Intra-Tier Interference Management using Massive MIMO for Spatial Channel Correlation with Pilot Contamination in HetNet

Heterogeneous Network (HetNet) is a cochannel deployment of macro base stations (mBSs) with very large antenna arrays as massive MIMO (Multiple Input Multiple Output) and a secondary tier of small cells (SCs) with a few antennas utilizing a synchronized time division duplexing (TDD) protocol in the network. The TDD protocol is a key enabler for a HetNet to provide ubiquitous coverage and unprecedented spectral area efficiencies in the network. The channel reciprocity in the proposed system enables not only the estimation of large-dimensional channels at the BSs, but also an implicit coordination between both tiers without the need to exchange user data or channel state information (CSI) over the backhaul. In the spatial channel correlation with pilot contamination for massive MIMO data transmission, the BSs and SCs suffer from dominant interference sub-space in the network. In order to overcome the problem in the HetNet, transmit precoding and different receive combining schemes are proposed to reduce the inta-tier interference in the network. The Least Square(LS) channel estimator for uplink (UL) and downlink (DL) increases an estimation quality, and UL and DL Spectral Efficiency (SE) based on channel estimation is implemented in the proposed system for improving Quality of Service (QoS) in the HetNet. The simulation results for SE in various receive combining schemes with trasmit precoding are implemented to increase the SE and reduce the intra-tier interference in the HetNet.