Joint Transmitter and Receiver Energy Minimization in Multiuser OFDM Systems

TL;DR

This paper addresses energy minimization in multiuser OFDM systems by formulating a weighted problem, analyzing extreme cases, and proposing a hybrid scheme that balances energy use between base stations and mobile terminals.

Contribution

It introduces a flexible energy minimization framework with novel hybrid multiple access schemes, including the TS-OFDMA, which generalizes existing methods.

Findings

D-TDMA is optimal for receiver energy minimization at mobile terminals.

OFDMA is optimal for transmitter energy minimization at the base station.

TS-OFDMA offers a flexible tradeoff between BS and MT energy consumption.

Abstract

In this paper, we formulate and solve a weighted-sum transmitter and receiver energy minimization (WSTREMin) problem in the downlink of an orthogonal frequency division multiplexing (OFDM) based multiuser wireless system. The proposed approach offers the flexibility of assigning different levels of importance to base station (BS) and mobile terminal (MT) power consumption, corresponding to the BS being connected to the grid and the MT relying on batteries. To obtain insights into the characteristics of the problem, we first consider two extreme cases separately, i.e., weighted-sum receiver-side energy minimization (WSREMin) for MTs and transmitter-side energy minimization (TEMin) for the BS. It is shown that Dynamic TDMA (D-TDMA), where MTs are scheduled for single-user OFDM transmissions over orthogonal time slots, is the optimal transmission strategy for WSREMin at MTs, while OFDMA is optimal for TEMin at the BS. As a hybrid of the two extreme cases, we further propose a new multiple access scheme, i.e., Time-Slotted OFDMA (TS-OFDMA) scheme, in which MTs are grouped into orthogonal time slots with OFDMA applied to users assigned within the same slot. TS-OFDMA can be shown to include both D-TDMA and OFDMA as special cases. Numerical results confirm that the proposed schemes enable a flexible range of energy consumption tradeoffs between the BS and MTs.