Optimal relay placement for coverage extension in LTE-A cellular systems

Third Generation Partnership Project (3GPP) Long Term Evolution-Advanced (LTE-A) has considered the deployment of Relay Nodes (RNs) for cost-effective throughput enhancement and coverage extension. The coverage extension (increase in cell radius) depends on the radial position of RNs in the cell. This is because the location of a RN affects the Signal-to-Interference-plus-Noise Ratio (SINR) of the received signal on the evolved-NodeB (eNB)-RN and RN-User Equipment (UE) links. In this paper, we investigate the problem of optimal relay placement for coverage extension in relay assisted LTE-A networks. Since DownLink (DL) and UpLink (UL) transmission scenarios in cellular networks are asymmetrical in terms of coverage (due to discrepancy in maximum transmit power), we consider both DL and UL transmission scenarios for optimal relay placement. In addition, we analyze the problem for the case when interference from neighbouring cells is taken into account.