GO_NA10_E1_1 GSM Dual-Band Network Planning & Optimization-79

7/28/2019 GO_NA10_E1_1 GSM Dual-Band Network Planning & Optimization-79

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GSM Dual-band Network

Planning & Optimization

ZTE university



Objective

After completing this course, you will be able to: Know the background of the introduction of dual-band

network

Know network construction and advantages of dual-

band network

Know the planning strategy of dual-band network

Know the definition of radio parameter and optimizing

strategy of dual-band network



Catalog

Dual-band Overview

Dual-band Network Planning Strategy

Dual-band Network Optimization Parameter

Tuning Dual-band Network Optimization Cases



Dual-band Overview

Background of Dual-band Network The earliest GSM digit mobile telecom network is 900M.

With the rapid growth of the users, demand of network

capacity is increasing tremendously. So limitation of

frequency resource and lack of radio channel capacitybecome choke point of network development.

GSM1800(DL：1805～1880MHz UL：1710～

1785MHz) network is introduced and

GSM900/GSM1800 dual-band network construction can

satisfy demand for GSM network capacity.



Dual-band Network Overview

advantages of DCS1800 Make up for GSM900 frequency resource shortage.

GSM 1800 is similar with GSM900 in Network

construction, engineering, network planning , and

network maintenance and service Share GSM 900 sites so as to save the construction

cost

GSM terminals supporting dual-band are now

being popularized.



GSM900

GSM1800 GSM1800

GSM900

＋＝

Dual-band Network Overview

Features of dual-band network GSM900M and DCS1800M can be adjacent cells of

each other.

These two serial of cells can be handed over and be

reselected.



Similarities & Difference between GSM900

and DCS1800

same networkconstruction

same voice coding

same modulating

technology same signaling procedure

same frequency planning

tool

.........

• different spectrum amplitude

• different radio propagation

discipline

• different coverage scope

• different output power

• .........



Dual-band Network Construction

network construction of GSM1800 and GSM900 Independent network constructing mode in different

MSC

Mixed constructing mode in one MSC

Mixed constructing mode sharing one BSC Mixed constructing mode sharing one BTS



Independent Network Construction Mode

Features GSM1800 and GSM900 have different BSC and MSC，sharing

one HLR, AUC and OMC etc.

900M cell and 1800M cell in the same physical area belong to

different location area, and MS in these two network systems will

arouse multiple location area upgrading.



Mixed Network Construction Mode Sharing MSC

Features GSM 1800 and GSM 900 share MSC/VLR, HLR/AUC and OMC etc.

BSS of GSM1800 and of GSM900 are connected to MSC/VLR via

A interface.

GSM 1800 shall be the major part with the support of DCS1800 in

dual-band network. GSM900 realizes favorable and full coverageand GSM1800 provides dense area with supplementary capacity.



Mixed Network Constructing Mode Sharing BSC

Features BSS equipment of GSM1800 and GSM900 should be from the

same manufacturer when Abid interface is unopened.

Shared BSC should support dual-band network with the equipment

coming from the same manufacturer, which can utilize the existing

BSC and MSC equipment for money saving purpose.



Mixed Network Constructing Mode Sharing BTS

Features Transceiving are encouraged in GSM900 and GSM1800 sharing

one BTS. BTS should support co-BCCH.

This network constructing mode is cost-saving and easy to conduct

and exiting network facilities can be utilized.



Contrast of Different Network Constructing Mode

The following is contrast of three typical dual-bandnetwork constructing mode from technology and

economics prospective.

dual-bandnetwork

constructing

mode

dual-band

handover speed

& signaling

some handover

speed & signaling

impact on GSM900 by

the projectinvestment

Independent

MSCslow/great fast/little little great

share MSC moderate moderate moderate moderate

share BSC fast/little slow/great Great little



Network Constructing Mode Recommended

Network constructing mode

(be careful)

Independent MSC

原因分析

Advantages of mode sharing BSC and mode sharing MSC

compared to mode MSC independent

Handover is easy to carry out and amount of signaling needed

to be handled is small while result comes out good.

