Pathloss determination of uplink power control for UL CoMP in heterogeneous network

The latest 3GPP LTE release enables coordinated multi-point (CoMP) operation in heterogeneous networks. In this context, a multitude of low power nodes can be deployed within the coverage area of a high-power macro node, allowing to configure different sets of network nodes for the uplink reception from and the downlink transmission to a target mobile terminal. The resulting asymmetry between the uplink composite channel for joint reception and the downlink channel for joint transmission precludes the mobile terminal to accurately estimate the uplink pathloss using standard estimation techniques based on measuring the signal strength of downlink reference signals. In this paper, we introduce the concept of virtual propagation loss for an uplink signal jointly received by multiple geographically separated points. We demonstrate how this new metric can readily be computed at a network controller (.g., the eNodeB in LTE systems), hence enabling a fast correction of the erroneous pathloss estimate at the mobile terminal side through a simple closed-loop feedback for power control. We evaluate our method with extensive system-level simulations, showing that the proposed power control scheme achieves 20% cell-average and 50% cell-edge throughput gain over the LTE Rel.-10.