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In this paper, we propose a load-based scheme for assigning channels to radio interfaces in multi-radio, multi-channel wireless mesh networks. We first construct a model for channel assignment as an optimization problem with the goal of minimizing the overall network interference. The problem is proven to be NP-Hard. We then apply the Lagrangian re...
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... account for this, the IEEE 802.11 standards provide multiple overlapping frequency channels to support multiple simultaneous transmissions in the same interference region. Figure 1 illustrates the use of multiple channels in a multi-radio wireless mesh network. While these multiple channels offer a way of minimizing interference, they raise additional issues of channel assignment for maximizing overall throughput. ...
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This paper considers the channel-assignment and scheduling in wireless mesh networks that employ multiple radios and multiple channels. In contrast to the various algorithms available in the literature, we explicitly model the delay overhead that is incurred during channel switching, and use that delay in the design of algorithms. We prove that the...
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... We now discuss some GA approaches. Sridhar et al. present a CA methodology for multi-radio WMNs that use only the Wi-Fi spectrum [38]. The optimisation goal is minimising interference. ...
In this work, we evaluate the application of four different metaheuristic optimisation algorithms for solving the channel assignment problem in a multi-radio multi-channel Wireless Mesh Network (WMN) using Dynamic Spectrum Access (DSA). The work advances a near optimal channel assignment (CA) in a WMN that uses DSA by applying soft computing methods. While CA in a WMN is well-studied, and CA for secondary user cognitive radio networks has also been studied in the literature, CA for our specific scenario of an infrastructure DSA-WMN is novel. This scenario poses new challenges because nodes are spread out geographically and so may have different allowed channels and experience different levels of external interference in different channels. A solution must meet two conflicting requirements simultaneously: 1) to avoid interference within the network and with external interference sources, and 2) maintain connectivity within the network; all while staying within the radio interface constraint, i.e., only assigning as many channels to a node as it has radios. We present a novel algorithm, used alongside the metaheuristic optimisation algorithms, which ensures the feasibility of solutions in the search space. Average Signal to Interference and Noise Ratio (
$SINR$
) over the network is used as the performance measure, with the goal of optimisation being to find the highest average
$SINR$
. This is a more realistic performance measure than the binary on/off conflict-based measures most common in the literature. Our energy-based method also has the unique advantage that it is protocol-agnostic, being able to avoid interference from external sources that use different protocols and standards. The algorithms that are compared in this work are Simulated Annealing (SA), the Genetic Algorithm (GA), Particle Swarm Optimisation (PSO), and Differential Evolution (DE). These algorithms were evaluated through the use of simulation in Network Simulator 3. Various parameters were experimented with for each of the employed algorithms. The resultant best set of parameters was used for the comparison of the four metaheuristic algorithms. It was found that the population-based algorithms (PSO, GA, and DE) all perform satisfactorily for this problem, although DE is superior to the others. SA can give acceptable solutions, but performs poorly in comparison to the population-based algorithms. The paper also considers the computational complexity of the methods. It is found that SA and DE perform well in this regard.
... Much work has been done on channel assignment, including on MRMC scenarios e.g. [3,5,15,21,26,28]. There has even been work that uses Simulated Annealing for the CA problem in WMNs [4]. ...
... In [26], the authors present centralised load-based CAs, one constructed by Lagrangian relaxation of the NP-hard Integer Linear Programming problem formulation, and the other using a Genetic Algorithm. They also present a hill-climbing-based distributed algorithm. ...
... This leads to relatively efficient medium access to curtail end-to-end delay and collisions among contending stations. Srikrishna Sridhar et.al, [15] have proposed a channel to radio mapping scheme in MRMC based WMNs. They have constructed a model for channel assignment as an optimization problem with the goal of minimizing the overall network interference. ...
Wireless Mesh Network (WMN) [1] deployment based on IEEE 802.11s [2] standard is a popular choice in setting up cost-efficient alternative to support broadband internet services to a larger population. They can provide network connectivity over large geography when compared to WLANs. WMN makes use of Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol with Binary Exponential Backoff (BEB) algorithm to avoid collision due to simultaneous transmissions by more than one user at the same time. These collisions bring the network performance drastically down if not handled properly. Thus this work tries to evaluate the suitability of the better efficient CA algorithms (EIED, EILD, MILD, PB, CCW, EBO, HBA…) which can replace BEB to support higher throughput for IEEE 802.11s networks (WMNs). The NS-3 [3] simulation results indicate that Polynomial Backoff (PB) performs better than others against the BEB algorithm in about 52 % of network scenarios and it is suggested to operate with TWO radios enabled with all access points.
... Connected Low Interference Channel Assignment (CLICA) [4] uses a depth first search approach to assign channels, Topology-controlled Interference-aware Channel Assignment (TICA) [5] is another approach that uses topology to assign channels by constructing Shortest Path Tree (SPT). Genetic Algorithm (GA) [6] is a population-based stochastic search approach to assign channels to WMN links. ...
