Two-way spinal codes

In this paper, we propose a rateless two-way spinal code. There exist two encoding processes in the proposed code, i.e., the forward encoding process and the backward encoding process. Rather than the original spinal code, where each message segment only has relationship with the coded symbols corresponding to itself and the later message segments, the information of each message segment of the proposed code is conveyed by the coded symbols corresponding to all the message segments. Based on this two-way coding strategy, we propose an iterative decoding algorithm. Different transmission schemes, including the symmetric transmission and the asymmetric transmission, are also discussed in this paper. Our analysis illustrates that the asymmetric transmission can be treated as a tradeoff between the performance and the decoding complexity. Simulation results show that the proposed code outperforms not only the original spinal code but also some strong channel codes, such as polar codes and raptor codes.