高效的联合卷积DQPSK编码调制方法

Efficient joint convolutional code-coded DQPSK method

在数字通信中,90°或者180°的相位模糊是影响正交相位偏移键控(quadrature phase shift keying,QPSK)相干接收机性能的重要因素。差分正交相位偏移键控(differential QPSK,DQPSK)可以克服相位模糊,但是会导致约2.3dB的性能损失。为了消除DQPSK的性能损失,提出一种低复杂度的基于迭代译码的联合卷积DQPSK编码调制方法,并且基于外信息转移图,提出了一种在DQPSK调制下优化卷积码生成多项式的算法。仿真结果表明,所提差分编码方案不仅可以克服相位模糊,而且通过迭代译码完全补偿了差分编码所导致的差分代价损失,甚至获得了3.5dB的性能增益。优化后的卷积码与IEEE 802.11n协议中给定的卷积码相比,获得了大约0.3dB的信噪比增益,和第3代合作伙伴计划(3rd generation partnership project,3GPP)长期演进(long term evolution,LTE)协议中的Turbo码相比,有大约1.1dB的性能增益。

In digital communications, 90° or 180° phase ambiguity between the receiver and transmitter car rier is a serious problem for the coherent demodulation. To remove their phase ambiguity, differential quadra ture phase shift keying （DQPSK） is proposed at the cost of a remarkable 2. 3 dB performance degradation. Based on the iterative decoding （ID） scheme, an efficient joint convolutional code （CC）coded DQPSK method is proposed to close the gap between quadrature phase shift keying （QPSK） and DQPSK. Using the extrinsic in formation transfer （EXIT） chart technique, the generator polynomial of the convolutional code is optimized. Simulation results show out that the proposed differential encoding method can overcome the phase ambiguity, and achieve a 3. 5 dB signalto noise ratio （SNR） per bit gain compared with the CCQPSK scheme by ID. Through optimization algorithm, the CC with an optimized generator polynomials outperforms the CC used in IEEE 802. lln protocol by 0.3 dB, and by 1. I dB compared with the Turbo code in the 3rd generation partner ship project long term evolution （3GPP LTE） protocol.