Showing papers in "Wireless Communications and Mobile Computing in 2010"
TL;DR: This paper proposes a novel approach based on a penalty function method and an interior point method (PM/IPM) to solve the joint optimization problem of sub-carrier assignment and power allocation in orthogonal frequency division multiple access (OFDMA) wireless networks.
Abstract: This paper studies a joint optimization problem of sub-carrier assignment and power allocation in orthogonal frequency division multiple access (OFDMA) wireless networks. A major challenge in solving the optimization problem is non-convexity caused by the combinatorial nature of sub-carrier assignment problem and/or non-convex objective functions. To address the combinatorial complexity, we formulate the resource allocation problem as an optimization problem with continuous variables. We propose a novel approach based on a penalty function method and an interior point method (PM/IPM) to solve the problem. In specific, using a two-step implementation, the penalty method is applied first to convert the non-convex feasible region to a convex one. Then, the interior point method is deployed to solve the problem which is non-convex only in the objective function. To evaluate the performance of PM/IPM, we apply a genetic algorithm (GA) that achieves near optimal solutions of the problem by iterative searching. Copyright © 2009 John Wiley & Sons, Ltd.
21 citations
14 citations
TL;DR: Inspired by the unconstrained blind maximum likelihood (UML) decoder, the proposed crite rion is a subspace method that efficiently exploits all the information provided by the STBC structure, as well as by the reduced-rank representation of the MIMO channel.
Abstract: In this paper, a new technique for the blind estimation of fre quency and/or time-selective multiple-input multipleoutput (MIMO) channels under space-time block coding (STBC ) transmissions is presented. The proposed method relies on a basis expansion model of the MIMO channel, which r educes the number of parameters to be estimated, and includes many practical STBC-based transmission scena rios, such as STBC-OFDM, space-frequency block coding (SFBC), time-reversal STBC, and time-varying STBC e ncoded systems. Inspired by the unconstrained blind maximum likelihood (UML) decoder, the proposed crite rion is a subspace method that efficiently exploits all the information provided by the STBC structure, as well a s by the reduced-rank representation of the MIMO channel. The method, which is independent of the specific sig nal constellation, is able to blindly recover the MIMO channel within a small number of available blocks at the rece iv r side. In fact, for some particular cases of interest such as orthogonal STBC-OFDM schemes, the proposed techniq ue blindly identifies the channel using just one data block. The complexity of the proposed approach reduces to the solution of a generalized eigenvalue problem (GEV) and its computational cost is linear in the number of su b-channels. An identifiability analysis and some numerical examples illustrating the performance of the pro posed algorithm are also provided. Copyright c © 2009 John Wiley & Sons, Ltd.
11 citations
9 citations
5 citations
5 citations
TL;DR: Development of communication channels for underwater sensor networks holds many unique challenges as the effects of reflection and refraction affect communication near the bottom of the ocean.
Abstract: Development of communication channels for underwater sensor networks holds many unique challenges. Communication near the bottom of the ocean is no exception as the effects of reflection and refrac...
4 citations
3 citations
TL;DR: In this article, the 3GPP working group proposed the Long-Term Evolution (LTE) system as the 4G mobile communications technology, which reduces the transmission latency in the radio access network.
Abstract: The 3GPP working group proposes the Long-Term Evolution (LTE) system as the 4G mobile communications technology. To reduce the transmission latency in the radio access network, Evolved Universal Te...
3 citations
TL;DR: In this paper, the authors investigated the disaster area communication system using relay assisted wireless network for first responders as mobile nodes (MNs), and a novel mobility model was proposed to descr...
Abstract: This paper investigates the disaster area communication system using relay-assisted wireless network for first responders as mobile nodes (MNs). Firstly, a novel mobility model is proposed to descr...
1 citations
TL;DR: In this paper, the authors used a kernel function to measure the similarities between sensor nodes and then used the kernel matrix to locate the nodes in a wireless sensor network using signal strength.
Abstract: This paper addresses the localization problem in wireless sensor networks using signal strength. We use a kernel function to measure the similarities between sensor nodes. The kernel matrix can be ...
TL;DR: A novel External Route Discovery scheme, Comprehensive External Route Judgment, (CERJ) is proposed and OPNET simulation models are developed to demonstrate the implementability and effectiveness of the proposed schemes.
TL;DR: A computationally efficient and practically deployable adaptive reference code-based multiple access interference (MAI) cancellation scheme, in which the conventional transmitter/receiver architecture is minimally modified only at the receiver (and/or transmitter) end, is proposed for direct sequence code division multiple access (DS-CDMA) communication.
Abstract: A computationally efficient and practically deployable adaptive reference code-based multiple access interference (MAI) cancellation scheme, in which the conventional transmitter/receiver architecture is minimally modified only at the receiver (and/or transmitter) end, is proposed for direct sequence code division multiple access (DS-CDMA) communication. Upon numerical and theoretical analyses, the proposed communications system is seen to always outperform the existing conventional communications system. The theoretical analyses and results as presented are generally useful and applicable to any situation wherein IS95 pseudo noise (PN) codes are employed towards multiple access. Copyright © 2009 John Wiley & Sons, Ltd.