Supporting Differentiated Service in Cognitive Radio Wireless Mesh Networks

This paper introduces a simple three-dimensional Markov chain model for the Enhanced Distributed Channel Access (EDCA) mechanism of IEEE 802.11e MAC under saturation condition. This new Markov chain model can be used to evaluate the throughput performance of IEEE 802.11e EDCA. This new model captures all of the major Quality of Service (QoS) specific features, namely Arbitration Interframe Space (AIFS), minimum contention window size, maximum contention window size and virtual collision, for the IEEE 802.11e EDCA mechanism and hence can provide a novel numerical approach to pick the set of EDCA parameter values to meet the QoS requirements. The results of our analytical model are then verified using simulations.

In this paper, an efficient approach is introduced where here cognitive medium access approach is used to improve the dynamic spectrum utilization of the licensed spectrum. Here the emphasis is made on channel negotiation, it helps to improve the spectrum management. A dynamic MCMC (Markov Chain Monte Carlo) approach is used to resolve the optimization problem for channel selection. In addition, this work offers a suite of mechanisms for the implementation of the principles proposed, including segmentation of long packets and arbitration that controls on power request-to-send function (RTS) and Clear-to-Send (CTS) level in a multi-channel environment. Here cyclostationary detection technique which at beginning will sense the channel and filter them for the further use, this way it will make the channel negotiation and access scheme to work more efficiently. Th NS-2 simulation is used to analyze the result with respect to proposed approach and examine its performance. It is observed that proposed mechanism can prove to be eminent that to the predefined control channels existing in the CR networks.

Emerging wireless applications has made the issue of spectrum scarcity inevitable. To resolve this issue, cognitive radio networks are proposed. Cognitive Radios are intelligent adaptable devices which intelligently sense the spectrum and find out spectrum holes. In this paper, a Token based MAC protocol is proposed for cognitive radio wireless mesh networks. This protocol consists of three phases namely sensing, control channel operation, and data channel operation. The proposed MAC protocol is simulated in NS2 and the simulation results are analyzed using network throughput under various number of channels. The simulation results indicate that the proposed MAC protocol outperforms the existing protocols.

The practical deployment of Wireless Mesh Networks (WMNs) using unlicensed ISM band within dense urban scenarios is difficult due to the increasing number of wireless devices operating in those licensed exempt frequencies. For this reason, current research on WMN is directed towards novel and more flexible network paradigms which would allow the WMN to dynamically adapt to the environmental interference conditions. Here, we propose Urban-X, which is a novel cross-layer architecture for self-organizing WMNs over urban scenarios. Urban-X combines elements from classical Multi-Radio Multi-Channel (MC-MR) technology with novel Dynamic Spectrum Access (DSA) mechanisms. The self-organizing behavior is achieved through a novel distributed channel assignment scheme, an adaptive multi-path routing scheme and a flexible layer 2.5 channel and path scheduler algorithm. Based on the current interference on each channel, Urban-X performs channel allocation among the nodes of the WMN, updates the available paths towards the gateways and distributes the internal traffic among the paths/channels in order to maximize the network throughput while minimizing interference to the external networks. Simulation results demonstrate the effectiveness of our cross-layer approach in terms of increased throughput compared to traditional routing schemes for WMNs, and its adaptiveness to the variation in channel conditions and external user traffic.KeywordsWireless Mesh NetworksMulti-RadioMulti-ChannelCross-Layer DesignPerformance Evaluation

In the emerging standard IEEE 802.11e, the Enhanced Distributed Channel Access (EDCA) is specified to support quality-of-service (QoS) in wireless local area networks (WLAN). This paper aims at providing a thoroughly analytical model that captures the operation of the AIFSs, contention window sizes and retry limits differentiation for different services of the EDCA mechanism under saturation condition based on a three-dimensional Markov Chain model. The analytical model is validated and provides an in-depth understanding and insights into the EDCA protocol, and effectiveness of different parameters on the system performance in terms of system throughput and frame dropping probability for differentiation services traffic is investigated through extensive numerical and simulation results. Moreover, the analytical model can be cooperated into the admission control algorithm with different parameters in terms of AIFS, contention window sizes and retry limits.

Most of the recent analytical studies for IEEE802.11e quality of service (QoS)-aware enhanced distributed coordination function require a large degree of complexity that are difficult to apply to a wide range of parameter settings for the evaluation of service differentiation mechanisms supported in enhanced distributed channel access (EDCA), including the contention window (CW) and arbitrary inter-frame space (AIFS) mechanisms. The authors propose a novel analytical model to analyse the throughput of EDCA with AIFS and CW differentiation schemes. The model is simplified by decomposing the problem into two easily solved Markov chains that can jointly be solved by numerical method. The authors present simulation and analytical results over a broad range of system parameters to demonstrate the accuracy of the proposed model. Compared to the previous models, our model is simple to implement and can be applied to a general configuration circumstances for the evaluation of EDCA. The results are valuable to facilitate proper design of parameters in 802.11e EDCA for the QoS support required by specific applications.

