Orthogonally-Filled Subframes for Optimum Operation of Co-Channel LTE HetNets
10 June 2014
In heterogeneous cellular networks (HetNets) for mobile communications, small cells (SC) are deployed within the coverage range of primary macro cells (MC) to provide for a localized capacity boost in traffic hotspots. Focusing on co-channel SC deployments in which the SCs reuse the communication channels of the hosting MCs, we show that the performance of LTE control signaling, the main performance bottleneck under inter-tier interference due to an inflexible and interference-unaware resource allocation, can be significantly improved by optimizing the seeds of the employed pseudo-random mapping algorithms - the physical cell identity (PCI) and user radio network temporary identifier (RNTI). The generalized proposal of orthogonally-filled subframes (OFS) is compliant with the LTE standards and formulated based on the notion of power-controlling UE-specific PDCCH channels. Simulations of a 3GPP-compliant HetNet deployed in Dublin show that configuring OFSs allows extending the SC coverage range up to 3-times, i.e. offload better the MC traffic, while guaranteeing the control channel reliability as well as a better capacity/fairness compared to the standardized subframe-blanking approaches. OFSs also enable high-load voice-over-LTE applications thanks to their ability of increasing the control-channel capacity up to 8-times.
