Multi-radio Mesh Networks Research Articles

A Routing Framework With Protocol Conversions Across Multiradio IoT Platforms

The proliferation of sensors as part of the Internet-of-Things (IoT) paradigm envisions a world of interconnected, interdependent deployments, involving one or multiple radio technologies. Multiradio mesh deployments facilitated using a network of low-cost IoT platforms, such as Raspberry Pis (RPis), ASUS Tinker Board S, Banana Pi M64, etc., seem an ideal fit as wireless backbones for such deployments, with many of these platforms having built-in support for multiple wireless technologies. However, the state-of-the-art routing solutions need to be revisited to suit the capabilities of low-power multiradio solutions, especially while performing best effort transmissions. This is because a majority of the existing routing solutions favor channel diversity while routing, ignoring the possible overheads associated with protocol conversions. We argue that in reality, these overheads can become quite significant in a multiradio network where the radios are quite different in terms of packet formats, sizes, data rates, etc. To prove this, we estimate the impact of these overheads using an experimental study performed across three popular IoT technologies—WiFi, Bluetooth, and ZigBee, using a real-time RPi-based testbed. We stress on how severe this impact could be, by estimating how often these conversions happen in a randomly chosen multihop path, using a probabilistic mathematical framework. Based on this, we develop Chorus, a first-of-its-kind routing algorithm, which estimates the least overhead path, inclusive of conversion overheads. Chorus achieves this by developing a comprehensive layered graph modeling of the given multiradio mesh network. The modeling is capable of handling all conversion overheads, including the factors associated with the possible fragmentation and aggregation. We implement Chorus in an indoor testbed comprising of RPis and demonstrate the performance improvement while routing across the network of RPis. Our results estimate that Chorus can provide an improvement close to 33% in battery usage per RPi with an average reduction of 25% in packet drops.

Energy-efficient activation of nodes and radios in multi-radio WLAN mesh networks

In multi-radio WLAN mesh networks (WMNs), it is an effective way to achieve energy saving through on-demand activation of network nodes and radios, that is, scheduling nodes on/off and switching radios on/off according to the current traffic demand. In this paper, we study the problem of joint node scheduling and radio switching for energy efficiency, which aims to minimise the power consumption of the network. We first present a mathematical model based on integer linear programming (ILP). Then, we propose an efficient heuristic algorithm, which iteratively finds routing paths for all mesh access points (MAPs) and activates as few nodes and radios as possible, while satisfying their traffic demand. Moreover, we also consider the dynamics of the traffic demand, and propose a fast update algorithm to adjust the activation of partial nodes and radios. Finally, extensive simulations are conducted to assess the effectiveness and efficiency of our proposed algorithms.

Channel assignment in multi-radio wireless mesh networks using an improved gravitational search algorithm

Wireless mesh networks have emerged recently to improve networking performance and other networking services. The combination of multi-radio nodes with multi-hop mesh architectures leads researcher to overcome some constraints of single-radio networks such as incapability of effective scale to exploit the increasing available system bandwidth. Therefore, a good channel assignment (CA) in multi-radio mesh networks can reduce the number of interference co-channels and improve the network throughput. In this paper, an improved version of gravitational search algorithm (IGSA) is proposed to solve CA problems; a local operator is combined with the gravitational search algorithm to find the best solution. In this study, the main goal is to minimize the overall interference and to increase the network throughput with ensuring network connectivity. The obtained results confirm the high performance of our algorithm in comparison with other related works.

Utility based channel assignment: A centralized channel assignment mechanism for multi radio multi channel wireless mesh networks

In this paper, we address the channel assignment problem in a multi-radio mesh network that involves assigning channels to radio interfaces for eliminating the effect of wireless interference. Due to the insufficient number of frequency channels and available radios per node, interference is still present which limits the available bandwidth on wireless links and eventually decreases the achievable throughput. In this paper, we investigate the effect of considering the diverse delivery probability of the wireless links on the channel assignment solutions. We show that it is possible to classify the wireless links and omit some of them to benefit from a more diverse-channel solution. We propose a new channel assignment mechanism aiming to minimize the interference over high performance links. Finally, a performance study is carried out to assess the effectiveness of our proposed algorithm. Evaluations show that the multi-channel network obtained from our proposed algorithm achieves significant improvement in terms of reducing the interference and increasing the network capacity. Key words: Wireless mesh network, channel assignment, multi-radio, multi-channel.

