04) radio network planning

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OBJECTIVESOBJECTIVES

•Describe the meaning of network optimization•Master the basic technology of network planning•State the meanings of various network optimization parameters•Master how to set network optimization parameters•Master the optimization of dual-band networks


• GSM cellular architecture• Site Capacity Planning • Cell design and coverage forecast• Frequency planning & interference prediction

Contents


Cellular Architecture

A


The multiplex area cluster

A3

C2B1

B3

A2C1

C3

B2A1

A3

C2B1

B3

A2C1

B3

A1C1

A1

A3A2

C3

B2A1

A3A3

C3

C1

B2A1B2A1

A2C1

B3


Definition of C/I and C/A• Co-channel Interference C/I ：

C/I refers to the interference of another cell using the same frequency to the current cell. The ratio of carrier to interference is called C/I.GSM specification regulates that C/I >9dB. In implementing, it requires C/I>12dB.

• Adjacent channel interference C/AC/A refers to interference of adjacent channel to the current channel. The ratio is called C/A. The GSM specification regulates that C/A>-9dB.


Calculation of C/I

• Where, Pown_cell is the signal strength of current cell; Pi_BCCH is BCCH signal strength of interfering cell i measured by MS.


Features of cellular system

• Multiplex of radio frequency resources ；• Automatic handover ；• Channel allocation and cell split.


Radio network planning Introduction

• Scope GSM: NSS+BSS+OMC GSM Network planning: Switch network planning Trunk circuits planning Radio network planning


With lowest cost• To provide certain service grade• To meet current and future traffic requirement• To satisfy current and future coverage requirement

Goal


System Requirement Analysis

System Capacity Limit

Routine Optimization & Adjustment

System Capacity Increment

Cut-over Optimization & Adjustment Project Implementation

Frequency Plan and Interference Analysis

Coverage Planning and Prediction

Survey & Site Layout

Capacity Planning

GSM Network Design & Optimization Cycle


Content

Site survey

Capacity

Coverage

Frequencyinterference

Parameterdesign

Implementation

Optimization

Evaluation

Planning OptimizationEngineering Implementation


• GSM cellular architecture • Site Capacity Planning • Cell design and coverage forecast• Frequency planning & interference prediction

Contents



•Method for calculating the system capacity•Methods for site capacity planning


Network DimensioningTo estimate the amount of sites and cells.

• How many Subscribers are supported by one site?• How many sites should be setup in the service area?

• How many TRX are supported by one site?

Capacity Planning


Some basic concept

Traffic （ Erlang ）Busy hour traffic per subscriber （ Erla

ng ）BHCA(Busy Hour Call Attempt)Erlang B tableCall loss rate


Some basic concept

• Traffic:A kind of measurement of the telephone load, which refers to the load volume of a telephone subscriber in a specified time period. (Erlang)

• BHCA: Busy hour calling amount or busy hour call attempt

• Erlang B table: define the relationship among call loss,channel numbers and traffic.


Some basic concept

• Busy hour traffic per subscriber:A =α·β·tα is the call amount per subscriber per dayβ is the busy hour concentration factor (i.e. ratio of the busy hour

traffic to the whole day traffic) t is the average channel seizure duration per conversation per

subscriber • Call loss rate: Ratio of call loss to the whole amount of calling.


StepsSubscriber prediction →Traffic density forecast →Site type and number

→Site layout → Channel configuration

Based Ona 、 Traffic and traffic densityb 、 GOSc 、 Available number of TCH/CCHd 、 Available frequency band and frequency reuse pattern

Traffic forecast and capacity planning


Subscriber Forecast

Near term: 1-2yearsLong term: 3-5years

• Growth trend forecast method• Population penetration method • Growth curve method• Conic method


