Novel Channel Assignment Algorithm for Handoff Support in Hierarchical Wireless Mesh Networks

This paper proposes an efficient, secure and anonymous routing protocol based on Weil pairing for wireless mesh networks (WMNs). The proposed protocol considers symmetric and asymmetric links during wireless communication in WMNs. A WMN integrates several types of wireless devices, and induces the asymmetric links that result from different transmission ranges of wireless devices. Enhancing the security and privacy of WMNs has been an important research focus in recent years. Most research on this topic has focused on providing security and anonymity for routing and data in symmetric links. However, the asymmetric links in these protocols have not been addressed. This paper proposes a novel distributed routing protocol suitable for WMNs that include symmetric and asymmetric links. The proposed protocol guarantees security, anonymity and high reliability in WMNs. The proposed protocol generates routes that are shorter than those of previous studies. The proposed scheme protects the real identities of the source and intermediate users, which remain unknown even to the mesh router, while still providing node authentication. Using the proposed protocol, mesh clients anonymously discover a secure route to the mesh router. This protocol also ensures data transmission anonymity and enhances WMN coverage, in addition to assuring security and anonymity.

A Wireless Mesh Network (WMN) is a multi-hop network that gains the benefits of low deployment cost, fast access speed, expanded service coverage and large network capacity. However, the multi-hop communication in WMNs limits the throughput capacity due to increased number of packet transmissions. As a result, network coding is a recently emerged paradigm that can enhance the throughput capacity (i.e. network throughput) by minimizing the quantity of network workload and at the same time it ensures the data transfer among all the users. Further, with network coding the transmission effectiveness of a node can be improved by encoding (combining) several packets collectively and verifies whether the coding strategies is satisfied or not. Subsequently, if the coding strategies are satisfied then it transmits only the resultant encoded packet to the desired destination. In other words, network coding can improve the network throughput in WMNs by minimizing the transmission counts needed to transfer several packets to the destination. It should be noted that, while employing network coding in WMNs there are several challenges that should be compensated such as (i) identifying packets that can be combined (encoded) collectively and (ii) integrating the coding strategies in routing protocols. In this paper, we proposed a new mesh routing protocol that integrates network-coding called as Network Coding Aware Routing (Net-CART) protocol. Therefore, to enjoy the whole benefit of network coding a Net-CART protocol uses the innovative routing metric called Code-Aware and Load-Aware Routing Metric. Additionally, to identify numerous ‘coding structures’ and to support number of ‘packet encodings’ an improved set of coding strategies known as Enhanced Universal Coding Strategies is also proposed. The proposed Net-CART protocol comprising an improved set of coding strategies and a new routing-metric considers both the coding-opportunities and “network workload”. The simulation study carried out in wide forms of network configurations showed that Net-CART gives more fairness performances than other protocols.

In community wireless mesh (CWM) networks following the IEEE 802.11s standard, wireless nodes combine the functionality of a client application host and a transit packet router. Not being subjected to tight administrative control, CWM nodes may act selfishly by refusing to forward transit packets along (selected) established routes or to participate in the route creation process. Unlike in a mobile ad hoc network (MANET), a CWM node is typically connected to mains electricity, hence unconcerned about energy expenditure; the only rational (as distinct from malicious) motivation behind selfish behavior is then to prevent the incoming transit traffic from competing with the source traffic and thereby achieve a higher source throughput. We examine through simulation the benefits and harms of selfish behavior with a cross-layer view and relate them to the router density, selfish routers' location and details of their behavior. We find many conclusions and intuitions valid in MANET environments incorrect in CWMs.

Operating on a frequency band occupying several nonoverlapping channels, IEEE 802.11 is now widely used in wireless mesh networks (WMNs). Many multichannel MAC protocols are proposed to improve the spatial reuse in the network under the assumption that the transmissions on nonoverlapping channels do not interfere with each other. Some joint routing and channel assignment algorithms are also designed to increase the network throughput based on the premise that we can switch between different channels freely. Although simulations show that great improvements on network throughput can be observed in both cases, two fundamental questions remain: 1) Can we really use multiple nonoverlapping channels freely in WMNs? 2) If we can, what will be the cost when we switch channels dynamically and frequently? In this paper, by conducting extensive experiments on our testbed, we attempt to answer these questions. We find that in spite of interference between both overlapping and nonoverlapping channels, we can still use multiple channels in mesh networks under certain conditions but with care. We also show that the channel switching cost is actually very significant in WMNs. We recommend not to switch the channels too frequently when designing the channel assignment algorithms, and those channel assignment algorithms selecting one channel for each packet are not really beneficial.

