Ping Pong Handover

As the cellular network growing, it requires addition of new sites to expand capacity and or coverage services. New mobile operators were expecting to grow their network in exponential order to gain market share against mature competitors. Without any intensive network performance maintenance, common problem such ping pong handover would be degrade user experience like bad voice quality ( SQI speech quality index, MOS mean opinion score ) or even dropped call.

Ping Pong handover is shown from the successful handover back to old cell within pre-defined time of total handover, e.g. less than 10 seconds. Since not all BSS vendors provide such performance counters it might be identified by simple metric that shall be expressed as total successful handover over number of call or connection, e.g. more than 200% indicates ping pong handover.

The actual ping pong handover is easily identified through drive test with sense of optimization engineer without require any calculation. Coverage holes might lead to Ping-Pong handover especially for slow moving mobiles. It may be cause by shadowing by high building. Several possible equal signals from two or more base stations might lead to Ping-Pong handover as well which is so called not optimized cell dominance.The following action items shall be used for optimization solutions:

Check the parameter setting such as hysteresis, offset, priority layer in dual-band case, etc. If poor parameters setting found, then correct the related parameters. Compare to default parameters design.

Check the output power BSPWR and BSPWRT which normally put on maximum value or compare to design.

Check path balance on transceiver link, e.g. loss in uplink and downlink chain. Defective RF modules might be the reason of imbalanced link.

Check the site location such as possible coverage holes or no dominant cells. Perform drive test on that particular area to check the signal strength, if the average of

signal strength of the neighbors are the same, no dominant cell is found. For Long term action if no dominant cell shall be adding new site, while short term action

shall be uptilt the most dominant cell as the serving cell for that area and reduce coverage for others.