Robust, FFT-based, single carrier, multiuser, SDPSK/DPSK block demodulation in the presence of symbol synchronization jitter

In this paper a robust, single carrier, multi-user, DSP-based implementation of an OFDM, differential phase shift keying (DPSK) block demodulator is suggested. It is shown that a direct, DSP-based implementation of the above system using a single FFT symbol is highly susceptible to artifacts induced by symbol timing errors (symbol synchronization jitter, SSJ). A dual symbol, FFT-based implementation is suggested to alleviate the effect of timing error on the demodulation process, even eliminate some of the SSJ-induced artifacts. The countermeasures used in the implementation do not assume any statistical model of SSJ nor are they dependant on a symbol synchronization scheme. Also a dual version of the demodulator is derived for an important, but less known, modulation technique called symmetric DPSK (SDPSK).

Keywords

SDPSK, DPSK, FFT, DSP, block demodulation

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Published 1 January 2005