In this paper we present the DES-Chan framework for experimentally-driven research on distributed channel assignment algorithms in wireless mesh networks. The implementation process of channel assignment algorithms is a difficult task for the researcher since common operating systems do not support channel assignment algorithms out of the box. DES-Chan provides a set of common services required by distributed channel assignment algorithms. The modular architecture of DES-Chan allows the extensions with further modules or the modifications of existing ones. As a proof of concept, we present a reference implementation of a distributed greedy channel assignment algorithm. We evaluate its performance in the DES-Testbed, a multi-transceiver wireless mesh network (WMN) with 100 nodes at the Freie Universitat Berlin.

Optimising channel assignment to prevent flow starvation and improve fairness for planning single radio WMNs in built environments

A wireless mesh network (WMN) comprises of mesh access points (MAPs), mesh routers and mesh clients (MCs), where MAPs are almost static and form the back-bone of WMNs. MCs are wireless devices and dynamic in nature, communicating among themselves over possibly multi-hop paths, with or without the help of MAPs. Security has been a primary concern in order to provide protected communication in WMNs due to the open peer-to-peer network topology, shared wireless medium, stringent resource constraints and highly dynamic environment. These challenges clearly make a case for building multi-layer security solution that achieves both broad protection and desirable network performance. In this paper, we propose a cross-layer secure protocol for routing, data exchange and ARP problems (in case of LAN based upon WMNs). Our protocol is a ticket-based ad hoc on demand distance vector (TAODV) protocol, a secure routing protocol that is based on the design of ad hoc on demand distance vector (AODV) protocol. Due to availability of the backbone, we incorporate the authentication server (AS) for the issuance of tickets which are further used for secure routing, transfer of public keys and MAC addresses in one single step. With the transfer of public keys, source and destination can easily generate their shared secret key based upon fixed Diffie-Hellman key exchange protocol for data encryption and decryption. Our protocol is secure against both active and passive attacks.

Impact of multiple channels and radios on the performance of a TDMA based wireless mesh network

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) algorithm to alleviate performance anomaly in multi-channel multi-rate WMNs. By exploiting multiple channels, the proposed algorithm alters a low-rate single-hop path to a high-rate multi-hop path. With RB-CA, a large volume of traffics in WMNs can be simultaneously delivered from or to the Internet via multiple non-overlapping channels as well as high-rate links. Extensive ns-2 simulation experiments have been performed to evaluate the performance of RB-CA and compared it with the existing WMN architecture. Our simulation results show that RB-CA outperforms existing scheme in terms of packet delivery ratio and end-to-end delay.

Breadth First Search Channel Assignment(BFSCA) is a hybrid channel assignment algorithm that utilize multiple radio interfaces to improve the throughput and minimize the interference within the wireless mesh network and between the mesh network and co-located wireless mesh networks. This new channel assignment scheme allows different nodes in the same network to communicate with each other without causing too much interference to their neighbors. It is introducing Multiradio Conflict Graph(MCG) to model interference in the wireless mesh network. Breadth First Search Channel Assignment considers both the fixed channels (static) and the dynamic channels to reduce interference of the network. BFSCA will increase the network throughput greatly.