In multi-radio multi-channel (MRMC) WMNs, interference alleviation is affected through several network design techniques e.g., channel assignment (CA), link scheduling, routing etc., intelligent CA schemes being the most effective tool for interference mitigation. CA in WMNs is an NP-Hard problem, and makes optimality a desired yet elusive goal in real-time deployments which are characterized by fast transmission and switching times and minimal end-to-end latency. The trade-off between optimal performance and minimal response times is often achieved through CA schemes that employ heuristics to propose efficient solutions. WMN configuration and physical layout are also crucial factors which decide network performance, and it has been demonstrated in numerous research works that rectangular/square grid WMNs outperform random or unplanned WMN deployments in terms of network capacity, latency, and network resilience. In this work, we propose a smart heuristic approach to devise a near-optimal CA algorithm for grid WMNs (NOCAG). We demonstrate the efficacy of NOCAG by evaluating its performance against the minimal-interference CA generated through a rudimentary brute-force technique (BFCA), for the same WMN configuration. We assess its ability to mitigate interference both, theoretically (through interference estimation metrics) and experimentally (by running rigorous simulations in NS-3). We demonstrate that the performance of NOCAG is almost as good as the BFCA, at a minimal computational overhead of O(n) compared to the exponential of BFCA.
... By minimizing interference in the overall network, CA increases its total capacity. The CA problem is NP-complete [5]. ...
... Each node has two functions [e.g., according the LA probability types, Eqs. (3)(4)(5)]. The intelligence of this method is derived from the LA, which can transform radio interface from static to dynamic states and conversely, according to environment feedback. ...
Wireless mesh networks (WMNs) consist of static nodes that usually have one or more radios or media. Optimal channel assignment (CA) for nodes is a challenging problem in WMNs. CA aims to minimize interference in the overall network and thus increase the total capacity of the network. This paper proposes a new method for solving the CA problem that comparatively performs more efficient than existing methods. The link layer in the TCP/IP model is a descriptive realm of networking protocols that operates on the local network link in routers discovery and neighboring hosts. TCP/IP employs the link-layer protocol (LLP) that is included among the hybrid states in CA methods, and learning automata are used to complete the algorithm with an intelligent method for suitable CA. We call this algorithm LLLA, which are short for LLP and learning automata. Our simulation results show that LLLA performs more efficient than ad hoc on-demand distance vector (AODV) types with respect to parameters such as packet drop, end-to-end delay, average goodput, jitter in special applications, and energy usage.
... If such a link exists, it is denoted with l u,v . Two links l u,v and l x,y interfere with each other if at least one of the following distances d u,x , d u,y , d v,x , d v,y is smaller than the interference radius r i [40]. ...
... For this reason, most algorithms introduce mechanisms to preserve the network topology throughout the channel assignment procedure, for instance by tuning one interface per node permanently to a common network-wide global channel [48]. The problem of channel assignment has been reduced to variations of the graph coloring problem and has thus proven to be NP-hard [36,40,54,55]. Thus, most proposed distributed channel assignment algorithms build on greedy methods in order to locally minimize the interference levels. ...
... Therefore, it is important to develop appropriate counter-measures, such as the synchronization of channel switches. Some algorithms also introduce restrictions regarding the channel assignment choices, such that each channel-link combination may only be assigned once throughout the channel assignment procedure [36,40]. While this helps guaranteeing the convergence and stabilization of the algorithm, it may lead to sub-optimal channel assignment and render the algorithm unadaptive to topology changes. ...
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.
... It is necessary that each of these two nodes has a radio and these radios be adjusted to a common channel. Because nodes can have connection to each other only if this connection is made through a common channel [2, 3]. One of the problems in wireless mesh networks is optimum Channel Assignment (CA) for nodes and interference. ...
Wireless mesh networks (WMNs) have emerged as a promising technology for providing ubiquitous access to mobile users, and quick and easy extension of local area networks into a wide area. Channel assignment problem is proven to be an NP-complete problem in WMNs. This paper aims proposing a new method to solve channel assignment problem in multi-radio, multichannel wireless mesh networks for improving the quality of communications in the network. Here, a new hybrid state channel assignment method is employed. This paper proposes a Link-Layard Protocol and Learning Automata (LLLA) to achieve a smart method for suitable assignment. Simulation results show that the proposed algorithm has better results compared to AODV method. E.g., it reduces the packet drop considerably without degrading.
... MCMR facilitates efficient bandwidth utilization and achieves a notable interference reduction. A new challenge will be raised, which is how to assign the channels to the radios in order to achieve the maximum throughput, and this problem was proven to be NPhard [1]. ...
... A load-based scheme for assigning channels to radio interfaces in MCMR wireless mesh networks was proposed in [1]. The channel assignment problem was addressed using the Lagrangian relaxation method to find lower bounds as well as near-optimal feasible solutions for large size networks. ...
