Spatially coupled repeat-accumulate coded cooperation

In this paper, a new coded cooperation scheme called spatially coupled repeat-accumulate coded cooperation (SC-RA-CC) is proposed for multiple access channels (MAC) with a large number of users and one common destination. The proposed approach combines two advantages of repeat-accumulate (RA) codes and spatial coupling. RA codes show the superior decoding performance with the simple encoding and spatial coupling exhibits the so-called threshold saturation behavior; the threshold of coupled codes with sub-optimal belief propagation (BP) decoding asymptotically achieves the optimal maximum a posterior (MAP) decoding threshold. Our SC-RA-CC can be considered as the distributed version of spatially coupled repeat-accumulate codes which provide the higher spatial diversity and coding gain when both the number of users and the size of packets are limited. The performance of the proposed coded cooperation is analyzed via density evolution (DE). Numerical results confirm that SC-RA-CC can efficiently obtain even higher diversity and coding gain than both direct transmission and conventional adaptive network coded cooperation (ANCC).