Analytical study on network spectrum efficiency of ultra dense networks

As radio interface approaches its practical capacity limit given limited spectrum resource, network architecture innovation/revolution would play a key role in boosting wireless communication system capacity and improving user experience. Deploying dense small cell networks overlaying the conventional macro cell networks is widely regarded as a key step towards network architecture revolution for improved spectrum and energy efficiency. In this paper, we analytically investigate the spectrum efficiency of densely deployed small cell networks in the downlink using tools from stochastic geometry. Unlike the conventional user-centric link-level spectrum efficiency analysis, we analyze network spectrum efficiency, defined as the average aggregate spectrum efficiency per cell. As the portion of cell-edge users, who would consume more spectrum resource in achieving a target rate, usually outweighs that of the cell-center users, network spectrum efficiency evaluation should count user distribution to portray the network performance as a whole. Based on the network spectrum efficiency results, we are able to find the optimal cell density and the corresponding optimal base station transmit power for achieving a high spectrum efficiency and/or energy efficiency.