2-3G Interworking

2G-3G Interworking

Suitable for Staff with P&O Skill Certificate III or Lower

Issued by GSM Network P&O Dept

GSM P&O GSM P&O Training Materials for Special SubjectsTraining Materials for Special Subjects

Internal Use Only▲

Version introduction

Version Date Writer Assessor Translator Amendment Records

V1.0 2009-03-01

Guo Hongchang

Zheng Hao Lu Yan No

Internal Use Only▲

Purpose of the course

To know 2G-3G interworking principles

To know similarities and differences of

2G-3G interworking solutions

To know the issue of the interference

between 2G-3G

一级目录标题楷体 GB2312(加粗 )

Arial(加粗 )白色

24 ～ 28号

2G-3G interworking targets

2G-3G interworking principles


2G-3G interworking implementation solutions suggested

2G-3G subscribers’ demand and technology support

2G-3G co-location and interference issues







二级目录标题楷体 GB2312(加粗 )

Arial(加粗 )红色 /黑色24 ～ 28号

5

2G-3G interworking targetsTo guarantee the continuity of 3G service by making full use of the present network investment

To solve the capacity problems in areas where 2G radio resources are already very limited

To achieve the communications of 2G and 3G network with minimum costs of network upgrade

Targets come from classification and organization of subscriber requirements. E.g.,2G/3G complementary coverage to guarantee the continuity of 2G/3GSolve 2G capacity problems in areas where 2G radio resources are limitedTry one’s best not to change the using habits of subscribers: no change of phone number, no change of card, and so onOperate together with 2G network including 2G network upgrade and evolutionUse same/different 3G PLMN numberPrevent unauthorized subscribers from being connected to 3G networkMinimize 2G/3G networking impact on 2G networkIssues about equipment compatibility of 2/3G networking and about charging……



6

2G-3G interworking targets at different stages With the improvement of network construction, 2G-3G interworking targets also change: evolution at different stages

Keep the continuity of 2G-3G service

Avoid impact on 2G network stability

Initial stage of construction

2G-3G network load balance

2G-3G network will manage the operation together

Mature stage of network

2G2G2G2G

3G3G3G3G



7

Initial planning of network—by 2/3G resources, develop 3G subscribers rapidly

Areas of high valueAreas of high valueImportant areasImportant areas

3G/HSDPA ： Voice/visual/medium or high rate data service3G/HSDPA ： Voice/visual/medium or high rate data service

Suburbs and countrysideSuburbs and countryside

GSM/GPRS ： Voice/low rate data services

Capacity:Capacity:

Coverage:Coverage: Full coverageContinuous coverage for important areas

Certain Capacity pressures

Idle, subscribers to be developed

Initial strategy of Initial strategy of

coexistence of two coexistence of two

networks:networks: 3G forms complete

coverage on basis of

GSM; GSM reduces expansion

pressures through 3G; With advantages of 3G,

develop 3G subscribers

rapidly2G/3G develop together One Radio Network2G/3G develop together One Radio Network



8

Middle planning of network—improve 3G coverage, make full use of resources released by 2G

Important areasImportant areas

3G/HSDPA ： Voice/visual/medium or high rate data service3G/HSDPA ： Voice/visual/medium or high rate data service

Suburbs and countrysideSuburbs and countryside

GSM/GPRS ： Voice/low rate data service

Capacity:Capacity:

Coverage:Coverage: Full coverage

Basically continuous coverage, and development towards the countryside

Become idle gradually

Rapid development, and pressures of urban areas

3G coverage is gradually improved, and countryside subscribers should be developed quickly. The number of 2G subscribers is reduced, and the network becomes idle gradually, so value areas can consider to use

released DCS 1800M resources to develop LTE. 64QAM will be introduced to urban HSDPA network, and software upgrade HSPA+ will be realized, and the competitive

power of data service will be enhanced. Planning of trial service in LTE value areas will be speeded up to experience super high rate data service.

