Dissertations / Theses on the topic 'Channel assignment'
To see the other types of publications on this topic, follow the link: Channel assignment.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Channel assignment.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Shepherd, Mark. "Radio channel assignment." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288047.
Full text
2
Gerke, Stefanie. "Weighted colouring and channel assignment." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325977.
Full text
3
Naveed, Anjum Computer Science & Engineering Faculty of Engineering UNSW. "Channel assignment in multi-radio multi-channel wireless mesh networks." Awarded by:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41500.
Full textAbstract:
Channel assignment in wireless mesh network (WMN) aims at improving the network throughput by utilizing multiple orthogonal frequency channels to minimize the interference. Interference can be categorized as coordinated and non-coordinated, depending upon the relative location of the interfering links. Compared to coordinated interference, non-coordinated interference has a severe adverse impact on throughput. This thesis is based on the hypothesis that the network throughput can be improved significantly, if channel assignment minimizes non-coordinated interference with priority. We propose a static and centralized channel assignment scheme CCAS to show the effectiveness of the hypothesis. The cluster-based approach of CCAS minimizes non-coordinated interference with reduced complexity. CCAS improves the network throughput by upto 80%, compared to the existing schemes. We propose topology control scheme MATS that constructs low interference multipath network topology using a subset of links from physical topology. We report an additional improvement of upto 10% in the network throughput, when CCAS assigns channels to the links selected by MATS. In the final part of the thesis, we formulate generalized channel assignment as an optimization problem, accounting for real network traffic. The objective of the problem is to select the channels for links such that maximum incident traffic can be transmitted over the links, while ensuring a fair distribution of throughput amongst links and elimination of non-coordinated interference. For a given network and incident traffic, the solution to this problem generates the channel assignment resulting in optimal network throughput. We propose dynamic and distributed scheme LYCAS as an approximate solution to the problem. LYCAS employs MATS to construct network topology and cluster-based approach of CCAS to minimize non-coordinated interference. In addition, it periodically updates the assignment of channels to adapt to the changing traffic load. LYCAS achieves upto 68% of the optimal network throughput and upto 72% of optimal aggregate end-to-end throughput of multi-hop flows. It outperforms the existing schemes by a factor of 2.
4
Giortzis, Athanasios. "Channel assignment in mobile radio networks." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266017.
Full text
5
Chong, Peter H. J. "Channel assignment schemes in cellular communication systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/NQ56660.pdf.
Full text
6
Amiri, Nehzad Maryam. "Channel assignment protocols for multi-radio multi-channel wireless mesh netwworks." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/104156.
Full textAbstract:
The increasing demand for large and low cost wireless coverage, ranging from campus to city wide areas, has motivated a high interest in multi-hop communications with Wireless Mesh Networks (WMN) based on IEEE 802.11s as the
most recent and significant standard.
Channel Assignment (CA) is mechanism which selects the best channels for an individual wireless node or the entire network aiming to increase the capacity of the network. Channel assignment has been extensively researched for
multi-radio WMNs, but it is still very challenging when it comes to its implementation. Although IEEE 802.11s introduces new inter-working, routing and wireless frame forwarding at the link layer, the multi channel architecture receives less attention due to many unsolved challenges that arises while mesh service set works over multiple frequencies.
This research work tries to give a solution to the needs of designing an efficient channel assignment mechanism.
As a result we have proposed a new static channel assignment based on the fact that not all wireless links are practically useful. Our mechanism prunes the network topology by removing weak wireless links and improves the network
performance by reaching a more diverse channel-radio assignation solution.
Toward designing a distributed channel assignment we propose a new game theory based formulation of channel assignment which is applicable to a realistic scenario with imperfect information at each router. We have proposed a distributed and hybrid channel assignment protocol based on the game formulation. The proposed channel assignment makes wireless router to
be able to follow the unpredictable changes in the wireless environment.
We also investigated the types of channel assignment protocols which can be adapted to the IEEE 802.11s based mesh network and improve the network good-put in terms of data delivery ratio and end-to-end delay.
7
Chiu, Hon-sun, and 邵漢新. "Channel assignment and routing in multi-channel multi-interface wireless networks." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42182050.
Full text
8
Chiu, Hon-sun. "Channel assignment and routing in multi-channel multi-interface wireless networks." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B42182050.
Full text
9
Grace, David. "Distributed Dynamic Channel Assignment for the wireless environment." Thesis, University of York, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288041.
Full text
10
Du, Peng. "Bandwidth allocation and channel assignment in WiMax mesh networks /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-cs-b30082547f.pdf.
Full textAbstract:
Thesis (Ph.D.)--City University of Hong Kong, 2009."Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 100-108)
11
Zheng, Zhihua, and 鄭智華. "Dynamic channel assignment for cellular mobile radio communication systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B31246333.
Full text
12
Irwin, Ryan. "Traffic-Aware Channel Assignment for Multi-Transceiver Wireless Networks." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/26601.
Full textAbstract:
This dissertation addresses the problem of channel assignment in multi-hop, multi-transceiver wireless networks. We investigate (1) how channels can be assigned throughout the network to ensure that the network is connected and (2) how the channel assignment can be adapted to suit the current traffic demands. We analyze a traffic-aware method for channel assignment that addresses both maintaining network connectivity and adapting the topology based on dynamic traffic demands.
The traffic-aware approach has one component that assigns channels independently of traffic conditions and a second component that assigns channels in response to traffic conditions. The traffic-independent (TI) component is designed to allocate as few transceivers or radios as possible in order to maintain network connectivity, while limiting the aggregate interference induced by the topology. The traffic-driven (TD) component is then designed to maximize end-to-end flow rate using the resources remaining after the TI assignment is complete. By minimizing resources in the TI component, the TD component has more resources to adapt the topology to suit the traffic demands and support higher end-to-end flow rate.
We investigate the fundamental tradeoff between how many resources are allocated to maintaining network connectivity versus how many resources are allocated to maximize flow rate. We show that the traffic-aware approach achieves an appropriately balanced resource allocation, maintaining a baseline network connectivity and adapting to achieve near the maximum theoretical flow rate in the scenarios evaluated.
We develop a set of greedy, heuristic algorithms that address the problem of resource- minimized TI assignment, the first component of the traffic-aware assignment. We develop centralized and distributed schemes for nodes to assign channels to their transceivers. These schemes perform well as compared to the optimal approach in the evaluation. We show that both of these schemes perform within 2% of the optimum in terms of the maximum achievable flow rate.
