On the Degrees-of-Freedom of the Large-Scale Interfering Two-Way Relay Network

Achievable degrees-of-freedom (DoF) of the large-scale interfering two-way relay network is investigated. The network consists of $K$ pairs of communication nodes (CNs) and $N$ relay nodes (RNs). It is assumed that $K\ll N$ and each pair of CNs communicates with each other through one of the $N$ relay nodes without a direct link between them. Interference among RNs is also considered. Assuming local channel state information (CSI) at each RN, a distributed and opportunistic RN selection technique is proposed for the following three promising relaying protocols: amplify--forward, decode--forward, and compute--forward. As a main result, the asymptotically achievable DoF is characterized as $N$ increases for the three relaying protocols. In particular, a sufficient condition on $N$ required to achieve the certain DoF of the network is analyzed. Through extensive simulations, it is shown that the proposed RN selection techniques outperform conventional schemes in terms of achievable rate even in practical communication scenarios. Note that the proposed technique operates with a distributed manner and requires only local CSI, leading to easy implementation for practical wireless systems.