Areas of high valueAreas of high value

LTE trial serviceLTE trial service

Trial service in value areas

Trial service of super high rate data service

Netw

ork strateg

yN

etwo

rk strategy

64QAM is introduced to some 3G areas to realize HSPA+ 64QAM is introduced to some 3G areas to realize HSPA+



24 ～ 28号















10


Principles: Manage to use 2G network to expand 3G coverage, and keep the

continuity of service for 3G subscribers;

Manage to reduce handover times between systems;

Manage to provide 3G subscribers with 3G network service;

Manage to avoid upgrade of present 2G/2.5G network;

Observe the principle of giving priority to subscribers’ experience.Node B

BTS

BTS

3/2G

2G

Dual mode

Dual mode



11

Suggestions for the realization of 2G-3G interworking

Manage to form continuous signal coverage within 3G coverage areas Reduce the zones which have no signals or weak signals, and especially avoid these zones in areas where there

is a high pedestrian flow. In these areas, 3G signals usually fade suddenly, and have no time to do measurement

or handover between systems, so the failure probability of handover between systems might be quite high.

Manage to choose areas where there is a low pedestrian flow as 3G

network edge Avoid the choice of edge in areas where there is a high pedestrian flow, like stations, docks and so on, so as to

reduce the possibility of intersystem handover. In addition, this can also avoid signaling interaction

delay/failure, and the following handover call drop, which result from inefficient processing ability.

Choose well covered GSM areas as 3G edge This is good for successful handover from 3G to GSM. In other words, there should be no overlapping areas

between GSM edge and 3G edge. This can reduce the possibility of intersystem measurement failure, signaling

interaction failure and the following call drop, which are caused by the problem of GSM network signal

strength.



24 ～ 28号




2G-3G interworking implementation solutions

suggested







suggested





13


Overview 2G network protocol doesn’t consider 2G-3G interworking until R99 edition, while

3G protocol starts to consider the issue of 2G-3G interworking from its initial

formulation.

Main network element related to the realization of 2G/3G

interworking 3G MSC/VLR, 3G SGSN, 3G HLR network element ； Dual mode mobile phone

Main implementation solutions of 2G-3G interworking Solution of no upgrade of 2G network equipment; Solution of a small number of upgrades of 2G network equipment; Solution of a large number of upgrades of 2G network equipment; (not

recommended)



14


Basic functions realized by 2G-3G interworking Choice of PLMN;

Cell reselection;

Handover

Main network element related to the realization of 2G/3G interworking 3G MSC/VLR, 3G SGSN, 3G HLR network element;

Dual mode mobile phone

Solutions to realize 2G-3G interworking All the interworking solutions consist of 3 interworking functions (choice of

PLMN, cell reselection, and handover). Each solution corresponds to a different 2G

network upgrade scale.



15

2G-3G interworking solution: No upgrade of 2G network equipment

The solution is realized through “The Selection of PLMN”

2G and 3G network are assigned a different PLMN number. The connection to 3G is realized by the reselection function of dual mode terminal HPLMN (home PLMN), and not by 2G equipment upgrade;

The premise is that HPLMN in SIM card or USIM card is 3G PLMN. So 3G 2G one-way handover and cell reselection can be realized.



16

UERNC 3G CNBSC 2G CN

66 minutesminutes

Some dual mode terminals firstly choose GSM network to Some dual mode terminals firstly choose GSM network to register.register.

Every six minutes, dual mode terminals, which use a new card, will try 3G network which Every six minutes, dual mode terminals, which use a new card, will try 3G network which performs as a home network.performs as a home network.

Problem: within the same coverage area, some dual mode terminals will firstly stay in GSM network, and can not use 3G service.

Theory of PLMN solution: 3G subscribers all use a newly made USIM card, 3G network uses a new network number, and the length of time for making a USIM card belongs to network choice information. So all 3G subscribers who use a new USIM card will firstly stay in 3G network.




17

3G3GGSMGSM

3G － >GSM： It is realized by cell

reselection, and voice

handover and PS handover

will be configured.

GSM － >3G： In idle state, reconnection to 3G is

realized by HPLMN reselection.

Voice handover is not configured, and

PS handover is not supported.

3G network must be constructed with a network number different from GSM

network. For 3G subscribers, 3G network will be configured as HPLMN.

