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| Joint timing and phase estimation algorithm for SOQPSK signals |
| College of Communications Engineering, Chongqing University, Chongqing 400030, China) |
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Abstract To solve the difficulty and complexity of synchronization problem in ternary shapedoffset quadrature phase shift keying(SOQPSK), a decisiondirected joint timing and carrier phase estimation algorithm was proposed. Based on Laurent representation of SOQPSK, the symbol sequence was recovered by maximum likelihood sequence detection(MLSD). The joint likelihood functions of timing and carrier phase parameter were simplified into the likelihood function of timing parameter. The estimated timing value was then recovered by parallel searching method to obtain the estimated value of carrier phase. According to the common signals of full response SOQPSK-MIL and partial response SOQPSK-TG, the complexityreduction implementation scheme of joint timing and carrier phase estimation algorithm was proposed. Simulation was completed under additive white Gaussian noise(AWGN) channel. The results show that the proposed algorithm is suitable for SOQPSK-MIL and SOQPSK-TG. The timing error variance curve is close to the theoretical limit. The carrier phase error variance is at 10-3-10-4 order of magnitude with timing offset, and close to theoretical limit without timing offset. Carrier phase error has little effect on the timing recovery algorithm.
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2011, Vol. 32 
