RNPS GSM Location Area Planning Solution V2.0

GSM 位置区网规解决方案 For Internal Use

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Product name Confidentiality level: INTERNAL

GSM BSS Department: Wireless Network Planning Solution Department

Product versionTotal 22 pages

Wireless Network Planning Solution

RNPS GSM Location Area Planning Solution V2.0

(INTERNAL)

Prepared by:Prepared by

Wireless Network Planning Solution

Department

Date:Date 2007-11-24

Reviewed by:Reviewed by

Date:Date

YYYY-MM-DD

Reviewed by:Reviewed by

Date:Date

YYYY-MM-DD

Approved by:Granted by

Date:Date

YYYY-MM-DD

Huawei Technologies Co., Ltd.All rights reserved

2007-11-24 Huawei Technologies Proprietary Page 1 of 22


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Revision RecordDate Version Description Author

2007-10-31

0.9 Draft completed Xie Yan

2007-11-24

1.00 Modified according to review suggestions Xie Yan



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Table of Contents

Chapter 1 Introduction.................................................................................................................5

1.1 Location Area Defining.........................................................................................................5

1.2 Location Area Planning........................................................................................................6

Chapter 2 Paging.......................................................................................................................11

2.1 Paging Group..................................................................................................................... 11

2.2 BS-AG-BLKS-RES.............................................................................................................11

2.3 BS-PA-MFRMS.................................................................................................................. 12

2.4 Relations between Paging Groups, BS-AG-BLKS-RES, and BS-PA-MFRMS...................12

2.5 Paging Capacity................................................................................................................. 13

2.6 Paging Policy..................................................................................................................... 13

Chapter 3 Location Area Calculation.........................................................................................15

3.1 Location Area Capacity Calculation...................................................................................15

3.2 Examples........................................................................................................................... 18

3.3 Conclusion......................................................................................................................... 19

Chapter 4 Impact of Data Services on Location Area Planning................................................20

4.1 Impact of Data Services on the Configuration Data...........................................................20

4.2 Impact of Data Services on the Efficiency of Paging Combination.....................................21

4.3 Impact of Data Services on the Paging Load.....................................................................21

4.4 Impact of Data Services on the Traffic Model.....................................................................21

4.5 Routing Area Planning.......................................................................................................22



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RNPS GSM Location Area Networking Technical Clarification V2.0

Key words: Location Area, Paging

Abstract: Based on the paging theories, this document describes how to calculate

and configure proper location areas in GSM network planning, and analyzes

the impact of data services on the location area planning. This document

matches “Tools for RNPS GSM Location Area Planning V3.0 20071124”.

Acronyms and abbreviations:

LA: Location Area

LAC: Location Area Code

MGW: Media GateWay

References: list the references related to this document.

ReferencesName Author SN Release

DateSources Publisher

“Extended BCH

Capacity Analysis”

“Answers to Planning of the BSC6000 LA”

Cao Jiang/00119586



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Chapter 1 Introduction

1.1 Location Area Defining

Location Area (LA) is an important concept in the GSM. Based on GSM protocols, the mobile communication network is divided into different traffic areas according to the Location Area Code (LAC). The network pages the mobile subscribers by sending paging messages in the whole LA.

The LA has the following function: To set up a call between the network and the MS, the location information of the MS must be recorded from time to time. Only in this way can paging be successful when necessary. The HLR on the network side stores the basic information of a registered user and the location information of the user (MSC/VLR information of the user for the moment).The MSC/VLR stores the basic information and the location information of the users camping on this MSC (the exact information of the location area). The SIM card stores the location information of users (the exact information of the location area).

When an MS is switched on and locks the broadcast channel, it begins to compare whether the location information stored in the SIM card is consistent with that sent on the broadcast channel (BCCH). If not, the MS initiates a location update procedure. In location updating, the MS registers a new LA in the MSC/VLR. If the location information in the MSC/VLR is different, the MSC sends signaling to the registered place, changes the location information in the MSC/VLR, and deletes the old information.

When an MS is in the standby state, it continuously listens to the location information carried on BCCH. If the location information is inconsistent with that in the SIM card, the MS initiates a location update procedure.

When an MS is in the conversation state, it listens to the location information carried on the fast associated control channel (FACCH). If the location information is inconsistent with that in the SIM card, the MS initiates a location update procedure after the conversation is complete.

The location information stored in the HLR, VLR, and SIM card must always be consistent with each other to ensure successful paging.

