Quasi-cyclic LDPC-coded signal space diversity with precoding over fading channels

Signal space diversity (SSD) has been viewed as a very efficient method to increase the diversity order and the reliability of wireless transmission over fading channels. The LDPC code can provide powerful error protection. The quasi cyclic structure which has significant advantage for memory efficiency, facilitates encoder and decoder implementation through shift register based circuits. The combination of quasi-cyclic LDPC codes and SSD is an effective technique to improve the performance of communication system for fading channel. This paper discusses a signal space diversity with a precoder by adding a simple encoder before applying the rotation matrix that can be viewed as a SSD with rate below 1. We propose three design criteria and two implementation method. And we further consider a quasi-cyclic LDPC-coded signal space diversity with precoding and their rate reallocation between channel coding and SSD. The simulation results show that our scheme outperforms the conventional coded-SSD over the fading channel when we get a better rate allocation that depends on the specific channel coding.