Growth trend forecast

0

500

1000

1500

2000

2500

( )用户数万

( )用户数万 1. 534. 7517. 763. 8 157 363 685 13642496

1990

1991

1992

1993

1994

1995

1996

1997

1998 0

500

1000

1500

2000

2500

3000

( )用户数万 1. 5 4. 8 18 64 157 363 685 136 249

1990

1991

1992

1993

1994

1995

1996

1997

1998


Growth trend forecast0

50

100

150

200

250

300

(%)年增长率 0 160 272 261 146 132 89 99 831990 1991 1992 1993 1994 1995 1996 1997 1998

0

50

100

150

200

250

300

(%)年增长率 160 272 261 146 132 89 99 831991 1992 1993 1994 1995 1996 1997 1998


Population penetration method

0

2000

4000

6000

8000

10000

用户数（万）

用户数（万）

363 685 1364

2496

3432

5053

7016

9219

1995

1996

1997

1998

1999

2000

2001

2002

0123456789

%普及率 0. 3 0.57 1. 14 2. 08 2. 64 3. 89 5. 4 7. 69

1995 1996 1997 1998 1999 2000 2001 2002


Traffic density forecast method

• Linear forecast • Linear forecast combined with manual

adjustment (population, income, vehicle)


Base station capacity planning

1. The number of BTS (Traffic limited)i. Estimate the largest possible capacity (Erl) of each bas

e station according to the frequency multiplex mode to be used.

ii. Derive the minimum number of base stations in an area by dividing the total traffic by the largest capacity of each base station.

2. The number of BTS (Coverage limited)Get the maximum number of base stations by dividing the area size by the (estimated) minimum coverage of a base station.


Base station capacity planning

3 ． Estimate the BS cell capacity I. Estimate the cell coverage area. Multiply the BS cell

coverage by the traffic density concerned, then you can get the present traffic of the cell.

II. Query the ErlangB table according to the traffic and specified call loss index, you can get the number of voice channels needed by the BS cell.

III. Add up the voice channels and the control channels that should be configured, then divide the number by 8, you can get the number of carrier frequencies of the BS and the cell.


Capacity Planning

• Allocation of CCH and TCH(In case of availability rate 98%, 0.025Erl per subscriber)

TRX 1 2 3 4 5 6 7 CCH 1 2 2 2 3 3 3 TCH 7 14 22 30 37 45 53 Traffic 2.93 8.2 14.9 22 28 35.5 43

Configuration planning


2% 5% 1 0. 020 0. 0532 0. 223 0. 3813 0. 602 0. 8994 1. 092 1. 5255 1. 657 2. 2186 2. 276 2. 9607 2. 935 3. 7388 3. 627 4. 5439 4. 345 5. 37010 5. 084 6. 21611 5. 842 7. 07612 6. 615 7. 95013 7. 402 8. 83514 8. 200 9. 73015 9. 010 10. 63316 9. 828 11. 54417 10. 656 12. 46118 11. 491 13. 33519 12. 333 14. 31520 13. 182 15. 24921 14. 036 16. 18922 14. 896 17. 13223 15. 761 18. 08024 16. 631 19. 03025 17. 505 19. 985

Erlang-B Table


The number of control channels

Suppose SDCCH average process time is 3s ， Location updating process is 9s,BHCA=2The traffic of SDCCH per subscriber is: (3×2 + 9) / 3600 = 0.0042 Erlang4SDCCH call loss=2% can support 1.092Erlang ， (1.092 / 0.0042 = 260sub) ×0.025 Erlang = 6.5Erlang look up in Erlang-B ， call loss=2% ， 6.5Erlang need 12TCH(2TRX) 。8SDCCH call loss=2% can support 3.627Erlang(3.627 / 0.0042 = 863sub) ×0.025 Erlang = 21.6ErlangLook up in Erlang-B ， call loss=2% ， 21.6Erlang need 30 TCH(4TRX) 。


Site expansion & cell split Tighter frequency reuse pattern Increase micro cell Building dual band network

