Achievable sum-rate of the two-user Gaussian interference channel through rate-splitting and successive decoding

Most coding schemes, proposed for the interference channel, take advantage of joint decoding to achieve a larger rate region. However, joint decoding significantly increases decoding complexity. This paper investigates the achievable sum-rate of the two-user Gaussian interference channel when successive decoding is employed instead of joint decoding. First, this study proves that when interference is strong and the powers of the transmitters satisfy certain conditions, the sum-capacity can be achieved by successive decoding. The number of the required splits, the amount of power allocated to each split, and the order of decoding at receivers are explicitly determined. Moreover, the maximum sum-rate loss when simultaneous non-unique decoding is replaced by successive decoding is characterized. Second, it is proved that successive decoding achieves the sum-rate of simultaneous non-unique decoding, when interference is weak and the powers of the transmitters satisfy certain conditions. Rate-splitting is shown to be beneficial, if the powers of the transmitters are greater than a threshold. However, when the powers are below the threshold, still single-split successive decoding can achieve the sum-capacity.