We develop a set of techniques for adapting the networkâ s channel assignment based on traffic demands, the second component of the traffic-aware assignment. In our approach, nodes sense traffic conditions and adapt their own channel assignment independently to support a high flow rate and adapt when network demand changes. We demonstrate how our distributed TI and TD approaches complement each other in an event-driven simulation.Ph. D.
13
He, Jingyi. "Routing and channel assignment in optical and wireless networks /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20HE.
Full text
14
Shzu-Juraschek, Felix. "Distributed channel assignment for interference-aware wireless mesh networks." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2014. http://dx.doi.org/10.18452/16957.
Full textAbstract:
Die Besonderheit der drahtlosen Kommunikation gegenüber den drahtgebundenen Netzwerken liegt im drahtlosen Übertragungsmedium. Aufgrund der Broadcast-Eigenschaft des Übertragungsmediums werden Nachrichten potentiell von allen Netzwerkstationen empfangen, welche sich in der Übertragungsreichweite des Senders aufhalten. Als Konsequenz können bei einem unsynchronisierten Medienzugriff mehrere Nachrichten beim Empfänger kollidieren und nicht korrekt empfangen werden. Dieses Phänomen wird auch als Interferenz bezeichnet. Um solche Interferenzen zu vermeiden, wurden spezielle Protokolle für den Medienzugriff in drahtlosen Netzen entwickelt. Ein solcher Ansatz für drahtlose Maschennetze ist die verteilte Kanalzuweisung. Bei der verteilten Kanalzuweisung werden sich nicht-überlappende Kanäle im verfügbaren Frequenzspektrum für Übertragungen verwendet, die auf dem gleichen Kanal Interferenzen erzeugen würden. Dieser Ansatz ist möglich, da die verwendeten Funktechnologien, wie zum Beispiel IEEE 802.11 (WLAN), mehrere nicht-überlappende Kanäle bereitstellen. Aufgrund der großen Verbreitung von IEEE 802.11, ist eine hohe Dichte von privaten wie kommerziellen Netzen im urbanen Raum die Norm. Diese räumlich überlappenden Netze konkurrieren um den Medienzugriff. Daher ist es für die Leistung von Kanalzuweisungsalgorithmen von großer Bedeutung, die Aktivität der externen Netze mit einzubeziehen. Die Leistung der vorgelegten Arbeit umfasst das Design, die Implementierung und Validierung von Modellen und Algorithmen zur Reduzierung von Interferenzen in drahtlosen Maschennetzen. Die Arbeit beinhaltet die Entwicklung eines Messungs-basierten Interferenzmodells, mit dem Interferenzabhängigkeiten der Maschenrouter untereinander effizient bestimmt werden können. Weiterhin wurde ein Algorithmus für die verteilte Kanalzuweisung entwickelt, der die Aktivität von externen Netzen berücksichtigt. Die Gesamtlösung wurde in einem großen drahtlosen Maschennetz experimentell validiert.Due to the broadcast nature of the shared medium, wireless transmissions are potentially received by all network stations in the communication range of the sender. With an unsynchronized medium access, multiple transmissions may be active at the same time and thus interfere with each other. In consequence, multiple transmissions may collide at the receiver side and cannot be properly decoded. For this reason, protocols have been developed on the MAC layer to synchronize the medium access and thus reduce interference effects. One of these approaches in wireless mesh networks is channel assignment. The idea of channel assignment is to minimize the network-wide interference by utilizing non-overlapping channels for otherwise interfering wireless transmissions. This is feasible, since wireless mesh routers are usually equipped with multiple radios and commonly used wireless network technologies, such as IEEE 802.11, provide multiple non-overlapping channels. Since IEEE 802.11 operates in the unlicensed frequency spectrum, the dense distribution of private and commercial network deployments of WLANs in urban areas poses a new challenge. Co-located networks compete for the wireless medium, thus decreasing the achievable network performance in terms of throughput and latency. Therefore, an important issue for efficient channel assignment is to also address external interference The contributions of this dissertation comprise the design, implementation, and validation of models and algorithms to enable wireless multi-hop networks to become interference-aware. This includes a measurement-based interference model suitable for large-scale network deployments. A distributed channel assignment algorithm has been developed that considers external sources of interference. The overall solution has been experimentally validated in a large-scale wireless multi-hop multi-radio testbed and has significantly increased the network performance with regard to the network capacity.
15
Choi, Sangil. "Minimum interference channel assignment for multicast in multi-channel multi-radio wireless mesh networks." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1468073.
Full text
16
González, Barrameda José Andrés. "Search Space Analysis and Efficient Channel Assignment Solutions for Multi-interface Multi-channel Wireless Networks." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20155.
Full textAbstract:
This thesis is concerned with the channel assignment (CA) problem in multi-channel
multi-interface wireless mesh networks (M2WNs). First, for M2WNs with general topologies,
we rigorously demonstrate using the combinatorial principle of inclusion/exclusion
that the CA solution space can be quantified, indicating that its cardinality is greatly
influenced by the number of radio interfaces installed on each router. Based on this analysis,
a novel scheme is developed to construct a new reduced search space, represented
by a lattice structure, that is searched more efficiently for a CA solution. The elements
in the reduced lattice-based space, labeled Solution Structures (SS), represent groupings
of feasible CA solutions satisfying the radio constraints at each node. Two algorithms
are presented for searching the lattice structure. The first is a greedy algorithm that
finds a good SS in polynomial time, while the second provides a user-controlled depthfirst
search for the optimal SS. The obtained SS is used to construct an unconstrained
weighted graph coloring problem which is then solved to satisfy the soft interference
constraints.
For the special class of full M2WNs (fM2WNs), we show that an optimal CA solution
can only be achieved with a certain number of channels; we denote this number as the
characteristic channel number and derive upper and lower bounds for that number as a
function of the number of radios per router. Furthermore, exact values for the required
channels for minimum interference are obtained when certain relations between the number
of routers and the radio interfaces in a given fM2WN are satisfied. These bounds are
then employed to develop closed-form expressions for the minimum channel interference
that achieves the maximum throughput for uniform traffic on all communication links.
Accordingly, a polynomial-time algorithm to find a near-optimal solution for the channel
assignment problem in fM2WN is developed.