Increase the network capacity


Site capacity calculationCity A: Required coverage area is 150km2 ，Target capacity=2k Erlang ，GOS=2% ， Busy hour traffic per subscriber=0.025Erlang ，available GSM900 frequency band=6.2MHz 。

Traffic forecast and capacity planning


LA Planning

PLMNMSC

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


LA Planning

• Minimize the Location Update numbers on condition that there is overload on PCH

• Paging load decide the maximum size of LA• Location Update Load decide the minimum size of

LA


LA Planning

• LA should not be too big or too small

• LA<300TRX• Plan LA on geographical

situation and subscriber behaviors


LA Plan in Dual band Network

Plan on Frequency band

18001800 180018001800

LA1

900900 900900LA2


Plan on geographical position

LA Plan in Dual band Network

900 900 900 900

1800 1800180018001800 1800

LA1 LA2



Contents



•BTS site selection procedures•Traffic volume prediction method•Cell capacity planning method•Antenna parameter selection


Coverage forecast

• In order to calculate the coverage,we should have:BTS location----BTS initial layoutCoverage field intensity requirementAntenna systemUplink/Downlink balanceDigital Map


Coverage forecast

Radio network planning software

BS positionAntenna power

HeightAzimuthDowntilt

PropagationDigital mapU/D balance

Field intensity

Coverage map and planning report

Planning software

Adjustment


BTS Site Layout and Survey

Scheme Determination

Frequency Planning & Interference Analysis

Cell Data Design & Coverage Prediction

Initial Site Layout

Capacity Planning

Site Selection & Survey Si

te L

ayou

t Adj

ustm

ent


• Cellular structure• Coverage• Traffic density distribution• Site condition• Cost

Limited factor



Site Layout Key Factors• High traffic area– traffic• Low traffic area– coverage• Middle traffic area—traffic+coverage For large cities, the field strength of the coverage area is not firstly considered, while the traffic distribution and propagation conditions are given more consideration.

BTS Site Preliminary Layout


• For dense city area---- three-sector-cell is preferred with a coverage radius of 0.5 ～ 1.0km

• For rural area----three-sector-cell or O site are preferred with a coverage radius of 2-8Km

• For middle size city or suburb---- three-sector-cell or O site are preferred with a coverage radius of 1 － 4Km

• For area along backbone highway or narrow area---- two-sector-cell is preferred with a distance of 15 ～ 25km from one to another.


Site Configuration



1. The BS layout shall conform to the cellular structure and cell split requirements

2. In consideration of the local planning and topographical structure:

a) The BS layout shall comply with the city development plan, and proper lead is allowed ；

b) Areas of important users shall be covered by the BS; c) Add microcell stations or carrier frequencies in the "hot

spot" areas of the cities; d) Add stations along the metro, in the underground

shopping market or stadium if necessary


1) Convenient traffic, reliable mains supply, safe environment and small area coverage.

2) When building less stations during the first phase of a network, the site selection principle is to guarantee the coverage of important users and downtown areas with dense subscribers.

BTS Site Location Considerations


3) Given that the base station layout is not influenced, please try to select the existing telecom hub buildings, post and telecom bureaus or microwave station as the base stations, and making use of their equipment rooms, power supplies, iron towers and other facilities.

4) Avoid setting up base stations in the UHF TV stations. If it is a must, please check if the interference exists or there are measures to evade such interference.



5) Avoid establishing base stations near the radar stations. If you are to do so, please take measures against interference and ensure security.

6) Avoid building base stations on high mountains because the stations there have large interference scope and affect the frequency multiplex. In the rural areas, the stations on high mountains are often unable to well cover the towns and villages in the basins.



7) Avoid setting up base stations in the woods. If you are to do so, please keep the antenna higher than the tree top.

8) In small cells (R=1 ～ 3km) of a city, you shall select the building higher than the average building height but lower than the highest building as the station site; in the micro cells, you shall select the building lower than the average building height as the station site, and the surrounding buildings have better shield effect.



