Detection of linear modulations in the presence of strong phase and frequency instabilities

The previously proposed noncoherent sequence detection (NSD) algorithms have a performance which approaches that of coherent detectors and are robust to phase negligible performance loss in the presence of a frequency offset, provided this offset does not exceed an order of 1% of the signaling frequency. For higher values, the performance rapidly degrades. In this paper, two detection schemes are proposed, characterized by high robustness to frequency offsets and capable of tolerating offset values up to 10% of the signaling frequency. More generally, these detection schemes are very robust to rapidly varying phase and frequency instabilities. The general case of coded linear modulations is addressed, with explicit reference to M-ary phase shift keying (M-PSK) and quadrature amplitude modulation (M-QAM)