Description about 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 down-tilt 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 down-tilt 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 downtilt 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 expressways, 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 expressways.

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 downtilt, 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 downtilt angle is no more than 10 degrees.
Suburb	Directional station	Normally, select antennas with high gains, permitting of electrically adjustable azimuth or mechanical downtilt angle.In addition, if some areas are not well covered in some directions, antennas with its horizonal half power beam width of 90 degrees may be selected.	If mechanical downtilt 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 perferred to use vertical single  polarization antenna.	Generally no downtilt angle is added.
	Omnidirectional station	First there must be zero point filled antenna without regard to angle of downtilt.	Generally no downtilt 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 downtilt angle is added.
Expressways( continue )	Directional station + omnidirectional station	First consider 210-degree antenna, then consider the combination of directional antenna+ omni-antenna	Generally no downtilt angle is added.
Mountainous areas	Omnidirectional station	First consider antenna with zero point filling function, then consider antenna of lower gain before adding a downtilt angle.	Generally no downtilt angle is added.
	Directional station	First consider antenna with low gain and vertical  beam width before adding a downtilt angle.	Generally no downtilt angle is added.

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.

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.

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:

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