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An Optimization Approach to Joint Cell, Channel and Power Allocation in Multicell Relay Networks
KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
2012 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 11, no 8, 2868-2875 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, we consider joint resource allocation of a multicell OFDMA-based networks, with fixed two-hop decode-and-forward relay stations. A joint cell, channel and power allocation problem is formulated as an overall optimization problem, where the objective is to maximize the minimum user throughput. Based on previous complexity results for the setting without relays, the overall optimization problem is shown not to be approximable, unless P is equal to NP. We propose a method for solving this challenging problem. First, a feasible cell allocation is obtained, either via greedy allocation or an exhaustive search. Thereafter, the channel and power allocations are alternately updated, either using a heuristic or optimization-based approach while holding the other two allocations fixed. These alternating channel and power allocations are repeated until no further improvement is obtained. The impact of relay stations is investigated by considering a model with relays as well as one without relays. The simulations show that substantial performance improvement can be made by introducing relays. They also indicate, somewhat surprisingly, that the heuristic channel allocation leads to better overall solutions than the corresponding optimization approach in the relay setting. The optimization-based power allocation significantly outperforms the heuristic power approach with as well as without relay stations.

Place, publisher, year, edition, pages
2012. Vol. 11, no 8, 2868-2875 p.
Keyword [en]
OFDMA, decode and forward relays, channel allocation, NP-hard; optimization
National Category
Computational Mathematics
URN: urn:nbn:se:kth:diva-40403DOI: 10.1109/TWC.2012.062012.111616ISI: 000307904600019ScopusID: 2-s2.0-84865384493OAI: diva2:441107

QC 20120928. Updated from manuscript to article in journal.

Available from: 2011-09-14 Created: 2011-09-14 Last updated: 2012-09-28Bibliographically approved
In thesis
1. Optimization of Joint Cell, Channel and Power Allocation in Wireless Communication Networks
Open this publication in new window or tab >>Optimization of Joint Cell, Channel and Power Allocation in Wireless Communication Networks
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis we formulate joint cell, channel and power allocation problems within wireless communication networks. The objectives are to maximize the user with mini- mum data throughput (Shannon capacity) or to maximize the total system throughput, referred to as the max-min and max-sum problem respectively. The complexity is stud- ied together with proposed optimization- and heuristic-based approaches.

In the first paper an overall joint cell, channel and power allocation max-min prob- lem is formulated. We show that the decision problem is NP-hard and that the op- timization problem is not approximable unless P is equal to NP, for instances with a sufficiently large number of channels. Further, it follows that for a feasible binary cell and channel allocation, the remaining continuous power allocation optimization problem is still not approximable unless P is equal to NP. In addition, it is shown that first-order optimality conditions give global optimum of the single channel power al- location optimization problem, although the problem is in general not convex.

In the following two papers heuristics for solving the overall problem are proposed. In the second paper we consider the single channel problem with convex combinations of the max-min and the max-sum objective functions. This variable utility provides the ability of tuning the amount of fairness and total throughput. The third paper investi- gates the multiple channel setting. On a system with three cells, eight mobile users and three channels, we perform an exhaustive search over feasible cell and channel alloca- tions. The exhaustive search is then compared to the less computationally expensive heuristic approaches, presenting potential earnings to strive for. A conclusion is that several of the proposed heuristics perform very well.

The final paper incorporates fixed relay stations into the overall joint cell, channel and power allocation max-min problem. The complexity is inherited from the formula- tion without relay stations. Further, we propose a heuristic channel allocation approach that shows good performance, compared to an optimization based approach, in numer- ical simulations on the relay setting.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2011. xxiv, 20 p.
Trita-MAT. OS, ISSN 1401-2294 ; 11:05
Wireless multicell networks, Optimization, OFDMA, Shannon capacity, Complexity, NP-hard, Relays, Allocation problems, Heuristic algorithms
National Category
Computational Mathematics Communication Systems Telecommunications
urn:nbn:se:kth:diva-40274 (URN)978-91-7501-084-7 (ISBN)
Public defence
2011-10-07, D3, Lindstedtsvägen 5, KTH, Stockholm, 10:00 (English)
Financial support by the Swedish Foundation for Strategic Research (SSF) QC 20110915Available from: 2011-09-15 Created: 2011-09-14 Last updated: 2011-09-15Bibliographically approved

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