A performance comparison of differential frequency hopping and fast frequency hopping

Abstract

This paper discusses the multiple access performance of the spread spectrum modulation called differential frequency hopping (DFH) and its associated signal processing algorithms, and compares DFH performance to the performance of fast frequency hopping (FFH) multiple access systems. To fairly compare FFH and DFH, it is necessary to carefully choose the parameters for each system, using the concept of efficiency. The single-user efficiency provides a fair way to set parameters when comparing FFH and DFH systems when there is no multiuser interference (MUI) present. We develop the multi-user efficiencies for the two waveforms, as a mechanism to determine comparable system parameters for FFH and DFH multiple-access systems. It is shown that, for the same bits/symbol, the data rate of a single-user DFH is larger than the FFH data rate if the hop dwell time is the same DFH is shown to be significantly more MUI-tolerant than the comparable FFH and FFH systems with interference cancellation, particularly at low and mid-level SNRs. Similarly, the theoretical same-efficiency DFH outperforms the non-optimal FFH at most SNRs and outperforms optimal FFH with collision resolution at SNRs above 7 to 11 dB, depending on the number of simultaneous users. The theoretical and simulation results consistently indicate that DFH is more MUI-tolerant than FFH for the same efficiency, which is desirable in ad hoc networks with multiple users.