Prior network constructing

mode

Sharing BSC

Sharing MSC



Catalog

Dual-band Overview

Dual-band Network Plann ing Strategy


Tuning Dual-band Network Optimization Cases



1800M coverageGSM900M

coverage

GSM900M MS

GSM dual-band MS

Dual-band Network Planning Principles

Planning Principle GSM 1800 shall be the major part with the support of

DCS1800 in dual-band network. GSM900 realizes

favorable and full coverage and GSM1800 provides

supplement capacity for dense area.



Dual-band Network Coverage Mode

Initial stage: hotspot Middle stage: small-coverage area

Later stage: continuous coverage

continuous coverage

DCS 1800 sitesNon-continuous

coverage DCS1800

site

GSM 900 sites



GSM900 layer

GSM1800 hitspot

Handover due to coverage

Intra-band handover due to capacity

only solve the

short-term capacity

shortage

Signalling load

increases due to

frequent handover ,

which results in

capacity loss.


Hotpot and small-coverage area




principle: co-bcch，GSM900 and GSM1800exists in one cell. BCCH and SDCCH channel are

configured on 900M frequency. Non-BCCH

frequency can be 900M or 1800M.

Advantage: save one BCCH TSL as well asexpanding the capacity (biggest advantage).

Configure 1800 carrier in 900M cell. Neighboring

relations of the cells need not to be changed,

network needn’t be planned again and dual-band

cell reselection and handover needn’t to be

considered again.



GSM1800 layer

GSM900 layer Inter-band handover due to coverage

inter-band handover due to capacity

Easy for expansion, and is

a l solution to long-term

capacity

Compared to hotpot

coverage, signalling load

reduces greatly, as a result,

capacity increases.


Continuous and large scale coverage



DCS1800 Project Construction

DCS1800 sites distribution We suggest to select sites already in GSM900 system and use site

equipment room, iron tower, power supply facilities, and transmit

devices in the sites for cost-saving purpose.

Antenna installation It’ s best that antenna of DCS1800 is 2-3m higher than that of

GSM900

Antenna direction of the two should be the same for traffic control

Half-power angel of both horizontal and vertical direction should besmall and similar.

DCS1800 main-lobe gain is greater than or the same with 2-5dBi.



DCS1800 Site Distance

Difference between propagation loss of 1800Mand of 900M

Macro-cell (radius>3 kil )

propagation consumption of 1800MHz is 12.8dB greater than

that of 900MHz Micro-cell

propagation consumption of 1800MHz is 6dB greater than that

of 900MHz

Indoor loss (power level both indoors and outdoor)

propagation consumption of 1800MHz is 12-17dB



900M

1800M

Penetration loss

DCS1800 Distance



Distances between DCS1800 Sites

Suggestions It’s possible that when average distance between sites

is 500-800 m, GSM1800 system can provide with

favourable both indoor and outdoor coverage.

Boosting antenna gain, site transmission power and

site reception sensitivity can add to GSM1800 coverage.

Some site’s traffic is high but the distance is much far.In this case, site need to be added and its power

capacity shall base on coverage and quality.



Catalog

Dual-band Network Overview Dual-band Network Planning Strategy

Dual-band Netwo rk Op tim izat ion Parameter

Adjus tment Dual-band Network Optimization Cases



GSM900

BTS DCS 1800BTS

MSC

BSC BSC

Paging establishmentand sending CM3

message during

handover


Adjustment

Switch can provide with handling Class Mark 3( CM3 ) message function



Tolerance (dB)

for conditions

extreme

2.5

2.52.5

2.5

2.5

Power GSM 900 DCS 1800

class Maximum output Maximum output

power power normal

1 - - - - - - 1 W (30 dBm) 2

2 8 W (39 dBm) 0.25 W (24 dBm) 23 5 W (37 dBm) 2

4 2 W (33 dBm) 2

5 0.8 W (29 dBm) 2

4 W (36 dBm)

Class Mark3



Class Mark3



Cell Selection

Cell Selection When MS powers on or enters from blind spot to

coverage spot, MS monitors cell signaling and

synchronizes with the cell, scan BCCH of cells and

select appropriate cells to stand according to cell priorityand C1>0 criterion.

According to cell priority and C1 value to select standing cell,

i.e. serving cell.



