ملخص: Centralized CDMA networks with unslotted Aloha random-access mode are considered. Users communicate with a central node by sharing a finite number of signature sequences assigned to the receivers at the central node. Two methods for sharing preamble codes are considered. In one method a common preamble code is used by all receivers, and in the other method a distinct code is assigned for each receiver. A unified analysis framework for evaluating the performance of centralized FH-CDMA networks is developed. Closed form expressions for packet decoding error probabilities are derived. Numerical results show that common preamble codes can support only low traffic levels. However, by appropriately selecting the design parameters, acceptable levels of packet loss probabilities are achievable with the receiver-based preambles.

لغة: إنجليزية