Adaptive resource allocation in multiuser OFDM systems with proportional rate constraints

Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless local area network (LAN) systems. The sum capacity of MU-OFDM is maximized when each subchannel is assigned to the user with the best channel...

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Bibliographic Details
Published in:IEEE transactions on wireless communications Vol. 4; no. 6; pp. 2726 - 2737
Main Authors: Zukang Shen, Andrews, J.G., Evans, B.L.
Format: Journal Article
Language:English
Published: New York IEEE 01.11.2005
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects:
Algorithms
Allocations
AWGN
Bit error rate
Cellular networks
Channel capacity
Downlink
dynamic resource allocation
Linear programming
Local area networks
Maximization
multiuser OFDM
OFDM
Optimization
Orthogonal Frequency Division Multiplexing
proportional fairness
Resource allocation
Resource management
Studies
Time division multiple access
water-filling
Wireless communication
Wireless LAN
ISSN:1536-1276, 1558-2248
Online Access:Get full text
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Summary:Multiuser orthogonal frequency division multiplexing (MU-OFDM) is a promising technique for achieving high downlink capacities in future cellular and wireless local area network (LAN) systems. The sum capacity of MU-OFDM is maximized when each subchannel is assigned to the user with the best channel-to-noise ratio for that subchannel, with power subsequently distributed by water-filling. However, fairness among the users cannot generally be achieved with such a scheme. In this paper, a set of proportional fairness constraints is imposed to assure that each user can achieve a required data rate, as in a system with quality of service guarantees. Since the optimal solution to the constrained fairness problem is extremely computationally complex to obtain, a low-complexity suboptimal algorithm that separates subchannel allocation and power allocation is proposed. In the proposed algorithm, subchannel allocation is first performed by assuming an equal power distribution. An optimal power allocation algorithm then maximizes the sum capacity while maintaining proportional fairness. The proposed algorithm is shown to achieve about 95% of the optimal capacity in a two-user system, while reducing the complexity from exponential to linear in the number of subchannels. It is also shown that with the proposed resource allocation algorithm, the sum capacity is distributed more fairly and flexibly among users than the sum capacity maximization method.
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ISSN:1536-1276
1558-2248
DOI:10.1109/TWC.2005.858010