Experimental results confirm the obtained theoretical results and demonstrate the
performance of the proposed schemes.
17
Shah, Ibrar Ali. "Channel assignment and routing in cooperative and competitive wireless mesh networks." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6568.
Full textAbstract:
In this thesis, the channel assignment and routing problems have been investigated for both cooperative and competitive Wireless Mesh networks (WMNs). A dynamic and distributed channel assignment scheme has been proposed which generates the network topologies ensuring less interference and better connectivity. The proposed channel assignment scheme is capable of detecting the node failures and mobility in an efficient manner. The channel monitoring module precisely records the quality of bi-directional links in terms of link delays. In addition, a Quality of Service based Multi-Radio Ad-hoc On Demand Distance Vector (QMR-AODV) routing protocol has been devised. QMR-AODV is multi-radio compatible and provides delay guarantees on end-to-end paths. The inherited problem of AODV’s network wide flooding has been solved by selectively forwarding the routing queries on specified interfaces. The QoS based delay routing metric, combined with the selective route request forwarding, reduces the routing overhead from 24% up to 36% and produces 40.4% to 55.89% less network delays for traffic profiles of 10 to 60 flows, respectively. A distributed channel assignment scheme has been proposed for competitive WMNs, where the problem has been investigated by applying the concepts from non-cooperative bargaining Game Theory in two stages. In the first stage of the game, individual nodes of the non-cooperative setup is considered as the unit of analysis, where sufficient and necessary conditions for the existence of Nash Equilibrium (NE) and Negotiation-Proof Nash Equilibrium (N-PNE) have been derived. A distributed algorithm has been presented with perfect information available to the nodes of the network. In the presence of perfect information, each node has the knowledge of interference experience by the channels in its collision domain. The game converges to N-PNE in finite time and the average fairness achieved by all the nodes is greater than 0.79 (79%) as measured through Jain Fairness Index. Since N-PNE and NE are not always a system optimal solutions when considered from the end-nodes prospective, the model is further extended to incorporate non-cooperative end-users bargaining between two end user’s Mesh Access Points (MAPs), where an increase of 10% to 27% in end-to-end throughput is achieved. Furthermore, a non-cooperative game theoretical model is proposed for end-users flow routing in a multi-radio multi-channel WMNs. The end user nodes are selfish and compete for the channel resources across the WMNs backbone, aiming to maximize their own benefit without taking care for the overall system optimization. The end-to-end throughputs achieved by the flows of an end node and interference experienced across the WMNs backbone are considered as the performance parameters in the utility function. Theoretical foundation has been drawn based on the concepts from the Game Theory and necessary conditions for the existence of NE have been extensively derived. A distributed algorithm running on each end node with imperfect information has been implemented to assess the usefulness of the proposed mechanism. The analytical results have proven that a pure strategy Nash Equilibrium exists with the proposed necessary conditions in a game of imperfect information. Based on a distributed algorithm, the game converges to a stable state in finite time. The proposed game theoretical model provides a more reasonable solution with a standard deviation of 2.19Mbps as compared to 3.74Mbps of the random flow routing. Finally, the Price of Anarchy (PoA) of the system is close to one which shows the efficiency of the proposed scheme.
18
Wentzell, Tania E. "Lower bounds from tile covers for the channel assignment problem." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0021/MQ49463.pdf.
Full text
19
Wong, Chi-Fai. "CACAO : client-assisted channel assignment optimization for uncoordinated home WLANs /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CSED%202007%20WONG.
Full text
20
Weston, Claire L. "Constraint models for multiple interference in the channel assignment problem." Thesis, Cardiff University, 2005. http://orca.cf.ac.uk/55996/.
Full textAbstract:
For the channel assignment problem, the adequacy of binary channel separation constraints based on the single interferer assumption and/or a constant re-use distance has been questioned by several authors. The single interferer assumption is convenient for channel assignment purposes as it leads to a generalised graph-colouring model which is simple to formulate and very popular. However, it is desirable to approximate the operational criteria more closely than a single interferer assumption model allows, by modelling the effects of multiple simultaneous interferers. This thesis addresses the problem of modelling multiple interferers in channel assignment using constraints, with a view to finding an efficient and convenient approach which offers resilience against multiple interference whilst minimising additional spectral requirements. Motivated by a discussion of the literature concerning single and multiple interference, the thesis analyses the coverage failure as progressively higher numbers of multiple simultaneous interferers occur, characterising those interferers which lead to coverage reduction. A hybrid sequential and simulated annealing heuristic is applied which obtains optimised channel assignments for analysis, created under the single interferer assumption, for two-hundred-and-forty problem cases. The library of test cases is created using a purpose-built problem generator which is applied to create problems with differing randomised distributions of transmission sites. The analysis informs the consideration of methods for the reduction/elimination of multiple interferer effects. A multiple interference model based on higher order constraints called co-channel set constraints is assessed. Results concerning the theoretical properties of these constraints, and their satisfaction, are presented. An alternative way forward is then considered, which involves challenging the commonly applied assumption that the multiple interferer assumption implies constraints are necessarily non-binary. New methods are introduced that incorporate multiple interference into the generalised graph-colouring formulation i.e. binary constraints. The methods are tested using the test problem library optimised assignments are made and their resilience against multiple interference and the spectral requirements are used to evaluate the approaches. Evidence is provided that one of the methods provides an improved model for channel assignment with multiple interference and can be recommended for use to provide constraints which perform well under the multiple objectives concerned.
21
Al-Khaled, Fahad Sulaiman. "Efficient radio channel assignment techniques for mobile satellite communication networks." Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391293.
Full text
22
Wang, Baobing. "Topology control and channel assignment in wireless multi-hop networks /." access full-text access abstract and table of contents, 2009. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?mphil-cs-b2375087xf.pdf.
Full textAbstract:
Thesis (M.Phil.)--City University of Hong Kong, 2009."Submitted to Department of Computer Science in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references (leaves 60-64)
23
Ahuja, Sandeep Kour. "ALGORITHMS FOR ROUTING AND CHANNEL ASSIGNMENT IN WIRELESS INFRASTRUCTURE NETWORKS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/195190.