Interference-Aware Bandwidth Reservation in multi-radio multi-channel mesh networks

In this paper, we propose the Interference-Aware Bandwidth Reservation (IABR) scheme for providing flow admission control and bandwidth reservation for end-to-end flows in 802.11 multi-radio multi-channel wireless mesh networks. The effects of inter-flow and intra-flow interference have often been neglected in existing solutions, which can lead to inaccurate bandwidth estimation and reservation. IABR models both the current inter-flow interference from existing flows and the expected intra-flow interference of the incoming flow to make accurate estimation of the available bandwidth and perform admission control. Moreover, IABR exploits wireless link diversity between neighboring nodes in multi-radio multi-channel mesh networks to improve flow admission ratio and ensure efficient load-balancing. Simulation results show that IABR provides accurate bandwidth estimation, excellent load distribution and high flow admission ratio.

Experiences with a Metropolitan Multiradio Wireless Mesh Network: Design, Performance, and Application

Wireless mesh networks comprise nodes with multiple radio interfaces, and can provide low-cost high-speed Internet access or connectivity for data transfer. In this article we report our experiences and investigations with an experimental metropolitan multiradio mesh network that covers an area of approximately 60 km <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> in the city of Heraklion, Crete. We present the design and deployment of the network, experiments to quantify the network's performance, and an application that runs on top of it and exploits it's low-cost wide-area connectivity. The metropolitan network consists of 16 nodes, among which six are core nodes, each with up to four 802.11a wireless interfaces and an additional wireless interface for management and monitoring. The distance between core mesh nodes varies from 1.6 to 5 km, and the mesh network contains two gateways that connect it to a wired network. Our performance experiments involve rate, power, and channel control for long-distance metropolitan links, and include investigations of the timescales for the operation for these mechanisms. Finally, we present a system for continuous online electromagnetic field monitoring and spectrum sensing, which utilizes the metropolitan mesh network for collecting wide-area measurements from low-cost EMF measurement devices.

Indoor Link Quality Comparison of IEEE 802.11a Channels in a Multi-radio Mesh Network Testbed

The most important criterion for achieving the maximum performance in a wireless mesh network (WMN) is to limit the interference within the network. For this purpose, especially in a multi-radio network, the best option is to use non-overlapping channels among different radios within the same interference range. Previous works that have considered non-overlapping channels in IEEE 802.11a as the basis for performance optimization, have considered the link quality across all channels to be uniform. In this paper, we present a measurement-based study of link quality across all channels in an IEEE 802.11a-based indoor WMN test bed. Our results show that the generalized assumption of uniform performance across all channels does not hold good in practice for an indoor environment and signal quality depends on the geometry around the mesh routers.

Ubiquitous robust communications for emergency response using multi-operator heterogeneous networks

A number of disasters in various places of the planet have caused an extensive loss of lives, severe damages to properties and the environment, as well as a tremendous shock to the survivors. For relief and mitigation operations, emergency responders are immediately dispatched to the disaster areas. Ubiquitous and robust communications during the emergency response operations are of paramount importance. Nevertheless, various reports have highlighted that after many devastating events, the current technologies used, failed to support the mission critical communications, resulting in further loss of lives. Inefficiencies of the current communications used for emergency response include lack of technology inter-operability between different jurisdictions, and high vulnerability due to their centralized infrastructure. In this article, we propose a flexible network architecture that provides a common networking platform for heterogeneous multi-operator networks, for interoperation in case of emergencies. A wireless mesh network is the main part of the proposed architecture and this provides a back-up network in case of emergencies. We first describe the shortcomings and limitations of the current technologies, and then we address issues related to the applications and functionalities a future emergency response network should support. Furthermore, we describe the necessary requirements for a flexible, secure, robust, and QoS-aware emergency response multi-operator architecture, and then we suggest several schemes that can be adopted by our proposed architecture to meet those requirements. In addition, we suggest several methods for the re-tasking of communication means owned by independent individuals to provide support during emergencies. In order to investigate the feasibility of multimedia transmission over a wireless mesh network, we measured the performance of a video streaming application in a real wireless metropolitan multi-radio mesh network, showing that the mesh network can meet the requirements for high quality video transmissions.

