Distributed Channel Assignment Research Articles

A QoS Routing Protocol with Bandwidth Allocation in Multichannel Ad Hoc Networks

Mobile multimedia applications have recently generated much interest in mobile ad hoc networks (MANETs) supporting quality-of-service (QoS) communications. Multiple non-interfering channels are available in 802.11 and 802.15 based wireless networks. Capacity of such channels can be combined to achieve higher QoS performance than for single channel networks. The capacity of MANETs can be substantially increased by equipping each network node with multiple interfaces that can operate on multiple non-overlapping channels. However, new scheduling, channel assignment, and routing protocols are required to utilize the increased bandwidth in multichannel MANETs. In this paper, we propose an on-demand routing protocol M-QoS-AODV in multichannel MANETs that incorporates a distributed channel assignment scheme and routing discovery process to support multimedia communication and to satisfy QoS bandwidth requirement. The proposed channel assignment scheme can efficiently express the channel usage and interference information within a certain range, which reduces interference and enhances channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel MANETs over existing routing algorithms. Simulation results show that the proposed M-QoS-AODV protocol can effectively increase throughput and reduce delay, as compared to AODV and M-AODV-R protocols.

Research on Line-graph based Distributed Channel Assignment Algorithm in Wireless Mesh Network

Research on Line-graph based Distributed Channel Assignment Algorithm in Wireless Mesh Network

Distributed channel assignment combined with routing over multi-radio multi-channel wireless mesh networks

In order to realize the reduction of equipment cost and the demand of higher capacity, wireless mesh network (WMN) router devices usually have several interfaces and work on multi-channels. Jointing channel allocation, interface assignment and routing can efficiently improve the network capacity. This paper presents an efficient channel assignment scheme combined with the multi-radio link quality source routing (MR-LQSR) protocol, which is called channel assignment with MR-LQSR (CA-LQSR). In this scheme, a physical interference model is established: calculated transmission time (CTT) is proposed as the metric of channel assignment, which can reflect the real network environment and channel interference best, and enhanced weighted cumulative expected transmission time (EWCETT) is proposed as the routing metric, which preserves load balancing and bandwidth of links. Meantime, the expression of EWCETT contains the value of CTT, thus the total cost time of channel assignment and routing can be reduced. Simulation results show that our method has advantage of higher throughput, lower end-to-end time delay, and less network cost over some other existing methods.

Cross‐layer scheduling for multi‐users in cognitive multi‐radio mesh networks

ABSTRACTA wireless mesh network has been popularly researched as a wireless backbone for Internet access. However, the deployment of wireless mesh networks in unlicensed bands of urban areas is challenging because of interference from external users such as residential access points. We have proposed Urban‐X, which is a first attempt towards multi‐radio cognitive mesh networks in industrial, scientific, and medical bands. Urban‐X first controls network topology with a distributed channel assignment to avoid interference in large timescale. In such a topology, we develop a new link‐layer transmission‐scheduling algorithm together with source rate control as a small‐timescale approach, which exploits receiver diversity when receivers of multi‐flows can have different channel conditions because of varying interference. For this purpose, mesh nodes probe the channel condition of received mesh nodes using group Request to Send and group Clear to Send. In this study, we establish a mathematical Urban‐X model in a cross‐layer architecture, adopting a well‐known network utility maximization framework. We demonstrate the feasibility of our idea using a simulation on the model. Simulation results show improved network throughput from exploiting receiver diversity and distributed channel assignment under varying external user interference. Copyright © 2012 John Wiley & Sons, Ltd.

Channel allocation algorithms for WLANs using distributed optimization

The performance of a wireless local area network (WLAN) depends on the channel assignments among interfering access points (APs). Due to the limited number of non-overlapping channels, severe interference scenarios may arise if no appropriated spectrum planning is employed. In our study we focus on WLANs scenarios where APs may belong to different administrative domains, which is actually a very common situation in dense urban deployments. In such cases the use of centralized algorithms is not feasible and the already proposed distributed methods does not guarantee optimal channel assignment. In this paper, therefore, we formalize the channel allocation as a distributed constraint optimization problem (DCOP) and propose a new distributed channel assignment algorithm named DCAA-O, which can find the optimal solution to the channel assignment problem for a group of APs. A suboptimal strategy denoted DCAA-S is also investigated, which aims at reducing the number of control messages to be exchanged between APs, while still achieving a suboptimal solution which is very close to the optimal one. The simulation results show that the proposed algorithms are able to outperform the best known techniques both in terms of solution quality and number of exchanged messages.