Full textAbstract:
Wireless communication is a rapidly growing segment of the communication industry, with the potential to provide low-cost, high-quality, and high-speed information exchange between portable devices. To harvest the available bandwidth efficientlyin a wireless network, they employ multiple orthogonal channels over multiple ra-dios at the nodes. In addition, nodes in these networks employ directional antennasas radios to improve spatial throughput. This dissertation develops algorithms forrouting and broadcasting with channel assignment in such networks. First, we com-pute the minimum cost path between a given source-destination pair with channelassignment on each link in the path such that no two transmissions interfere witheach other. Such a path must satisfy the constraint that no two consecutive links onthe path are assigned the same channel, referred to as "channel discontinuity con-straint." To compute such a path, we develop two graph expansion techniques basedon minimum cost perfect matching and dijkstra's algorithm. Through extensive sim-ulations, we study the effectiveness of the routing algorithms developed based onthe two expansion techniques and the benefits of employing the minimum cost per-fect matching based solution. Secondly, we study the benefits of sharing channelbandwidth across multiple flows. We model the routing and channel assignmentproblem in two different ways to account for the presence and absence of inter-flowbandwidth sharing. Benefits of multiple paths between a source-destination pairmotivates the problem of computing multiple paths between a source-destinationpair with channel assignment such that all the paths can be active simultaneouslyto achieve maximal flow between the pair in the considered network. Since finding even two such paths is NP-hard, we formulate the problem as an integer linearprogram and develop efficient heuristic to find these paths iteratively. Thirdly, wecompute a broadcast tree from a given root with channel assignment such that all the links in the broadcast tree can be active simultaneously without interferingwith each other. Since finding such a tree is an NP-hard problem, we formulatethe problem as an integer linear program (ILP) and develop heuristics to find thebroadcast tree with channel assignment. We evaluate and compare the performanceof the developed heuristics with respect to their success rate, average depth of theobtained tree, and average path length from root to a node in the network. Thisdissertation also analyzes the blocking performance of a channel assignment schemein a multi-channel wireless line network. We assume that the existing calls in thenetwork may be rearranged on different channels to accommodate an incoming call.The analysis is limited to single-hop calls with different transmission ranges.Finally, this dissertation evaluates the performance of disjoint multipath routingapproaches for all-to-all routing in packet-switched networks with respect to packetoverhead, path lengths, and routing table size. We develop a novel approach basedon cycle-embedding to obtain two node-disjoint paths between all source-destinationpairs with reduced number of routing table entries maintained at a node (hence thereduced look up time), small average path lengths, and less packet overhead. Westudy the trade-off between the number of routing table entries maintained at anode and the average length of the two disjoint paths by: (a) formulating the cycle-embedding problem as an integer linear program; and (b) developing a heuristic.We show that the number of routing table entries at a node may be reduced toat most two per destination using cycle-embedding approach, if the length of thedisjoint paths are allowed to exceed the minimum by 25%.
24
Li, Xiaoguang. "Channel Switching Control Policy for Wireless Mesh Networks." Master's thesis, Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/164788.
Full textAbstract:
Computer and Information ScienceM.S.
Dynamic channel assignment algorithms allow wireless nodes to switch channels when their traffic loads exceed certain thresholds. These thresholds represent estimations of their throughput capacities. Unfortunately, the threshold estimation may not be accurate due to co-channel interference (CCI) and adjacent-channel interference (ACI), especially with high traffic loads in dense networks. When the link capacity is over-estimated, these channel assignment algorithms are not effective. This is because channel switch is not triggered even with overloaded data traffic and the link quality decreases significantly as the channel is overloaded. When the link capacity is under-estimated, the link is under utilized. Moreover, when link traffic load increases from time to time, channel switch occurs frequently. Such frequent channel switches increase latency and degrade throughput, and can even cause network wide channel oscillations. In this paper, we propose a novel threshold-based control system, called \emph{balanced control system} (BCS). The proposed threshold-based control policy consist of deciding, according to the real time traffic load and interference, whether to switch to another channel,{which channel should be switched to and how to perform the switch. Our control model is based on a fuzzy logic control. The threshold which assists to make the channel switch decisions, could be deduced dynamically according to the real-time traffic of each node. We also design a novel dynamic channel assignment scheme, which is used for the selection of the new channel. The channel switch scheduler is provided to perform channel-switch processing for sender and receiver over enhanced routing protocols. We implement our system in NS2, and the simulation results show that with our proposed system, the performance improves by 12.3\%-72.8\% in throughput and reduces 23.2\%-52.3\% in latency.
Temple University--Theses
25
Kakumanu, Sandeep. "Component Based Channel Assignment in Single Radio, Multichannel Ad hoc Networks." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19870.
Full textAbstract:
In this work, we consider the channel assignment problem in single radio multi-channel mobile ad-hoc networks. Specifically, we investigate the granularity of channel assignment decisions that gives the best trade-off in terms of performance and complexity. We present a new granularity for channel assignment that we refer to as component level channel assignment. The strategy is relatively simple, and is characterized by several impressive practical advantages. We also show that the theoretical performance of the component based channel assignment strategy does not lag significantly behind the optimal possible performance, and perhaps more importantly we show that when coupled with its several practical advantages, it significantly outperforms other strategies under most network conditions.
26
Tenneti, Shivaram Venkata. "Channel assignment for throughput improvement in multi-radio wireless mesh networks." Thesis, Montana State University, 2007. http://etd.lib.montana.edu/etd/2007/tenneti/TennetiS1207.pdf.
Full text
27
Kundu, Titir. "Exploring Capture Effect for Efficient Channel Assignment in Wireless Sensor Network." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439309020.
Full text
28
Park, Sangtae. "Optimal Access Point Selection and Channel Assignment in IEEE 802.11 Networks." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4687/.
Full textAbstract:
Designing 802.11 wireless networks includes two major components: selection of access points (APs) in the demand areas and assignment of radio frequencies to each AP. Coverage and capacity are some key issues when placing APs in a demand area. APs need to cover all users. A user is considered covered if the power received from its corresponding AP is greater than a given threshold. Moreover, from a capacity standpoint, APs need to provide certain minimum bandwidth to users located in the coverage area. A major challenge in designing wireless networks is the frequency assignment problem. The 802.11 wireless LANs operate in the unlicensed ISM frequency, and all APs share the same frequency. As a result, as 802.11 APs become widely deployed, they start to interfere with each other and degrade network throughput. In consequence, efficient assignment of channels becomes necessary to avoid and minimize interference. In this work, an optimal AP selection was developed by balancing traffic load. An optimization problem was formulated that minimizes heavy congestion. As a result, APs in wireless LANs will have well distributed traffic loads, which maximize the throughput of the network. The channel assignment algorithm was designed by minimizing channel interference between APs. The optimization algorithm assigns channels in such a way that minimizes co-channel and adjacent channel interference resulting in higher throughput.