Advantages

There is no need of the functions of GSM present

network to upgrade software.

There are fewer cooperating tests of GSM and 3G. Disadvantages

If GSM subscribers become 3G subscribers, SIM card must be

changed.

HPLMN reselection needs 6 minutes, so subscribers may be less

dissatisfied.

Requirements of the solutionRequirements of the solution

Choice of PLMN solution is suitable for those mobile telecommunications carriers who can’t realize GSM to 3G cell reselection.Choice of PLMN solution is suitable for those mobile telecommunications carriers who can’t realize GSM to 3G cell reselection.




18

2G-3G interworking solution: Small scale upgrade of 2G network equipment

The result of this solution is that “priority is given to connection to 3G network, and one-way

voice handover between 2G/3G network is realized”.

Service handover between 2G/3G systems is rapidly realized by cell reselection and handover. Voice handover, data service handover, and cell reselection function from 3G to 2G are all realized.

2G to 3G data service handover and cell reselection function are both realized.



19

UERNC 3G CNBSC 2G CN

Some terminals firstly choose GSM network to Some terminals firstly choose GSM network to register.register.

Configuration of broadcast message parameter makes it easy for dual mode terminals to realize Configuration of broadcast message parameter makes it easy for dual mode terminals to realize 2G-3G reselection.2G-3G reselection.

SomeSomesecondsseconds

System broadcast messageSystem broadcast message

Parameters configuration delivered by RNC makes terminals to stay in 3G network if possible.Parameters configuration delivered by RNC makes terminals to stay in 3G network if possible.

Problem: within the same coverage area, some dual mode terminals will firstly stay in GSM network, and can not use 3G service.

Theory of cell reselection solution: 2G BSC delivers broadcast message to require dual mode terminals to be reconnected to 3G by intersystem cell reselection.




20

3G3GGSMGSM

3G － >GSM： It is realized by cell

reselection, and voice

handover and PS handover

will be configured.

GSM － >3G： In idle state, reconnection to 3G is

realized by cell reselection.

Voice handover is not configured and

PS handover is configured.

Both same network numbers or different network numbers are

accepted. Construction of the same network numbers is

recommended. GSM network is required to support 2G ->3G cell reselection

function.

Requirements of the solutionRequirements of the solution

Advantages

Subscribers don’t need to change SIM card and

phone number.

Rapid return from 2G to 3G makes subscribers

feel satisfied. Disadvantages

Upgrading GSM network is required to support 2G->3G cell reselection.

Debugging of present network involves a lot of work.

The cell reselection solution is a 2G-3G interworking solution which is preferred by world mainstream mobile telecommunications carriers at present in this industry.The cell reselection solution is a 2G-3G interworking solution which is preferred by world mainstream mobile telecommunications carriers at present in this industry.




21

2G-3G interworking solution: Large scale of upgrade of 2G network equipment (not recommended)

The result of this solution is that “priority is given to connection to 3G network, and 2G/3G

networking realizes one-way speech handover”.

Service handover between 2G/3G systems is rapidly realized by cell reselection and handover. Voice handover, data service handover, and cell reselection function from 3G to 2G are all realized.

2G to 3G data service handover and cell reselection function are both realized.



22

2G-3G interworking solutions: Comparison of these three solutions Comparison of functions and upgrade requirements

First solution:Choice of PLMN

Second solution:One-way speech handover

Third solution:Two-way handover

Functions 3G2G voice handover: √ 3G2G PS handover: √ 3G2G cell reselection: √ 2G3G voice handover: × 2G3G cell reselection: × 2G3G PS handover: ×

3G2G voice handover: √3G2G PS handover: √3G2G cell reselection: √ 2G3G voice handover: ×2G3G cell reselection: √2G3G PS handover: √

3G2G voice handover: √3G2G PS handover: √3G2G cell reselection: √ 2G3G voice handover: √2G3G cell reselection: √2G3G PS handover √：

Similarities Upgrade 2G HLR or construct a new 3G HLR based on the number portability feature supported by the network

2G MSS/BSSequipmentmodifyingrequirements

No modification BSS modifies system message SI2ter to add WCDMAadjacent cell information; add system messageSI2quater (optional); modify system message SI3If PLMN in system broadcast message is different, 2GMSC location upgrade response message andthe like need to be upgrade to R99 protocol edition.

