Performance Analysis of Interference Penalty Algorithm for LTE Uplink in Heterogeneous Networks

Heterogeneous networks (Hetnets) introduce an imbalance between downlink and uplink because the downlink transmit powers of the macro and pico eNodeBs can differ by as much as 16 dB. However, the user equipment (UE)´s maximum uplink transmit power is the same regardless of whether the UE is connected to the macro or the pico eNodeB. The uplink throughput performance depends both on the SINR that the UEs see and the number of PRBs that each UE can get allocated. Due to the difference in the transmit powers of the eNodeBs, the number of UEs that attach to the pico eNodeB is typically smaller than the number that attach to the macro eNodeB. In this work, we consider these impacts and optimize the power control settings of the macro and pico UEs so that the cell-edge and average UE throughput are improved. We study the performance under two different power control schemes: Fractional Power Control (FPC) and Interference Penalty Algorithm (IPA). Using simulations, we study the impact of various parameter settings on the performance of IPA. Based on our studies, we can conclude that the macro UE´s transmit power needs to be larger than that of the pico UE to overcome the larger number of UEs attaching to the macro eNodeB. We also study the impact of imperfect knowledge of neighbor cell path losses on the uplink performance of IPA.