Performance Evaluation of Routing with Load-Balancing in Multi-Radio Wireless Mesh Networks

Wireless mesh networks (WMNs) face several challenges such as architectural design and network protocol design issues. The capacity of WMNs is very limited, such as the result in an available single channel bandwidth system compared to a multi-channel system. Two problems affect the capacity of mesh networks; i.e. load balancing and interference. To support the mesh network infrastructure, it is necessary to balance the traffic load and reduce the interference. One important direction for improving the capacity of WMNs is to use multiple radio interfaces and multiple channels simultaneously. The proposed load balancing routing algorithm method provides the load balance for multi-radio mesh networks by using a good routing metric, which captures the differences in transmission rates, packet loss ratio, traffic load and intra/inter flow interferences. The simulation results of this study, which used the network simulation NS-2, showed the capacity improvement that helps distributing the traffic load for efficient resource utilization.

Channel Assignment with Topology Preservation for Multi-radio Wireless Mesh Networks

Channel assignment is one of the most important issues in the multi-radio multi-channel wireless mesh networks. An improper channel assignment may lead to network partition or link failure. In this paper we focus on the channel assignment problem with the original topology preservation for the multi-radio mesh networks, and aim at minimizing the overall network interference. We have formulated an Integer Line Programming (ILP) which can be used to find the optimized solution for the channel assignment problem in small-size network. In this paper we also have developed a distributed algorithm for the channel assignment due to the NP-hardness of the ILP. Extensive simulation results have demonstrated that our algorithms have good performance in both dense and sparse networks compared with related works. The theoretic and experiment results have shown that the proposed algorithms serve as a practical solution to the channel assignment problem in the multi-channel multi-radio wireless mesh networks.

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.

A topology control approach for utilizing multiple channels in multi-radio wireless mesh networks

We consider the channel assignment problem in a multi-radio wireless mesh network that involves assigning channels to radio interfaces for achieving efficient channel utilization. We propose the notion of a traffic-independent base channel assignment to ease coordination and enable dynamic, efficient and flexible channel assignment. We present a novel formulation of the base channel assignment as a topology control problem, and show that the resulting optimization problem is NP-complete. We then develop a new greedy heuristic channel assignment algorithm (termed CLICA) for finding connected, low interference topologies by utilizing multiple channels. Our extensive simulation studies show that the proposed CLICA algorithm can provide large reduction in interference (even with a small number of radios per node), which in turn leads to significant gains in both link layer and multihop performance in 802.11-based multi-radio mesh networks.

Routing with Load-Balancing in Multi-Radio Wireless Mesh Networks

This paper addresses the interference and load imbalance problems in multi-radio infrastructure mesh networks where each mesh node is equipped with multiple radio interfaces and a subset of nodes serve as Internet gateways. To provide backbone support, it is necessary to reduce interference and balance load in Wireless Mesh Networks (WMNs). In this paper, we propose a new Load-Aware Routing Metric, called LARM, which captures the differences in transmission rates, packet loss ratio, intra/inter-flow interference and traffic load in multi-radio mesh networks. This metric is incorporated into the proposed load-balancing routing, called LBM, to provide load balancing for multi-radio mesh network. Simulation results show that LARM provides better performance compared to WCETT and hop-count routing metrics in LBM routing protocol.

Interference-aware broadcasting in multi-radio multi-channel mesh networks

A vast number of broadcasting protocols have been developed for wireless networks. To the best of our knowledge, however, most of these protocols assume a single-radio single channel network model and/or a generalized physical model, which does not take into account the impact of interference. In this paper, we present a Distributed Interference-aware Broadcasting (DIB) protocol for multi-radio multi-channel mesh networks. The protocol has two phases. In the first phase, each node constructs a local structure by removing bad links and channels. In the second phase, a high-performance broadcasting tree is built by using message passing procedures. Our research distinguishes itself in a number of ways. First, a multi-radio multi-channel mesh network model is used. Second, comprehensive link and channel quality metrics are defined to fully take into account interferences. Third, four design principles have been identified in the tree building process to combat inter-node and intra-node interferences. Finally, a comprehensive performance metric, called power, is defined which includes reliability, receiving redundancy, latency, and goodput. Analytical and simulation studies verify that the DIB protocol is able to achieve 100% reliability, less broadcasting redundancy, low broadcasting latency, and high goodput.