29
FRAIHA, SERGIO LUIZ NORONHA. "ANALYSIS OF THE PROBLEM OF TRAFFIC CHANNEL ASSIGNMENT IN MOBILE CELLULAR SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1996. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8955@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho aborda o problema da alocação dos canais de tráfego em sistemas móveis celulares. A utilização de métodos de alocação mais eficientes constitui uma das principais alternativas para a melhoria do desempenho de sistemas congestionados. Além disto, a constante redução do tamanho das células exige a aplicação de métodos mais flexíveis no que diz respeito ao pré-planejamento das freqüências. Alguns dos inúmeros métodos já propostos são apresentados, e dois deles - CBWL e Segregação de Canais - são simulados em um sistema FDMA micro-celular-uni- dimensional. É feita uma comparação do desempenho oferecido por estes dois métodos, e os resultados obtidos indicam a necessidade da utilização de alguma estratégia de prioridade para o atendimento das solicitações de handoff.
In this work the problem of traffic channel assignment in móbile cellular systems is adressed. The use of more efficient assignment methods represents one of the main alternatives to enhance the performance of congested systems. Moreover, the ceaseless reduction of cell sizes requires the adoption of more flexible methods already proposed are presented, and two of them - CBWL and Channel Segregation - are simulated in FDMA 1-dimensional microcellular system. The performance offered by these two methods is compared, and the results indicate the need of using some priority strategy for attending handoff requests.
30
Chen, Tai Chun, and 陳泰均. "An Optimal Channel Assignment Algorithm." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/86675405311240095921.
Full textAbstract:
碩士國立臺北大學
電機工程研究所
98
This thesis presents an optimal channel assignment algorithm based on the famous Left-Edge Algorithm (LEA) and the data structure of buckets for printed circuit boards, electronic design automation, and scheduling. Meanwhile, this algorithm can be applied to channel assignment with the minimal number of tracks. The time and space complexities are both O(N) ,where N is the number of trunks.
31
Chung, Yi-Fang, and 鍾依芳. "Distributed Channel Assignment in Multi-channel Wireless Mesh Network." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/78916500809284034399.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
99
In IEEE 802.11, channel resources are very limited and scarce. Thus channel assignment schemes which can effectively utilize available channels is one of the important issues in multi-channel wireless mesh networks. There are two approaches for channel assignment: centralized and distributed. We focus on distributed channel assignment, i.e., each node chooses its channel based on local information. The advantages of distributed approach are better flexibility and fault-tolerance. However, the problem of distributed channel assignment is channel oscillation which results that the channel assignment cannot converge for a long time and nodes change its channel repeatedly, and therefore the network throughput is throttled. In this thesis, we propose a new distributed channel assignment scheme to solve the channel oscillation problem, and to maximize the network throughput. Performance evaluation shows that our proposed algorithm improves the throughput and end-to-end delay in comparison to previously proposed distributed channel assignment schemes.
32
Lin, Chi-Wen, and 林啟文. "Channel Assignment Strategy in Cellular Network." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/06108476275660350125.
Full textAbstract:
碩士銘傳大學
資訊管理學系碩士在職專班
90
Department of Information Management Ming Chuan University Abstract With an increasing demand for wireless communication services and the limitation of channel bandwidth, the channel assignment becomes crucial. This paper presents an efficient channel assignment scheme for improving spatial frequency—spectrum reuse in a wireless network with heterogeneous demands, in which each cell has different channel demand. The proposed strategy can be further divided to two strategies, the homogeneous strategy and the inhomogeneous strategy. The homogeneous strategy, based on the distance-k model, is applied to assign channels when most of cells has channel requirement. When the channel requirement of most cells has been satisfied, the inhomogeneous scheme then is utilized. Moreover, the Neural-networks are employed to determine if the channel requirement is sparse. Simulation results show that the proposed scheme is better than previous schemes.
33
Hung, Shih-Jia, and 洪世嘉. "On Channel Assignment Of Regular Graphs." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/84175782045294494603.
Full textAbstract:
碩士國立嘉義大學
資訊工程學系研究所(Graduate School of Computer Scie
98
The channel assignment problem which was modeled by graphs was introduced by Hale in 1980. They used the vertices to denote the transmitters and the edges to indicate two transmitters being “very closed”. A k-L(2,1) labeling f for a given graph G=(V,E), is a function f:V→{0,1,2,...,k} such that for every pair of vertices x, y in V, |f(x)-f(y)|>=2 if d(x,y)=1, and |f(x)-f(y)|>=1 if d(x,y)=2 where d(x,y) denotes the distance between vertices x and y. The channel assignment problem can be solved by finding the minimum k such that G has a k-L(2,1) labeling. This thesis established the bounds of L(2,1) labeling, for some regular graphs such as star-like, pancake, burnt pancake, folded hypercube,locally twisted cube, and twisted N-cube graph.
34
Chiang, Yueh-Yiing, and 蔣岳穎. "Channel assignment in mobile communication systems." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/18747524935326992249.
Full text
35
Liang, Yi-An, and 梁逸安. "Distributed Flexible Channel Assignment in WLANs." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/41500499129730453969.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
100
Abstract Flexible channel enable access points and clients to use one pair of several channel widths and center frequencies to transmmit packets. Using different channel widths will bring each link different transmmision throughputs and tranmission ranges. The channel assignment in the WLANs will be more flexible and the throughput of the system will improve. In this thesis we introduce a distributed flexible channel assignment algorithm called DFCA. In DFCA, each link decides the channel width and center frequency based on the transmmission weight, channel width, center frequency and interference relation of neiboring nodes. Every link will choose the channel width and center frequency greedily which can bring it the highest throughput and consequently improve the total throughput of the system. We compared our DFCA algorithm with other fixed channel width and flexible channel width channel assignment algorithms in the total throughput of the system on the network simulaor NS-2. FLUID, one of our compared flexible channel assignment algorithms, is a complete research about flexible channel in recent years. FLUID uses a central controller to manage the per-packet scheduling and assign each packet a pair of channel width and center frequency used to transmmit the packet. According to the simulation result on NS-2, DFCA can reach at least 90% in throughput compared to the FLUID.
