Leveraging the D2D-gain: Resource efficiency based mode selection for device-to-device communication

It has been postulated in literature that three gain types are introduced into the radio access part of cellular networks by device-to-device communication, namely the proximity gain, hop gain and reuse gain. These gain types have further been shown to be captured by a resource efficiency metric. We investigate the influence of mode selection and scheduling on the resource efficiency gains in the D2D overlay case. We formulate mode selection as a resource efficiency maximization problem and find that for proper mode selection, the achieved resource efficiencies of schedulers must be anticipated correctly. Because this is very complex, we propose a simple, channel state based mode selection scheme and investigate how well it performs using different schedulers. We show that our proposed scheme is optimal for schedulers that do not leverage frequency diversity and optimizes a tight lower bound for those that do leverage diversity. Simulations show that in any case, our scheme produces higher D2D-gains than the state of the art.