A performance comparison of the CDMA IS-95B and IS-95A soft handoff algorithms

Code division multiple access (CDMA) networks typically register high occurrences of soft handoff. Handoff is warranted when signal diversity is essential, ensuring that grade of service (GOS) criteria and capacity requirements are met. However, excess handoff can reduce network capacity and increase base station (BTS) hardware requirements. The IS95B soft handoff procedure attempts to dynamically reject excess soft handoff. This paper compares the performance of the IS95B soft handoff procedure to its predecessor, IS95A, via a combined physical and network layer simulator. The results indicate that the IS95B soft handoff procedure has the ability to reduce and maintain the average Walsh code per user and hardware elements per user to near constant levels as network loading drops. However, it does not provide any capacity gain over IS95A when operating the network at 1% call blocking levels.