In the GSM system, the paging message is broadcast by LA. That is, the paging message for an MS is transmitted to all the cells of an LA. An LA may contain one or several BSCs, but an LA must be in the same MSC. Figure 1-1 shows the division:

PLMN

MSC

C E L LLA

C E L L

C E L L

C E L L

C E L LLA

C E L L

C E L L

C E L L

MSC

C E L LLA

C E L L

C E L L

C E L L

C E L LLA

C E L L

C E L L

C E L L

Figure 1-1 Traffic area division



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1.2 Principle of Location Area Planning

In the GSM system, the coverage of every Public Land Mobile Network (PLMN) is divided into many LAs to identify the location of an MS easily. The size of the location area (the coverage area of a Location Area Code (LAC)) is a key factor that should be taken into account in the GSM system. The location area planning plays a very crucial part in the network planning. Thus, ensure that the location updates are minimized under the condition that the paging is not overloaded. For network operators, if the locations are updated frequently, the network resources are wasted but no revenue is gained. The paging load determines the maximum range of an LA; likewise, the location update load in the cells at the edge of the LA determines the minimum range of the LA. Mainly, the maximum paging capacity of the BTS determines the coverage range of the LA.

During LA planning adhere to the following principles: 1. The LA should not be too large or too small.

If the coverage of an LA is too small, the location update is more frequent, and the signaling flow is increased. On the contrary, if the coverage of an LA is too large, the same paging message is broadcast in many cells, the Paging Channel (PCH) load becomes heavy, and the signaling flow on the Abis interface increases. At the early stage of network deployment, the traffic volume is low, and the number of TRXs in an LA can be larger than the maximum capacity of the system. However, it is still very necessary to monitor whether the PCH load becomes heavy or the traffic volume increases.2. To minimize the location updates at the edge of an LA, the geographical locations and habits of the mobile subscribers must be taken into account during the planning of the LAC.

The followings are the detailed principles for planning the location area:

Scenarios Principles for LA planning

Urban area

In urban areas, the traffic volume is high. If there are more than two ALs, the mountains, rivers, or other natural resources should be set as the boundary of the LA to minimize coverage overlapping of different cells in two neighboring LAs. If there is no mountain or river, the streets or the high land (for example malls) should not be set as the boundary of the LA. Generally, the boundary of the LA should not be parallel or vertical to the streets but beveled to the streets. Generally, the boundary of an LA should be set in the area with least traffic instead of in the area with high traffic (such as rural-urban fringe zone) to avoid frequent location updates.

Suburban area

If continuous coverage is unavailable between urban area and suburban area, the MSs may not be able to update the location when it is time for periodic location update. When the protection time (set in the MSC) is up, implicit IMSI detach occurs. At this time, the LAC in the urban area is consistent with that in the suburban area, but some MSs cannot update the location immediately, so the called subscriber cannot be reached though the signals can be received. Therefore, in LA planning, the suburban areas have their own LAs that are different from those in the urban areas. The LAs are planned like a concentric cell (many LAs may be planned for the



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overlaid urban area due to capacity reasons; the overlaid area can also be divided into several LAs or be planned as a concentric area with one overlaid area surrounded by several underlaid areas, or the combination of these two methods). This enables the subscribers to be reached. It proves that this method of LA planning can ensure that the called subscriber is reached, and increase the calling party completion rate and the called party completion rate. See Figure 1-2.

LACn

LACn

LACn

LACn LACn

LAC1

LAC2

LAC3

LAC5

LAC4

urban

suburban

suburban

suburban suburban

suburban

Figure 1-2 Division of the LAC

3. Geographically, the LA should be planned in a continuous way to avoid the segmental networking of BTSs in LAs.4. In dual-band network, there are new requirements for LA planning. The following is some experience on LA planning in dual-band network:

If the MSC for the GSM1800 cells and that for the GSM900 cells are

independent of each other, they must be in different LAs. A parameter

should be set to ensure that the MSs in the GSM1800 cells that are capable

of absorbing traffic, thus reducing the dual-band handover and reselection.

Load on the system brought by location updates should be taken into

account and signaling channels should be planned accordingly.

At the early stage of the network deployment, if the GSM1800 cells and the

GSM900 cells share one MSC, the same LA is recommended when

possible. If the paging capacity is limited and there must be two or more

LAs, two planning methods are recommended: planning by geographical

locations or by frequency bands. See Figure 1-3:



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GSM900 cell GSM900 cell GSM900 cell

GSM1800 cell GSM1800 cell GSM1800 cell GSM1800 cell

LA1

LA2

Figure 1-3 Planning by frequency bands

GSM900 cell

GSM1800 cell

GSM900 cell GSM900 cell GSM900 cell

GSM1800 cell GSM1800 cell GSM1800 cell GSM1800 cell GSM1800 cell

LA1 LA2

Figure1-4 Planning by geographical locatons

When LAs are planned by frequency band, the dual-band handover and reselection leads to frequent location updates. A parameter should be set to ensure that the MSs in the GSM1800 cells that are capable of absorbing traffic, thus reducing the dual-band handover and reselection. Load on the system brought by location updates should be taken into account and signaling channels should be planned accordingly. When LAs are planned by geographical location, frequent location updates brought by dual-band handover and reselection can be avoided. But the original global data must be changed. Meanwhile, handover and reselection within the same band and between the two bands lead to location updates in the boundary of the LA, thus increasing the signaling traffic. Therefore, the boundary of the LA must be planned with caution.5. Example:

When the competitor' equipment is replaced by Huawei equipment in Chengdu, the planning of the boundary of the LA must comply with the following principles:

Choose the original boundary of the LA when possible.

