On Cooperation and Interference in the Weak Interference Regime
Abstract: Handling interference is one of the main challenges in the design of wireless networks. In this paper, we study the application of cooperation for interference management in the weak interference (WI) regime, focusing on the Z-interference Z channel with a causal ausal relay (Z-ICR), (Z ICR), in which the channel coefficients are subject to ergodic phase fading, all transmission powers are finite, and the relay is fullfull duplex. The phase fading model represents many practical communications systems in which the transmission path impairments mainly affect the phase of the signal, such as non-coherent non coherent wireless communications and fiber optic channels. In order to provide a comprehensive understanding of the benefits of cooperation in the WI regime, we characterize, for the first time, two major performance measures for the ergodic phase fading Z-ICR Z ICR in the WI regime: the sum-rate rate capacity and the maximal generalized degrees-of-freedom degrees freedom (GDoF). In the capacity analysis, we obtain conditions on the channel coefficients, subject to which the sum-rate rate capacity of the ergodic phase fading ZZ--ICR is achieved by treating interference as noise at each receiver, and explicitly state the corresponding sum-rate rate capacity. In the GDoF analysis, we derive conditions on the exponents of the magnitudes magnitudes of the channel coefficients, under which treating interference as noise achieves the maximal GDoF, which is explicitly characterized as well. It is shown that under certain conditions on the channel coefficients, relaying strictly increases both the sum-rate s rate capacity and the