Bounds on the Capacity of the Multiple Access Diamond Channel with Cooperating Base-Stations

A diamond network is considered in which the central processor is connected, via backhaul noiseless links, to multiple conferencing base stations that communicate with a single user over a multiple access channel. We propose coding techniques along with lower and upper bounds on the capacity. Our achievability scheme uses a common cloud coding strategy based on the technique proposed by Wand, Wigger, and Zaidi (2018) and extends it beyond two relays. Our upper bounds generalize the method proposed by Bidokhti and Kramer (2016) and lead to new bounds for the multiple conferencing relay setting. Specializing our upper bounds to the two relay scenario, we provide new bounds and improve the state-of-the-art.

I. Introduction

As the demand for steadily growing data transmission increases, capacity stands as the main challenge for every emerging generation of mobile networks [1]. In this regard, ultra-dense cell deployment with cooperative operations is expected to become a key technology for enabling modern, reliable, ultra-bandwidth, scalable, and fast communication systems [2]. Initially proposed in [3], C-RAN is an emerging network architecture that enables large-scale cooperation among base stations [4]. As opposed to traditional architectures where radio and baseband processing functionality is solely implemented inside a base station (BS), in C-RAN, the BS performs digital processing, digital to analog conversion, analog to digital conversion, power amplification, and filtering, while baseband processing is performed in a central processor (CP) connected to multiple BSs via finite capacity backhaul links. The characteristic of this architecture makes C-RAN capable of dealing with intensive inter-cell interference in future ultra-dense, multi-tier networks [5]. Comprehensive surveys on C-RAN can be found in [6]–[8]. This work will consider a multi-hop architecture of C-RAN’s downlink with multiple conferencing BSs. Such architecture, which gives an excellent value-for-money, has the potential to provide a very-high capacity gains.