Plan a new boundary or split the old boundary according to the following



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principle: in continuous area but not the high-traffic area (trestles, squares,

malls, main streets, and so on).

Split the boundary within the original LAs to avoid too many new boundaries.

If the new boundary affects the boundary of the Media Gateway (MGW), the

boundary of the MGW must be adjusted accordingly.

After the planning of the LAs, the BSC must be adjusted to ensure that the

BSC controls three LAs at most.

In practice, the boundary of the LA should be planned with slight changes according to the location update statistics of the original network and the map of the Google Earth.

Figure 1-5 shows the relations between the new boundary of the LA and the old one (the orange boundary is the new one, and the BTSs in the same color used to be in the same LA).

MGW23

MGW24

MGW21

MGW22

MGW20

MGW25

MGW27

MGW19

MGW26

LAC32

LAC36

LAC23

LAC24

LAC31

LAC35

LAC39

LAC29

LAC30

LAC22

LAC38

LAC25

LAC34

LAC17

LAC19

LAC18

LAC33

LAC07

LAC03

LAC04

LAC21

LAC27

LAC28

LAC12

LAC08

LAC37

LAC26

LAC02

LAC01

LAC40

LAC06

LAC09

LAC20

LAC11

LAC16

LAC14

LAC10

LAC05

LAC13

LAC15

Figure 1-5 New and the old boundary of the LA

Figure 1-6 shows relations between the boundary of the new LA and the new boundary of the BSCs (the orange boundary is the new boundary of the LA, and the BTSs in the same color are in the same BSC).



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MGW23

MGW24

MGW21

MGW22

MGW20

MGW25

MGW27

MGW19

MGW26

LAC32

LAC36

LAC23

LAC24

LAC31

LAC35

LAC39

LAC29

LAC30

LAC22

LAC38

LAC25

LAC34

LAC17

LAC19

LAC18

LAC33

LAC07

LAC03

LAC04

LAC21

LAC27

LAC28

LAC12

LAC08

LAC37

LAC26

LAC02

LAC01

LAC40

LAC06

LAC09

LAC20

LAC11

LAC16

LAC14

LAC10

LAC05

LAC13

LAC15

Figure 1-6 Changes of the boundary

Figure 1-7 shows the adjustments to the inappropriate boundary planning in the original network. The original boundary (in yellow) is along the river. Location updates occur frequently because the river is next to a busy road. Now the boundary is planned along the green line.

Figure 1-7 Changes of the boundary



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Chapter 2 Paging

2.1 Paging Group

After decoding the BCCH and the system information successfully, the MS can determine which paging channel to listen to. The OMC defines the size of the paging group, which means the number of paging sub-channels on a specific paging channel in a cell. In actual network, if the Discontinuous Reception (DRX) function is enabled on an MS, the MS only listens to the associated paging sub-channel. For details, see GSM Rec. 05.02 and 05.08.

If the paging group is large, the number of paging sub-channels in a cell increases, thus reducing the number of MSs served by each paging sub-channel (see the formula for calculating the paging group in the GSM Rec. 05.02), prolonging the average work time of the MS battery and enlarging the paging capacity of the system. But the average delay of paging messages increases and the average serving performance of the system drops.

If the paging group is small, the paging response time increases. But the work time of MSs is shortened and the number of paging sub-channels is reduced.

The parameter BS-AG-BLKS-RES and the parameter BS-PA-MFRMS determine the number of the paging sub-channels.

2.2 BS-AG-BLKS-RES

In Huawei BSC, the parameter BS_AG_BLKS_RES specifies the number of the Common Control Channel (CCCH) blocks reserved for the Access Grant Channel (AGCH). After CCCH configuration, the value of this parameter is actually usage of AGCH/PCH among CCCH. This parameter affects the paging response time of an MS and the system service performance. If all the AGCHs are occupied while the PCHs are idle, the MS can receive the immediate assignment command on the PCHs.

