Radio Network Planning Part2

VI.Work involved in GSM Network planning

1.Planning working contain

Planning working contain：BTS distribution, channel allocation, cell parameter planning. It is important to provide a full design to construct network. This plan may differ from the as-built.

The location of BTS.
2)The channel distribution.
3)Example of cell parameter planning/BSC Network features --- Cell load sharing, Double BA list and etc.

2.Key points in planning

- Provide a good coverage prediction.
- Influence of site distribution to network coverage and capacity.
- Nnetwork long-term development and on the whole planning.

Interference from all kinds of sources ( building, Environmental, co-channel, adjacent channel and etc ) has make the nominal cell planning difficult.
During the engineering design, the above interferences have to be taken into account carefully.
As the network capacity increase, the limited allocated number of frequencies is a challenge for cell planning and cell optimization engineer.
The network capital investment is an important consideration.

VII.GSM technology overview

- Coverage planning

- Antenna selection, Parameter design , Installation

- Capacity planning

- Base station survey

- ASSET planning software

- Frequency planning

- Parameter design

-> Coverage planning is to be performed in the cell planning phase. In the coverage planning phase, we need to know the requirements in coverage planning and know the coverage area’s special property.

Link budget should be taken into account. Proper frequency reuse and understanding the interferences should be carefully considered.

1.Coverage planning

- Coverage requirements

-->Plan of coverage district

- Analysis

-->City、town、rural，plain、a mountains area etc.

-->Field Strength of the Edge of the Coverage Area and coverage rate

-->Sensitivity、decade protection、loss、frequency band diversity

- Power budget

-->Evaluating balance of upling and downlink

- Special region analysis

-->High building，underground，tunnel,etc

2.Coverage Requirement

Requirements:
C/I≥9dB，C/A≥-9dB ( In actual engineering environment, C/A≥-12dB )
2)90% of the coverage area should be inside the PLMN coverage area. Within the coverage area, MS should be able to access the network 99% of the time.

- macrocell
->coverage radius 1km ~10km，often useful macocell。
- microcell
->coverage radius 500~1000m，can 。
- Picocell
->around coverage radius 200m，solute point coverage area capacity and indoors coverage.
- Extended macrocell
->coverage exceed 35km，main use low traffic and open area ，example sea、grassland。

3.Link budget

Abbreviations:
Pinm : Power received at the MS side ;
Mf : Loss suffers from fading and other residual losses.
Poutb :Transmitter output power;
Lcb : Loss in combiner ;
Lfb : Loss in feeder;
Gab : BTS antenna’s gain ;
Ld : Path Loss
Gam : MS antenna’s gain ;
Pmn : Noise suffered at the MS side ;
Pinb : Power received at the BTS side
Pout : MS output power ;
GdB : BTS antenna diversity gain ;
Pbn : Noise suffered at the BTS side

Downlink path consideration : Pinm (–102dBm) + Mf = Poutb － Lcb －Lfb + Gab －Ld + Gam － Pmn ------------ （1）
Uplink path consideration : Pinb + Mf = Poutm +Gam －Ld +Gab + GdB － Lfb －Pbn ------------ （2）
Assume :Pmn = Pbn ;
Poutb = Poutbal ;
Pinm = Mssens ;
Pinb = BTSsens
From (1) and (2), we get :
Poutb – Pinm = Poutm + GdB – Pinb + Lcb ==>
Poutbal = Poutm + GdB + Lcb + ( Pinm – Pinb ) ==>
Poutbal = Poutm + GdB + Lcb + ( MSsens – BTSsens )
Footnote :Poutbal denote the BTS output power when link budget is achieved.

4.Coverage of special area

Adopt distributed antenna in high building

- Tunnel , subway , underground
- Industrial and commercial area
- High-rise
- Blind area

VIII.Antenna selection

a.coverage area characteristic

b.Common antenna product

The choice of antenna has an important effect on the network coverage.

The requirements on antenna :
- Satisfying the coverage area. AND
- Does not cause interference to other cells.

