SOFT HANDOFFS IN CDMA MOBILE SYSTEMS

This article presents an overview of soft handoff, an idea which is be coming quite important because of its use in the IS-95 code-division m ultiple access (CDMA) cellular phone standard. The benefits and disadv antages of using soft handoff over hard handoff are discussed, with mo st results drawn from the available literature. The two most well-know n benefits are fade margin improvement and higher uplink capacity, whi le disadvantages include increased downlink interference and more comp lex implementation. Handoff parameter optimization is extremely import ant, so various studies on the trade-offs to be considered when select ing these parameters are surveyed, from both the link quality and reso urce allocation perspectives. Finally, research directions and future trends are discussed.