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78
Approximately achieving Gaussian relay network capacity with latticebased QMF codes
, 2010
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SourceSync: A Distributed Wireless Architecture for Exploiting Sender Diversity
"... Diversity is an intrinsic property of wireless networks. Recent years have witnessed the emergence of many distributed protocols like ExOR, MORE, SOAR, SOFT, and MIXIT that exploit receiver diversity in 802.11like networks. In contrast, the dual of receiver diversity, sender diversity, has remained ..."
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Cited by 42 (6 self)
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Diversity is an intrinsic property of wireless networks. Recent years have witnessed the emergence of many distributed protocols like ExOR, MORE, SOAR, SOFT, and MIXIT that exploit receiver diversity in 802.11like networks. In contrast, the dual of receiver diversity, sender diversity, has remained largely elusive to such networks. This paper presents SourceSync, a distributed architecture for harnessing sender diversity. SourceSync enables concurrent senders to synchronize their transmissions to symbol boundaries, and cooperate to forward packets at higher data rates than they could have achieved by transmitting separately. The paper shows that SourceSync improves the performance of opportunistic routing protocols. Specifically, SourceSync allows all nodes that overhear a packet in a wireless mesh to simultaneously transmit it to their nexthops, in contrast to existing opportunistic routing protocols that are forced to pick a single forwarder from among the overhearing nodes. Such simultaneous transmission reduces bit errors and improves throughput. The paper also shows that SourceSync increases the throughput of 802.11 last hop diversity protocols by allowing multiple APs to transmit simultaneously to a client, thereby harnessing sender diversity. We have implemented SourceSync on the FPGA of an 802.11like radio platform. We have also evaluated our system in an indoor wireless testbed, empirically showing its benefits.
Distributed cooperative MAC for multihop wireless networks
 IEEE Commun. Mag
, 2009
"... Abstract: This article investigates distributed cooperative medium access control (MAC) protocol design for multihop wireless networks. Cooperative communication has been proposed recently as an effective way to mitigate channel impairments. With cooperation, singleantenna mobile terminals in ..."
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Cited by 35 (8 self)
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Abstract: This article investigates distributed cooperative medium access control (MAC) protocol design for multihop wireless networks. Cooperative communication has been proposed recently as an effective way to mitigate channel impairments. With cooperation, singleantenna mobile terminals in a multiuser environment share antennas from other mobiles to generate a virtual multipleantenna system that achieves more reliable communication with a higher diversity gain. However, more mobiles conscribed for one communication induces inevitably complex medium access interactions, especially in multihop wireless ad hoc networks. To improve the network throughput and diversity gain simultaneously, we investigate the issues and challenges in designing an efficient MAC scheme for such networks. Furthermore, based on IEEE 802.11 DCF, a crosslayer designed cooperative MAC protocol is proposed. The MAC scheme adapts to the channel condition and payload length.
Cooperative communications in multihop wireless networks: Joint flow routing and relay node assignment
 in Proc. IEEE INFOCOM
, 2010
"... Abstract—It has been shown that cooperative communications (CC) have the potential to significantly increase the capacity of wireless networks. However, most of the existing results are limited to singlehop wireless networks. To illustrate the benefits of CC in multihop wireless networks, we solv ..."
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Cited by 25 (4 self)
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Abstract—It has been shown that cooperative communications (CC) have the potential to significantly increase the capacity of wireless networks. However, most of the existing results are limited to singlehop wireless networks. To illustrate the benefits of CC in multihop wireless networks, we solve a joint optimization problem of relay node assignment and flow routing for concurrent sessions. We study this problem via mathematical modeling and solve it using a solution procedure based on the branchandcut framework. We design several novel components to speedup the computation time of branchandcut. Via numerical results, we show the significant rate gains that can be achieved by incorporating CC in multihop networks. I.
The Anderson model of localization: a challenge for modern eigenvalue methods
 SIAM J. Sci. Comp
, 1999
"... Abstract. We present a comparative study of the application of modern eigenvalue algorithms to an eigenvalue problem arising in quantum physics, namely, the computation of a few interior eigenvalues and their associated eigenvectors for the large, sparse, real, symmetric, and indefinite matrices of ..."
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Cited by 17 (6 self)
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Abstract. We present a comparative study of the application of modern eigenvalue algorithms to an eigenvalue problem arising in quantum physics, namely, the computation of a few interior eigenvalues and their associated eigenvectors for the large, sparse, real, symmetric, and indefinite matrices of the Anderson model of localization. We compare the Lanczos algorithm in the 1987 implementation of Cullum and Willoughby with the implicitly restarted Arnoldi method coupled with polynomial and several shiftandinvert convergence accelerators as well as with a sparse hybrid tridiagonalization method. We demonstrate that for our problem the Lanczos implementation is faster and more memory efficient than the other approaches. This seemingly innocuous problem presents a major challenge for all modern eigenvalue algorithms.
Constructing Combinatorial Designs by Local Search
 DIGITAL SYSTEMS LABORATORY, HELSINKI UNIVERSITY OF TECHNOLOGY
, 1993
"... In this work probabilistic search heuristics are used in search for covering designs, packing designs and tdesigns. Each covering design gives an upper bound for C (v; m; k; t), the minimum size of a t \Gamma (v; m; k; ) covering design, while each packing design gives a lower bound for D (v; m; k; ..."
