Diversity-Multiplexing Tradeoff of the Two-User X-Channel with Two Antennas

Abstract

Besides maximizing multiplexing gain, improving diversity is important for reliable communications in the presence of interference. In this context, on-off switched interference alignment (IA) is investigated, where IA is intermittently utilized by switching IA on/off in order to improve diversity gain in an interference channel and hence to maximize diversity multiplexing tradeoff (DMT). This paper adopts Alamouti coding based IA for the on-off switched IA, which requires only local channel state information at the transmitter. Optimizing the portion of IA utilization of the proposed scheme in closed form, we derive the achievable DMT and show that the intermittent utilization of IA with simultaneous non-unique decoding can improve DMT in the 2-user X-channel with two antennas. The proposed scheme, to the best of our knowledge, surpasses any other existing schemes for the 2-user X-channel with two antennas and is closed to the ideal DMT.