In a multi-channel multi-radio (MCMR) wireless network, each user is equipped with multiple transceivers (radios) that can be used simultaneously. Each radio is dynamically tuned to a given carrier frequency with fixed bandwidth, allowing a user to choose from a fixed number of orthogonal channels. Extensive efforts have been devoted to propose efficient channel assignment protocols. One of these protocols is the link layer protocol that is designed to utilize multi-channels multi-radio. The proposed protocol enhances the throughput performance over the protocol that uses a single channel on all hops; however self interference along the route still exists. In this work we use adaptive transmission power management to overcome the self interference. Adaptive transmission power management allows multiple interference-limited concurrent transmissions. Reducing the interference would improve the throughput performance of the network. We use network simulator 2 (NS2) to verify our theoretical expectation, which shows a significant increase in the network's throughput.
... One solution is to switch a dedicated interface to a common global channel to preserve the network connectivity [8]. Link-based channel approaches preserve the network topology by assigning channels to links instead of interfaces [2], [9], thus being transparent to the routing layer. Another solution is to have one interface per node on a fixed channel for receiving and dynamically switch to the channel of the receivers fixed interface for sending [10]. ...
... The former metrics are used to measure the decrease of interference achieved by the particular algorithm according to the used interference model. Usually, the overall network interference is measured after the application of the channel assignment algorithm and compared to a single channel network or random channel assignment [9]. While it is a good approach to take the cause of the problem into account, it has to be kept in mind that the interference model is a simplification of the complex interference effects in reality. ...
Channel assignment for multi-radio wireless mesh networks has been proven efficient to increase the network performance by decreasing the interference of simultaneous transmissions. Many algorithms have already been proposed, however, a meaningful comparison of their performance is difficult. The main reasons are that different experimentation environments and performance metrics are used for their evaluation. Thus, finding a universal methodology for the performance evaluation that ensures comparability is complicated. In this paper, we close this gap with a methodology for the performance evaluation of channel assignment algorithms in wireless testbeds. We developed domain-specific performance metrics that express the decrease of network-wide interference. Using these metrics, we developed benchmarking scenarios for performance measurements in wireless testbeds. We present the benchmarking results of a distributed link-based channel assignment algorithm and compare the results to a random-based algorithm and a single channel network. The evaluation was run on the DES-Testbed, a 128 node multi-radio testbed at the Freie Universität Berlin.
... Various schemes that attempt to make efficient use of multiple orthogonal channels in WMNs have been reported in the literature [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These schemes can be broadly categorized into two types: the centralized schemes [9][10][11][12][13]18] and the distributed schemes [14][15][16][19][20][21][22][23]. ...
... Various schemes that attempt to make efficient use of multiple orthogonal channels in WMNs have been reported in the literature [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. These schemes can be broadly categorized into two types: the centralized schemes [9][10][11][12][13]18] and the distributed schemes [14][15][16][19][20][21][22][23]. For centralized channel assignment schemes, channel assignment is performed at one central location and global information needs to be known before assigning channels. ...
... Assuming that each node is equipped with multiple radio interfaces, Huang et al. investigated the capability that WMNs can offer the wireless nodes to transmit/receive packets across the gateways over multiple orthogonal channels [24]. The centralized channel assignment schemes suggested in [9] and [10] adopt linear programming (LP) and graph theory to assign a channel to each communication node's interface. In recent years, realizing the cross-dependency between channel assignment and routing, a few centralized, joint multi-channel assignment and routing schemes have been proposed in [11][12][13]. ...
Use of multiple orthogonal channels can significantly improve network throughput of multi-hop wireless mesh networks (WMNs). In these WMNs where multiple channels are available, channel assignment is done either in a centralized manner, which unfortunately shows a poor scalability with respect to the increase of network size, or in a distributed manner, where at least one channel has to be dedicated for exchanging necessary control messages or time synchronization has to be utilized for managing the duration of data packet transmission, causing excessive system overhead and waste of bandwidth resource. In this paper, we first formulate multi-channel assignment as a NP-hard optimization problem. Then a distributed, heuristic temporal–spatial multi-channel assignment and routing scheme is proposed, assuming every wireless node in the network is equipped with a single-radio interface. Here the gateway node is set to use all the channels sequentially in a round-robin fashion. This temporal scheme ensures all the nodes that need to directly communicate with the gateway node shall have a fair access to it. For those non-gateway nodes, a spatial scheme where channels are assigned based on their neighbors’ channel usage is adopted to exploit parallel communications and avoid channel interference among nodes. Furthermore, since the routing factors, including channel usage of neighbor nodes, node hop count, node memory size, and node communication history, are all considered along with the channel assignment, network performance, measured by packet delivery latency, channel usage ratio, and memory usage ratio, tends to be considerably enhanced. The simulation results have confirmed that, compared with a couple of well-known multi-channel assignment schemes, such as LCM [21] and ROMA [15], the proposed scheme shows substantial improvement in network throughput with a very modest collision level. In addition, the proposed scheme is highly scalable as the algorithm complexity is only linearly dependent on the total number of channels that are available in the network and the number of neighbors that a network node directly connects to.
