Design and optimization of joint network-channel LDPC code for wireless cooperative communications

In this paper, we develop a joint design method of network-channel low density parity check codes (LDPC) codes by constructing joint network-channel parity check matrix. Random network coding is performed to provide side information for both the source and relay¿s transmission. This system matrix makes an easy way to collect all independent signal copies to provide a spatial diversity gain. And the complexity of network coding is linear to the block length ~O(n). Then, the optimization of joint network-channel LDPC code is conducted in term of maximizing the system rate. Based on the joint network-channel LDPC codes, we presents a protocol for wireless cooperative communications, which is very effective to combat the channel fading without much rise in system bandwidth and transmitting power. A traditional three-node model is built to describe the protocol where relay not only helps source to transmit but also has its own information to transmit.