A geometrical approach for power optimization in relay-based cellular networks

Relays are considered as a feasible way to increase coverage and capacity of cellular networks. However, optimization of relay-enhanced networks is still a matter of research. This paper proposes a simple geometrical approach to derive the optimal long-term relay downlink transmit power with the aim of maximizing the average spectral efficiency in a relay-based cellular network. In our model, a User Equipment (UE) is served by the network node from which it receives the highest power. The spectral efficiency at the UE location is maximized when this serving node is also the one that provides the best Signal to Interference Ratio (SIR). Our approach thus consists in setting the relay node (RN) power such that its serving area and its SIR area coincide as much as possible. Results show that our algorithm provides a fine approximation of the optimal RN transmit power under a wide range of RNs location scenarios and propagation parameters.