Sharpe ratio for joint user association and subcarrier allocation design in downlink heterogeneous cellular networks

Abstract

This paper considers a user association (UA) design for the base station (BS) and subcarrier (SC) allocation where a BS allocates different number of SCs to different users associated to it in a downlink heterogeneous cellular network. In jointly optimising the UA and SC allocation, we propose to use the Sharpe Ratio as the utility function for the optimisation objective. The Sharpe ratio is defined as the ratio between the mean of user achievable rates to its standard deviation. With this objective, the achieved user rates will be closer to each other, leading to a fair network access. To reduce the computational complexity of the solution, a simplified method based on binary Belief Propagation (BP) algorithm is proposed. Simulation results show that the achievable user rates are doubled in comparison with other schemes. The low computational complexity of the proposed method is achieved through BP solver by reducing the edges of the factor graph.