Energy and Spectral Efficiency Gains From Multi-User MIMO-based Small Cell Reassignments

TL;DR

This paper explores reassigning UEs between small cells to leverage MU-MIMO for spectral efficiency and energy savings, formulating the problem as a set covering optimization and demonstrating significant benefits in LTE scenarios.

Contribution

It introduces a novel MU-MIMO-based reassignment strategy for small cells, optimizing energy efficiency and spectral gains through a set covering formulation.

Findings

Significant reduction in active small cell base stations.

Increased spectral efficiency in LTE scenarios.

Effective energy savings through cell sleep modes.

Abstract

In this work we investigate the reassignment of User Equipments (UEs) between adjacent small cells to concurrently enable spatial multiplexing gains through Multi-User MIMO (MU-MIMO) and reductions in energy consumption though switching emptied small cells to a sleep state. We consider a case where UEs can be reassigned between adjacent small cells provided that the targeted neighbouring cell contains a UE with which the reassigned UE can perform MU-MIMO without experiencing excessive multi-user interference, and whilst achieving a minimum expected gain in spectral efficiency over the previous original cell transmissions as a result. We formulate the selection decision of which UEs to reassign as a set covering problem with the objective of maximising the number of small cell base stations to switch to a sleep state. Our results show that, for both indoor and outdoor LTE small cell scenarios, the proposed MU-MIMO-based reassignments achieve significant reductions in the required number of active small cell base stations, whilst simultaneously achieving increases in spectral efficiency.