Sector Swapping Drive Test

Types of Cable swapping

1)Complete Cross feeder(GSM or DCS)

2)Composite Swap(GSM or DCS)

3)GSM or DCS cable Swap

4)Wrong Antenna installation

1)Complete Cross feeder(GSM or DCS)

•Analysis

           Completely crossed feeder cable of two sectors.

           coverage area of the two adjacent  cells or swapped.

•Problem

            Frequent INTRA Cell handover

            Handover failure

            Sometimes call drops

Figure : Complete Cross feeder(GSM or DCS)

2)Composite Swap(GSM or DCS)

• Analysis

          Feeder Cable  of two or three sectors or partially swapped.

         Tx  feeder Cable is correct Rx feeder cable is swapped.

         Tx feeder Cable Swapped Rx came cable are correct.

•Problem

         fluctuation in Rx level continually when we near to site.

Figure : Composite Swap(GSM or DCS)

 3)GSM-DCS Cable Swap

•Analysis

          GSM feeders or connected to DCS

• Problem    

        Frequent INTRA Cell handover.

        Handover failure.

          Sometimes call drops.

Figure : GSM-DCS Cable Swap

4)Wrong Antenna installation

•Analysis

          Sub case of composite Swap and mostly in complex  site.

          Wrong installation in inside the cabinet.

          Knowledge of TRX configuration will helpful to solve this problem.

•   Problem

             Lot of handover failure.

           Call drops due to missing neighbors.

Figure : Wrong Antenna installation

Sector/Cable swap

Problem Due to Swap

Figure;1

figure : Problem Due to Swap

Figure 2;

Figure : Problem Due to Swap

Reason for Sector Swap and Wrong installation;

              Due to very huge and fast deployment sector swap and  wrong installation is common.
The main reason  is behind in hardware installation.
Antenna and feeders  are installed at one time and  BTS and other hardware  are installed an power up at other  time.
Here the responsibility of acceptance team comes who need  to verify these  type of problems very carefully in field.
 Case Study I ;
Pre-Drive
There was a sector swap between sector 2 and sector  3 in 900 band.
This can be categorized into  “Complete Cross Feeder” .
But  here No swap was found in complete cable trace from BTS to top of Antenna.
But sector was found inside the Cabinet cabling between TRx and Duplexer.
It Cause result:  Handover Failure

Figure : Pre drive

Post Drive
Swap was removed by the help of BSS engineer and Rigger

Figure : Post Drive

Case study II

 Pre-Drive
In sector 2  GSM Feeder cable is connected to DCS duplexer and DCS  Feeder Cable is connected to BTS Duplexer.This can be categorized into GSM/DCS  Cable Swap.In this type  there is no clear  identification, But drive tester may observed .ProblemFrequent  INTRA Handovers.
Handover failures.
Some times call drop due to Low Rx level  even near  to  BTS.

Figure : Pre Drive

 Post-Drive

Figure : Post Drive

 Example for Swapping

Figure : Examples of Swappping