Improving Energy Efficiency Through Multimode Transmission in the Downlink MIMO Systems

TL;DR

This paper proposes an adaptive mode switching strategy for downlink MIMO systems that optimizes energy efficiency by adjusting bandwidth, power, and transmission schemes, considering imperfect channel information.

Contribution

It introduces a novel ergodic capacity based mode switching method that enhances energy efficiency in MIMO systems with imperfect CSIT, including optimal parameter derivation and capacity estimation strategies.

Findings

Mode switching significantly improves energy efficiency.

Optimal parameters depend on scenario-specific conditions.

Capacity estimation strategies effectively handle imperfect CSIT.

Abstract

Adaptively adjusting system parameters including bandwidth, transmit power and mode to maximize the "Bits per-Joule" energy efficiency (BPJ-EE) in the downlink MIMO systems with imperfect channel state information at the transmitter (CSIT) is considered in this paper. By mode we refer to choice of transmission schemes i.e. singular value decomposition (SVD) or block diagonalization (BD), active transmit/receive antenna number and active user number. We derive optimal bandwidth and transmit power for each dedicated mode at first. During the derivation, accurate capacity estimation strategies are proposed to cope with the imperfect CSIT caused capacity prediction problem. Then, an ergodic capacity based mode switching strategy is proposed to further improve the BPJ-EE, which provides insights on the preferred mode under given scenarios. Mode switching compromises different power parts, exploits the tradeoff between the multiplexing gain and the imperfect CSIT caused inter-user interference, improves the BPJ-EE significantly.