The key considerations of the antenna are :
- Antenna gain.
- Antenna azimuth
-Antenna polarization

Different choice of antenna is being used in the following situations :
- urban, sub-rural and rural area
- Mountain, flat land ( sea ), highway and tunnel area
- Building interior

Common antenna supplier :
Andrew , Allgon , Antel, Kathrein , and etc

c. How to Choose An Antenna

- How to Choose An Antenna is an important part that may determine the network quality.
- Antenna shall be selected as per the coverage, service quality requirements within the base station service area, traffic distribution, topographic, landscape conditions, and consideration to the coverage and interference details of the entire network;
- The usage of antennas may be divided into the following types according to the topographic conditions or traffic distribution:
->Urban, suburb, rural area, highway, hilly area, coastal area, tunnel, indoor, etc.

d.Antenna feeder design-antenna selection

- Base station antenna selection in urban area
a、the horizontal beam width of the urban area antenna should be 60~65°;
b、better to select 15-18dBi gain antenna;
c、suggest to be 3-6 degree downtilt of directional antenna ;
d、.advise to select dual polarized antenna;

- Base station antenna selection in suburban area
a、Select antenna with horizontal beam width of 65 degree.
b、Select 15～18dBi medium or high gain antenna,
c、 It will be decided by the practical situations if the preset downtilt angle is used or not.
d、Suggest to select dual or single polarized antennas

Choice of antenna used in urban area :
1)In order to control the coverage area of the antenna used in urban area, the azimuth of the urban antenna ( omni or directional ) should not be equal of greater than 90 degree.
2)Due to that large coverage area of the urban antenna is not required, therefore it is suggested to used middle-gain antenna. At the same time, we can choose a lighter urban antenna and a smaller size urban antenna. This can cut down the cost of installation of the urban antenna.
3)Because of the strict restriction of the urban antenna’s coverage, therefore the down-tilt of the urban antenna is usually great. Choosing the electric adjustment antenna can allow a greater adjustment of the down-tilt. The electric adjustment antenna is useful in controlling the interference level.
4)Due to the limited available space in the urban area, it is suggested to use dual-polarized antenna.

Choice of antenna used in sub-rural area :
1)The sub-rural area environment is matched in between the urban and rural environment. As according to the actual situations, the sub-rural antenna can be chosen with reference to the guidelines given in urban and rural area antenna.
2)With the consideration of future expansion, omni antenna is not recommended.
3)When the down tilt of the antenna is used, the down tilt angle is usually small.
4)The effect of using vertical polarized antenna or dual polarized antenna is about the same. Therefore antenna installation and the cost of antenna are the criterions when choosing the antenna in the sub-rural area.

Base station selection in countryside
a、antenna select the 90°、120°directional antenna according to the practical situation and requirements;
b、we suggest to select the directional antenna of high gain （16～18dBi）;
c、 we suggest to select antennas without preset downtilt angle,and utilize zero point stuffing when hang height is over 50 meters ;
d、suggest to select single and vertical polarized antennas in country sides;

Base station selection along highway
a、The narrow beam high-gain directional antennas could be used,and “8” shape antenna.
b、There would be much require to highway covering distance, we suggest to select no preset down-tilt antenna;
c、Suggest to select vertical polarized antennas;
d、the forward to back ratio of selected directional antennas should not be too high;

Rural area :
1) Number of the BTS is limited and the coverage area of each BTS is large.
2)When the coverage area has no obvious direction and the traffic distribution is scatter in the required coverage area, then it is suggested to use omni- antenna.
3)When there is a need to cover a larger coverage area, then directional antenna is utilized to realize this. Usually, the directional antenna azimuth is 90 degree, 105 degree or 120 degree and etc.
4)When the coverage area has an obvious shape, then 210-degree antenna can be used.
5)Because the antenna’s coverage area in rural area is requested to be large, therefore we will use antenna that has large gain.
6)Because the preset-down tilt- antenna has a restriction on the antenna coverage area, therefore this preset-down tilt- antenna is not recommended.
7)Due to the signal propagation characteristics, vertical polarized antenna is most recommended.