A Framework for External Interference-Aware Distributed Channel Assignment

DES-Chan is a framework for experimentally driven research on distributed channel assignment algorithms in wireless mesh networks. DES-Chan eases the development process by providing a set of common services required by distributed channel assignment algorithms. A new challenge for channel assignment algorithms are sources of external interferences. With the increasing number of wireless devices in the unlicensed radio spectrum, co-located devices that share the same radio channel may have a severe impact on the network performance. DES-Chan provides a sensing component to detect such external devices and predict their future activity. As a proof of concept, the authors present a reference implementation of a distributed greedy channel assignment algorithm. The authors evaluate its performance in the DES-Testbed, a multi-transceiver wireless mesh network with 128 nodes at the Freie Universität Berlin.

CACAO: Distributed Client-Assisted Channel Assignment Optimization for Uncoordinated WLANs

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 self-configure 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 NP-hard, and propose an efficient, simple, and distributed algorithm termed CACAO (Client-Assisted 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.

ZAP: a distributed channel assignment algorithm for cognitive radio networks

AbstractWe propose ZAP, an algorithm for the distributed channel assignment in cognitive radio (CR) networks. CRs are capable of identifying underutilized licensed bands of the spectrum, allowing their reuse by secondary users without interfering with primary users. In this context, efficient channel assignment is challenging as ideally it must be simple, incur acceptable communication overhead, provide timely response, and be adaptive to accommodate frequent changes in the network. Another challenge is the optimization of network capacity through interference minimization. In contrast to related work, ZAP addresses these challenges with a fully distributed approach based only on local (neighborhood) knowledge, while significantly reducing computational costs and the number of messages required for channel assignment. Simulations confirm the efficiency of ZAP in terms of (i) the performance tradeoff between different metrics and (ii) the fast achievement of a suitable assignment solution regardless of network size and density.

Coloring Spatial Point Processes With Applications to Peer Discovery in Large Wireless Networks

In this paper, we study distributed channel assignment in wireless networks with applications to peer discovery in ad hoc wireless networks. We model channel assignment as a coloring problem for spatial point processes in which <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> nodes are located in a unit cube uniformly at random and each node is assigned one of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">K</i> colors, where each color represents a channel. The objective is to maximize the spatial separation between nodes of the same color. In general, it is hard to derive the optimal coloring algorithm, and we therefore consider a natural online greedy coloring algorithm first proposed by Ko and Rubenstein in 2005. We prove two key results: 1) with just log <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> /log log <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> colors, the distance separation achieved by the greedy coloring algorithm asymptotically matches the optimal distance separation that can be achieved by an algorithm which is allowed to optimally place the nodes but is allowed to use only one color; and 2) when K=Ω(log n), the greedy coloring algorithm asymptotically achieves the best distance separation that can be achieved by an algorithm which is allowed to both optimally color and place nodes. The greedy coloring algorithm is also shown to dramatically outperform a simple random coloring algorithm. Moreover, the results continue to hold under node mobility.

GDCA: A Distributed Channel Assignment Mechanism for Multi-radio Multi-Channel Wireless Mesh Networks

C hannel assignment is one of the most important problem in the research of the multi-radio multi-channel wireless mesh networks ((MRMC-WMN) . Aiming at minimizing the overall network interference and optimizing the usage of channel resource, channel assignment problem must obey the constraint of limited radios and available channels for MRMC-WMN. The above optimization problem is known to be NP-complete. This paper focuses on the study of channel assignment in MRMC- WMN . We propose a new grid-loop-based mechanism for dynami c c hannel a ssignment . Our mechanism exploits the group which we called grid-loop, which is constructed on distributed minimum spanning tree by self-organized. Our new GDCA scheme has many advantages over cluster-based scheme. The analysis and comparison demonstrates its feasibility, stability, cost-saving and efficiency.