9) The base stations of two systems in the city shall share sites or stay close as much as possible.

10) Avoid selecting the sites where there may be new buildings affecting the coverage or causing cofrequency interference.



11)Necessary station building conditions: a) The building has available mains supply and

lightning protection ground system; b) The floor load can meet the technological

requirements; c) The top of the building has the space for

installing the antenna.



12) Select the equipment rooms with little expansion cost or buildings with less rent as the station sites. If possible, select the offices, equipment rooms or office buildings of your own organization as the station sites.



Design cell parameters

Parameters in designing a cell• Coverage field intensity• Coverage radius• Edge completion probabilityWhich are related to the following parameters： system redundancy, degradation storage caused by fast

fading and artificial noise, losses of various types, route loss, BS antenna input power, antenna parameter, diversity gain, tower amplifier, MS RF performance, and the calculation of the uplink and downlink balance.


The successful probability of the MS makingsatisfactory conversation along the edge of a radiocoverage area (or inside the area), including thelocation probability and time probability. • The variation of communication probability with the time is far

less than the variation with the location

• In China, we use the radio completion rate index along the cell edges, – Suburb: 75% ， City:90%

Communication probability

Design cell parameters


• Degradation definition: the addition of the receiving level necessary for the attainment of the same voice quality as that when there is only the receiver noise in case there are multi-path propagation effect and artificial noise (mainly the interference of the car spark. )

• In high-way planning the degradation storage is a must;

• The general degradation storage is 8~10dB. .

Design the cell parameters


• Building penetration loss:

City: 15dB rural area:10dB

• Human body loss: 3dB.

• Vehicle loss:8-10dB

Losses of various type


Cell Data Design

• Antenna Selection• Antenna Height, Direction(Azimuth) and Downtilt• diversity Technique• Balanced transmission power


BS antenna input power

• EIRP:equivalent isotropic radiation power • BS antenna input power = transmitter

output power － (combiner loss+feeder cable loss+connector loss+other component losses)

• EIRP=BS antenna input power + BS antenna gain


Antenna Gain

• Antenna gain: The more concentration of transmitting directions (vertical or horizontal) of antennas, the higher the antenna gain.

Omni-directional antenna:9-11dBiDirectional antenna: 17-18.5 dBi 14.5-16 dBi• Select principle:Coverage size


Antenna gain

•City （ coverage distance is not far, around 15.5dBi ）

Distance

Distance

•Suburb （ coverage distance is relatively long ， around 17dBi ）


Antenna parameters

• Back and front ratio: (>20dB)• Polarization: vertical, +450/-450 slant• 3dB Beam width:

Horizontal:65-city;90-suburb, O-rural areaVertical: 60-90 -city,120-150 -suburb


Antenna height and direction

• The effective antenna height: the antenna height above the sea level minus the average topographical height above the sea level: hte= hts-hga.

• Direction(Azimuth)Facing to high traffic density area,Avoid pointing to the street directly


Inclined angle

• Inclined angle of antenna ：When the antenna is installed in the vertical direction, its transmitting direction is horizontal. Due to the cofrequency interference and time dispersion, the cellular network antennas usually have an declination angle. The antenna declination is divided into mechanical declination and electronic declination.

• Selection principle ：Rely on coverage, traffic and interference.In city use electronic declination.


Inclined angle

Adjust the inclined angle according to the target coverage area. Generally,with the increase of cell capacity,required coverage size decrease, we always increase the inclined angle to counteract the interference.


Diversity technology

• The antenna diversity refers to space diversity or polarization diversity

• Space diversity refers to the space between two receiving antennas so as to reduce the correlation between the received signals and improve the receiving quality.

• Polarization diversity means to make the polarization angle of two receiving antennas into 90°to get better diversity gain.


