Impact of adding sites on PN offset planning in CDMA networks

Addition of cell sites in problematic areas to improve QoS and increase capacity is an option, which is frequently used in CDMA network deployments. Though such growth sites mitigate the problem of traffic overload and reduce coverage holes, they also contribute adversely to the interference and some times necessitate a complete network-wide retune of PN offsets in the CDMA network. The impact of adding a growth site in an urban capacity-limited CDMA network is studied on the resulting performance. Three strategies to assign PN offsets to this growth site in the network are explored, involving a full, partial or no retune of the remaining sites in the network. The resulting network performance for each strategy is studied in terms of offset protection possible with a state-of-the-art PN offset planning algorithm. A pilot power reduction technique is also used to reduce interference around the growth site without sacrificing QoS (quality of service). It is shown that an appropriate retune strategy coupled with this pilot power reduction technique significantly improves QoS and capacity in problematic areas.