36
Lo, Kuen-Rong, and 羅坤榮. "Channel Assignment Schemes for Hierarchical Cellular Systems." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/84177540136138851638.
Full textAbstract:
博士國立交通大學
電子工程系
88
In this dissertation, channel assignment schemes of hierarchical cellular systems with overlaying macrocells and overlaid microcells are studied. First, a combined channel assignment (CCA) mechanism is proposed. The objective of the proposed CCA mechanism is to reduce the new-call blocking probability, decrease forced termination probability, and increase the channel utilization for the whole system. The proposed CCA mechanism combines overflow, underflow, and reversible schemes to reduce both the new-call blocking probability and forced termination probability. Also, it adopts the buffering scheme and considers load balancing between macrocell and microcell to obtain a high channel utilization. Next, a novel scheme, a fuzzy channel allocation controller (FCAC), is proposed for hierarchical cellular systems. The objective of the proposed FCAC scheme is to increase the channel utilization for the whole system and to guarantee the required QoS of handoffs as well. The FCAC mainly contains a fuzzy channel allocation processor (FCAP) which is designed to be in a two-layer architecture: a fuzzy admission threshold estimator in the first layer and a fuzzy channel allocator in the second layer. The FCAP chooses the handoff failure probability, defined as quality-of-service (QoS) index, and the resource availability as input linguistic variables for the fuzzy admission threshold estimator. The Sugeno''s position-gradient type reasoning method is applied in the fuzzy admission threshold estimator to adaptively adjust the admission threshold for the fuzzy channel allocator. For achieving channel allocation with flexible admission and soft rate control, a neural fuzzy channel allocation controller (NFCAC) is designed for multimedia services in hierarchical cellular system. The design concept of NFCAC is to support flexible resource allocation and soft rate control so that the high blocking rate in a hierarchical cellular system providing multi-channel services can be reduced. The NFCAC mainly contains a neural fuzzy channel allocation processor (NFCAP) which is designed to be in a two-layer architecture that consists of a fuzzy channel selector (FCS) in the first layer and a neural fuzzy call-admission and rate controller (NFCRC) in the second layer. FCS is a fuzzy control logic, and it can properly determine which channel in either macrocell or microcell to be allocated. The NFCRC is a five-layer neural fuzzy controller with the reinforcement learning architecture to perform the flexible admission control and soft rate management. 2. Hierarchical Cellular Systems 3. A Combined Channel Assignment Mechanism 4. A QoS-Guaranteed Fuzzy Channel Allocation Controller 5. A Neural Fuzzy Channel Allocation Controller for Multimedia Services 6. Conclusions
37
Chen, Chih-Jen, and 陳至仁. "Genetic Algorithms for Channel Assignment in PCS." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/69522928725215801693.
Full text
38
Lee, Ming-Hsi, and 李明羲. "Adaptive Channel Assignment Scheme for Wireless Networks." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/35125111400168946673.
Full textAbstract:
碩士銘傳大學
資訊管理研究所
89
In this paper, an adaptive channel assignment scheme is proposed to ensure the quality of services for the wireless networks. The proposed scheme based on the FCA (fixed channel assignment) strategy divides the channels into two categories, the guard channels and the shared channels. The number of guard channels is estimated by the Markov Model. The shared channels can be used by both new calls and handoff calls. This new scheme based on the fuzzy process can allocate most guard channels to the handoff calls and few to the new calls. In addition, the proposed scheme provides a load balance method for balancing the channel utilization between adjacent cells. From the simulation, the proposed scheme significantly improves the drop rate and the block rate in comparison with the existing methods.
39
Deora, Sanjeev K. "Channel assignment algorithms in cellular radio networks." Thesis, 1995. https://thesis.library.caltech.edu/3587/1/Deora_sk_1995.pdf.
Full textAbstract:
In this thesis, we study and compare the performance of several distributed channel assignment algorithms (CAAs) in a cellular system. The CAA which is used to assign a channel to a new call greatly influences the amount of traffic the system can support. We are interested in the design and analysis of algorithms which perform well, but at the same time are relatively easy to implement. In this thesis, we have analyzed the performance of a very simple CAA which we call the Timid Algorithm, in the limiting case of a large number of channels. We have been able to show that, under a plausible mathematical hypothesis, the algorithm is asymptotically optimal, where "asymptotically" refers to a system with a large number of channels. This is very surprising as there are algorithms of much higher complexity which provably do not have this property.
The Timid Algorithm is asymptotically optimal, but it requires a large number of channels for a satisfactory performance. We looked at some algorithms which retain the simplicity of the Timid algorithm but which can be expected to give a good performance even with a smaller number of channels. We called one such algorithm the Modified DCAA. We present some simulation results which show that this algorithm gives a reasonably good performance even when the number of channels is small. One of the ways to increase the capacity of a cellular system is through the use of micro-cells. The Modified DCAA, because of its distributed nature and low complexity, is particularly suitable for such microcellular systems.
We also present a method for computing the upper bound on the performance of any CAA in a cellular system with adjacent channel constraints. The method, although computationally intensive, may be useful for determining how close an algorithm's performance is to the optimal performance.
Finally, we discuss ways of obtaining the set of "allowable" states for a system. We also present some "measurement-based" algorithms and compare their performance with "prediction-based" algorithms.
40
Wu, Chih-Jen, and 鄔智仁. "A HIERARCHICAL CLUSTERING CHANNEL ASSIGNMENT SCHEME FOR MULTI-CHANNEL WIRELESS NETWORKS." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/01402476635845315673.
Full textAbstract:
碩士國立清華大學
通訊工程研究所
94
Channel assignment is an important issue in high throughput multi-channel wireless networks. Previous works on channel assignment use a common control channel to negotiate data channels by exchanging RTS/CTS. However, these schemes require time synchronous mechanism for starting to negotiation in each contention window, which is hard to achieve in wireless networks. Moreover, the above negotiation-based scheme may incur the channel switching delay during channel assignment in each hop of a multi-hop communication. In this paper, we propose an asynchronous scheme for channel assignment based on clustering all nodes in a wireless network into a hierarchical clustering architecture. With the hierarchical clustering architecture, our scheme can elect the cluster head of highest level and allocates channels by the cluster head of highest level to all leaves in a level-by-level basis. Simulation results show that the proposed channel assignment scheme outperforms the negotiation-based schemes in terms of packet collision, end-to-end delay, and overall throughput.
