'Institute of Electrical and Electronics Engineers (IEEE)'
Abstract
This paper proposes a very simple, near capacity achieving coding scheme for an amplify-and-forward two-way relaying system with imperfect side information, in which two sources communicate with their respective destinations with the help of one relay. To avoid heavy computational complexity at the destinations, we assume a very short memory convolutional code. At the destinations iterative decoding between Joint-over- Antennas (JA) demapper and channel decoder is used to separate and decode the two signals. We present extrinsic information transfer (EXIT) chart analysis of the system. It is shown that demapper and decoder EXIT curves intersect each other before (1, 1) mutual information (MI) point, causing an error floor in the bit-error-rate (BER) performance. With a rate-1 doped accumulator (D-Acc) following the short memory convolutional encoder via an interleaver, the demapper curve and the decoder curve match very well, and the convergence tunnel opens until the (1,1) MI point, and thus the error floor can be completely removed. Simulations were conducted in two cases: without side information, and with imperfect side information. Simulation results show that in case of no side information turbo cliff happens at 1.25 dB away from the Shannon limit of a single link. With the help of side information, cliff happens at a value of received signal-to-noise power ratio even closer to the limit
