Handoff Initiation and Performance Analysis in Cdma Cellular Systems

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Addis Ababa University


Mobile terminals allow users to access services while on the move. This unique feature has driven the rapid growth in the mobile network industry, changing it from a new technology into a massive industry within less than two decades. Handoff is the essential functionality for dealing with the mobility of the mobile users. Compared with the conventional hard handoff employed in the GSM mobile networks, the soft handoff used in IS-95 CDMA and being proposed for 3G has better performance on both link and system level. In this thesis, an in-depth study of the soft handoff effects on the uplink direction of IS-95 CDMA networks is carried out, leading to optimize soft handoff for capacity under perfect power control approach. We analyze the performance of different handoff algorithms on the forward link or downlink of a CDMA cellular system. Unlike the reverse link, soft handoffs on the forward link requires additional resources such as CDMA codes and transmit power and also causes additional interference. If handoff requests can be processed and completed instantaneously, transmission from the base station with the best link to the user would achieve a significant fraction of the macro diversity gain without utilizing additional resources. However, in practical systems, there is a nonzero handoff completion delay and soft handoff provides the required robustness to delays, although it comes at the expense of additional network resources. Thus, there is a tradeoff between the extent of soft handoff required and the handoff execution delay. We present an analytical framework to study this tradeoff and also discuss simulation results simulated with the help of Matlab. For this, handoff dropping probability is minimized up to 0.1%. Markov concept is applied to describe the system’s statistic behavior in steady state. System performances such as blocking and dropping probabilities and channel efficiency are also determined



Cellular Systems