Diversity technology

• The diversity gain: 3-5 dB• Outdoor :Space diversity is better than polarization

diversity• Space diversity distance:

Antenna height/10>4m (900M) Antenna height/20>2m (1800M)


• To get BS maximum transmit power and coverage radius

• To avoid invalid down-link coverage • To lower the interference and system noise

Up and Down Link Power Budget

• Up-link Power Budget analysis• Down-link Power Budget analysis• Up and Down link Budget

Balance analysis


Up and Down Link Balance

Uplink Downlink MS output power BS transmitter power Human body loss Combiner Building penetration loss Duplexer Path loss Feeder and other loss Antenna gain Antenna gain Diversity gain Feeder and other loss Path loss

Duplexer Building penetration loss Splitter Human body loss BS receiver sensitivity MS receiver sensitivity


Uplink Analysis

– Uplink Analysis：MS transmitting power （ 1W ） 30 （ dBm ）Human body loss 3 （ dB ）Building loss 17 （ dB ）MS effective output power 10 （ dBm ）BS receiver sensitivity -108 （ dBm ）BS antenna gain 17 （ dBi ）Feeder and connector loss 4 （ dB ）Diversity gain 2 （ dB ）System redundancy 6 （ dB ）BS effective receive power -117 （ dBm ）Indoor allowed path loss 127 （ dBm）Outdoor allowed path loss 144 （ dBm）


Downlink power analysis

– DownlinkBS transceiver output power （ 20W ） 43 （ dB

m ）Combiner loss 5 （ dB ）BS Antenna gain 17 （ dBi ）Feeder & connector loss 4 （ dB ）BS effective output power 51 （ dBm ）

MS receive sensitivity -101 （ dBm ）Human body loss 3 （ dB ）Build loss 17 （ dB ）System redundancy 6 （ dB ）MS receive power -75 （ dBm ）Indoor allowed path loss 126 （ dBm）Outdoor allowed path loss 143 （ dBm）


Field intensity coverage design

Field intensity coverage:

1. Indoor coverage level in the bustling areas of large cities: -70dBm

2. Indoor coverage level in the ordinary city areas: -80 dBm

3. Outdoor coverage level in city areas:4. -90 dBm5. In rural areas: -94 dBm


Digital map


Coverage Prediction


Coverage forecast

m

N

Coverage forecast



Contents



•State Basic concept of Frequency Planning•Grasp the Frequency Plan Application•Describe the anti-interference technologies


FREQUENCY RE-USEFREQUENCY RE-USE

Basic Concept:

–Frequency Reuse Cluster–Frequency Reuse Factor–Frequency Reuse Distance–C/I and C/A


FREQUENCY RE-USE DISTANCEFREQUENCY RE-USE DISTANCE

•The following equation is used to estimate frequency reuse distance:

D = 3 N * R

D —— frequency reuse distanceR —— cell radius

N - frequency reuse factor. N=9 for “3 3” N=12 for “4 3”• For “3/9” frequency reuse, D=5.2R• For “4/12” frequency reuse, D=6R


DEFINITION OF C/I AND C/ADEFINITION OF C/I AND C/A

Co-channel Interference C/I ：C/I refers to the interference of another cell

using the same frequency to the current cell. The ratio of carrier to interference is called C/I.

GSM specification regulates that C/I >9dB. In implementing, it requires C/I>12dB. Adjacent channel interference C/A

C/A refers to interference of adjacent cell to the current cell. The ratio is called C/A. The GSM specification regulates that C/A>-9dB.


CALCULATION OF C/ICALCULATION OF C/I

Where, Pown_cell is the signal strength of current cell; Pi_BCCH is BCCH signal strength of interfering cell i measured by MS.


Frequency Reuse

Ordinary frequency reuse: “43”, “33” and more close “26” and “13”.

MRP: different layers adopt different frequency reuse patterns.

Concentric: the Underlay and Overlay adopt different frequency reuse patterns respectively.