C1 is cell path loss judge criterion para.C1 = (A-Max(B,0))

A=RXLEVEL－DL-RXLEV_ACCESS_MIN

B = MS _TXPWR_MAX - P

RXLEVEL is average level received by MS

DL-RXLEV_ACCESS_MIN is allowable minimum level received by MS

MS_TXPWR_MAX is maximum power level of control channel

P：MS maximum output level

C1 Criterion



CBA、CBQ

CellBarQualif

y

CellBarAcces

s

Cell Select

priority

Cell Reselect

Status

0 0 Normal Normal

0 1 Barred Barred

1 0 Low Normal

1 1 Low Normal



Cell Selection

In order to let 1800 frequency be the priority, set 1800frequency cell to be high priority cell in which CBQ equals

0 and CBA equals 0 and Set 900 frequency cell to be low

priority cell in which CBQ equals 1 and CBA equals 0.

900M cell：CBQ = 1，CBA = 0，C1=15

1800M cell：CBQ = 0，CBA = 0，C1=10

Cell selection after MS powered on



When PT doesn’t equal to 11111,

C2＝C1＋CRO－TO×H（PT－T）

When PT＝11111,

C2＝C1－CRO

In which：

When x<0，H（x）＝0；

When x0，H（x）＝1

CRO：cell reselect offset

TO：temporary offset（temporary value of C2, In this period of time, C2

depends on PT.）

PT：punishment time

Use PT/TO to reduce

C2 value in fixed time

so as to reducereselection of this cell.

C2 Parameter



Dual-band Network Mobile Standing Principle 1

DCS1800 Network as priority

In idle state, MS sets calls and finishes it in GSM1800.

After the call, MS resides in GSM1800.

900M cell：C1=15，C2=5

1800M cell：C1=10，C2=20

Cell selection in idle

mode



Dual-band Network MS Standing Principle 2

GSM900network as priority

In idle state, MS sets calls and resides on GSM900.

After the call, reselect to reside on GSM 900 network.

900M cell：C1=15，C2=21

1800M cell：C1=10，C2=16

Cell reselection in idle

mode



Handover

Handover type Intra-cell Handover: traffic channels belongs to one cell

and handover is implemented by cell affiliated BSC.

Inter-cell handover in BSC：the two cells are in the

control of one BSC. Intra-MSC inter-BSC handover ：the two cells are

controlled by separate BSC which belong to one MSC.

Inter-MSC handover: the two cells are in the control of

two MSC. This operation involves multiple MSC’s andBSC‘s engagement.



Handover

Handover can be classified into the following: Rescue handover:

Interference handover

Strength handover

Quality handover

TA handover

Fast fading handover

……

Marginal handover

PBGT handover （Better Cell）



PBGT Handover

PBGT(n) = ( RXLEV_NCELL(n)－ (RXLEV_DL+PWR_C_D))－

(min(MS_TXPWR_MAX(n), P)－ min(MS_TXPWR_MAX, P))

- MS_TXPWR_MAX：maximum allowable Tx power of MS in serving cells

RXLEV_DL：DL level mean in this measurement report

PWR_C_D：Difference between BTS max power and reported BTS power

MS_TXPWR_MAX(n) ：MS max allowable Tx power in the adjacent

cell

P：MS maximum power

RXLEV_NCELL(n)：DL level mean of the adjacent cell



Traffic Handover

Traffic Handover Handover because of traffic. This happens when the serving cell is

or on the way to becoming congested while adjacent cell isrelatively idle. MSC sends Handover Candidate Enquiry messageto BSC and some MS are handed over from resource cell to targetcell.

Candidate principle. BSC will select from specific cells the cell with

worst quality to be handover candidate and apply handover fromMSC. Guidelines are uplink and downlink reception quality, uplinkand downlink reception level, and MS-BTS distance. Useweighting average equation to get cell service quality.

Handover target cell limitation. Candidate MS can’t be MS that itsadjacent cell measurement report doesn’t include any cell in the list

provided by MSC. Handover time limitation. The interval between last handover time

of candidate MS and current time is smaller than minimumallowable handover time duration. This MS can’t be candidate inorder to avoid frequent handover.



Priority Handover

Priority Handover Static priority

Dynamic priority



Fast Fading Handover

When fast fading happens, and BSC catches that call signaling

strength value is lower than the threshold T for several times, BSC will

conduct fast fading handover and target cell is the cell in serving area.

