On the Delay-Energy Tradeoff in Multiuser Fading Channels

Prasanna Chaporkar,Kimmo Kansanen,Ralf R Müller

doi:10.1155/2009/198903

Abstract

We consider the delay-energy tradeoff on a fading channel with multiuser diversity. For fixed arbitrary rates of the users, the total transmitted energy is minimized subject to a delay constraint. To achieve this goal we propose a scheme which schedules a subset of all users simultaneously. The scheduled users are allocated power to guarantee successful separation at the detector by successive decoding. In this way, we can benefit from both multiuser diversity and the near-far situation via scheduling and simultaneous transmission, respectively. We analytically show that when the number of users goes to infinity the energy required to guarantee the required user rates can be made as small as required at the cost of a higher delay "delay-energy tradeoff". We explicitly compute the delay under the proposed scheduling policy and discuss how delay differentiation can be achieved. We extend the results to multiband multiaccess channel. Finally, all the results can be generalized in a straightforward fashion to broadcast channel due to the Gaussian multiaccess-broadcast channel duality.

Highlights

A comprehensive treatment of multiaccess fading channels can be found in [1, 2]
Tse and Hanly have characterized the so-called throughput capacity and delay-limited capacity of the multiaccess block fading channel with Gaussian noise assuming that perfect channel state information (CSI) is causally available at the transmitters and the receiver
In Theorem 4.6 we show that the asymptotic energy efficiency of Δ∗(κ) decreases monotonically with κ

Summary

Introduction

A comprehensive treatment of multiaccess fading channels can be found in [1, 2]. In these papers, Tse and Hanly have characterized the so-called throughput capacity and delay-limited capacity of the multiaccess block fading channel with Gaussian noise assuming that perfect channel state information (CSI) is causally available at the transmitters and the receiver. The throughput capacity region quantifies the achievable rate region with average power constraint for ergodic fading. For the delay limited capacity, each user must be given the required rate irrespective of its fading state. Slot refers to the time duration required to transmit a block of symbols over which the fading state remains unaltered. The slot duration is smaller than the channel coherence time

Objectives

Discussion

Conclusion