4 X 3 FREQUENCY RE-USE PATTERN4 X 3 FREQUENCY RE-USE PATTERN

• “4 3” frequency reuse pattern is that each site is divided into 3 sector. 12 frequencies form a group which are distributed to 4 different sites. Each site owns 3 frequencies.

A3

D2B1

C3

B2D1

D3

A2C1

B3

C2A1

B3

C2A1

A3

A1B1

D1

D3D2

C3

B2A1

C3D2

C3

C1

D2B1C2A1

A2C1

D3



A3

C2B1

B3

A2C1

C3

B2A1

A3

C2B1

B3

A2C1

B3

A1C1

A1

A3A2

C3

B2A1

A3A3

C3

C1

B2A1B2A1

A2C1

B3

• “3 3” frequency reuse pattern is that each site is divided into 3 sector. 9 frequencies form a group which are distributed to 3 different sites. Each site owns 3 frequencies.



TRX A1 B1 C1 A2 B2 C2 A3 B3 C3

1 1 2 3 4 5 6 7 8 9

2 10 11 12 13 14 15 16 17 18

3 19 20 21 22 23 24 25 26 27


MRP

• It’s unreasonable to adopts idealized and regular frequency reuse pattern indiscriminately, which will cause low frequency utilization rate and difficult to ensure the C/I requirement.

• Multiple frequency Reuse Pattern (MRP) is an irregular and dynamic frequency reuse mode designed according to GSM features.

• That is, dividing frequency band into different combinations, each combination adopting different frequency reuse pattern. Each carrier of a cell may adopts different frequency reuse pattern.


TCH2 FRF=6

BCCH FRF=12TCH1 FRF=9

For Microcell

MRP

FRF:Frequency Reuse Factor

Bandwidth=6 MHz


BCCH

“4×3”

TCH1

“3×3”

TCH2

“2×3”

TCH3

“1×3”

MRP+FH+DTX+DPC


China mobile:MRPFrequency bandwidth: 7.2MHzAFN: （ 60 ～ 95 ），Divide 36 carrier frequencies into 4 group as per 12/9/8/7

Application of MRP

Channel type

Logic channel TCH1 service channel

TCH2 service channel

TC3 service channel

Channel number

60 61 62 63 64 6566 67 68 69 70 71

72 73 74 75 76 7778 79 80

81 82 83 84 85 86 87 88

89 90 91 9293 94 95


6064

68

6266

70 6367

716165

69

7275

78

7376

79 7275

787477

80

8991

93

9092

94 9092

9489

91

93

8183

85

82 84

86 8284

8183

85

86

Application of MRP

1) BCCH 4 3 2) TCH1 3 3

4) TCH3 2 3 3) TCH2 2 3


MRP Characters

Increase network capacity greatly and decrease average frequency reuse factor to 8, thus increasing frequency reuse efficiency greatly.

Flexible channel allocation. Different frequency reuse pattern may be adopted step by step according to capacity requirement.

Some carriers can be released for micro-cells. Should combine with FH, DPC and DTX to lower

interference. Especially for sites distributed unevenly.


Multiplex mode BS configuration Average station capacity （ subscriber ）

Capacity ratio

6MHZ 4×3 3/2/2 or 3/3/2 1440 1

3×3 3/3/3 1788 1 ． 24

1×3 4/4/4 2640 1 ． 83

MRP （ 12, 9, 6 ）**

3/3/3 1788 1 ． 24

2×6 2/2/2/2/2/2 2160 1 ． 5

9.6MHZ 4×3 4/4/4 2628 1

3×3 5/5/5 3384 1 ． 29

1×3 6/6/6 4272 1 ． 63

MRP （ 12, 9, 6 ）**

6/6/6 4272 1 ． 63

2×6 3/3/3/4/4/4 4416 1 ． 68

Comparison of the system capacities between normal multiplexing and MRP technologies


22

2

2

2

2

2 2 22

22

2

2

2

Concentric


Concentric

• The principle of ordinary concentric is that a cell is divided into underlay and overlay,

• The coverage of Underlay is the same as that of ordinary cell, while the Overlay use small transmitting power and thus has smaller coverage.