41
Huang, Wun-Yuan, and 黃文源. "Channel Assignment Study for Multi-Channel Multi-Radio Wireless Mesh Networks." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/03868574855987716539.
Full textAbstract:
碩士國立東華大學
資訊工程學系
97
With the popularity and development of networks in recent years, the wireless network has become an important research topic. Most research efforts on this area are to improve the performance of wireless network, particularly using multiple channels. While traditional wireless networks use single channel, there is no way to carry out many simultaneous transmission links at the same time, but multi-channel networks can solve the problem. However, there are some problems when using multi-channels. These problems are the interference and split problems. The split problems can be solved by using of multiple radios. The interference problem is a hot topic that lots of researchers try to solve. This paper focused on the architecture of the wireless mesh networks. The main research issue is how to improve network performance under multi-channel and multi-radio environments. We have to consider the interference problem for having good performance. There should be a good channel assignment mechanism to avoid interference. There are two types of methods on channel assignment: distributed channel assignment and centralized channel assignment. The difference between them is that when using the distributed channel assignment nodes decide which channel to use by themselves, but there is a controller in the centralized channel assignment. Our research focused on the centralized channel assignment. In this paper, three different centralized channel assignment algorithms were mentioned: 1. Load-aware channel assignment, 2. Coloring based load-aware channel assignment, and 3. Hybrid channel assignment. These three methods are compared in the multi-channel and multi-radio system under the architecture of the wireless mesh network. We use the NS2 network simulation tool to perform our experiments. We compare these three algorithms in terms of packet loss rate, end-to-end delay, and throughput.
42
Ko, Hsu-Feng, and 柯旭峰. "An Interference-Aware Channel Assignment Strategyin Multi-Radio Wireless Mesh NetworksAn Interference-Aware Channel Assignment Strategyin Multi-Radio Wireless Mesh NetworksAn Interference-Aware Channel Assignment Strategy in Multi-Radio Wireless Mesh." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/92623274949977330122.
Full textAbstract:
碩士國立高雄應用科技大學
資訊工程系
97
Next-generation wireless communication technologies will make life more convenient. The wireless mesh networks evolved into a key technology in wireless communication development. The wireless mesh networks can quickly increase the coverage of wireless service. While single radio mesh nodes operating on single channel suffer from interference. Because more and more demand for wireless networks, wireless interference is becoming more and more serious. Interference of overlapping channel maybe leads to packet loss. Multi-radio mesh node using non-overlapping channel can significantly alleviate the interference problem and increase the aggregate bandwidth available to the network, but spectrum is scarce that interference impact remains in multi-radio wireless mesh networks. However, the assignment of channel to the radio poses significant challenges in the scarce spectrum. The goal of channel assignment strategy is to minimize interference and improve network performance. In this article we analyzed interference impact and traffic patterns that designed an interference-aware channel assignment strategy called ICAS. ICAS incorporates interference impact and traffic pattern issues in order to assign adaptive channel to multi-radio wireless mesh networks.
43
Chan, Hsuan-Hao, and 詹烜皓. "Rate-Adaption Channel Assignment and Routing Algorithm forMulti-Channel WirelessMAN Mesh Networks." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/65vm8a.
Full textAbstract:
碩士國立中央大學
資訊工程研究所
94
Wireless mesh networks provide an easy deployed and extensi- ble solution to access Internet or communicate with each other for both enterprises and individuals. With the help of multi-channel and multi- radio, wireless mesh network can support more tra¢ c load to meet higher and higher bandwidth requirement in this modern time. There have been researches that focus on channel assignment and routing al- gorithm for IEEE 802.11 multi-channel environment to achieve better network throughout. However, the data rate and transmission range of 802.11 is limited and is not suitable for a large area metropolitan mesh network deployment. This thesis presents a rate-adaption chan- nel assignment and routing algorithm for IEEE 802.16 multi-channel multi-radio network in mesh mode which is expected as the last-mile wireless broadband connectivity. We takes 802.16 TDMA characteris- tic and modulation/rate adaption into consideration. The Simulation results show that our channel assignment procedure uses fewer chan- nels and better channel utilization than the migrated 802.11 greedy approach. Among the three comparing routing protocols, our protocol performs better in multi-rate 802.16 mesh network and results in higher aggregate throughput.
44
Hsu, Kun-Jin, and 許坤進. "Channel Assignment and Performance Evaluation of directional Multi-Channel Wireless Mesh Networks." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/99337367505530116796.
Full textAbstract:
碩士國立臺灣大學
資訊管理學研究所
93
IEEE provides non-overlapping channels for multiple transmissions to transmit at the same time. But most IEEE 802.11-based networks today use only a single channel. As a result, these networks can’t exploit the peak performance because of packet collision and interference. In this thesis, we study the interference problems including hidden terminal problem and exposed terminal problem in wireless mesh networks. We proposed a new architecture of directional multi-channel wireless mesh networks and TwoHop channel assignment algorithm. Compared to the single-channel network, we only revise the systematic procedure to support the multi-channel transmission with multiple network interface cards to transmit at the same time. Using our channel assignment algorithm to assign channels on links can lower the interference problems in wireless LANs and improve the network overall received goodput. We verify the performance improvement of the proposed algorithm through ns2. From the result, our approaches indeed improve the network performance and the success rate of the long route packets.
45
Liu, Pei-Shiun, and 呂佩勳. "A Channel Assignment Scheme for Concentric-Hexagon based Multi-Channel Wireless Networks." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/94059459556904430042.
Full textAbstract:
碩士東海大學
資訊工程學系
98
In a wireless network environment, a multi-hop communication performed on a single channel may lead to hidden node and radio signal interference problems which are also the key reasons why network transmission efficiency is often not as expected. In fact, the hidden node problem is caused by radio signal interference, i.e., the key reason is signal interference. Currently, many studies have used multi-channel schemes to solve the single channel interference problem. Multi-channel can increase the network capacity. But it raises other problems, e.g., multi-channel hidden terminal problem and how to allocate channels to wireless nodes so that interference problem can be avoided and transmission performance can be significantly improved. Basically, a well-defined channel assignment algorithm can solve the problems. Therefore, in this study, we proposed an AP deployment scheme, called concentric-hexagon-oriented multi-channel assignment (CHOMA for short) which supports multi-channel mechanism and is suitable for use in a metropolitan-scale wireless network system. With this scheme, the deployed APs are arranged as concentric-hexagon (C-hexa for short), and available channels are grouped and allocated to the C-hexas. We also schedule channels allocated to a C-hexa so as to reduce radio interference among its APs, consequentially improving the transmission capability and performance of a wireless network.