Minimum Interference Channel Assignment in Multiradio Wireless Mesh Networks

In this paper, we consider multihop wireless mesh networks, where each router node is equipped with multiple radio interfaces, and multiple channels are available for communication. We address the problem of assigning channels to communication links in the network with the objective of minimizing the overall network interference. Since the number of radios on any node can be less than the number of available channels, the channel assignment must obey the constraint that the number of different channels assigned to the links incident on any node is at most the number of radio interfaces on that node. The above optimization problem is known to be NP-hard. We design centralized and distributed algorithms for the above channel assignment problem. To evaluate the quality of the solutions obtained by our algorithms, we develop a semidefinite program and a linear program formulation of our optimization problem to obtain lower bounds on overall network interference. Empirical evaluations on randomly generated network graphs show that our algorithms perform close to the above established lower bounds, with the difference diminishing rapidly with increase in number of radios. Also, ns-2 simulations, as well as experimental studies on testbed, demonstrate the performance potential of our channel assignment algorithms in 802.11-based multiradio mesh networks.

A Multi-radio 802.11 Mesh Network Architecture

The focus of this paper is to offer a practical multi-radio mesh network architecture that can realize the benefits of multiple radios. Our architecture provides solutions to challenges in three ke...

Gateway Placement for Throughput Optimization in Wireless Mesh Networks

In this paper, we address the problem of gateway placement for throughput optimization in multi-hop wireless mesh networks. Assume that each mesh node in the mesh network has a traffic demand. Given the number of gateways to be deployed (denoted by k) and the interference model in the network, we study where to place exactly k gateways in the mesh network such that the total throughput is maximized while it also ensures a certain fairness among all mesh nodes. We propose a novel grid-based gateway deployment method using a cross-layer throughput optimization, and prove that the achieved throughput by our method is a constant times of the optimal. Simulation results demonstrate that our method can effectively exploit the available resources and perform much better than random and fixed deployment methods. In addition, the proposed method can also be extended to work with multi-channel and multi-radio mesh networks under different interference models.

Channel Assignment Strategies for Multiradio Wireless Mesh Networks: Issues and Solutions

Next-generation wireless mobile communications will be driven by converged networks that integrate disparate technologies and services. The wireless mesh network is envisaged to be one of the key components in the converged networks of the future, providing flexible high- bandwidth wireless backhaul over large geographical areas. While single radio mesh nodes operating on a single channel suffer from capacity constraints, equipping mesh routers with multiple radios using multiple nonoverlap- ping channels can significantly alleviate the capacity problem and increase the aggregate bandwidth available to the network. However, the assignment of channels to the radio interfaces poses significant challenges. The goal of channel assignment algorithms in multiradio mesh networks is to minimize interference while improving the aggregate network capacity and maintaining the connectivity of the network. In this article we examine the unique constraints of channel assignment in wireless mesh networks and identify the key factors governing assignment schemes, with particular reference to interference, traffic patterns, and multipath connectivity. After presenting a taxonomy of existing channel assignment algorithms for WMNs, we describe a new channel assignment scheme called MesTiC, which incorporates the mesh traffic pattern together with connectivity issues in order to minimize interference in multi- radio mesh networks.

Joint Topology Control and Routing in IEEE 802.11-Based Multiradio Multichannel Mesh Networks

Due to low cost, ease of deployment, increased coverage, and enhanced capacity, multiradio mesh networks that utilize inexpensive and readily available Institute of Electrical and Electronics Engineers (IEEE) 802.11 wireless interfaces are touted as the new frontier of wireless networking. In a multihop mesh system, the close interaction between topology control and routing selection affects the system throughput of a wireless network. This paper proposes a novel joint topology control and routing (JTCR) protocol for a multiradio multichannel wireless mesh network to exploit both channel diversity and spatial reusability. It resides between medium access control and the network layer and aims to improve the network throughput by coordinating transmission power, channel assignment, and route selection among multiple nodes in a distributed way. JTCR jointly coordinates the transmission power at each node, the channel selection on each wireless interface, and the route selection among interfaces based on the traffic information that is measured and exchanged among two-hop neighbor nodes. An equivalent channel air time metric (ECATM) is presented to quantify the difference of various adjustment candidates. This protocol achieves the efficient utilization of available channels by selecting a feasible adjustment candidate with the smallest EC ATM value and coordinating affected nodes to realize the adjustment. Our NS-2-based simulation results show that the network throughput can be significantly improved by using our proposed solution.