Performance of chip-level differential detection with phase noise

Chip-level differential encoding/detection of direct-sequence spread-spectrum signals has been shown to improve receiver robustness in the presence of oscillator frequency offsets and fast fading channels. These gains are achieved at the expense of SNR performance in an AWGN channel, with spreading factor governing the tradeoff. This paper explores the performance of chip-level differential detection in the presence of oscillator phase noise. It is shown that phase noise mitigation is an additional benefit of chip-level differential detection, with higher spreading factors permitting the use of lower-cost, noisier oscillators. Simulations of a DS/SS BPSK system illustrate the relationship between phase noise tolerance and spreading factor, and a simple analytical model is derived for efficient evaluation of systems with high spreading factor.