A Comparison of CDMA and Frequency Hopping in a Cellular Environment

Abstract

This paper compares the performances of Direct Sequence Code Division Multiple Access (CDMA) and Frequency Hopping (FH) schemes in a cellular multiuser environment. Our multiuser channel model incorporates the effects of propagation, frequency selective fading, and interference among users in the presence of a constrained system bandwidth. The CDMA and FH systems are compared using BPSK modulation. The main point of contrast between these systems is that the orthogonal hopping patterns in a FH system result in a decreased additive interference power, however the frequency spreading nature of CDMA results in the ability to combat fading. An information theoretic analysis is presented, which shows that system capacity is larger for CDMA than for FH. Hence, for this channel, with sufficient coding the CDMA system can achieve a higher level of performance than the FH system. However, it is unclear what level of complexity would be required to achieve such performance, and what effect such complexity would have on the practicality of the system.

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