Designing Interference-Robust Wireless Mesh Networks Using a Defender-Attacker-Defender Model

Resource allocation and admission control algorithm based on non-cooperation game in wireless mesh networks

As an inexpensive, scalable internet-access network, a wireless internet-access mesh network ( WIMNET ) is composed of multiple access-points ( APs ) connected by wireless links. WIMNET can improve the dependability to link or AP failures by allocating APs redundantly in the network field. Because redundant APs may increase the operational cost and degrade the performance due to increasing radio interferences, only the necessary APs for communications between the hosts and the internet gateway should be activated in conventional situations. Previously, we proposed an active AP selection algorithm to select the minimum number of APs to be activated such that the overall throughput is maximised, assuming that every link has the same constant speed. However, our preliminary experiments for the emerging high-speed IEEE802.11n protocol that should be introduced into WIMNET, found that this speed is greatly affected by the link environment such as the distance. In this paper, we present an extension of the active AP selection algorithm to efficiently select active APs under link speed changes. Besides, we extend the routing tree algorithm used in the algorithm procedure and the WIMNET simulator for throughput evaluations. We verify the effectiveness through extensive simulations in three instances.

Capacity bounds of deployment concepts for Wireless Mesh Networks

The vehicular ad-hoc network (VANET) is a promising technology in near future. VANET allows vehicles to communicate with each other and with roadside units (RSUs). Wireless Access in Vehicular Environment (WAVE), defined by IEEE, provides the Internet connectivity for vehicles as well as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication. RSUs can form a wireless mesh network (WMN) as a backbone infrastructure to enhance the performance of VANET. However, WAVE supports only one-hop communications for IP packets in VANET, and existing researches do not consider the compatibility between VANET and WMN infrastructure formed by RSUs. We propose the extended WMN (ExWMN) which has the feasibility to extend WMN to VANET domain. In ExWMN, the vehicles can send IP packets to an access router by using the multi-hop capability of WMN. ExWMN uses the addressing scheme of WMN for the extended VANET domain and exploits geographical routing protocols instead of existing routing protocols of WMN due to VANET characteristics such as mobility and dynamically changing network topologies. ExWMN supports the compatibility between the extended VANET and a WMN infrastructure due to RSUs, which provide a bridging function between them. This paper presents the architecture and the detailed procedures of the ExWMN.

The wireless mesh network (WMN) is an economical low-power solution to provide wireless broadband access in intelligent transportation systems (ITSs). This paper investigates how to deploy access points (APs) to improve throughput and quality-of-service (QoS), when the multihop communication is used to extend the coverage of wireless ITS network. Frequency planning is suggested to improve the capacity with QoS provisioning and to make the system more scalable. To investigate the overall tradeoffs among QoS, throughput, and coverage, we develop an analytical model to evaluate throughput, frame delay, and jitter for the considered ITS WMN using the carrier-sense multiple-access (CSMA) medium access control (MAC) protocol. Then, we apply an optimization approach to determine the optimal separation distances between APs with the delay requirement. To provide a guideline for network planning, we compare the uniform-spacing and increasing-spacing AP deployment strategies. The uniform-spacing strategy is to make all the APs with the same separation distance. In the increasing-spacing strategy, the separation distances between APs are increased from the central AP to the outer APs. Because of the shorter separation distance, the AP closer to the central AP can deliver higher traffic. It is shown that the increasing-spacing strategy outperforms the uniform-spacing strategy in terms and a profit function, considering the capacity and the total cost for deploying APs.

In emergency cases of the building, users need to grasp the disaster situation and evacuation routes for an efficient and rapid evacuation. It is expected that multihop wireless network systems such as a wireless mesh network are useful to share the disaster information among users. The wireless mesh network is configured by user terminals and base stations which are deployed at the specified area by the administrators of the building. User terminals communicate with the others through the wireless mesh network without the aid of the infrastructure network and the central server. Access points are possible to work by battery power so that the wireless mesh network system is tolerant to the power outage. This paper proposes an evacuation route guidance scheme for building evacuation using wireless mesh network systems. User terminals grasp the up-to-date disaster situation in the building through the wireless mesh network, and then provide the evacuation route to the users. The timing of transmitting messages to share the information among users is crucial for the efficient and rapid evacuation. We implement the system into the network simulator and conduct the simulation experiments to confirm the network performance and the users’ evacuation time. Finally, we show the effect of the wireless mesh network and the effectiveness of the evacuation route guidance scheme.

