Forwarding interfering signals in wireless ad hoc networks under MRC receiver processing

Abstract

Cooperation in wireless networks is embraced today both from cellular and device-to-device (D2D) communication standards. The reason is that this communication paradigm offers much-needed improvements in the spectral efficiency of wireless communication. Its foundation is the cooperation between nodes that are physically in close proximity. This means that it can fit very well in modern networks that are characterized by increased densities of both infrastructure and users. However, higher node density and higher number of opportunities for cooperation means also more interference. In this paper we investigate the potential throughput gain in a densely deployed interference-limited wireless network when the nodes cooperate. We consider a simple cooperative protocol that allows the relays to overhear the interfering signals and then they amplify and forward (AF) the received composite signal. We consider that the final destination employs maximum ratio combining (MRC) of the directly received signal and the forwarded interference. Given the previous protocol and decoding algorithm, we formulate the problem of link scheduling and cooperative interference forwarding (LSCIF) as a mixed integer non-linear program (MINLP) that is solved numerically. In the proposed problem formulation the aggregate signal-to-interference ratio (SIR) expression is decomposed into two separate SIR constraints. In practice this means that the signal that is received at a relay is allowed to be forwarded (the relay link is scheduled) even if the SIR of this particular signal is below the level that the final receiver can decode. Results are presented for the optimal solution and a polynomial time approximation algorithm for different traffic loads, number of relays, and demonstrate significant performance gains. © 2015 IEEE.