Micro 1

Micro 2

A1 2

3 4 ast-moving MS

RH TH=-96 dBm

RH N=4

Set Micro2 to be

cell in serving

area

Fast Fading Handover



Multi-band Indication

Multi－

bandReport

Indication

0 MS reports measurement result of 6 adjacent cells of which

signaling is strongest and NCC is known and allowable, regardless

of which band they belong to.

1 MS reports measurement result of one adjacent cell of all band

(band which serving cell belongs to excludes) with strongest

signaling in reported adjacent cell table. On remaining area reportadjacent cells of the band of serving cell. If there are still area left,

report other adjacent cell regardless of the band.

2 MS reports measurement report of two adjacent cells of all band

(band which serving cell belongs to excludes) with strongest

signaling in reported adjacent cell table. On remaining area report

adjacent cells of the band of serving cell. If there are still area left,


3 MS reports measurement report of three adjacent cells of all

band (band which serving cell belongs to excludes) with strongest

signaling in reported adjacent cell table. On remaining area report

adjacent cells of the band of serving cell. If there are still area left,




Directed Retry

Definition In designation process, if serving cell has nochannel to allocate to, system will use directedretry function to allocate other channel of adjacent cells for MS.

Function This is a special handover process which can

reduce call drop. Type

It’s categorized into intra-BSC directed retryand inter-BSC retry. The former needn’t MSCinvolvement while the later calls for MSCinteraction.



Handover Algorithm

Recommended Path Loss/TA algorithm When path loss is greater than Lmax, or TA is greater

than TAmax, handover will be demonstrated from cell 2

to cell 1.

When path loss is smaller than one threshold Lmin,and TA is smaller than TAmin, handover will be

demonstrated from cell 1 to cell 2 .



Cell 2

Lmax

Lmin

Cell 1

Handover Algorithm

Take handover model of path loss L for example:



Handover algorithm

Path loss C/I

algorithm

Reaches cell handover threshold and MS

supports subcell 2 dual-bandandover

judge

Target

channel

selection

Subcell 2 channelubcell 1 channel

satisfy unsatisfy

Channel Allocation Algorithm

Subcell channel request



Intra-cell

handover

Path loss or C/I

UL & DL

interference

Inter-cell

handover

or directed

retry

Exterior

handover in or

exterior

directed retry

If source cell is subcell 1, system will select

Subcell 2 channel only; If source cell is

subcell 2 , system will select subcell 1

channel only.

System can only select subcell 1

If source cell is subcell 1, system will select

Subcell 2 channel only; If source cell is

Subcell 2 , system will select subcell 1

channel only.

Co-location

Non-location

Channel Allocation Algorithm

Subcell channel request when conducting handover



Dual-band Co-bcch Parameters

SubcellUsed: cell use subcell or not description： whether to use subcell or not

value： 0：not use 1：use

setting： 1

FreqBand: band of subcell No.1 description：band of subcell 1 is the frequency band

that subcell 1 is using

value： as

setting： 1

value connotaion

0 Basic GSM900 band P-GSM（ARFCN = 1 ~ 124） 1 Extended GSM900 band E-GSM（ARFCN = 0 ~ 124，975 ~ 1023）

2 DCS1800 band DCS1800（ARFCN = 512 ~ 885）

3 Railway GSM900 band R-GSM（ARFCN = 0 ~ 124，955 ~ 1023）

4 GSM1900 band GSM1900（ARFCN = 512 ~ 810）

7 GSM850 band（ARFCN = 128~251）



Dual-band Co-bcch Parameter SubFreqBand: frequency band which subcell No.2

uses description： frequency band which subcell No. 2 uses

value： see the above table

setting： 2

HoControl: handover control

Description：In criteria, various kinds of handover triggeringconditions are described. What’s more, micro-cell’s introductionbrings about various kinds of handover algorithm. It’s unnecessarysometimes to demonstrate other handover type besides handover based on reception strength and quality. HoControl defineshandover type that must be realized in the cell.

value： see the table

setting：1 Locati

onconnotation

bit18 1：subcell handover are allowed due to path loss and TA

0：subcell handover are not allowed due to path loss and

TA



Dual-band Co-bcch Parameter

PathLossMax : maximum value of path loss description： maximum value of path loss and one of

subcell handover parameter.

value： 0~150 db

setting： 126(by default)

PathLossMin: minimum value of path loss

description： one of parameter of subcell handover

and the minimum value of path loss.

value： 0~150 db




Dual-band Co-bcch Parameter

SubCellTAMax: maximum value of TA description： parameter of subcell handover and the

maximum value of TA. value： 0~63


SubCellTAMin: minimum value of TA

description：parameter of subcell handover and the

minimum value of TA.

value： 0~63




Form a pattern with GSM900 ensuring

network coverage and DCS1800

absorbing the traffic left.