Wireless mesh network is a network implemented over a wireless local area network (LAN), and its infrastructure type is decentralized, relatively inexpensive, reliable, and resilient since the wireless routers are often static and not powered by batteries. In addition, the access points (routers) seldom change their positions in wireless mesh networks, and some wireless nodes have gateway functions to provide the connectivity to the Internet. Therefore, such networks behave almost like wired networks with infrequent topology changes and limited node failures. Due to these good properties and potential applications such as providing commercial Internet access to residents and local businesses, wireless mesh networks have drawn a lot of attention in recent years. For example, wireless mesh networks are being used as the last mile for extending the Internet connectivity for mobile nodes. In addition, some commercial deployments of multihop wireless meshes are already in the works. For instance, a number of mesh networks have been deployed in some cities of the United States, including Medford, Oregon, and cities in Minnesota [4]. Unlike traditional wired network, close-by mesh routers share certain wireless channels and the capacity of wireless mesh network will be increased tremendously when extending from a single channel model to a multiradio, multichannel, multihop model. For example, if two nodes vi and v j could communicate with each other by channel f1, and both nodes have at least one more available network interface cards, which could operate on another channel f2, if f2 is also available for both nodes, vi and v j could use both f1 and f2 to communicate simultaneously. When such cases are applied to more wireless nodes, the throughput of a wireless network will be increased tremendously.

A lot of access points (APs) in wireless mesh networks (WMNs) are battery powered. In order to minimize their energy consumption, the APs can adaptively adjust their transmission power and time based on various network conditions. In this paper, the problem of minimizing the AP energy consumption is formulated as an optimization problem with the constraint to satisfy the throughput requirements of associated mobile stations (MSs). Balancing the energy consumption of the APs can be important to prolong the network lifetime, particularly in a network with high and random user mobility, which can easily result in unbalanced traffic load and energy consumption among the APs. Two distributed handoff schemes are proposed for a WMN with adaptive transmission power and rate. One scheme attempts to achieve balanced energy consumption among the APs during each scheduling interval, and the other scheme balances the AP energy consumption over a longer term. Numerical results show that both schemes achieve much longer network lifetime than the traditional distance-based handoff scheme, while the long-term based handoff scheme can achieve the objective with approximately the same number of handoffs as the distance-based handoff.

Wireless Mesh Network (WMN) is emerging as key technology for the next generation network due to its features like providing broadband access with low cost and applicability to versatile areas. WMN's are basically multi-hop networks, in which data is forwarded to backbone through a gateway from the client nodes and vice versa. The client nodes may be wired or wireless and may be mobile with varying client network architecture. Gateway has fixed bandwidth to be shared by all the clients for communication. It causes reduction in per client throughput as the number of clients is increasing and thus may lead to overall performance degradation. Associating clients to gateway is a crucial point in deciding performance as is gateway placement, routing and scheduling at the gateway. Associating nodes to a single nearest gateway causes reduction in capacity of WMN and unfairness amongst the nodes. Clients can be associated to multiple gateways. WMN are dynamically self-organizing and self-healing and this imposes even more responsibility on gateways. Having multiple gateways in clustered WMN can improve performance significantly.

Wireless mesh networks have an advantage of building backbone infrastructure easily, where access points, which have been conventionally connected by wired LANs, are connected by an ad-hoc network using wireless LANs. However, the wireless mesh network still has various problems such as the realization of a seamless handover, the securing of a communication bandwidth, and the selection of the most suitable routing protocol. WAPL (wireless access point link) which we propose in this paper can solve all these problems. Namely, WAPL enables a constant seamless handover. It does not give much influence on the traffic. It can also select ad-hoc routing protocols freely. To realize a seamless handover, WAPL is aware of communication routes all the time and sends an advertising message that reports its handover in a unicast mode. To reduce the traffic of control messages, it generates mapping information, which is the relation between access points and terminals on demand. In WAPL, the function generating mapping information is completely independent of an ad-hoc routing protocol. In this paper, we implemented WAPL in network simulator ns-2, and compared it with the existing methods. We succeeded in showing the features of WAPL quantitatively.

