Phase Estimation Algorithm for Frequency Hopped Binary PSK and DPSK Waveforms with Small Number of Reference Symbols
June 2005
Benjamin Wiederholt, The MITRE Corporation
Mario Blanco, The MITRE Corporation
ABSTRACT
In military satellite communication systems that use frequency hopped waveforms, it is difficult to coherently detect phase shift keying (PSK) (binary or M-ary) signals unless many reference symbols are used to aid with phase estimation of the received signal. For this reason, many systems use differential phase modulations, such as differential phase shift keying (DPSK), which can be detected noncoherently without the use of phase information. However, the use of DPSK over PSK results in reduced power efficiency. This paper presents a novel approach to phase estimation that provides improved power efficiency through coherent detection of phase modulated signals (with and without differential encoding) using few reference symbols. More specifically, the algorithm presented herein uses signal processing techniques to estimate the phase of each hop by using both reference and information symbols in a hop. This paper focuses on binary PSK and DPSK waveforms where data is transmitted in blocks with only one or two reference symbols per block. The performance of this algorithm was evaluated for the case of additive white Gaussian noise (AWGN) and Rayleigh fading channels via Monte Carlo simulations. At bit error rates (BER) of interest, the results indicate that, depending on the environment and modulation used, performance gains of up to 3 dB were realized when hops contain as few as two reference symbols. The results also show that coherent detection of binary phase shifting keying (BPSK) and DPSK modulated waveforms containing one reference symbol per hop performed more efficiently than noncoherent detection in all channels considered.
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