Modifications of the second solution +upgrade to support measurementcontrol for handover between systemshandover judgment, andhandover signalingprocedure. BSS and MSC of 2G systemboth need to be modified.

Requirementfor theoriginalsubscribers

The card must be changed. None None

HandoverSpeedBetweensystems

3G2G is realized by cell reselection, and is quick;2G3G is realized by the choice of HPLMN, and is slow.

3G2G two-way handover is realized by cell reselection, and is quick.

The same as the second solution



23

2G-3G interworking solution: Analyses of risk costs

Comparative analyses of risk costsFirst solution: Choice of PLMN

Second solution: One-way speech handover

Third solution: Two-way handover

Networking risks

No risks BSC needs to do a small number of software upgrades, and there is some risk.

A large number of upgrades of both BSS and MSC, and there is a high upgrade risk.

Networking costs

3G networkconstruction costs

First solution + 2G network software upgrade costs 1 (system message)

The second solution + 2G network software upgrade costs 2 (judgment process of intersystem handover)

Operation and maintenance costs

3G network operation and maintenance costs

3G network operation and maintenance costs + 2G network operation and maintenance costs

3G network operation and maintenance costs + 2G network operation and maintenance costs

Subscriber costs

The card must be changed/or the mobile phone has preferred access function.

No requirements No requirements



24

2G-3G interworking solution: Construction solutions at different stages

In consideration of the interworking features described above, construction solutions

at different stages are recommended.

Network status Interworking solutions recommended

Remarks

First stage

At the initial construction stage, present network equipment upgrade requirements can’t be satisfied. So in a short term, requirements for 2G3G cell reselection can’t be satisfied.

First solution Subscribers use a new SIM card to realize preferred access to 3G by HPLMN reselection.

Second stage

2G equipment upgrade conditions are mature

Second solution From 2G/3G interworking to the same PLMN network number



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HLR construction solution:

Cell configuration strategy

Local area network networking strategy

Signaling network sharing, long distance tandem switch

Network element sharing

Influence over performance and functions caused by the combination of PLMN and LAI

2G-3G interworking implementation solutions suggested: Main points



27

2G/3G use the same network number:

2G and 3G HLR entity are integrated. 2G HLR has the function to support 3G subscribers to create an account. 2G HLR needs to be upgraded to support contracting service for 3G subscribers. (recommended)2G and 3G each has an independent HLR entity. They use different IMSI, MSISDN section number to distinguish 2G HLR and 3G HLR. HLR doesn’t need to be upgraded. However, its obvious disadvantage is that original 2G subscribers must use a new MSISDN number, if they want to use 3G service.

2G/3G network use different network numbers:

2G and 3G HLR entity are integrated. 2G HLR has the function to support 3G subscribers to establish a new account. 2G HLR needs to be upgraded to support contracting service for 3G subscribers, and telephone number function of different network numbers.2G and 3G HLR entity are independent. Number portability service is used to keep MSISND of subscribers so as to provide the subscribers with the greatest convenience. 2G HLR doesn’t need to be upgraded. By number portability, the original 2G subscribers can change SIM card. In this way, the subscribers can not only firstly use 3G service but also make full use of the advantage of number portability, that is, MSISDN number is reserved for subscribers. (recommended)

2G-3G interworking implementation solutions suggested: HLR construction solution



28

Strategy recommended:

Within 3G coverage areas, 3G2G interworking is not supported, but the edge of 3 coverage areas support handover towards 2G, and cell reselection.

Disadvantages of 3G->2G handover supported by the whole network:

High probability of call drop will exist, because success rate of intersystem handover is much lower than that of intra-system handover.

It is hard to control the target coverage area which is selected during cell reselection and handover, because of the ping-pong effect.

If the compact model is used, it can increase downlink emission power of the base station and the mobile phone, increase interference, and reduce capacity.

