Tradeoff between loop update rate and loop bandwidth for low data rate communications in the presence of phase noise

Low data rate communication links require less power to close the link; however as the data rate becomes very low given a fixed E_b/N₀, phase cycle slips due to infrequent carrier loop updates in the presence of oscillator phase noise become problematic. Assuming coherent demodulation, a cycle slip will cause loss of sync which is unlikely to be recovered until a new frame header is received. This paper presents experimental results for the mean time to cycle slip (MTCS) given a data rate and phase noise combination. A decision directed carrier tracking loop is used for all experiments, while the loop bandwidth (BW) and E_b/N₀ are varied. This paper also considers an alternative approach where the carrier loop BW is kept constant, but loop updates are made multiple times per symbol. The two methods, varying the carrier loop BW and sampling the carrier tracking loop more frequently are compared.