Improving densely deployed wireless network performance in unlicensed spectrum through hidden-node aware channel assignment

It is well known that a wireless local area network (WLAN) based on the IEEE 802.11 standard suffers from interference and scalability problems due to the limited number of non-overlapping channels. In order to mitigate the interference problem, channel assignment algorithms has been a popular research topic in recent years. It has been shown that such algorithms can greatly reduce the interference among wireless access points. However, in this paper, we show that previously proposed channel assignment algorithms may lead to an increased number of hidden nodes in dense network deployments. We also show that this can significantly decrease the performance of the network. Furthermore, we present results from experiments showing that the Request to send (RTS)/Clear to send (CTS) mechanism is unable to solve the hidden node problem in infrastructure WLANs, and therefore careful consideration needs to be taken when choosing channel assignment strategies in densely deployed wireless networks. To this end, we propose both a centralized channel assignment algorithm and a distributed channel assignment algorithm. Using a simulation study, we show that the proposed algorithms can outperform traditional channel assignment in densely deployed scenarios, in terms of QoS sensitive VoIP support without compromising the aggregate throughput, and that they are therefore a better performing alternative in such settings.

Insights from Experimental Research on Distributed Channel Assignment in Wireless Testbeds

This article presents the DES-Chan framework for experimental research on distributed channel assignment algorithms in wireless mesh testbeds. The implementation process of channel assignment algorithms is a difficult task for the researcher since common operating systems do not support channel assignment algorithms. DES-Chan provides a set of common services required by distributed channel assignment algorithms and eases the implementation effort. The results of experiments to measure the channel characteristics in terms of intra-path and inter-path interference according to the channel distance on the DES-Testbed are also presented. The DES-Testbed is a multi-radio WMN with more than 100 nodes located on the campus of the Freie Universität Berlin. These measurements are an important input to validate common assumptions of WMNs and derive more realistic, measurement-based interference models in contrast to simplified heuristics.

A distributed channel assignment control for QoS support in mobile ad hoc networks

Recently, one of the most critical issues in mobile ad hoc networks (MANETs) is providing quality of service (QoS) through routing, access/admission control, resource reservation, and mobility management. However, most existing solutions do not provide QoS effectively due to the interference arising from mobility. In this paper, we refer to interference as a quasi-exposed node problem. To solve this problem, a new algorithm, named a distributed channel assignment control, is proposed that focuses on performance enhancements related to QoS and mathematical analysis techniques for the channel bandwidth. This novel algorithm uses channel assignment control with a power control to reduce the negative effects induced by the quasi-exposed node problem, and then the channels are adaptively negotiated to allow communication in the interference region. The proposed algorithm has been evaluated via extensive simulations, and the results show that it can successfully guarantee QoS by maintaining good throughput, reducing control message overhead, and enhancing delay.

Coloring spatial point processes with applications to peer discovery in large wireless networks

In this paper, we study distributed channel assignment in wireless networks with applications to peer discovery in ad hoc wireless networks. We model channel assignment as a coloring problem for spatial point processes in which n nodes are located in a unit cube uniformly at random and each node is assigned one of K colors, where each color represents a channel. The objective is to maximize the spatial separation between nodes of the same color. In general, it is hard to derive the optimal coloring algorithm and therefore, we consider a natural greedy coloring algorithm, first proposed in [5]. We prove two key results: (i) with just a small number of colors when K is roughly of the order of log(n) loglog(n), the distance separation achieved by the greedy coloring algorithm asymptotically matches the optimal distance separation that can be achieved by an algorithm which is allowed to select the locations of the nodes but is allowed to use only one color, and (ii) when K = Omega(log(n)), the greedy coloring algorithm asymptotically achieves the best distance separation that can be achieved by an algorithm which is allowed to both optimally color and place nodes. The greedy coloring algorithm is also shown to dramatically outperform a simple random coloring algorithm. Moreover, the results continue to hold under node mobilities.

SeCA: A framework for Secure Channel Assignment in wireless mesh networks

To maximize the available throughput in multi-channel multi-radio wireless mesh networks (WMNs), it is a critical issue to design a channel assignment scheme efficiently utilizing orthogonal channels. However, most channel assignment schemes are vulnerable to the misbehaviors of nodes participating in channel assignment, and existing secure channel assignment schemes do not address all of the vulnerabilities. In this paper, we address the threats to channel assignment in WMNs resulting from node misbehaviors and present a generic verification framework to detect such misbehaviors. We develop a concrete verification scheme based on this framework and an existing distributed channel assignment scheme. We validate our approach by implementing the verification scheme and evaluating it through simulation. The results show that our approach improves misbehavior detection with minimum performance overhead.

