554 IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. 61, NO. 2, FEBRUARY 2013 On Asymmetric Interference Channels with Cooperating Receivers Hieu T. Do, Student Member, IEEE, Tobias J. Oechtering, Senior Member, IEEE, and Mikael Skoglund, Senior Member, IEEE Abstract—This paper studies a model for communications in wireless networks supported by designated cooperation links. In particular, a 2-user Gaussian one-sided interference channel with two rate-limited and orthogonal communication links between the receivers is considered. A communication protocol for the channel is proposed, which combines rate-splitting and superpo- sition encoding techniques with the conventional decode-forward and compress-forward strategies. It is shown that a careful design of codebooks and coding scheme, which is obtained from intuition based on superposition coding, can greatly reduce the complexity of the strategy. Analytical and numerical results show that the proposed scheme, although not universally optimal, can achieve the capacity region or sum capacity exactly or asymptotically in certain scenarios. Various limits of sum capacity gain due to cooperation are also discussed. Index Terms—Interference networks, receiver cooperation, multi-cell communication, coordinated multipoint, backhaul. I. I NTRODUCTION A one-sided interference channel [1] is a model for a communication scenario with two transmitter–receiver pairs, where only one receiver is affected by interference. In this work, we extend the model by allowing the two receivers to cooperate through designated cooperation links, which neither interfere with each other nor with the main channel. We call this channel the Asymmetric Interference Channel with Receiver Cooperation (AIC-RC). As a special case of the classical 2-user interference chan- nel, where both receivers suffer from interference from the unintended transmitter, the one-sided interference channel has been studied for many years. On the one hand, this channel model is motivated by relevant situations in wireless and wireline networks where the interference/crosstalk to one receiver is blocked or is made negligible by barriers or by distance. One such example is when a mobile terminal in a cellular network is located at the cell edge, as shown in [2]. Another situation is when there exists a barrier between one transmitter and one receiver in the satellite (line of sight) Manuscript received November 23, 2011; revised July 11 and August 25, 2012. The associate editor coordinating the review of this paper and approving it for publication was V. Stankovic. This work was funded in part by the Swedish Research Council (VR) and the Swedish Foundation for Strategic Research (SSF). The authors are with the School of Electrical Engineering and the ACCESS Linnaeus Center at KTH Royal Institute of Technology, Stockholm, Sweden (e-mail: {hieu.do, tobias.oechtering, mikael.skoglund}@ee.kth.se). The material in this paper was presented in part at the 47th Allerton conference on Communication, Control, and Computing, 2009, and at the IEEE ICC 2010. Digital Object Identifier 10.1109/TCOMM.2013.010913.110799 communication. On the other hand, the existing work on the one-sided interference channel has helped shed light on the general interference channel. This is because removing one interference link leads to an upper bound on the capacity region of the interference channel while knowing how to mitigate the remaining interference provides insight into how to construct codes to approach the capacity. Despite its simpler structure compared to the general interference channel, the capacity region of the one-sided interference channel is still unknown in general. Only limited results have been obtained for the capacity region and the sum capacity or maximum throughput [3]. Recently, with the advances of cooperative communications, especially new results for the relay chan- nel, the study of interference channels with some forms of cooperation has drawn increasing interest. For example, the interference channel with cooperative transmitters has been thoroughly studied in [4]–[7], while [2], [4], [8]–[10] study the cooperation at the receivers’ side. The cooperation can occur either in the same spectral resource with the main channel, namely in-band cooperation [4], [9], or in an orthogonal spectral resource with the main channel, namely orthogonal or out-of-band cooperation [8], [10]. In the present paper, we consider the Gaussian one-sided interference channel in which both receivers can exchange information over rate-limited cooperation links. We focus on cooperation links modeled as orthogonal spectral resources which are reserved for the purpose of cooperation, i.e., out- of-band cooperation. For example, the base stations in a cellular network can be connected by wireline backhaul links or by microwave channels whose rates are pre-allocated and guaranteed. Another scenario is when wireless receiving nodes are close enough to each other to be able to establish reliable cooperation links. As such, the channel under consideration can be regarded as an element in the Wyner’s asymmetric cellular model or Wyner’s soft-handoff model for multi-cell communications in wireless cellular networks, see [2], [11]– [15] and references therein. A. Summary of Results The paper’s main results are summarized as follows: 1. We propose a communication scheme which is built upon the coding techniques for: i) the interference channel, i.e., rate-splitting technique; ii) the broadcast channel, i.e., superposition coding; and iii) for the relay channel, i.e., compress-forward and decode-forward. It is shown that by careful design of codebooks and encoding/decoding strategies, 0090-6778/13$31.00 c  2013 IEEE