• The frequency reuse factor of overlay differs from that of underlay.

• The BCCH and SDCCH are used by Underlay, in which the call will be set up.

• A brand new switching algorithm should be added.


Concentric

• The absorbing of traffic by overlay is limited by traffic lay-out and coverage. It will increase the capacity by 10-30% and is related to traffic distribution.

• The overlay is more suitable for outdoor traffic concentrated in the vicinity of BTSs because of its smaller transmitting power.

• On the condition that the network quality will not be affected, a closer frequency reuse pattern should be adopted. At the same time, DPC and DTX technology should be adopted to ensure network quality.


C/I-based Concentric IUO

222

222

222

222

2

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22

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2


IUO

• IUO has the same network structure as ordinary concentric, consisting of Overlay and Underlay.

• In general, the two layers share the same site and antenna. Similar to ordinary cell, the Underlay adopts 4*3

frequency reuse pattern, while the Overlay adopts closer pattern.

• Same like ordinary concentric, the control channel functions within Underlay where calls are established.


IUO• Different from ordinary concentric, the Underlay and

Overlay of IUO both use the same transmitting power.• Because the Overlay adopts closer frequency reuse

pattern, the chances of co-channel and adjacent channel interference increase.

• IUO adopts a handover algorithm based on C/I to solve this problem.

• It functions as follows: the call is established within Underlay, the BSC continuously monitor the downward C/I in Overlay. When C/I reaches applicable threshold, the call will be handed over to Overlay. At the same time, the C/I is monitored continuously and the call will be handed over to Underlay if it deteriorates to inapplicable threshold.


IUO

• The implementation of IUO is easy. Little modification is needed and no special requirement to MSs.

• Because of adopting special algorithm on handing over, measurement and estimation on C/I, the speech quality can be guaranteed while increasing the system capacity.

• Because both Underlay and Overlay have the same transmitting power, it’s very suitable for absorbing traffic inside building which has a strong isolation capability to radio signal.


• Concentric– U lay smaller transmitting

power– Handover based on power or

TA– Underlay coverage is fixed

but not reasonable– Absorb limited traffic– Handover algorithm is easy

• IUO– U/O same transmitting po

wer– Handover algorithm based

on C/I– Underlay coverage is fixed

and reasonable– Absorb more traffic– Handover algorithm is co

mplicated

Comparison


Capacity of C/I Based Concentric Technology

Capacity comparison with “4x3”pattern ：Grade of Service (GOS) ： 2 %Per subscriber traffic at busy hour ： 0.03 ErlBandwidth: 6MOverlay adopts “4x3” pattern

0 500 1000 1500 2000 2500 3000 3500 4000 4500

Standard 4X3

Underlay 3x3

Underlay 2x3

Underlay 1x3

Subsc./bts2TRXs Overlay1TRXs Overlay All overlay


Principle of frequency plan

• The frequency in same site can not be reused• In same cell,the frequency distance between BCCH

and TCH is at least 400khz• The frequency distance of TCH should be more than

400khz if FH is not adopted.• Frequency can not be reused in its directly adjacent

sites if it is not 1*3 pattern• Try to avoid to use the same frequency when the two

sites are relatively near


Principle of frequency plan

• Pay more attention to co-frequency reuse case.avoid to set same BSIC to BCCH with same frequency

• When 1*3 mode is adopted, ensure the frequencies of hopping is at least twice as the number of TRX involved in FH..


Dynamic power control (DPC)

Discontinuous transceiving (DTX)

Diversity receiving technique

FH technique

Anti-interference technique

Interference Analysis


Discontinuous transmission (DTX)

Two aims can be achieved by adopting DTX mode. One is to lower the total interference level in the air, and the other is to save transmitter power. The DTX mode and the normal mode are optional, since the former will slightly lower the transmission quality.