The principles for configuring this parameter are: when the AGCHs are not overloaded, the parameter should be set as small as possible, thus reducing the paging response time of the MS and improving the system service performance. When the immediate assignment message is prioritized over the paging message, set this parameter to 0, and then the immediate assignment message is sent to the MS on the PCH. Refer to the following table:

Application Scenario Type BS_AG_BLKS_RES

Default value 2Popularized urban area 0Urban area 1Suburban area 2Rural area 2Coverage for Fast-Moving MS 2


Document Title Security Level:

Hot-spot area 0

2.3 BS-PA-MFRMS

In Huawei BSC, the parameter BS-PA-MFRAMS specifies the number of multi-frames in a cycle on the paging channel. This parameter actually specifies the number of paging sub-channels on a specific paging channel in a cell. When BS-PA-MFRAMS is set to 9, the MS in a particular paging group is paged every nine multi-frames and the interval time is 2.1s (235.4 ms x 9). The higher this parameter is set, the larger the number of paging sub-channels in a cell.

When an MS is in the idle state, the radio link counter also has impact on this parameter: initial value of the radio link counter = 90/BS-PA-MFRMS. Therefore, the larger this parameter, the smaller the initial value of the radio link counter, and the MS may drop from the network more easily.

The principle for configuring this parameter is: when the PCHs are not overloaded, the parameter should be set as small as possible. The load of the PCHs should be periodically measured on the running network. The value of this parameter should be adjusted appropriately on the basis of the load. A paging message must be sent simultaneously in all the cells in an LA. Thus, the capacity of the PCHs in a cell should be the same as or similar to that in other cells of the LA. On the live network, the parameter is usually set to 2.

2.4 Relations between Paging Groups, BS-AG-BLKS-RES, and BS-PA-MFRMS

Number of paging groups combined BCCH/SDCCH = (3-AGB) x BS-PA-MFRMS

Number of paging groups non-combined BCCH/SDCCH = (9-AGB) x BS-PA-MFRMS

The following shows their relations:

3 paging bloksper multiframe

AGB=0


AGB=1


AGB=0


AGB=12 0.47 6 4 18 163 0.71 9 6 27 244 0.94 12 8 36 325 1.18 15 10 45 406 1.41 18 12 54 487 1.65 21 14 63 568 1.89 24 16 72 649 2.12 27 18 81 72

Number of paging groupsCombined BCCH/SDCCH

Number of paging groupsNon-combined BCCH/SDCCHTime between

transmission ofeach paging

group

BS-PA-MFRMS

2023-04-19 HUAWEI Confidential Page12, Total22


2.5 Paging Capacity

In fact, the capacity of an LA means the number of subscribers or the number of TRXs in the LA. It is closely related to the paging capacity of the cell, so we need to calculate the paging capacity first.

The paging messages are broadcast on the BCCH timeslot 0. The followings are the sub-channels on the timeslot 0:

Broadcast Channel (BCH): Frequency Correction Channel (FCCH), Synchronization Channel (SCH), and Broadcast Control Channel (BCCH).

Common Control Channel (CCCH): Paging Channel (PCH), and Access Grant Channel (AGCH).

Dedicated Control Channel (DCCH) (for Combined BCCH/SDCCH): Stand-alone Dedicated Control Channel (SDCCH), Slow Associated Control Channel (SACCH), and Cell Broadcast Channel (CBCH) (when the cell broadcast is used).

Logically, timeslot 0 of the physical channels are comprised of multi-frames, each is 235.4 ms in duration. Channels can be configured in different modes, such as combined BCCH/SDCCH or non-combined BCCH/SDCCH. The paging capacities in different configurations differ from each other.

Non-combined BCCH/SDCCH

There can be nine paging blocks per multi-frame when non-combined BCCH/SDCCH is configured. Timeslot 0 on the BCCH TRX excludes SDCCH and CBCH.Therefore, if an extended BCCH is configured, the capacity of the PCH is enlarged, but a TCH is disabled. Generally, the extended BCCH should be configured for the 24-TRX cell instead of the 12-TRX cell (for details, refer to “Extended BCH Capacity Analysis”).

Combined BCCH/SDCCH

There can be three paging blocks per multi-frame when combined BCCH/SDCCH is configured. Timeslot 0 on the BCCH TRX carries four SDCCH sub-channels (no CBCH) or three SDCCH sub-channels plus one CBCH sub-channel.The combined BCCH/SDCCH configuration has great impact on the paging capacity. Only three paging blocks can be in every multi-frame instead of nine as on the non-combined BCCH/SDCCH. Therefore, when the combined BCCH/SDCCH is configured, the maximum paging capability is one-third of that when the non-combined BCCH/SDCCH is configured.

2.6 Paging Policy

If the location area of the MS is known in the VLR, the paging message is broadcast only in the location area where the MS is registered. This is called local paging. If the paging message is broadcast in all the cells in the whole MSC, the paging is called global paging.