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Cited by 13 (0 self)
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In this work probabilistic search heuristics are used in search for covering designs, packing designs and tdesigns. Each covering design gives an upper bound for C (v; m; k; t), the minimum size of a t \Gamma (v; m; k; ) covering design, while each packing design gives a lower bound for D (v; m; k; t), the maximum size of a t \Gamma (v; m; k; ) packing design, and each tdesign establishes the existence of such a design. The designs are constructed using probabilistic combinatorial optimization methods including simulated annealing, tabu search, threshold accepting, great deluge algorithm and recordtorecord travel. Implementation issues of these algorithms, such as cost functions and neighborhood structures are discussed. Comparisons of the performance of these algorithms on some designs is carried out. Some elementary search methods including steepest descent algorithm and random walk are included in the comparisons. Finally, the results of the searches are tabulated. The objec...
Building a Green WirelessOptical Broadband Access Network
 IEEE/OSA Journal of Lightwave Technology
, 2010
"... Abstract—Access networks consume a significant portion of overall Internet energy consumption. With the increase of bitrate requirements in access networks, futureproof access technologies should be energy efficient. In this paper, we show how we can build a very highthroughput “green ” hybrid wi ..."
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Cited by 12 (1 self)
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Abstract—Access networks consume a significant portion of overall Internet energy consumption. With the increase of bitrate requirements in access networks, futureproof access technologies should be energy efficient. In this paper, we show how we can build a very highthroughput “green ” hybrid wirelessoptical broadband access network (WOBAN). We devise novel energysaving techniques for WOBAN to improve its energy efficiency and network utilization. We present a mixed integer linear program (MILP) model, which acts as a benchmark for evaluating our techniques. We analyze the impact of energyaware design and protocols on the performance of WOBAN over dynamic traffic profiles. Illustrative numerical examples show that, with suitable design parameters, we can efficiently reduce energy consumption in WOBAN without significantly impacting the network performance.
Cooperative Wireless Networks: From Radio to 1 Network Protocol Designs
"... Cooperative communication has been shown as an effective way of exploiting spatial diversity to improve the quality of wireless links. The key feature of cooperative transmission is to encourage singleantenna devices to share their antennas cooperatively such that a virtual and distributed antenna ..."
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Cited by 10 (0 self)
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Cooperative communication has been shown as an effective way of exploiting spatial diversity to improve the quality of wireless links. The key feature of cooperative transmission is to encourage singleantenna devices to share their antennas cooperatively such that a virtual and distributed antenna array can be constructed and, as a result, reception reliability can be improved and power consumption can be reduced significantly. With a better understanding of such physicallayer technique, it becomes critically important to study how the performance gain of cooperative diversity at the physical layer can be reflected at the networking layer, thus ultimately improving application performance. This article presents an overview of the network performance in cooperative wireless networks. I.
Languages for Configuration Programming: A Comparison
, 1994
"... The computing community needs distributed systems to satisfy its need for harnessing more computers solving more problems more quickly. Yet is still hard for programmers to write programs for such systems. Recently, configuration languages have emerged which have the aim of making distributed progra ..."
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Cited by 8 (1 self)
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The computing community needs distributed systems to satisfy its need for harnessing more computers solving more problems more quickly. Yet is still hard for programmers to write programs for such systems. Recently, configuration languages have emerged which have the aim of making distributed programming easier, more robust and more flexible. So far, each of these is confined to a small user community, and there is a wide range of features and facilities offered. In this paper, we consider the basic responsibilities of configuration languages and then look at four sample languages in detail. These are Darwin, Durra, PCL and Polylith. The study starts with simple static configuration programming and proceeds to dynamic programming and change management. The producer consumer example is used throughout, and the comparative code fragments shown are a novel feature of the paper. From the results of the comparison we deduce a tenpoint scheme of criteria for evaluating a language in terms o...
Wireless Network Simplification: the Gaussian NRelay Diamond Network”, arXiv:1103.2046  arxiv.org
"... Abstract—We consider the Gaussian Nrelay diamond network, where a source wants to communicate to a destination node through a layer of Nrelay nodes. We investigate the following question: What fraction of the capacity can we maintain by using only k out of the N available relays? We show that in e ..."
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Cited by 8 (6 self)
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Abstract—We consider the Gaussian Nrelay diamond network, where a source wants to communicate to a destination node through a layer of Nrelay nodes. We investigate the following question: What fraction of the capacity can we maintain by using only k out of the N available relays? We show that in every Gaussian Nrelay diamond network, there exists a subset k k+1 of k relays which alone provide approximately of the total capacity. The result holds independent of the number of available relay nodes N, the channel configurations and the operating SNR. The result is tight in the sense that there exists channel configurations for Nrelay diamond networks, where every subset k k+1 of k relays can provide at most of the total capacity. The approximation is within 3logN +3k bits/s/Hz to the capacity. This result also provides a new approximation to the capacity of the Gaussian Nrelay diamond network which is up to a 1 k+1 multiplicative gap of and additive gap of 3logN +3k. The current approximation results in the literature either aim to characterize the capacity within an additive gap by allowing no multiplicative gap or vice a versa. Our result suggests a new approximation approach where multiplicative and additive gaps are allowed simultaneously and are traded through an auxiliary parameter. 1 I.