Network configuration and maintenance is complicated. The initial optimization and manual configuration involves much work, and signaling costs a lot.

2G-3G interworking implementation solutions recommended: Cell configuration strategy



29

Hybrid networking

Create dual mode MSC/SGSN or upgrade the original 2G MSC/SGSN to 2G/3G dual mode MSC/SGSN.

Independent networking

Create 3G MSC/SGSN, and keep the original 2G MSC/SGSN; local traffic between 3G network and 2G network is connected by GMSC of 2G.Independent networking can support independent service of the two networks. They won’t influence each other, but they can integrate with each during their development.

2G-3G interworking implementation solutions suggested: Local area network



30

Signaling network sharing, and long distance tandem exchangeLocal switch terminates BICC signaling (by SIGTRAN) and IP bear traffic, traditional TDM interface is provided outside.

Network element sharingEquipment sharing GMSC/SCP/GGSN/SC

2G-3G interworking implementation solutions suggested: Make use of network sharing function



3131

2G-3G interworking implementation solutions suggested: Network element and requirements for equipment version

Functions Network

element

Version

requirements

Special needs

2G3G

cell reselectionBSC R99

3GPP TS 05.08

3GPP TS 04.18

ARD control access CN R6 3GPP TS 29.002

Compatible with original 2G equipment

3G MSCMAP ： Compatible with MAP-Prep-Handover

req of MAP Phase 2

3G MSCCompatible with original BSC equipment, and

capable of circumventing influence from SAI

3G MSC Forced to add Cipher information

Video phone fall back 3G CN R6 MAP ： Alternative Channel Type

UE R6 Support CS64 decline to AMR processing

RNC R6 Alternative RAB Parameters



3232

2G-3G interworking implementation solutions suggested: Influences over PLMN and LAI

3G3GGSMGSM

Cell reselection solution

Different PLMN solution

2G/3G2G/3G interworkinginterworking

Same PLMN, different LAI Different PLMN

IMSI (SIM card) No change Change the card

Choice of

network

Connected to the network by cell

reselection

Choose the network by cell

reselection and HPLMN

Access control HLR controls whether 2G

subscribers will be allowed to be

connected to 3G network.

MSC/VLR/SGSN can control

whether subscribers will be

connected to 3G network.

The mainstream mobile telecommunications carriers The mainstream mobile telecommunications carriers

will prefer the reselection solutionwill prefer the reselection solution－－ e.g., adopt the solution of using different network numbers e.g., adopt the solution of using different network numbers

of Hutchof Hutch

Suggestion: Upgrade the present GSM equipment Suggestion: Upgrade the present GSM equipment

according to the requirements of the according to the requirements of the target network target network

so as to guarantee the satisfactory experience of so as to guarantee the satisfactory experience of

future 3G subscribers!future 3G subscribers!

The mainstream mobile telecommunications carriers The mainstream mobile telecommunications carriers

will prefer the reselection solutionwill prefer the reselection solution－－ e.g., adopt the solution of using different network numbers e.g., adopt the solution of using different network numbers

of Hutchof Hutch

Suggestion: Upgrade the present GSM equipment Suggestion: Upgrade the present GSM equipment

according to the requirements of the according to the requirements of the target network target network

so as to guarantee the satisfactory experience of so as to guarantee the satisfactory experience of

future 3G subscribers!future 3G subscribers!



24 ～ 28号





suggested







suggested





3434

Requirements analysis of user policy and technology support

Reduced costs of switch to other

networks

Subscribers can use 3G service without the

change of card or number.

Controllable subscribers’ switch to

other networks

Some areas have the demand for controlling

subscribers’ switch to other networks

Convenient and rapid switch to other

networks

Both telephones and business halls will be ready for 3G service.

Business marketing

2/3G use the same network number.

Adopt cell reselection solution.

ARDControl subscribers’ access connection to

3G

Initial demand from carriers

Analyses of demand

Technology support

IMSI section number segment number

controls subscribers’ connection to 3G.

