Virtual soft-handoff with resource blanking in Heterogeneous Networks

Heterogeneous Networks (HetNets) comprising overlays of macro-cells and small-cells provide an effective solution to address the ever-increasing capacity demand in mobile networks. However, in co-channel deployments where small cells are placed within the coverage area of high-power macros and operate in the same frequency band, excessive interference between macro and small cell transmissions may limit potential system capacity and cell edge (i.e., 5^th percentile user) performance. For the downlink, partial blanking of macro-cell transmissions has been proposed to mitigate interference but this does not address the uplink interference problem and also leads to under-utilization of the uplink as an undesirable byproduct. In this paper, we address this problem by proposing a class of low-complexity, cooperative interference mitigation schemes referred to as Virtual Soft-Handoff techniques which exploit uplink/downlink asymmetry in selecting the best uplink reception point for each user while mitigating interference. Studies of these techniques show substantial gains in cell-edge throughput (up to 100%) compared to a 3GPP LTE based HetNet while still achieving modest improvements of around 10% in average throughput.