Wireless mesh networks (WMNs) have emerged as a scalable, reliable, and agile wireless network that supports many types of innovative technologies such as the Internet of Things (IoT), Wireless Sensor Networks (WSN), and Internet of Vehicles (IoV). Due to the limited number of orthogonal channels, interference between channels adversely affects the fair distribution of bandwidth among mesh clients, causing node starvation in terms of insufficient bandwidth distribution, which impedes the adoption of WMN as an efficient access technology. Therefore, a fair channel assignment is crucial for the mesh clients to utilize the available resources. However, the node starvation problem due to unfair channel distribution has been vastly overlooked during channel assignment by the extant research. Instead, existing channel assignment algorithms equally distribute the interference reduction on the links to achieve fairness which neither guarantees a fair distribution of the network bandwidth nor eliminates node starvation. In addition, the metaheuristic-based solutions such as genetic algorithm, which is commonly used for WMN, use randomness in creating initial population and selecting the new generation usually leading the search to local minima. To this end, this study proposes a Fairness-Oriented Semichaotic Genetic Algorithm-Based Channel Assignment Technique (FA-SCGA-CAA) to solve node starvation problem in wireless mesh networks. FA-SCGA-CAA maximizes link fairness while minimizing link interference using a genetic algorithm (GA) with a novel nonlinear fairness-oriented fitness function. The primary chromosome with powerful genes is created based on multicriterion links ranking channel assignment algorithm. Such a chromosome was used with a proposed semichaotic technique to create a strong population that directs the search towards the global minima effectively and efficiently. The proposed semichaotic technique was also used during the mutation and parent selection of the new genes. Extensive experiments were conducted to evaluate the proposed algorithm. A comparison with related work shows that the proposed FA-SCGA-CAA reduced the potential node starvation by 22% and improved network capacity utilization by 23%. It can be concluded that the proposed FA-SCGA-CAA is reliable to maintain high node-level fairness while maximizing the utilization of the network resources, which is the ultimate goal of many wireless networks.

Wireless Mesh Networks (WMNs) cannot completely guarantee good performance of traffic sources such as video streaming. To improve the network performance, this study proposes an efficient engineering solution named Wireless-to-Ethernet-Mesh-Portal-Passageway (WEMPP) that allows effective use of wired communication in WMNs. WEMPP permits transmitting data through wired and stable paths even when the destination is in the same network as the source (Intra-traffic). Tested with four popular routing protocols (Optimized Link State Routing or OLSR as a proactive protocol, Dynamic MANET On-demand or DYMO as a reactive protocol, DYMO with spanning tree ability and HWMP), WEMPP considerably decreases the end-to-end delay, jitter, contentions and interferences on nodes, even when the network size or density varies. WEMPP is also cost-effective and increases the network throughput. Moreover, in contrast to solutions proposed by previous studies, WEMPP is easily implemented by modifying the firmware of the actual Ethernet hardware without altering the routing protocols and/or the functionality of the IP/MAC/Upper layers. In fact, there is no need for modifying the functionalities of other mesh components in order to work with WEMPPs. The results of this study show that WEMPP significantly increases the performance of all routing protocols, thus leading to better video quality on nodes.

The nature of wireless transmission leads to vulnerabilities to many malicious activities, and communication in wireless mesh networks (WMNs) must be protected by proper security measures. This paper focuses on symmetric pair wise key establishment and presents a new matrix-based pair wise key establishment scheme for mesh clients. In WMNs, mesh routers are much more powerful than mesh clients, both in communication and computation. By taking advantage of this heterogeneity, our new scheme delegates energy-consuming operations to mesh routers when establishing pair wise keys for mesh clients. Additionally, neighbor mesh clients in our scheme can directly establish pair wise keys with significantly reduced communication and storage costs, due to the use of both pre and post deployment knowledge.

A delay-constrained and priority-aware channel assignment algorithm for efficient multicast in wireless mesh networks

In this paper, we propose a distributed algorithm for channel assignment in multi-radio, multi-channel mesh networks. Channel assignment in multi-radio mesh networks is complicated because, in addition to affecting the interference between spatially closely located links, binding interfaces to channels affects the topology of the network. If the channel assignment is done without taking the topology into consideration, distance between any two nodes may increase arbitrarily. We propose a novel distributed channel assignment algorithm that reduces interference and at the same time provides bounds on the distance between any two nodes in the topology resulting from channel assignment. Our algorithm is based on the concept of spanners. We also develop and implement a modification of AODV, which uses the cumulative metric WCETT [4] as the routing metric. We use this routing algorithm to analyze the performance of our channel assignment algorithm. Through extensive simulations in NS-2, we show that the proposed channel assignment algorithm provides nearly 30% improvement in throughput over a simple, minimal-connectivity preserving channel assignment algorithm.