46
Chun-Kit, Ng, and 吳俊傑. "Channel-Aware Fairness Scheduling in WiMAX Downlink Assignment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/36444865823585358416.
Full text
47
Chen, Wen-Jiang, and 陳文江. "Researches on Channel Assignment Schemes for Cellular Systems." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/72250434909172210252.
Full textAbstract:
碩士國立中正大學
電機工程研究所
83
For cellular Time Division Multiple Access (TDMA), channel assignment algorithm is one of the most crucial techniques in increasing system capacity and radio spectrum utilization efficiency. Traditional analog Frequency Division Multiple Access(FDMA) Systems, e.g. AMPS, adopted central-controlled prediction-based fixed channel assignment while the second generation TDMA systems, e.g. PACS, DECT, adopt disbibuted measurement-based dynamic channel assignment and directed retry techniques. Conversation quality is also an important performance measure in addition to system capacity and spectrum utilization. In this thesis, in order to take into account both factors of system capacity and coversation quality, we define a performance measure, Grade Of Service (GOS), to assess the performance of various systems. In this thesis, we set up a TDMA cellular frequency reuse system by using BONeS (Block Oriented Network Simulator) simulation tool. Based on this simulation system, we first investigate several distributed measurement-based channel selection algorithms in fixed channel assignment system. Besides, a new method with adaptive threshold concept is presented to improve the performance of these channel selection algqorithms. Next, we study the performance of directed retry and load sharing techniques. Finally, a new algorithm called hybrid time-slot selection is proposed to improve the system performance.
48
Sun, Ming Hong, and 孫銘鴻. "Improved Dynamic Channel Assignment Scheme -Using Factor Graph." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/13051555986901810241.
Full textAbstract:
碩士長庚大學
電機工程學系
98
In order to enhance the frequency reuse factor and therefore increase the system throughput, the base station of wireless communication system use antenna array with multiple antennas to sector its cell coverage so that multiple in-cell users can share the same channel resources, including frequency spectra and time slots. In this study, we use the factor graph to serve the purpose of dynamic channel assignment. The sum-product algorithm is adopted to pass the messages of channel assignment in the factor graph constructed by the base stations and the mobile stations of a wireless cellular network. This study is fundamentally an improved approach of the original work proposed by Chen[1]. As compared to Chen’s previous work, in this study we propose a two-stage method to perform the channel assignment. In the first stage, the proposed approach first assigns channel to the nearest mobile station in each sector. After the first round distance-based channel assignment, in the second stage, the remaining un-assigned in-cell mobile stations will be taken to form the variable nodes of the factor graph and then their channel availability will be determined by the sum-product algorithm. As compared to Chen’s work, the proposed approach possesses lower channel blocking rate and significantly reduced computational overheads.
49
Chich, Cheng Tseng, and 曾志成. "The Study of Channel Assignment Strtegies in Microcellular." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/09795344389656047950.
Full textAbstract:
碩士國立台灣工業技術學院
電子工程技術研究所
85
In this thesis, we consider a seven-cell microcellular mobile communication system to study its channel assignment strategies. In order to check if a call generated in neighboring cells will be handed off to the target cell, we define the handoff region as a rectangular about cell boundaries. From this definition, the time that handoff calls stay in this region, i.e. dwell time, can also be computed. The distribution of dwell time obtained in this thesis shows that the exponential distribution assumption in previous works is not reasonable. For the study of channel assignment strategies with handoff in microcellular mobile communication networks, both the preemptive and non- preemptive disciplines are employed in the double queue model and the single queue model. The basic concept of channel assignment strategy we used is borrowed from the fixed channel assignment with guard channels. The impacts of emergency calls on the system performance are also considered by using guard channels. We observe the variation of the blocking probability of general calls, emergency calls and the forced termination probability of handoff calls by changing the number of emergency guard channels and handoff guard channels. As to the preemptive service discipline, we define the dropping probability as the probability for ongoing general calls being preempted by emergency calls which find no available channels upon arrival. Two cost functions are defined to compute the costs of different schemes. We compare the performance of the above schemes with that of the FIFO scheme and the results show that the single queue with preemptive scheme is a better channel assignment strategy than the other schemes.
50
Lai, Chang-Cheng, and 賴昌成. "Adaptive Channel Assignment Scheme for Wireless Cellular Networks." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/88982174673842521793.
Full textAbstract:
碩士國立東華大學
資訊工程學系
87
Abstract Because the radio spectrum is limited, how to manage the limited spectrum is an important issue since before. When radio spectrum is divided into channels, the way to manage spectrum is called channel assignment management. When channel assignment strategies are compared based on the manner in which co-channels are separated, they can be divided into Fixed Channel Assignment (FCA), Dynamic Channel Assignment (DCA), and Hybrid Channel Assignment (HCA). FCA performs well under heavy traffic load, DCA performs well under light traffic load, and HCA is suited to moderate traffic load. In this research we propose a new HCA scheme which takes advantage of all three schemes to reach the best performance, and the new HCA scheme is consisted kinds of channel assignment schemes. In our research the new call blocking probability and handoff call blocking probability are referred to as the performance indices. The first determines the fraction of new calls that are blocked, while the second is the fraction of admitted calls that terminate prematurely due to dropout. We use an analytical method to do the performance measurement, and the wireless cellular system is modeled as a multi-dimensional Markov chain under appropriate statistical assumptions. In fact from the point of view of a subscriber we prefer to block a new call request rather than block a handoff call request, so we include the handoff priority methods to our proposed HCA scheme. Our proposed HCA scheme has the lowest average new call and handoff call blocking probabilities because it takes advantage of the existing channel assignment schemes. Besides the analytical model, we also propose a transition mechanism of channel assignment schemes according to the analytical results. Keywords: Channel Assignment Scheme, Fixed Channel Assignment, Dynamic Channel Assignment, Hybrid Channel Assignment, Wireless Cellular Networks, Markov Chain