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CACAO: Distributed ClientAssisted Channel Assignment Optimization for Uncoordinated WLANs
"... Abstract—IEEE 802.11 WLANs are becoming more and more popular in homes and urban areas. As compared to traditional WLAN setups (such as in campuses) where knowledgeable network administrators can make centralized decisions on channel selection, access points (APs) in these networks are often deploye ..."
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Abstract—IEEE 802.11 WLANs are becoming more and more popular in homes and urban areas. As compared to traditional WLAN setups (such as in campuses) where knowledgeable network administrators can make centralized decisions on channel selection, access points (APs) in these networks are often deployed by network nonspecialists in an uncoordinated manner, leading to unplanned topologies, interference, and therefore unsatisfactory throughput performance. We consider in this paper a distributed channel assignment algorithm for uncoordinated WLANs, where APs can selfconfigure their operating channels to minimize interference with adjacent APs. We first formulate the optimization problem on channel assignment which overcomes some of the weaknesses encountered by uncoordinated WLANs. We show that the problem is NPhard, and propose an efficient, simple, and distributed algorithm termed CACAO (ClientAssisted Channel Assignment Optimization). In CACAO, the clients feed back traffic information to their APs. This leads to better network condition knowledge and better channel assignment decisions at the APs. We conduct extensive simulation study and comparisons using Network Simulator 2 (NS2). Our results show that CACAO outperforms other traditional and recent schemes in terms of TCP and UDP throughputs with a similar level of fairness. Furthermore, it converges quite fast and reduces cochannel interference significantly. Index Terms—Wireless, channel assignment, clientassisted, traffic aware. Ç 1
A Lower Bound on the Area of a 3Coloured Disc Packing
"... Given a set of unitdiscs in the plane with union area A, what fraction of A can be covered by selecting a pairwise disjoint subset of the discs? Rado conjectured 1/4 and proved 1/4.41. Motivated by the problem of channelassignment for wireless access points, we consider a variant where the selecte ..."
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Given a set of unitdiscs in the plane with union area A, what fraction of A can be covered by selecting a pairwise disjoint subset of the discs? Rado conjectured 1/4 and proved 1/4.41. Motivated by the problem of channelassignment for wireless access points, we consider a variant where the selected subset of discs must be 3colourable, with discs of the same colour pairwisedisjoint. For this variant of the problem, we conjecture that it is always possible to cover at least 1/1.41 of the union area and prove 1/2.77. We also provide an O(n 2) algorithm to select a subset achieving our 1/2.77 bound, and a proof that this problem is 3SUMhard, providing strong evidence that our algorithm is optimal. 1
A Lower Bound on the Area of a 3Coloured Disk Packing
, 2008
"... Given a set of unitdisks in the plane with union area A, what fraction of A can be covered by selecting a pairwise disjoint subset of the disks? Rado conjectured 1/4 and proved 1/4.41. Motivated by the problem of channelassignment for wireless access points, in which use of 3 channels is a standar ..."
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Given a set of unitdisks in the plane with union area A, what fraction of A can be covered by selecting a pairwise disjoint subset of the disks? Rado conjectured 1/4 and proved 1/4.41. Motivated by the problem of channelassignment for wireless access points, in which use of 3 channels is a standard practice, we consider a variant where the selected subset of disks must be 3colourable with disks of the same colour pairwisedisjoint. For this variant of the problem, we conjecture that it is always possible to cover at least 1/1.41 of the union area and prove 1/2.09. We also provide an O(n 2) algorithm to select a subset achieving a 1/2.77 bound.
PACA: PeerAssisted Channel Assignment for Home Wireless LANs
"... Abstract — A home network is a residential local area network, in which users are networking their PCs, laptops or wireless multimedia appliances to use a single residential access point (AP) or gateway connecting to the Internet. As networkcapable appliances continue to gain momentum in the home, h ..."
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Abstract — A home network is a residential local area network, in which users are networking their PCs, laptops or wireless multimedia appliances to use a single residential access point (AP) or gateway connecting to the Internet. As networkcapable appliances continue to gain momentum in the home, home networks are becoming increasingly popular. The problem arising from the increasing number of “wireless home ” is the interference introduced from neighbor’s home networks which leads to throughput dropped precipitously. This problem is different from the traditional channel assignment problem in WLAN. We are considering how home wireless network can selfconfigure its operating channel to minimize interference with other networks instead of how network administrator assigns channel to different APs. In this paper, we propose a peerassisted channel assignment algorithm, termed PACA, for home wireless LAN based on local information. A newly power on AP automatically configures itself to operate on a channel with least interference. Mobile node helps other APs to do channel assignment and switching dynamically by providing traffic load information. Our simulation and experimental measurements show that the algorithm reduces interference among different networks and improves user throughput. I.
Authors Declaration for Electronic
"... I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. public. I understand that my thesis may be made electronically available to the ii Multihop wireless networks based on 802.11 are being ..."