Interference makes it difficult for a wireless network to provide robust performance and could sometimes lead to transient failures. Dynamic channel switching (DCS) allows a wireless network interface (NIC) to operate in different frequency channels during different time periods without disrupting network connections that traverse the NIC. DCS enables a wireless mesh network to avoid frequency channels with serious interference in certain parts of its coverage area by switching to more idle channels. Although DCS provides additional radio agility, it significantly increases the complexity of the wireless mesh network's routing protocol. This paper describes the design, implementation and evaluation of a wireless mesh network system called Carlsbad, which supports both DCS and load-balancing/fault-tolerant routing, and successfully runs on low-cost commodity IEEE 802.11-based access points. Performance experiments on the first Carlsbad prototype show that despite the additional overhead it introduces, DCS can indeed improve the overall throughput of an IEEE 802.11-based wireless mesh network, sometimes by a factor of more than 2, for both TCP and UDP connections.

The wireless mesh networks (WMNs) have become one of the popular technologies of the wireless network utilization. WMN provides reliable and scalable wireless network because of its features such as dynamic self-organizing, self-configuring, Self-managing and self-healing. Routing protocols play an essential role in finding and establishing an active route from a source to a destination in WMNs. This article focuses on the performance evaluation and comparison of some routing protocols commonly used in WMNs for VoIP application: AODV, DSR, OLSR and TORA has been investigated over client Wireless Mesh Networks based on OPNET simulation in a different network sizes and mobility. This article presents a background of some designs and solutions based on an elaborated simulation investigation. The performance comparisons are carried out with regard to the node variation in network sizing and mobility. Based on the empirical outputs, the authors suggested that to utilize a specific routing protocol in certain situations.

Wireless mesh networking has trans pired as a gifted technology for potentialbroadband wireless access. In a communication network, wireless mesh network plays a vital role in transmission and are structured in a mesh topology. The coordination of mesh routers and mesh clients forms the wi reless mesh networks which are routed through the gateways.Wireless mesh networks uses IEEE 802.11 standards and has its wide applications broadband home networking and enterprise networking deployment such as Microsoft wireless mesh and MIT etc. A profes sional Qos provisioning in intra cluster packet level resource allocation for WMN approach takes power allo cation, sub carrier allocation andpacket scheduling. This approach combines the merits of aKarush-Kuhn-Tucker (KKT) algorithm and a genetic algorithm (GA) based approach. The KKT algorithm uses uniform power allocation over all the subcarriers, based on the optimal allocation criterion. The genetic algorithm is used to generate useful solutions to optimization and search problems and it is also used for search problems. By combining the intrinsic worth of both the approaches, it facilitates effective QOS provisioning at the packet level. It is conclude d that, this approach achieves a preferred stability between system implementation and computational convolution.

Wireless mesh networks (WMN) are delivering wireless services for a large variety of applications in personal, local, campus, and metropolitan areas. Unlike WLANs, WMN are self-configuring systems where each Access Point (AP) can relay messages on behalf of others, thus increasing the range and available bandwidth. IEEE 802.11 has a drawback that it does not provide differentiation for better service for real-time multimedia traffic as compared to best-effort traffic applications. Further, it supports only single hop networks. These drawbacks motivate us to overcome these we implement an IEEE 802.11e amendment to IEEE 802.11 that defines a set of Quality of Service (QoS) enhancements for wireless LAN applications through modifications to the Media Access Control (MAC) layer. Basic NS2 environment does not provide 802.11e EDCA and HCCA standards but here we implement 802.11e EDCA for wireless network simulations in the network simulator tool (NS2) and to do performance analysis for multi hop WMNs. Our simulations show improved performance throughput in applications and also reduced degradation with increase in number of nodes to be serviced in the network.

Seamless handoff support is an essential issue to ensure continuous communications in wireless mesh networks (WMNs). Due to the existence of multi-hop wireless links, traditional handoff schemes designed for single-hop wireless access networks can hardly guarantee the low handoff latency requirement in WMNs. Existing solutions on reducing the handoff delay in WMNs ignore one important factor for the long handoff delay: the channel access delay of handoff signaling packets over the multi-hop wireless mesh backbone network. Various WMN channel assignment algorithms are designed to optimize the performance of data packets, but they do not address how to resolve the contentions between data packets and handoff signaling packets. In this paper, we propose a novel channel assignment algorithm in WMNs to reduce the channel access delay of handoff signaling packets over multihop wireless links. In addition, handoff solutions under the new channel assignment scheme are proposed. OPNET simulation results show that handoff performance can be improved by our proposed handoff schemes, as compared to existing solutions.