Soft Handoff Parameters Evaluation in Downlink WCDMA System

Abstract

Mobility is an essential feature of mobile wireless communication systems. Handoff is a feature that deals with the mobility of the user in order to provide seamless phone call when the user cross the cell borders to another one. WCDMA system is the third generation system, implements soft handoff (SHO) technique while hard handoff (HHO) which is used in GSM system. Soft handoff is a technique which allows the user equipment in the overlap region to link with two or more base stations. The effect of soft handoff on the downlink direction of WCDMA will be studied because the downlink is considered as the limiting parameter in CDMA systems. The effect of soft handoff on the most important parameters of the downlink in WCDMA is investigated using simulation. Other related parameters of WCDMA system optimization such as load factor, noise rise, and parameters related to the quality of service like bit error rate (BER) are investigated. The results reveal that a user in soft handoff consumes less power from its serving base station. This reduction in the power leads to reducing the total interference in the cell and hence improving the performance of WCDMA system by reducing the load factor (loading) and noise rise, and increasing the capacity and enhancing the quality of service. Furthermore , the results assure why 2-way soft handoff is commonly used in CDMA system.