Make use of advantages of 3G and

adopt positive marketing strategies

Obvious costs advantages of 3G voice

and data service



3535

User policy—ARD-based access control of 2/3G subscribers

Upgrade 2G and 3G HLR, add an information ID field: Subscriber data extension in HLR is used to add control information ID field (ARD: Access Restriction Data)

to show subscriber access attribute. 2G and 3G subscriber access control is realized by ARD. During location upgrade, the ADR information is transmitted to MSC Server/VLR by extended “Insert

Subscriber Data” signaling.

Core network equipment MSC Server/VLR distinguishes the radio networks which

subscribers are connected to: VLR distinguishes the radio network property used by a subscriber, that is, whether the subscriber logs in from

BSS or UTRAN. According to the radio network attribute used by a subscriber, and ARD value delivered in ISD operation, VLR

defines the relationship between the subscriber property and access network property, and corresponding

application scenarios. This is shown in the following table:

Access resultAccess result Meaning of ARD field Meaning of ARD field ARDARD valuevalue Application scenariosApplication scenarios

UTRAN system access denied UTRAN Not Allowed 01 Control whether to be connected

to 3G network

GREAN system access denied GREAN Not Allowed 10

Constraints:

Both HLR and VLR need to support ARD function.ARDUser Data

01: UTEAN not allowed

10: GREAN not allowed



3636

Business policy of analyzing demand and technology support

Attach importance to subscriber experience

Make use of 3G service advantages, and make full use of

3G service

Fewer parameter configurations

No ping-pong handover

Improve service QoS

2/3G service continuity

Convenient

deployment / maintenance

3G selective

preference strategy

Reliable 2/3G

handover Cell reselection

2G BSC is only

configured with 3G

frequency points

One-way handover Cell parameter

control

Initial demand from carriers

Analyses of demand

Technology support



3737

Service strategy–3G selective preference in cell reselection, improvement of service QoS

Criterion for UE starts measurement of UTRAN :

Qsearch_I <=7 && RLA_C< R(Qsearch_I)

If Qsearch_I =7 ， R(Qsearch_I) = +

3G 3G prioritypriority

Unconditional measurement of 3G signal

Voice service If average GSM MOS value is 3.45, and average

3G MOS value reaches 4.2, user experience is

high .

Data service 3G provides special service like video phone, and

video streaming media and so on, which can’t be

provided by 2G.

Download rate of HSDPA is 13 times higher than

that of GPRS and 7 times higher than that of

EDGE. So internet surfing is more smooth.* Hong Kong 3G network values measured in practice

Test scenario

MOS value

(Sampling of more than

one hundred times of

calling)

Intra-NodeB calling* 4.245

Inter-NodeB calling (not pass

Iur)*4.284

Inter-NodeB calling (pass

Iur)*4.125

Average GSM MOS value 3.54



24 ～ 28号





suggested







suggested





39

Analysis of the need for 2/3G co-location construction

330

920

470390

GSM1800 GSM900 WCDMACS12.2K

WCDMACS64K

m Reduce space of equipment

room, and need of antenna feeder

Reduce project construction

difficulty, and speed up project

construction progress

Save costs

Transmission sharing

Layout of 2G site may not guarantee

the best quality of 3G network.

Some solutions may lead to

deteriorated loss.

Interference isolation needs to be

considered.

The original 2G network performance

may be influenced.

AdvantagesAdvantagesAdvantagesAdvantages DisadvantagesDisadvantagesDisadvantagesDisadvantages

GSM and 3G co-location is GSM and 3G co-location is based on GSM1800 and this based on GSM1800 and this

guarantees continuous coverage guarantees continuous coverage of video phone service.of video phone service.

According to overseas network construction According to overseas network construction

experience of ZTE, 2/3G co-location can help carriers experience of ZTE, 2/3G co-location can help carriers

to build a network with low costs but in a high speed.to build a network with low costs but in a high speed.

