Cooperative communications is a well known technique to yield transmit diversity in a multi-user environment. Network coding can increase the spectral efficiency in networks. These two techniques can be combined to achieve a double diversity order for a maximum coding rate Rc = 2/3 on the Multiple Access Relay Channel (MARC), where two sources share a common relay in their transmission to the destination. However, codes have to be carefully designed to obtain the intrinsic channel diversity. Up till now, no full-diversity capacity achieving code for the MARC at a coding rate Rc = 2/3 has been published. We present a strategy to produce excellent low-density parity-check (LDPC) codes with rate 2/3, i.e., exhibiting full-diversity and operating close to the outage probability limit. Simulation of the word error rate performance of the new proposed family of LDPC codes for the MARC confirms the full-diversity
Abstract-In wireless scenarios an effective protocol to increase the reliability for time-varying channels is the hybrid automatic repeat request (H-ARQ). The H-ARQ scheme with cross-packet channel coding (CPC) is a recently published extension of H-ARQ with several advantages. No full-diversity low-density paritycheck (LDPC) code design for the whole range of coding rates yielding full-diversity has been published. In this paper the authors provide a new outage behavior analysis and a new structured LDPC code ensemble achieving full-diversity for H-ARQ with CPC by exploiting the rootcheck principle. Simulation results show that the new code design outperforms the previous approaches, providing full-diversity and good coding gain, also at high coding rates.
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