A Joint Network Coding and Device Association Design for Optimal Local Data Exchange in Fiber-Wireless Access Network

For many emerging mobile broadband services and applications, the source and destination are located in the same local region. Consequently, it is very important to design access networks to facilitate efficient local data exchange. In the past few years, most existing studies focus on either the wired or wireless domains. In this paper, we aim to exploit both the wired and wireless domains. Specifically, we consider a fiber-wireless access network in which a passive optical network (PON), consisting of one optical line terminal and multiple optical network units (ONUs), connects densely deployed base stations. In such a scenario, we propose two novel access schemes to utilize both network coding and device association in the following two cases: each device can be associated with one ONU for uploading and downloading its data packets; and each device can be associated with two different ONUs for uploading and downloading its data packets, which are referred to as, the network coding design and symmetric device association (NCsDA) problem and the network coding design and asymmetric device association (NCaDA) problem, respectively. To understand the potentials of NCsDA, we first formulate a mixed integer non-linear programming to minimize the weighted number of packet transmissions (WNT), which is related to both the energy consumption and system capacity. We then theoretically analyze the tight upper bounds of the minimal WNT in the PON, which helps us to approximate the NCsDA problem by mixed integer linear programming. We also give theoretical analysis on the NCaDA problem and formulate it as a mixed integer linear programming. Next, we develop efficient algorithms based on linear programming relaxation and give network coding designs to solve the NCsDA problem and the NCaDA problem. To validate our design, we conduct extensive simulations, which demonstrate the impact of important network parameters and the promising potentials of the proposed NCsDA and NCaDA schemes.