Discontinuous transmission (DTX)

• DTX contributes very little to the interference during the quiet period, its power can be regarded as 0 (inactive state). Suppose the DTX active factor is , then the gain.

log10log10log10)(/ IC

ICdBIC



A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A3

A1

A2

From the figure we can see that, in the dynamic power control situation, when the interfering MS is only at the cell borders, the BTS can work with the maximum transmitting power.



Obviously, the interfering MS location is a probability. This case is especially apparent in the frequency hopping situation.

Suppose the DPC factor is p:

pdBIC IC

pIC log10log10log10)(/


Frequency hopping

• Frequency hopping is to avoid external interference. In other words, it is to prevent or greatly reduce co-channel interference and frequency selective fading effect by converting frequencies to an extent that interference cannot catch up with

• The hopping sequences in the GSM are mainly described by two parameters:

• HSN （ hopping sequence number ） • MAIO （ mobile assignment index offset ）


Frequency hopping

• The advantage of the frequency hopping is the so-called effect of Frequency Diversity and Interference Diversity. The former actually expands the network coverage scope, and the latter improves the network capacity.


Frequency diversity gain

• Frequency diversity refers to its capability to resist the Rayleigh fading. As the Rayleigh fadings on different TRXs are somewhat uncorrelated (the bigger the frequency difference, the smaller the correlation is) , thus the bursts distributed on different TRXs will not be affected by the same Rayleigh fading.

• Gain=1.5-6.5dB


Interference diversity gain

• Interference diversity refers to its capability to suppress the interference signals of other cofrequency multiplexed cells

• Gain=

• Where n-the frequency number of FH set m-TRX number

mnlog10


A3

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A3

A1

A2

1*3＋ FH＋ DPC＋ DTX

Most densely reuse patternBCCH (4*3)Combined with anti-interference technologyGenerally ， only use 50% of the whole available frequency

C/I= 9.43 dB

13 Frequency Reuse


13 Frequency Reuse

Let's look at the “1×3” multiplex interference to see the contribution of the antiinterfering technology to the reduction of the interference and the increase of the system capacity.

Compared to “4×3” multiplex, the “1×3” multplex brings about the interference degradation:

CIR 4×3- CIR 1×3 =18 - 9.43 8.57 dB“1×3”hopping, 50% frequency load brings about the interference diversity gain:

10log10(2/1) = 3dBSuppose the frequency hopping length is 12 frequency points, then the frequency

diversity gain is about 2dBSuppose the DTX active factor is 0.5, then the gain is:

-10log10(0.5) = 3dBSuppose the DPC factor is 0.9, then the gain is: -10log10(0.9) =0.5dBThe total gain is: 3+2+3+0.5=8.5dBFrom the above analysis, we can see that the antiinterference technology can basic

ally offset the interference degradation cause by the denser multiplex mode.


Frequency planning and interference forecast

Coverage designField strength

Manual Fre. planAuto Fre. Plan by software

Interference forecast

Planning report andInterference forecast map

Satisfied?

Manual adjustment

Adjust antenna par

a



Verifying reasonability and availability of cell planningInterference protection ratio: co-channel: C/I=9dB(12dB) adjacent channel: C/A=-9dB(-6dB) Second adjacent channel: C/A=-41db(-38dB)•Same/adjacent frequency interference analysis prediction:Same/adjacent frequency interference analysis prediction: To verify if the network planning satisfies the same/adjacent frequency interference rated value.

•Cell plan parameter partly adjustment and re-analysis:Cell plan parameter partly adjustment and re-analysis: Reasonable selection for antenna azimuth angle and downtilt Reasonable selection for antenna azimuth angle and downtilt angleangle

under coverage satisfaction premise, reduce overlapped coverage area to the best


Co-frequency interference

:

m

N

Co-channel

interference


Interference of adjacent frequency

:

m

N

Adjacent channel

interference

04) radio network planning

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