Drop Call Rate




Drop call rate is Main KPI that very important in RF Optimization. This indicator is used to measure the percentage of calls dropped due to technical problems or coverage gaps in the service provider’s network as a ratio of the total number of calls successfully established.

Reasons and Solutions for Call Drop

       Hardware Problem.

If the problem is coming from hardware, percentage of drop call rate would be very high and you have to replace bad module with good module. For example in GSM Network you have to check and make sure TRX module such as GRFU or Combiner working properly. To make sure the problem was coming from hardware or bad module, you can identify by trying Swap module first.

       Frequency Interference. 

Frequency interference is include in problem that can impact to high drop call rate because the Noise(Interference Signal) is very high and affecting to Carrier( primary Signal) and also affect to bad vice quality. There are two type of Frequency Interference that called Co-Channel Interference and Adjacent Channel Interference. Identify the root cause of interference and retune the frequency.

        Overshooting Cells

Overshooting cell can be the one that causing high drop call rate in the network. To overcome this issue you have to change tilt configuration of Antenna, for example adjust Mechanical Tilt or Electrical tilt of RF Antenna. Overshoot is common problem for both GSM and UMTS that causing drop call due to bad RX level in the edge of Coverage or bad RSCP and Ec/No in UMTS Network. The solution is same for both GSM and UMTS that is change Antenna configuration tilt/Down tilt.

Missing neighbor

Missing neighbor also will causing High drop call rate in your network. You have to check and make sure relation of the cells is complete and no missing neighbor.

WrongParameter Configuration

Wrong parameter configuration will causing high drop call rate in your network. Make sure to check all parameter and configure accordingly. In GSM there is parameter related drop call rate KPI such as: RLT (Radio Link Timeout).
       You can set by increase RLT to reduce drop call but will affect to Customer Experiences because release call is too long even when radio environment is poor and conditionally should be released. The other solution to reduce drop call related parameter is by adjust HO Parameter to make fast handover to a good cells in surrounding closest cells such as adjust PBGT, RXLEVMIN to target Cells. Making fast HO to good cells can be implemented on both GSM and UMTS Network.

Power or Transmission Problem

Power problem can make high drop call rate in the network. You have to make sure no power problem by check the alarm and Cell Availability. If the problem occurred you need to follow up the problem to Field Maintenance Team to fix it.
Transmission problem also can make drop call rate very high and affecting to your KPI. You need to check alarm related transmission and make sure also cell availability is stable. If you found transmission problem the you have to follow up the problem to Transmission Team to check and fix it.

Contour Problem (Hilly/Rural Contour)

Bad contour can be the one that causing high drop call rate especially if your network in Hilly or Rural area. Check and identify your cells by drive test to make sure the problem is causing by contour or check the coverage by Simulation. If the problem is bad contour then you have to adjust tilt of the cell or re-azimuth make sure coverage continuous.

Discontinuous Coverage

If your coverage discontinue due to lack of site then you need to propose new site to your operator. Discontinue coverage also can occurred due to wrong antenna configuration such as over tilt. You need to check tilt configuration of the antenna and make sure no over tilt that causing coverage become discontinue.

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