Coordination of regenerative relays and direct users in wireless cellular networks

The area of wireless cooperation/relaying has recently been significantly enriched by the ideas of wireless network coding (NC), which bring substantial gains in spectral efficiency. These gains have mainly been demonstrated in scenarios with two-way relaying. Inspired by the ideas of wireless NC, recently we have proposed techniques for coordinated direct/relay (CDR) transmissions. These techniques embrace the interference among the communication flows to/from direct and relayed users, leveraging on the fact that the interference can be subsequently canceled. Hence, by allowing simultaneous transmissions, spectral efficiency is increased. In our prior work, we have considered CDR with non-regenerative relay that uses Amplify-and-Forward (AF). In this paper we consider the case of regenerative Decode-and-Forward (DF) relay. This refers also to joint decoding of the interfering flows received over a multiple-access channel. Our analysis shows that the assumption of regenerative relaying brings new parametrization of the CDR schemes, such that the the transmission times used by each node are subject to optimization. We show how these parameters should be chosen if the sum-rate needs to be optimized. Our results confirm the high gains in spectral efficiency over the reference schemes.