Statistics of 2/3G co-location Statistics of 2/3G co-location

proportion of overseas carriersproportion of overseas carriers

Comparison of GSM and 3G coverage performance (dense urban areas)



40

Antenna and feeder design solution 1 — 2/3G independent antenna and feeder

Site of SSite of Shang Bu Industry and hang Bu Industry and Trade Mansion in Trade Mansion in

Huaqiangbei in ShenzhenHuaqiangbei in Shenzhen

Site of Heng Xun Site of Heng Xun Communications building Communications building

in Shenzhenin Shenzhen

GSM 900

3G

GSM 900

GSM 1800

3G

Advantages

1. It doesn’t influence the original system.

2. Optimization adjustment of each system is totally

independent.

DisadvantagesThe costs is high, because each system needs an additional

antenna and feeder.

Application

scenarios

1. There is enough installation space and isolation space between

the base station and the antenna.

2. The additional costs of installation pole and antenna is

controllable.

When a new antenna and feeder is added, the configuration of antenna azimuth and antenna downtilt parameters can refer When a new antenna and feeder is added, the configuration of antenna azimuth and antenna downtilt parameters can refer

to that of 2G system so as to guarantee the two systems cover the same range. In other words, “2/3G networks are integrated to that of 2G system so as to guarantee the two systems cover the same range. In other words, “2/3G networks are integrated

into one network”.into one network”.



41

Antenna and feeder design solution 2 — 2/3G use a same feed line but a different antenna

WCDMA

GSM 900/PCS 1800

A site in Hong KongA site in Hong Kong

Advantages1. The optimization adjustment of each system is totally independent.

2. It saves investment of feed line.

Disadvantages The combiner causes extra loss, and this influences the original system coverage.

Application

scenariosThe feed lines’ installation space and length is a major impact on rent costs.



42

A multiport wide beam antenna, whose downtilt can be

adjusted, is recommended so as to guarantee relatively

independent optimization adjustment of each system.

Antenna and feeder design solution 3 – 2/3G use a same feed line and a same antenna

A site in Hong Kong (six ports and tri-band A site in Hong Kong (six ports and tri-band antenna)antenna)

Advantages It saves investment of feed lines.

Disadvantages

1. The combiner causes extra loss, and this influences the

original system coverage.

2. Since the antenna is shared, it makes RF optimization

adjustment for each system more difficult. So intersystem

coordination is needed.

Application

scenarios

There isn’t enough installation space and isolation space

between the base station and the antenna.



43

Antenna and feeder design solution 4 – 2/3G use a same antenna and a different feed line

Advantages 1. It saves the investment for antenna and feeder.

2. It avoids the use of combiner, and the loss caused by it.

Disadvantages Since the antenna is shared, it is more difficult to do RF optimization

adjustment for each system. So intersystem coordination is needed.

Application

scenarios

There isn’t enough installation space and isolation space between BBU and

the antenna.

RRU is directly installed under the

multiport wide beam antenna, this method

saves the investment for a combiner and

avoids the loss caused by it.

Improvement

of path loss

Coverage area

improvement %

1dB 7%

2dB 14%

3dB 22%

4dB 30%

5dB 40%

A site of Gang Ao Shopping Mall in Huaqiangbei in Shenzhen

(GSM1800+WCDMA)

If 7/8’ feed line is at 2100MHz frequency band, 100 meters’ loss is 6.3 dB. As to China

Unicom’s equipment room environment for present network, the proportion of feed

lines which are longer than 50 meters is not small, especially in dense urban areas, the

proportion is larger. However, RRU solution can avoid this kind of loss.



44

Summary of the adoption of a wide beam antenna

Possible influences over the original network caused by the use of a wide beam antenna

Directional antennaDirectional antenna Isotropic antennaIsotropic antenna

Interference degradationInterference degradation

In areas where there are dense sites, the slight change of antenna

indicator will not have much influence over network coverage

performance.

Directional broadband antenna can be adopted to replace narrowband

antenna without any negtive impact.

After the replacement of antenna, the primary service area of the

cell may change.

The traffic attribution of the edges of the original cell may change,

and then influence the load distribution of the cell.

For those areas where there is the coverage performance

degradation, the traffic may be lost.

An “accidental problem”:

After the adoption of a wideband antenna, there is a

slight 5dB effect interference degradation.