Huawei MSC supports the retransmission of up to five paging messages, by TMSI or by IMSI. During network swapping, parameters setting must comply with that of the original MSC. Adjustments should be made according to the actual conditions and the following principles:



1. Choosing the LA paging or global pagingThe planning of the LA and the distribution of subscribers determine whether to

choose the LA paging or the global paging. For the dense urban areas where the coverage of the LA is small and the cross-LA paging is possible, the global paging is recommended for the last paging. For marginal areas where the coverage of the LA is large and the cross-LA paging can be avoided, the global paging is not the best choice. If the PCHs are or will be overloaded, the LA paging is recommended for the second or third paging. For the segmental network where cells in the same LA are not in continuous coverage and the planning cannot be modified, the global paging is recommended for the last paging when possible.

2. Choosing the IMSI paging or the TMSI pagingWhen the PCHs are or will be overloaded, the TMSI paging is recommended to

lower the possibility of the PCH overloading. Generally, when the TMSI paging is used, some mistakes may occur and the MS may not respond to the paging. Therefore, the TMSI paging is recommended for the first paging and the IMSI paging is recommended for the second and third paging.

3. Setting paging times and paging durationThe paging time and paging duration is calculated by analyzing the signaling

flow on the A interface. For example, the paging times and paging duration are set according to the paging response delay (the majority paging delay and the longest paging delay) and the second paging response. The paging times are recommended to be more than 2 times, and the total paging duration is recommended to be 10s, no more than 20s.

4. Setting IMSI Implicit Off-line TimerThe network optimization experience shows that reducing the duration of the

IMSI Implicit Off-line Timer helps much in improving the paging success rate when the duration of the timer is set to more than two hours. The shorter the duration is set, the quicker the offline MS is known. Therefore, the MSs in implicit off-line state are not paged, thus reducing paging failure rate. Although the paging success rate is increased, the problem of “the subscriber you dialed is power off” occurs more often.

Therefore, you are advised to set the duration of the IMSI Implicit Off-line Timer to 1.1-2.1 times as the duration of periodic location update in the BSC. If the duration of the periodic location update is less than 30s, the duration of this timer is recommended to be set to five minutes plus twice the duration of the periodic location update. If the duration of the periodic location update is more than 30s, the duration of this timer is recommended to be set to 5-10 minutes plus the duration of the periodic location update. 5. Example:

When the competitor’s equipment is replaced by Huawei equipment in Dongguan, parameter setting must comply with that of the original network as follows:

The secondary paging policy is applied. The first paging lasts for 6s and the

second paging lasts for 9s.

The LA paging is recommended for the first paging and the global paging for

the second.

The TMSI paging is recommended for the first paging and the IMSI paging

for the second.



The IMSI Implicit Off-line Timer is recommended to be set to 2. After equipment swapping, the network performance is basically the same as before.

Chapter 3 Location Area Calculation

3.1 Location Area Capacity Calculation

The capacity of an LA is calculated as follows:Number of paging blocks per second x number of paging messages per paging block = number of pagings per second. From the number of pagings per second, you can get the number of pagings per hour, the traffic volume allowed per LA, and the number of TRXs per LA.

(1) Number of paging blocks per secondI frame = 4.615 ms, 1 multi-frame = 51 frames = 0.2354s. Suppose that BS-AG-

BLKS-RES is AGB, the paging blocks per second is calculated as follows:

Non-combined BCCH: number of paging blocks per second =

(9-AGB)/0.2354 (blocks/second)

Combined BCCH: number of paging blocks per second = (3-AGB)/0.2354

(blocks/second)

Non-combined BCCH: In Huawei BSC, when AGB = 2, number of paging blocks per second = 29.7 blocks/second. When AGB = 0, number of paging blocks per second = 38.2 blocks/second. Combined BCCH: when AGB = 0, number of paging blocks per second = 8.5 blocks/second. When AGB = 0, number of paging blocks per second = 12.7 blocks/second.

Therefore, the bigger BS-AG-BLKS-RES is, the smaller the number of paging blocks per second is, and the smaller the paging capacity. The paging capacity on the combined BCCH is much smaller than that on the non-combined BCCH.

Usually, the combined BCCH and the non-combined BCCH cells should not be configured simultaneously in an LA, and BS-AG-BLKS-RES should be consistent among the cells in the same LA. Otherwise, the paging capacity of the LA is reduced and even becomes the lowest one. If the LA capacity and the LAC resources are insufficient, the combined BCCH and the non-combined BCCH can be configured in an LA to increase the traffic channels of the O1 and S111.

(2) Number of pagings per paging block (x)According to the content in 9.1.22 in GSM 0408, every paging block contains 23

bytes and sends two IMSI pagings (a) or two TMSI pagings and one IMSI paging (b) or four TMSI pagings (c).

According to Huawei MSC paging policy, if the IMSI paging is used, number of pagings per paging block (x) = 2 pagings/block.

If the TMSI paging is used, number of pagings per paging block (x) = 4 pagings/block.

