Antenna Selection Guideline

                         ANTENNA SELECTION GUIDELINE

 

 

1.0  Objective

 

The objective of this document is to frame a general guideline for selection of antenna at proposed CDMA BTS sites in various circles. Selection of correct antenna type is of utmost importance for the optimum performance of RF network.

 

2.0  Selection of Antenna Type

 

Two major categories of antennas have been finalized for deployment at proposed BTS sites viz. i) antennas with 65° horizontal beamwidth and ii) 90° horizontal beamwidth.

 

3.0  Deployment of 65° Antennas

 

The broad category of 65° antennas has been further classified in three subgroups mentioned below.

 

a)     65° antenna with 6° electrical downtilt

b)     65° antenna with 4° electrical downtilt

c)      65° antenna with 2° electrical downtilt

 

 

3.1 Deployment of 65°-6° Antenna

 

In case of this antenna, the vertical beamwidth of antenna is provided with an electrical downtilt of 6° below horizon. These antennas are proposed to be deployed in the following cases:

 

a)     Cities having 15 or more BTSs.

b)     Sectors oriented towards dense urban or urban morphology.

c)      Site to site distance is upto 1.5 km

 

3.2 Deployment of 65°-4° Antenna       

 

65°-4° antennas are proposed to be deployed in the following cases:

 

a)     Cities having more than 7 BTS sites.

b)     Sectors oriented towards the city area with urban, low urban clutter.

c)      Site to site distance is between 1.5 km and 2.0 km

 

Due to site-specific requirement like hilly terrain, lesser site-to-site distance, deviations from above guideline were made in the following cities.

 

 

Amritsar (7 Sites)                        :                       3 Sites

Jodhpur (7 Sites)                        :                       2 Sites

Mysore (7 Sites)                          :                       1 Site

Udaipur (6 Sites)             :                       4 Sites

 

3.3 Deployment of 65°-2° Antenna

 

For this type of antenna, vertical beam is provided with an electrical downtilt of 2° below horizon. These antennas are proposed to be deployed in the following cases:

 

a)     Cities/towns having more than 2 BTS sites and upto 15 BTS sites.

b)     Sectors oriented towards the city areas having urban, low-urban or suburban morphology.

c)      Site to site distance should be more than 2 km.

 

4.0  Deployment of 90° Antenna

 

This category has been subdivided into two groups.

 

a)     90° antenna with no downtilt

b)     90° antenna with 2° electrical downtilt

 

4.1  Deployment of 90°-0° Antenna

 

These antennas are proposed to be deployed in

 

a)     Every sector of single/two BTS city/towns

b)     Sectors directed towards rural areas and highways of medium sized cities having upto 8 sites.

 

4.2  Deployment of 90°-2° Antennas

 

These antennas are proposed to be deployed in following cases:

 

a)     Sectors of BTSs directed towards rural areas or highways of cities having more than 8 BTS sites.

 

In big cities, sites located at good clutter type but at one extreme corner of the city limits have been proposed to have a combination of 65°-4° and 90°-2° antennas. In these cases, 90°-2° antenna type was preferred to 90°-0° as sidelobes/backlobes of 90°-0° may result in coverage overlap with 65°-4° antennas deployed in other sectors.

 

 

5.0 City Specific Antenna Selection

 

For all city/towns, barring a few specific requirements, antennas have been selected on the basis of the following guidelines. Combining all technical requirements together, cities can be classified in the following groups:

 

a)     A-Category: Top cities having combination of 65°-6°, 65°-4° and 90°-2°. For big cities, since number of BTS sites are more, use of 65°-2° may result in coverage overlap leading to pilot pollution. Also, this combination will make material handling much easier without deteriorating the performance of RF network. Among all the big cities, the combination has not been followed in Calcutta due to Radio Network requirement.

 

b)     B-Category: Other major cities having combination of 65°-4°, 65°-2° and 90°-2°. This combination is used in case of medium sized cities where site-to-site distance is more than 1.5km. There are a few exceptions in this case also as mentioned earlier.

 

 

c)      C-Category: Other cities having combination of 65°-2° and 90°-0° or 65°-2° and 90°-2°. Cities/towns in this group are having only a few BTSs and main aim in these cases is to use the antenna type which can extend coverage span to the maximum extent.

 

d)     D-Category Towns having upto 2 BTS sites. In these cases, only 90°-0° antennas have been proposed to maximize the SDCC coverage boundary.

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