A distributed channel assignment protocol for rate separation in wireless mesh networks

Wireless Mesh Networks (WMNs) support the cost-effective broadband access for Internet users. Although today’s IEEE 802.11 PHY and MAC specifications provide multi-channel and multi-rate capabilities, exploiting available channels and data rates is a critical issue to guarantee high network performance. In multi-rate wireless networks, high-rate links heavily suffer from performance degradation due to the presence of low-rate links. This problem is often referred to as performance anomaly. In this paper, we propose a Rate-Based Channel Assignment (RB-CA) protocol to alleviate performance anomaly by using multiple channels in WMNs. RB-CA exploits a new metric, called Prioritized Transmission Time (PTT), in order to form High-rate Multi-channel Paths (HMPs). With HMPs, a large volume of traffics can be simultaneously delivered from or to the Internet via multiple non-overlapping channels as well as high-rate links. Extensive ns-2 simulations and experiments in a real test-bed have been performed to evaluate the performance of RB-CA and then we compared it with a well-known existing WMN architecture. Our simulation and experimental results show that RB-CA achieves improved performance in terms of aggregate throughput, packet delivery ratio, end-to-end delay, and fairness.

Distributed Channel Assignment Scheme Supporting Various Traffic Loads in Microcellular Systems

In this letter, we propose a distributed channel assignment where each basestation selects a set of channels shared by multiple users through time domain scheduling for best effort services. The proposed scheme distributedly assigns the channels considering a cochannel interference from neighboring basestations and its own traffic load condition. The computer simulation demonstrates that the proposed scheme appropriately assigns the channels to the basestations taking into account these requirements.

Minimum neighbour and extended Kalman filter estimator: a practical distributed channel assignment scheme for dense wireless local area networks

Dense deployments of wireless local area networks (WLANs) are becoming a norm in many cities around the world. However, increased interference and traffic demands can severely limit the aggregate throughput achievable unless an effective channel assignment scheme is used. In this work, a simple and effective distributed channel assignment (DCA) scheme is proposed. It is shown that in order to maximise throughput, each access point (AP) simply chooses the channel with the minimum number of active neighbour nodes (i.e. nodes associated with neighbouring APs that have packets to send). However, application of such a scheme to practice depends critically on its ability to estimate the number of neighbour nodes in each channel, for which no practical estimator has been proposed before. In view of this, an extended Kalman filter (EKF) estimator and an estimate of the number of nodes by AP are proposed. These not only provide fast and accurate estimates but can also exploit channel switching information of neighbouring APs. Extensive packet level simulation results show that the proposed minimum neighbour and EKF estimator (MINEK) scheme is highly scalable and can provide significant throughput improvement over other channel assignment schemes.

A Petri-Net-Based Automated Distributed Dynamic Channel Assignment for Cellular Network

In this paper, we propose a Petri-net (PN)-based automated distributed dynamic channel assignment (DDCA) method for the cellular network. We view DDCA as a discrete event system (DES) and propose a PN to model the automated DDCA. The spontaneous handshaking mechanism in the proposed PN can resolve the hard constraint of the cellular network so that no two cells within the channel reuse distance can use the same channel. Instead of the commonly adopted packing and resonance conditions for channel assignment and reassignment, we propose available channel-based channel-selection and channel-reassignment schemes. We rigorously prove the adequacy of the proposed PN and the satisfaction of hard constraint. We also test the proposed PN-based automated DDCA method using numerous test cases. The test results show that our method outperforms the comparing methods in terms of blocking probability.

Practical, distributed channel assignment and routing in dual-radio mesh networks

Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to radios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load. This paper presents ROMA, a practical, distributed channel assignment and routing protocol that achieves good multi-hop path performance between every node and one or more designated gateway nodes in a dual-radio network. ROMA assigns non-overlapping channels to links along each gateway path to eliminate intra-path interference. ROMA reduces inter-path interference by assigning different channels to paths destined for different gateways whenever possible. Evaluations on a 24-node dual-radio testbed show that ROMA achieves high throughput in a variety of scenarios.