In practice, the efficiency of paging combination is estimated on the basis of the number of messages in the PCH queue and the paging mode as follows:



Input

Parameter configuration Paging modeNumber of messages in the PCH queue = 0 5.00% Paging Success Rate 80%Number of messages in the PCH queue = 1

10.00% Paging mode (from the

first paging to the fourth one)

2Number of messages in the PCH queue = 2

10.00% 3

Number of messages in the PCH queue = 3

10.00%

Number of messages in the PCH queue > 4

65.00%

Sum100.00

%Currently, the default setting is used for the number of messages in the PCH queue. In later version (BSC6000V9R9), it can be calculated from the traffic statistics. The paging success rate and the paging mode can be obtained from the MSC. For details, refer to “Calculation of the efficiency of paging combination” in GSM LAC Planning V3.0. (3) Number of pagings per second (p)

Formula:

Non-combined BCCH: P = (9-AGB)/0.2354 (blocks/second) x (pagings/block)

Combined BCCH P = (3-AGB)/0.2354 (blocks/second) x (pagings/block)

In the IMSI paging mode, when non-combined BCCH is configured, if AGB = 2, P = 59.47 pagings/second; if AGB = 0, P = 76.47 pagings/second. When combined BCCH is configured, if AGB = 1, P = 16.99 pagings/second; if AGB = 0, P = 25.49 pagings/second.

In the TMSI paging mode, when non-combined BCCH is configured, if AGB = 2, P = 118.95 pagings/second; if AGB = 0, P = 152.93 pagings/second. When combined BCCH is configured, if AGB = 1, P = 33.98 pagings/second; if AGB = 0, P = 50.98 pagings/second.

Therefore, the paging capacity in the IMSI mode is one half of that in the TMSI mode. In other words, when two networks are on the same scale and the data is configured in the same way, the paging capacity of China Mobile is smaller than that of China Unicom.

(4) Traffic volume allowed per LA (T)One important principle in planning the LA capacity is that the capacity per LA

must be lower than the maximum capacity. For the capacity expansion, the delivered paging messages in busy hour transmitted by the BSC on the OMC are converted into the pagings per second. The number must be smaller than the earlier result.

If the traffic statistics data is unavailable in a newly deployed network, the traffic volume per LA can be calculated from an assumptive traffic model.

Average call duration: 60s



The ratio of the successful terminated calls (paging and traffic are enabled)

to the total terminated calls: 30%

The ratio of the total pagings (the total number of the pagings caused by

calls and short messages) to the pagings caused by calls: 1:0.5

If call duration = 60s, the traffic volume = 1/60 pagings/ (s x Erl), in which 30% traffic volume comes from terminated calls. Therefore, the traffic volume generated by terminated calls is: 1/60 x 30% = 0.005 successful terminated calls/ (s x Erl). On the live network, the results can be calculated according to the traffic statistics data. For details, refer to the remarks in “LAC planning Tool V3.0”.

Suppose that 75% MSs respond to the first paging, 25% MSs respond to the second paging and the MSs responding to the third paging can be ignored (on the live network, refer to the actual data on the MSC). Therefore, a successful terminated call of the MS needs 1.25 pagings (25% pagings need to be retransmitted):

Y = 0.005 x (1 + 25%) = 0.00625 pagings/(s x Erl)The short message has impact on the paging (Short Message Modifying Factor in “LAC planning Tool V3.0”), so the pagings per second are as follows:

Y = 0.005 x (1 + 25%) x 1.5 = 0.009375 pagings/(s x Erl)Suppose that congestion occurs on the signaling channel when the capacity is

150% of the maximum capacity. That is, if the capacity is less than 150% of the maximum capacity, the original paging messages will not be discarded by the BTS though the paging queue is overloaded. Therefore, the pagings per second are P x 50%.

Suppose that the average paging load over the Um interface is 80% (it is low because of the unbalance of pagings between different paging groups at different time), the pagings in a second equal to P x 50% x 80%.

Note: The values of PCH Congestion Busy Threshold and Average Paging Load at BTS should be obtained through the algorithm design and simulation test. At present, the empirical values (50% and 80%) are used.

In the IMSI paging mode, the traffic volume per LA is:T = P x 50% x 80%/Y = 2537.527 Erl (if AGB = 2 and the non-combined BCCH

is configured.)T = 3262.533 Erl (If AGB = 0 and the non-combined BCCH is configured)T = 725.0067 Erl (If AGB = 1 and the combined BCCH is configured)T = 1087.507 Erl (If AGB = 0 and the combined BCCH is configured)In the TMSI paging mode, the traffic volume per LA is:T = 5075.053 Erl (If AGB = 2 and the non-combined BCCH is configured)T = 6525.06 Erl (If AGB = 0 and the non-combined BCCH is configured)T = 1450.013 Erl (If AGB = 1 and the combined BCCH is configured)T = 2175.02 Erl (If AGB = 0 and the combined BCCH is configured)