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Interference control principle for wireless communications

Mutual interference between different communication systems (interference dead zone)

-3000 -2000 -1000 0 1000 2000 3000-2500

-2000

-1500

-1000

-500

0

500

1000

1500

2000

2500

ZTE emulation research

U M T SB S

I n t e r f e r e n c e

G S MB S

D e a dZ o n e

G S Mm o b i l e

The purpose of interference protection and control is not to totally

eliminate the interference, but to control the interference at an

acceptable level with reasonable costs so as to guarantee the normal

operation of different communication systems.

The basic solution for solving the problem of interferences from

different wireless communication systems is frequency government

and standardization of equipment standard specifications. Since the

spectrum resources decrease gradually, it is more difficult to do

interference protection control.

When 3GPP establishes the technical specifications for 3G

equipment, the interference with the present equipment has been

fully considered, which normally satisfies30dB base station space

isolation.

However, during the time when the other existing networks (GSM

and PHS and so on) are constructed, it is not possible to take into

consideration the future networks like 3G. So the interference with

3G is inevitable, and this must be solved in construction.



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2/3G mutual interference main consideration (1) — GSM900/1800

According to the theoretical analysis, based on 3PP protocol, the blocking requirement of

WCDMA to GSM, or WCDMA to GSM1800, is 43dB. The intermodulation isolation of

GSM1800 to WDCMA is 94dB.

Since WCDMA duplexer has 80dB out-band rejection, 94dB intermodulation isolation only needs

12dB spatial separation, so it can be completely neglected.

Similarly, GSM1800 has 80dB out-band rejection, so the blocking interference can be neglected.

30dB isolation is enough to satisfy the mutual interference of WCDMA2100,

GSM900/1800the isolation design for multi-band antenna port is 30dB.

Interference

mechanism

3GPP theoretical isolation （ dB）

WCDMA to

GSM1800

GSM1800 to

WCDMA

WCDMA to

GSM900

GSM900 to

WCDMA

Spurious isolation 25 28.87 25 28.87

Blocking isolation 43 30 35 30

Intermodulation

isolation

-- 94 -- 94

Duplexer 80dB No influence after filtering

30dB



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Practical engineering solution for GSM-3G interference coexistence

No interference coexistence can be realized by drawing on the rich overseas

3G engineering experience, and making use of the excellent anti-interference

performance indicator of ZTE 3G equipment.

For 65 degree horizontal beamwidth sector antenna, the vertical isolation

should be less than 0.2 meter, and the horizontal isolation should be less than

0.4 meter.

3G independent antenna and feeder, spatial isolation solution3G independent antenna and feeder, spatial isolation solution

2/3G independent feed line, replacement of wide beam antenna 2/3G independent feed line, replacement of wide beam antenna

solutionsolution

The isolation of multiport wide beam antenna is relatively low, 30dB isolation between different

dipoles can guaranteed, which satisfies the isolation indicator described above.900M, 1800M, and

2100M can share an antenna.

A G/D/U tri-band antenna of Tian Di

Hotel site in Shenzhen

Spatial isolation of a site in Huaqiangbei in

Shenzhen

Note: For a wide beam antenna, its interference with PHS, and 1.9G Note: For a wide beam antenna, its interference with PHS, and 1.9G

CDMA decreases by 5dB!CDMA decreases by 5dB!



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Summary of interference

Interference of GSM900, and GSM1800 is not the main problem.

Interference of PHS, and CDMA1.9G of some areas must be solved during the

construction of WCDMA network.

Each area needs to consider its actual situation, and offers instructive suggestions

about interference and makes preparations as soon as possible.

－ National policy of radio frequency spectrum; improvement of old equipment indicator



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Summary of 2G – 3G network sharing operation

Result of 2G – 3G integration － One Radio Network

Network interworking

Service, load, and subscriber interworking

System equipment, terminals

Terminals

System equipment: CN 、 Node B ； RNC/BSC and network

management

Project construction and network maintenance

Site locationcoordination/sharing

Feeders and antennascoordination/sharing

Power transmissionsharing

2-3G Interworking

Documents

Transcript of 2-3G Interworking