Harmonized Cellular and Distributed Massive MIMO: Load Balancing and Scheduling

TL;DR

This paper proposes a harmonized approach for cellular and distributed massive MIMO systems, utilizing load balancing and scheduling to enhance cell-edge performance without extensive channel information exchange.

Contribution

It introduces methods for coordinated operation of distributed and cellular massive MIMO, optimizing resource allocation and scheduling to improve network performance.

Findings

Significant performance gains at cell edges with proposed methods

Distributed MIMO CoMP improves cell-edge throughput

Resource allocation strategies approach optimal efficiency

Abstract

Multi-tier networks with large-array base stations (BSs) that are able to operate in the "massive MIMO" regime are envisioned to play a key role in meeting the exploding wireless traffic demands. Operated over small cells with reciprocity-based training, massive MIMO promises large spectral efficiencies per unit area with low overheads. Also, near-optimal user-BS association and resource allocation are possible in cellular massive MIMO HetNets using simple admission control mechanisms and rudimentary BS schedulers, since scheduled user rates can be predicted a priori with massive MIMO. Reciprocity-based training naturally enables coordinated multi-point transmission (CoMP), as each uplink pilot inherently trains antenna arrays at all nearby BSs. In this paper we consider a distributed-MIMO form of CoMP, which improves cell-edge performance without requiring channel state information exchanges among cooperating BSs. We present methods for harmonized operation of distributed and cellular massive MIMO in the downlink that optimize resource allocation at a coarser time scale across the network. We also present scheduling policies at the resource block level which target approaching the optimal allocations. Simulations reveal that the proposed methods can significantly outperform the network-optimized cellular-only massive MIMO operation (i.e., operation without CoMP), especially at the cell edge.