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I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. public. I understand that my thesis may be made electronically available to the ii Multihop wireless networks based on 802.11 are being used more widely as an alternative technology for lastmile broadband Internet access. Their benefits include ease of deployment and lower cost. Such networks are not without problems. Current research on such networks aims at a number of challenges, including overcoming capacity limitation and poor fairness. The focus of our research is for achieving fairness in multichannel multihop wireless networks. First, we review the literature for different methods for representing linkcontention areas, and the existing singlechannel fairness computational model. Second, we generalize the fairness constraints applied to each linkcontention area, defined in the existing singlechannel fairness reference model, to multichannel models. Third, by adopting the concepts of linkusage matrix and mediumusage matrix to represent network topology and flow status, and using Collision Domain theory and Clique Graph theory to represent linkcontention area, we develop a computational model to compute optimal MAClayer bandwidth allocated to each flow in a multichannel multihop WMN. We simulate various network configurations to evaluate the performance of the fairness algorithm based on the above computational iii model in different scenarios. We have found that in the multichannel environment, our extension to the Collision Domain model generally provides a more accurate estimation of network capacity. Based on this model, we have extended the sourceratelimiting mechanism, which limits the flow rate to its fair share computed by the computational model. Experimental results that validate these findings are presented in this thesis. iv
InterferenceConstrained Wireless Coverage in a Protocol Model ABSTRACT
"... We present an O(n log n) algorithm to compute the coverage map of a given set of transmitters under interference constraints. That is, we compute the set of points that lie within the transmission range of one transmitter and lie outside the interference range of every other transmitter. To our know ..."
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We present an O(n log n) algorithm to compute the coverage map of a given set of transmitters under interference constraints. That is, we compute the set of points that lie within the transmission range of one transmitter and lie outside the interference range of every other transmitter. To our knowledge, there is no existing satisfactory algorithm for this purpose. We assume that the transmission and interference ranges of each transmitter are circular disks. We show that for an appropriate choice of ‘distance measure’, coverage at each point can be computed by considering only certain ‘proximate ’ transmitters. Hence, we partition the plane into proximity regions and the coverage in these proximity regions is computed considering only proximate transmitters. We use an extension of Voronoi diagrams, called ‘Power ’ diagrams, to represent the proximity regions.
Supplementary Material I. RELATED WORK
"... Much work has been done with the primary objective to reduce interference and increase total throughput of WLANs. Optimal AP placement schemes optimizing power level and network throughput have been proposed in [1]–[3]. Measurement based WLAN deployment schemes have been proposed in [4] and [5]. Unl ..."
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Much work has been done with the primary objective to reduce interference and increase total throughput of WLANs. Optimal AP placement schemes optimizing power level and network throughput have been proposed in [1]–[3]. Measurement based WLAN deployment schemes have been proposed in [4] and [5]. Unlike our work, these studies all assume that network administrators conduct site surveys and do propagation modeling before network deployment. In [3], the authors propose methods to identify hot spots where high traffic is expected and try to assign channels accordingly. This is a static approach, and any changes or deviation from the expected traffic pattern can lead to suboptimal channel assignment. Athanasiou et al. propose LoadAware Channel Selection (LAC) [6], a distributed scheme making use of traffic information. However, this scheme cannot dynamically
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"... Abstract — Nowadays due to easily available hardware and availability of unlicensed frequency spectrum the use of WLANS has increased tremendously. Such WLANS are set up by untrained system administrators with no topology planning. The Access Points are also placed haphazardly. The performance of su ..."
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Abstract — Nowadays due to easily available hardware and availability of unlicensed frequency spectrum the use of WLANS has increased tremendously. Such WLANS are set up by untrained system administrators with no topology planning. The Access Points are also placed haphazardly. The performance of such Uncoordinated WLANs is greatly affected due to availability of limited number of nonoverlapping channels. The cognitive radio provides the clients to make use of free channels from licensed spectrum when they are not in use by primary users. Thus in cognitive environment more channels are available to the clients. This paper describes a novel channel assignment scheme for cognitive radios.
and Applied Sciences (IJETCAS) www.iasir.net Channel Assignment Scheme for Cognitive Radios
"... Abstract:Nowdays due to easily available hardware and availability of unlicensed frequency spectrum the use of WLANS has increased tremendously. Such WLANS are set up by untrained system administrators with no topology planning. The Access Points are also placed haphazardly. The performance of such ..."
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Abstract:Nowdays due to easily available hardware and availability of unlicensed frequency spectrum the use of WLANS has increased tremendously. Such WLANS are set up by untrained system administrators with no topology planning. The Access Points are also placed haphazardly. The performance of such Uncoordinated WLANs is greatly affected due to availability of limited number of nonoverlapping channels. The Cognitive Radio provides the clients to make use of free channels from licensed spectrum when they are not in use by primary users. Thus in Cognitive environment more channels are available to the clients. This paper describes a novel channel assignment scheme for Cognitive Radios.