Things shall be taken into account to

ensure the two network will not be

congested and there are no

unnecessary cell reselection and dual-

band handover.

Cell reselection and handover areusually conducted within the

frequency except when MS stays in

blind spot or signaling strength of

other frequency is much higher.

Objective

Principle

Traffic Control Strategy



Cell belongs to designated PLMN？

Cell are not barred ？

LAC of cell are not prohibited from roaming ？

C1>0？

If the above are fulfilled, MS will stand on this cell.

Cell Selection



In PHASE2+ criterion，cell priority parameter are added to BCCH

broadcast message.

CBA CBQ

0

1

0

1

0

0

1

1

Cell Select Priority Cell Reselect Priority

Normal

Barred

Low

Low

Normal

Barred

Normal

Normal

Cell priority are defined based on setting of CBQ and CBA.

CBQ（Cell Bar Qualify）and CBA（Cell Bar Access）

Cell Selection



900M

1800M

PRI

C1

Make priority level GSM 1800 is higher

than that of GSM 900, thus dual-band

MS will first choose to be connected to

GSM1800 and then GSM 900.

C1>0

Cell Selection



900M

1800M

CBQ=1,CBA=0

C1=15

CBQ = 0，CBA = 0

C1=10

Cell Selection



cell reselection setting principle

CRO of 1800 cell is at least 10 dB greater than 900

Increase weighting of GSM 1800 by adding CRO value, and valueadded is up to loading condition of GSM 1800.

Try to avoid detached island effect due to great CRO value.

Cell Reselection



Cell1

Cell 2

Cell 1 can’t be accessed or fault occurs in cell 1?

Are there cell 2 that offer better services?

When conducting cell reselection, MS will sort and select adjacent

cells based on their priority level and check whether the selected cell

fulfills the standing condition. If conditions are met, MS will stand on

this cell.

Cell Reselection



Cell 1

Cell 2C1=10，C2=5

C1=5，C2=15

Cell Reselection



When GSM 900 and GSM 1800 share the same site, there will be lots of PBGT

handover( handover due to better cell) in dual-band network coverage area. In the

condition that both GSM900 and GSM 1800 have a favorable coverage, PBGT

handover will occupy 80% of the total handover, as a result, this should be prohibited.

900M cell

1800M cell

rescuehandover

PBCGhandover

Dual-band Handover



When handover is to be conducted, cell fulfilling the requirement outside

the band gives priority to fulfilling cell in the same band.

Rescue Handover

900M cell

1800M cell

Dual-band Handover



When PBGT handover is conducted, MS can either be handed over to

cell in the band or outside the band. But we suggest to make the

condition of handover outside the band more rigorous. The degree of

rigor is up to cell load.

PBGT handover

900M cell

1800M cell

Dual-band Handover



Serving cell

Adjacent cell1

（7）

Adjacent cell2

（5）

Serving cell

Adjacent cell1

（4）

Adjacent cell2

（5）

When there are no traffic ,adjacent

cell 2 gives priority to adjacent cell 1.

With the change of traffic, priority

level of adjacent cell2 1 may be

lower than adjacent cell 1.

Dual-band Handover

dynamic optimization handover algorithm



In network running, percentage of channel occupied will be

estimated. When the threshold is reached, handover will be

conducted so that MS near the cell margin will be handed over to

an adjacent cell.

Traffic handover algorithm

Dual-band Handover

D l b d H d



Advantage of ZTE handover algorithm

Handover due to traffic volume is provided, thus congestion of GSM

1800 is avoided.

Directed retry between the two band. For example, when GSM

1800 is congested, call will be handed over to BSC or MSC to

which GSM 900 belongs to and enhance call through rate of

GSM 1800. Fast fading handover algorithm targets fast fading and

helps to avoid call drop caused by bad quality of the serving cell.