Highway :

1).Traffic load is low. MS travel in high speed . Coverage area is the key element.
2)To cover express ways, 8-shaped antenna may be used for this purpose.In this way, the number of base stations may fall, so as to achieve the coverage of express ways.

Land form	Station type	Recommendation for antenna selection	Remark
Urban area	Directional station	Normally, select antennas with low or medium gains and fixed electric angle of down tilt, subject to the density of base stations; if an antenna with electrically adjustable azimuth is available, it should also be selected.	While installing an antenna, make sure that the mechanical down tilt angle is no more than 10 degrees.
Suburb	Directional station	Normally, select antennas with high gains, permitting of electrically adjustable azimuth or mechanical down tilt angle. In addition, if some areas are not well covered in some directions, antennas with its horizontal half power beam width of 90 degrees may be selected.	If mechanical down tilt angle is to be installed, the angle should not be too large.
Plains & rural areas	Directional station	Generally, select an antenna of 90 degrees or of 120 degrees. It is preferred to use vertical single polarization antenna.	Generally no down tilt angle is added.
	Omnidirectional station	First there must be zero point filled antenna without regard to angle of down tilt.	Generally no down tilt angle is added.
Expressways	Directional station	First consider 8-shaped antenna and then consider 0.5/0.5 configuration using power splitter; it is preferred to have zero point filling.	Generally no down tilt angle is added.
Express ways( continue )	Directional station + omnidirectional station	First consider 210-degree antenna, then consider the combination of directional antenna+ Omni-antenna	Generally no down tilt angle is added.
Mountainous areas	Omnidirectional station	First consider antenna with zero point filling function, then consider antenna of lower gain before adding a down tilt angle.	Generally no down tilt angle is added.
	Directional station	First consider antenna with low gain and vertical beam width before adding a down tilt angle.	Generally no down tilt angle is added.

e.Antenna Height

Principle for Determining Antenna Height

- The antennas for different cells within one base station can be of different heights, which may be restricted by the installation space in a certain direction.
- In urban areas with smooth terrain, the effective height for ordinary antennas shall be at about 25m;
- For suburban and rural base stations, the heights of antennas can be increased to about 40m.
- Too high antenna may decrease the coverage level near the antenna (which is known as “Under-Tower Black”); the problem of “Under-Tower Black “ for an omnidirectional antenna is extremely serious.
- Too high antenna may result in serious problems such as handover failure.
- Co-channel and adjacent channel interference would affect the network quality.

f.Antenna Azimuth Angle

Principle for Determining Antenna azimuth Angle

- The antenna azimuth angle shall be determined from the entire network.

- The main lobe of antenna shall point at the area with dense traffic to focus the signal intensity in that area and improve the conversational quality;

- The main lobe of the antenna shall be kept away from the same frequency cell to effectively decrease interference;

- The inter-coverage between antennas in neighboring sectors in an urban area shall not exceed 10%;

- The inter-coverage between neighboring cells in a suburb area, or rural area shall not be too large.

- To avoid handover failure, in the area with concentrated cities, the main lobe of antenna shall orient towards straight streets.

g.Antenna Feeder Design—Down-tilt

Principle for Determining Antenna Down-tilt

- The wave beam tilt of antenna is a basic technology to improve frequency multiplex capability;

- Antenna Down-tilt technology can effectively control the coverage and decrease the interference within the system;

- The antenna Down-tilt angle shall be determined according to the practical conditions so as to decrease the interference between cells of the same frequency and to ensure meeting the coverage requirements;

- Determination of down-tilt shall give overall consideration to the transmission power of the base station, height of the antenna, cell coverage, wireless broadcast environment, and other factors;

- Antenna wave beam tilt can adopt electric or mechanical pattern: The electric Down-tilt is related to the mode of the antenna selected; Mechanical Down-tilt can be adjusted but will be limited by installation fittings. It shall not exceed 15°;

- Electric Down-tilt and mechanical Down-tilt may lead to different surface radiation; when the Down-tilt is small, there is little difference; but with the increase of Down-tilt, the difference becomes bigger: