On Achievability for Downlink Cloud Radio Access Networks with Base Station Cooperation

摘要

This work investigates the downlink of a cloud radio access network (C-RAN)in which a central processor communicates with two mobile users through twobase stations (BSs). The BSs act as relay nodes and cooperate with each otherthrough error-free rate-limited links. We develop and analyze two codingschemes for this scenario. The first coding scheme is based on Liu-Kang schemefor C-RANs without BS cooperation; and extends it to scenarios allowingconferencing between the BSs. Among few other features, our new coding schemeenables arbitrary correlation among the auxiliary codewords that are recoveredby the BSs. It also introduces common codewords to be described to both BSs.For the analysis of this coding scheme, we extend the multivariate coveringlemma to non-Cartesian product sets, thereby correcting an erroneousapplication of this lemma in Liu-Kang's related work. We highlight key aspectsof this scheme by studying three important instances of it. The second codingscheme extends the so-called compression scheme that was originally developedfor memoryless Gaussian C-RANs without BS cooperation to general discretememoryless C-RANs with BS cooperation. We show that this scheme subsumes theoriginal compression scheme when applied to memoryless Gaussian C-RAN models.In the analysis of this scheme, we also highlight important connections withthe so-called distributed decode--forward scheme, and refine the approximatecapacity of a general $N$-BS $L$-user C-RAN model in the memoryless Gaussiancase.