning for paging based on CN ID of TMSI

According to the value formula for the n value in Chapter 4, we can work out

that n=1, that is, NRA＝NLA.

Note: For the tools used, refer to WCDMA RNP Paging Area Planning Tool.

6 Precautions in the Paging Area Planning

6.1 Paging Area Size Restriction

As a paging message of the network paging mobile station will be sent in many

cells, the coverage of the paging area will be too large, which will lead to overload of

the paging channel, and increase the signaling flow at the Iub interface. In addition,

the excessive paging messages will be discarded in the case of re-transmission

failure within the specified re-transmission times. This will result in paging failure to

the active UEs within the service area (that is the UE is out of service). The upper

limit of the paging area (the number of cells that can be supported by the area) is

H RAPerDRXCycleLengthInNErlang



limited by the bandwidth of the paging channel. The analysis in the above chapters

is mainly to determine the upper limit of the paging area.

On the contrary, if the paging area is too small, the UE will encounter frequent

location update in the traveling process, which increases the signaling flow of the

system. In the initial stage of network construction, the number of paging requests

are small, it is not necessary to plan the RA in a small size, but with the n being 1

instead. With the ever evolution of the network, the demands for PS serviced

increases. In this case, the size of the RA can be cut down. Of course, if the RA is

too small, the paging area update in the traveling process will be frequent, which will

enlarge the signaling overhead of the network side, and will shorten the standby time

of the mobile phone.

The lower limit of the RA cannot be determined by means of quantitative

analysis, which is a pending problem.

In addition, the equipment of higher version may support one cell being

configured with multiple PCCH paging channels. To ensure the balance of paging

load, the cells with the same paging channel numbers should be divided into the

same paging area (with the precondition that the cells with the same paging channel

numbers are in the same geographical area).

6.2 Geographic Distribution of Paging Area

The geographic distribution for the paging area is very important. Making the

best of the geographic distribution and behaviors of the mobile subscribers can lower

the location update frequency at the border of the paging area.

When the suburb is not covered within a continuous area with the urban area,

the location of the mobile phone cannot be updated when the periodical location

update time comes. After the protection time is time-out (set in the MSC), the system

will take that the IMSI is separated from the mobile phone. Suppose the mobile

phone travels the urban area, whose LAC is consistent with that of the suburb area,

some mobile phones will not perform normal location update immediately. In this

case, the mobile phone can receive signal but out of service. Therefore, for the

division of location area, the suburb area (county area) will be put into a location

area separate from the urban area. The location area distribution is similar to

concentric circles (the inner urban area may be set with several location areas due

to the capacity factors. The inner circle can adopt the fragmentation mode, or

inner-outer ring mode, or mixed mode), which can avoid the above problem

effectively. It is proved by practice that such a division can not only reduce the



out-of-service problem, but also greatly improve the connection completion rate and

the call completion rate.

Figure 6 Schematic diagram of location area division

On the other hand, if more than two location areas exist in a city with

high-volume traffic, they can be divided by the geographic factors such as mountain

and river, for minimizing the overlap between different cells in the two location area.

If such a geographic factor is not available, the border between two areas should be

oblique crossing with a street instead of parallel or vertical with the street. Moreover,

the border should not be a street or the place with high-volume traffic (like

department store). In the intersection of the urban area and suburb, the border

between urban area and suburb area should be put at the base station of the

periphery instead of the intersection with high-volume traffic, so as to avoid frequent

location update in the intersection.

6.3 Paging Area Crossing MSCs and RNCs

It is described in the first chapter that when several MSC shares one VLR, and

the location area/routing area can cross MSC/SGSN areas. But in practice, one

MSC is bound with one VLR in most cases, so the LA/RA can cross RNC areas

instead of MSC/SGSN areas.

However, in the actual network application, if the location area/routing area

cross multiple RNCs, the paging will be delivered to multiple RNCs, and this

increases the signaling flow and the processing difficulty. The same as the lower

limit of paging area, quantitative analysis cannot be made for the impact on the



system. The primary conclusion is: the location area/routing area should be set

within the RNC without crossing RNCs.

The multi-module RNC has the same problem. If an LA/RA corresponds to

multiple RNC modules, the paging signaling initiated by the CN will be forwarded

from module to module, till to the module corresponding to this TRX. The more

modules the LA/RA corresponds to, the much signaling flow the forwarding brings.

The same as the lower limit of paging area, quantitative analysis cannot be made for

the impact on the system. The primary conclusion is: The impact on the SPU is not

serious, and can be ignored.

7 Summary of Pending Problems

The pending problems are as follows:

For the traffic modeling independent paging, the load analysis is quite

complicated with many uncertain factors, requiring further analysis on the

influence on the paging. The primary analysis result is:

1. For location service: As the usage frequency of location service is not

high, the impact on the paging capacity will be small. At present, the

scheme is one RNC supports a maximum of 400 users at the same time

(queuing supported, with the maximum queuing time of 5s).

2. For the paging caused by the security mode command, as the CN will

not frequently update the encryption or the completeness protection

parameters, the impact on the paging capacity is small.

3. The system message update occupies a small signaling load, so the

impact can be ignored.

4. Cell update will be caused by downlink data transmission or release of

RRC connection by the CN side. The former cause is considered in the

traffic modeling, and the latter one seldom occurs, so the impact can be

ignored.

5.

The lower limit of the paging area cannot be defined by means of

quantitative analysis. It is affected by two factors:

1. Frequent location update increases the system signaling load.

2. Fast mobile phone power consumption

For the first factor, the upper limit of the SPU processing capability of the

RNC is restricted by the occupation rate of the CPU, while the CPU

occupation is not only related to the signaling flow for location update. So

quantitative analysis must be performed by means of test in the lab



environment based on some assumption conditions. Figure 7 shows the

test result of Huawei’s RNC performed by Motorola with the typical

parameter setting. We can learn that the contribution of the location update

signaling load is big. As to the second factor, research can not be

performed yet.

There is no reasonable specification for the average value of cell paging

load L% yet. It is 30% in Ericson’s documentation and 90% in the relevant

documents of CDMA2000 (CDMA System Design Optimization).

The re-transmission interval of CN is also restricted by the paging area size

and minimum time of response to paging. Especially every NodeB works

asynchronously without GPS, the paging efficiency and paging success

rate will be affected in a large degree.

The PCCH has two formats: 240bit/10ms TTI and 80bit/10ms. Obviously,

the paging capability of the former one is greater than the latter one. But, it

is necessary to analyze the advantage of the latter one (for example,

whether the demodulation success rate is higher than the former one). This

is responsible by the link emulation working team.

Figure 7 Motorola test result



List of reference:

[1] Location Area Capacity Planning Guideline, GSM Network Planning Department 2002/04,

internal document

[2] CDMA1X Location Area Planning Guideline Shenzhen Subdivision of Radio Network

System Department, 2003/01, Internal document

[3] Concepts about Area in the PLMN Architecture Tai Xiaomei 2001/12 Internal document

[4] 23.121,23.002,23.003,25.331,25.413 3GPP 2002/06 Internet

[5] WCDMA Paging Area Analysis Report Zhang Jingrong 2001/05 Internal document

[6] LOCATION AREA DIMENSIONING GUIDELINE CME 20 R6 Ericsson 1996/12

Unknown

[7] WCDMA-Dimensioning-tool Gu Jufeng 2003/01 Internal document

WCDMA RNP Paging Area Planning Guidance

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