Analysis of fade margins for soft and hard handoffs

Abstract

CDMA wireless systems are believed to require smaller fade margins (than TDMA or FDMA systems) because of their ability to get into what is known as soft handoff. A mobile in soft handoff maintains simultaneous radio links with multiple base-stations which enables it to make use of the best quality leg most of the time. We present an analysis of fade margins for systems allowing soft handoffs (e.g. CDMA) and those where only hard handoffs are possible (e.g. FDMA, TDMA). Our analysis is based on a model for hard handoffs with hysteresis and connection delay, and validates the claim that systems permitting soft handoff indeed require smaller fade margins.