Effect of propagation loss coefficient on the performance of a packet CDMA PCN

Spread spectrum CDMA based cellular systems are currently under consideration for a range of personal communication network (PCN) applications. While CDMA has been shown to offer significant capacity advantage over narrowband TDMA alternatives, these gains are very sensitive to the propagation loss coefficient gamma . Most analytical studies for CDMA system capacity are based on an assumption of propagation loss coefficient gamma =4, consistent with large cell sizes associated with present day cellular radio. However, in microcellular (i.e., cell sizes with radius approximately 100's of meters) environments, the path loss coefficient can vary in the range of 2 to 4. In addition, attenuation measurements using low antenna heights for microcells have indicated that the path loss coefficient may not be a constant, increasing with distance between the base station and the subscriber terminal. A distance-dependent model for the propagation loss coefficient gamma is considered and used to compute the capacity of a cellular packet CDMA system operating in an integrated voice/data PCN environment. System-level performance measures such as channel utilization, voice packet loss probability and data delay are derived from a detailed channel event based simulation model, and compared for alternative scenarios with constant gamma and distance dependent gamma .<
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