(5) Number of TRXs per LA NTRXOn average, there are 7.2 TCHs on every TRX. In the ERLANG traffic model, if

the call loss rate is 2%, the average traffic volume per TRX in an hour is 2.93Erl.In the IMSI paging mode, the number of TRXs per LA is:NTRX = T/2.93 = 867 TRX/LA (If AGB = 2 and the non-combined BCCH is

configured)NTRX = 1114 TRX/LA (If AGB = 0 and the non-combined BCCH is configured)NTRX = 248 TRX/LA (If AGB = 1 and the combined BCCH is configured)



NTRX = 372 TRX/LA (If AGB = 0 and the combined BCCH is configured)In the TMSI paging mode, the number of TRXs per LA is:NTRX = 1733 TRX/LA (If AGB = 2 and the non-combined BCCH is configured)NTRX = 2227 TRX/LA (If AGB = 0 and the non-combined BCCH is configured)NTRX = 495 TRX/LA (If AGB = 1 and the combined BCCH is configured)NTRX = 743 TRX/LA (If AGB = 0 and the combined BCCH is configured)

On the live network, the average traffic volume per TRX can be estimated through the traffic statistical data. For details, refer to the remarks in “LAC planning Tool V3.0”.

The maximum number of TRXs per LA is 900-1000 (refer to “Answers to Planning of the BSC6000 LA”). If the estimated result is higher this value, two or more BSCs should be used to ensure a sufficient capacity for the LA.

3.2 Examples

When the competitor's equipment is replaced by Huawei equipment in Chengdu, the secondary paging is used. The TMSI paging is used for the first time, and the IMSI paging is used for the second time. The first paging success rate is about 80% and the second is 20%.

The efficiency of paging combination can be calculated through the first paging success rate and the paging mode as follows:

Input

Parameter configuration Paging modeNumber of messages in the PCH queue = 0 5.00% Paging Success Rate 80%Number of messages in the PCH queue = 1

10.00% Paging mode (from the

first paging to the fourth one)

2Number of messages in the PCH queue = 2

10.00% 3

Number of messages in the PCH queue = 3

10.00%

Number of messages in the PCH queue > 4

65.00%

Sum100.00

%Therefore, the total efficiency of paging combination is 2.64, as in the following table:

Efficiency of paging combination 2.64

The traffic model in Chengdu Mobile is as follows:

Average call duration: 60s

MTC Ratio: 50%

Average traffic volume per TRX (ERL): 2.93

Ratio of the total pagings to the pagings caused by calls: 1:0.85

Calculate through the tools for the location area planning:



Scenarios1

CCCH Conf

Data configurationNumber of CCCH Blocks in the Corresponding BCCH Multi-Frame

9

BS_AG_BLKS_RES 2BS-PA-MFRAMS 2

Efficiency of Paging Combination2.63992

4126PCH Congestion Busy Threshold 50%Second Paging Ratio 20%Average Paging Load at BTS 100%MTC Ratio 50%Average Call Duration (s) 60Average Traffic Volume per TRX (ERL) 2.93Short Message Modifying Factor 1.85

The results are:Number of pagings per hour per location area

117754

Traffic volume allowed per location area (ERL)

2122

Number of TRXs per location area 724 In Chengdu Mobile, the total traffic volume is 79029 Erl, so the traffic volume per

LA is 2122 Erl and 38 LAs are needed. The number of TRXs per LA is 724, so the BSC6000 has a sufficient capacity for the LAs. The target LAs are planned on the basis of the LA planning of the original network and the number of pagings. If the paging capacity of the LA is insufficient, the LA can be split. Choose the original boundary of the LA when possible and adjust the inappropriate boundary in the original network.

Remarks: In theory, there should be 38 LAs. In practice, choose the original boundary of the LA when possible and split the LAs whose estimated traffic volume is higher than the designed. Therefore, there are 40 LACs.

3.3 Conclusion

The paging mode, BS_AG_BLKS_RES, and the BCCH configuration type all have impact on the LA capacity. In an LA, if BS_AG_BLKS_RES and the BCCH configuration are inconsistent with each other, the minimum PCH capacity determines the capacity of the LA. Therefore, in LA planning, BS_AG_BLKS_RES and the BCCH configuration in an LA should be consistent with each other.

The number of TRXs per LA should not be larger than that calculated from the above formula. Otherwise, the overloaded paging messages are discarded if they cannot be sent within the number of retransmissions of the paging message configured in the MSC. Thus, the subscribers cannot be paged though they are in the serving cell.

If some TRXs are used for coverage expansion instead of traffic improvement,


user, 09/22/08,

请您替换


there can be more TRXs.If the traffic volume of point-to-point message sharply increases, the paging

capacity is enlarged, thus reducing the subscribers. Therefore, flow control is needed.

