Handoff Initiation and Performance Analysis in Cdma Cellular Systems
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Date
2007-02
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Addis Ababa University
Abstract
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
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Keywords
Cellular Systems