Interval protection. Limit the handover times between dual-band cells

in order to reduce signaling flow in BSC, and finally to guarantee the

favorable call quality.

Dual-band Handover



To control cell selection: C1，CBA，CBQ

To control cell reselection：C2

To control dual-band handover

：PBGT，priority

Traffic Control Means

T ffi B l h d 1



Traffic Balance—method 1

In MS idle mode, select DCS1800 to stay and start calls.

Make DCS1800 set the priority by setting CBA and

CBQ.

Use C2 as criterion for reselection

900M cell：C1=15，C2=5

1800M cell：C1=10，C2=20

T ffi B l th d 1




When MS is in call state, it’s better to stand on the band

where call is initiated so as to avoid unnecessaryhandover.

PBGT handover between different band is prohibited.

multi-band report setting

Only rescue handover is allowed for foreignfrequency.

T ffi B l th d 1




When MS is in idle mode, it will select bestnetwork.

Priority level of GSM 1800 and GSM 900 is the same

Use C2 as reselection criterion

Difference of C2 of the two band is less than 6dB；

900M：C1=18，C2=20

1800M：C1=10，C2=16

T ffi B l M th d 2



Traffic Balance—Method 2

When MS is in call state, make DCS 1800 a priority andkeep traffic balanced through handover

PBGT handover between different band is allowed

Multi-band indicator setting

Flexible control of rescue handover

T ffi B l Oth th d



Traffic Balance-Other method

Other method to control traffic

Traffic handover

Band control

threshold

directed retryduration

priority handover

Static priority

Dynamic priority

C t l



Catalog

Dual-band Network Overview Dual-band Network Planning Strategy


Adjustment

Dual-band Netwo rk Optim izat ion Cases

Xi’ D l b d N t k



Network Construction

Ever since ZTE dual-band network is adopted by Xi’an

Telecom in December of 2002, DCS1800 network

running by Xi’an Telecom exceeds 100 with Trxs over

2000.

There are two Topomap existing in current network: ZTE GSM900，ZTE DCS1800； A serial

Siemens GSM900, ZTE DCS1800；B serial

Co-location and co-site

Xi’an Dual-band Network

Xi’ D l b d N t k



Dense urban Suburb

900M

1800M

continuous coveragehotspot coverage


Xi’an Dual band Network




Traffic Balance- Network A

In idle mode, give GSM 1800 priority and start calls on

GSM 1800.

Try to stand on GSM 1800

PBGT handover of foreign fequency is prohibited





Traffic Balance-Network B In idle mode, give GSM 900 priority

In call mode, select GSM 1800 to share the traffic

Open PBGT；

Traffic handover




ERL

0

200

400

600

800

1000

1200

Z T E_

D C S

S I E M

E N S

Z T E_

D C S

S I E M

E N S

Z T E_

D C S

S I E M

E N S

Z T E_

D C S

S I E M

E N S

Z T E_

D C S

S I E M

E N S

ZTE_DCSSIEMENS

Xi an Dual-band Network




Xi an Dual-band Network

SDCCHblock

rate

Busy-hour voicechannel

occupancy times

(including

handover)

Busy-hour voicechannel overflow

times (including

handover)

TCHblock

rate

Radioaccess

success

rate

Traffic(Erl)

Handover success

rate(%)

Call droptimes Voicechannel

call drop

rate

Call dropratio

0.26% 213201.00 587.00 0.28% 99.47% 1572.73 91.85% 1012.00 0.47% 93.24

0.29% 222599.00 624.00 0.28% 99.43% 1631.92 91.68% 1014.00 0.46% 96.56

0.22% 223967.00 597.00 0.27% 99.51% 1652.17 91.92% 1048.00 0.47% 94.59

0.12% 243280.00 1013.00 0.42% 99.47% 1818.79 91.41% 1119.00 0.46% 97.52

0.28% 221836.00 562.00 0.25% 99.47% 1632.34 91.59% 1005.00 0.45% 97.45

0.06% 139721.00 266.00 0.19% 99.75% 978.16 91.72% 641.00 0.46% 91.56

0.23% 199751.00 530.00 0.27% 99.50% 1755.10 91.79% 892.00 0.45% 118.06



Documents

GO_NA10_E1_1 GSM Dual-Band Network Planning & Optimization-79