There are different traffic models in different regions at different time. Therefore, the parameters should be set to different values.

The traffic volume differs, so it is recommended that the combined BCCH cell, the non-combined BCCH cell and the Multi-BCCH cell are respectively planned in their own LA. In the combined BCCH/SDCCH cell, the LA can be planned as larger as possible under the condition that the paging capacity of the BTS is sufficient. The paging messages are broadcast to all the cells in the LA; therefore, the combined BCCH/SDCCH cell is the bottleneck of the LA.

In LA planning, minimize the location updates when possible.

Chapter 4 Impact of Data Services on Location Area Planning

After the General Packet Radio Service (GPRS) is enabled, an LA can be divided into several routing areas on the basis of geographical locations and the GPRS traffic difference in the LA.

If the SGSN needs to transmit data to an MS, it initiates packet paging to locate the MS. The SGSN sends a paging request message to the PCU through the Gb interface. The PCU converts the paging request message into the packet paging request message and sends the message to the MS over the Um interface. If the PCCCH is configured in the BSS system, the message is sent on the PPCH. If the PCCCH is not configured in the system, the PCU forwards the message to the BSC through the Pb interface and then the BSC sends the message on the PCH. The current network mainly applies the second paging mode, so we take this mode into account.

The data services affect the input of the LA planning. Based on the earlier chapter, the input of the LA planning can be classified into several types:

Configuration data: CCCH configuration, BS-AG-BLKS-RES, and BS-AG-

BLKS-RES.

Export: Efficiency of Paging Combination

Default values: PCH Congestion Busy Threshold and Average Paging Load

at BTS

Traffic statistics: Second Paging Ratio, MTC Ratio, Average Call Duration,

Average Traffic Volume per TRX, and Short Message Modifying Factor.

The following focuses on the impact of the data services on the input.

4.1 Impact of Data Services on the Configuration Data

The data services do not have great impact on the configuration of BS-AG-



BLKS-RES. However, the CCCH configuration and BS_AG_BLKS_RES should be adjusted according to the actual situation.

The PCU forwards the packet paging message to the BSC through the Pb interface and then the BSC sends the message on the PCH. See the following table:

CCCH ConfNumber of CCCH Blocks in the

Corresponding BCCH Multi-Frame1 Compounding CCCH 31 Non-compounding CCCH 92 Non-compounding CCCH 183 Non-compounding CCCH 274 Non-compounding CCCH 36

You can increase the number of CCCH blocks in the corresponding BCCH multi-frame to enlarge the capacity of the PCH.

Likewise, you can reduce the value of BS_AG_BLKS_RES to enlarge the capacity.

4.2 Impact of Data Services on the Efficiency of Paging Combination

When the PS services are enabled, the number of messages in the PCH queue is increased. Therefore, the number of messages in the PCH queue should be adjusted on the basis of the existing CS services.

The final input is incremented by the first paging success rate of the MSC and that of the SGSN.

4.3 Impact of Data Services on the Paging Load

For the CS service, the default value of PCH Congestion Busy Threshold is 50%, and the default value of Average Paging Load at BTS is 80%. When the data service is enabled, the paging load is increased, so you are advised to adjust these two to proper values.

4.4 Impact of Data Services on the Traffic Model

The data services also have impact on the traffic model.Currently, statistics of the second paging ratio is unavailable in data service.

Thus, the second paging ratio cannot be calculated when the data service is enabled.

In CS service, you can calculate the ratio of terminated calls is by dividing the number of successful terminated calls (paging and traffic are enabled) by the total number of terminated calls. The transmission of the downlink packet data to an MS by the SGSN is closely related to the MM state of an MS. When an MS is in the standby state, the SGSN sends a packet paging message to the PCU. When an MS is in the ready state, the uplink TBF is established without the paging. Therefore, in data service, the ratio of terminated calls is difficult to calculate.

The data services also have impact on the average call duration and the



average traffic volume per TRX. A PDCH can serve several MSs simultaneously, so the corresponding traffic volume cannot be calculated at the present time. Therefore, the average call duration and the average traffic volume per TRX cannot be calculated when the data service is enabled.

You can calculate Short Message Modifying Factor by dividing the total pagings (the total number of the pagings generated by calls and short messages) by the pagings generated by calls. When the data service is enabled, the total pagings should be the existing pagings plus the pagings generated by the data service that are collected from the SGSN.

4.5 Routing Area Planning

Generally, there is one or several LAs in an SGSN, and there is one or several routing areas in an LA. Currently, the data service volume is relatively small on the GPRS network, so the routing areas are planned in the same way as the LAs. When the data service volume increases, the routing areas can be split according to the actual conditions. When planning the boundary of the routing area, refer to the planning principles of the boundary of the LA.


Documents

RNPS GSM Location Area Planning Solution V2.0