A novel power control scheme for macro-pico heterogeneous networks with biased association

In this work, a heterogeneous network with low power pico nodes overlaid in macro cell coverage area is considered. Biased association is used at picos to achieve load balancing, which results in cell range expansion (CRE). The user equipments (UEs) in CRE region will associate to a weak pico node and experience severe interference from macro eNodeB. Blanking subframes at macro, coupled with scheduling pico CRE users in these protected subframes has been introduced in the LTE-Advanced standard to protect the CRE UEs from macro interference. This considerably improves the performance of CRE UEs at the cost of macro resources and additional macro-pico signalling overhead. It is also proposed to reduce the transmit power of macro instead of blanking in order to avoid the loss of resources. In this paper, a power control scheme that adapts the transmit power of each pico independently in some subframes based on the requirement of CRE UEs is proposed. The system simulation results show that the proposed scheme achieves better performance for both macro UEs and pico CRE UEs compared to when macro transmit power is reduced, even while utilizing all the resources at macro and without any additional signalling between macro and pico nodes.