Virtual-Soft-Handoff-Enabled Dominant Interference Cancellation for Enhanced Uplink Performance in Heterogeneous Cellular Networks

Heterogeneous cellular networks comprising overlays of macro-cells and small metro-cells are susceptible to excessive interference on the uplink because of the asymmetry between the uplink and downlink signal strengths. While soft handoffs can be used to mitigate this problem, existing methods applied in homogeneous macro-cellular deployments rely on more symmetric coverage in both directions and are not as beneficial in asymmetric coverage scenarios. In this paper, we propose a novel cooperative uplink reception scheme called "Virtual Soft Handoff (VSHO)" that enables cells suffering excessive interference to cancel out-of-cell interference or decode out-of-cell users in close proximity by canceling in-cell interference, leading to significant improvement in spectral efficiency and cell-edge throughput. As an important side benefit, virtual soft handoffs also enable users served by macrocells to benefit from selection diversity, leading to further improvement in system performance. Keywords- Heterogeneous Networks, Handoffs, Soft Handoffs, Interference Cancellation, Selection Diversity. I. INTRODUCTION Wireless cellular networks with asymmetry between uplink and downlink signal strengths are susceptible to performance problems related to excessive interference. Such asymmetry is particularly pronounced in heterogeneous networks comprising large macro cells and small metro cells. Typically, the radius of a macro cell, based on its downlink signal strength, is much larger than the radius of a metro cell.