Cognitive Radio (CR) technology constitutes a promising approach to increase the capacity of Wireless Mesh Networks (WMNs). Using this technology, Mesh Routers (MRs) and the attached Mesh Clients (MCs) are allowed to opportunis- tically transmit on the licensed band, but under the constraint not to interfere with the Primary Users (PUs) of the spectrum. Thus, the effective deployment of CR- WMNs require that each MR must be able to: sense the current spectrum, select an available PU-free channel and perform the spectrum handoff to a new channel in case of PU arrival on the current one. How to coordinate these actions in the optimal way which maximizes the performance of the CR-WMNs while minimizing the interference to the PUs constitutes an open research issue in CR systems. In this paper, we propose an adaptive spectrum scheduling and allocation scheme which allows a MR to identify the best schedule of (i) when to sense the current channel, (ii) when to transmit, (iii) when to perform a spectrum handoff. Due the large number of parameters involved, we propose Reinforcement Learning (RL) techniques to allow a MR to learn by itself the optimal balance between spectrum sensing-exploitation- exploration actions based on network feedbacks coming from the MCs. We perform extensive simulations which confirm the adaptivity and efficiency of our approach in terms of increased throughput when compared with non-learning based schemes for CR-WMNs.

Cognitive radio presents a new approach to wireless spectrum utilization and management. In this work, the potential performance improvement gained by applying cognitive radio to wireless mesh networks is investigated. Specifically, the potential benefits in terms of QoS provided to users and the efficiency of resource utilization are quantified in a system consisting of a collection of one or more service provider wireless networks. To achieve this, we formulate the problem mathematically using integer linear programming. It is shown that the cognitive radio abilities provide an advantage over the classical network, either by improving QoS through increasing the probability of accepting connection requests, or by reducing the resources needed to fulfill the QoS requirements of users. This advantage is gained without impacting the service of primary clients. More importantly, we show that virtual wireless networks can be created, utilizing only the residual wasted bandwidth of the primary service providers. These virtual networks are able to support large volumes of users, while still ensuring that QoS reliability requirements, such as acceptance probability guarantees, are achieved.

With the provisioning of high-speed wireless LAN (WLAN) environments, multi- media services (e.g., VoIP and video-conference) with different QoS requirements will be available in next generation WLANs. Multimedia services could be categorized into multiple traffic classes and different priorities will be applied to access the wireless me- dium. The IEEE 802.11 working group has been developing a new generation distributed access protocol, called enhanced distributed channel access (EDCA), to support service differentiation in the 802.11 MAC layer. Service differentiation is achieved by assigning different values of EDCA access parameters (i.e., minimum contention window, maxi- mum contention window, and arbitration interframe space) to different traffic classes. To investigate the system performance under various network conditions, it is helpful to have a theoretical model for EDCA. In this paper, we introduce an analytical model for EDCA so that the saturation bandwidth can be estimated by closed-form formulas for each traffic class. We use ns-2 simulator to validate the analytical model. Some numeri- cal results are provided to evaluate the performance of EDCA. The numerical results demonstrate the corresponding effects for tuning different EDCA access parameters.

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

Wireless Mesh Networks (WMNs) integrate the advantages of WLANs and mobile Ad Hoc networks, which have become the key techniques of next-generation wireless networks in the context of emergency recovery. Wireless Mesh Networks (WMNs) are multi-hop wireless networks with instant deployment, self-healing, self-organization and self-configuration features. These capabilities make WMNs a promising technology for incident and emergency communication. An incident area network (IAN) needs a reliable and lively routing path during disaster recovery and emergency response operations when infrastructure-based communications and power resources have been destroyed and no routes are available. Power aware routing plays a significant role in WMNs, in order to provide continuous efficient emergency services. The existing power aware routing algorithms used in wireless networks cannot fully fit the characteristics of WMNs, to be used for emergency recovery. This paper proposes a power aware routing algorithm (PARA) for WMNs, which selects optimal paths to send packets, mainly based on the power level of next node along the path. This algorithm was implemented and tested in a proven simulator. The analytic results show that the proposed power node-type aware routing algorithm metric can clearly improve the network performance by reducing the network overheads and maintaining a high delivery ratio with low latency.

Empowered by the cognitive radio technology, and motivated by the sporadic channel utilization, both spatially and temporally, dynamic spectrum access networks (also referred to as cognitive radio networks and next generation wireless networks) have emerged as a solution to improve spectrum utilization and provide more flexibility to wireless communication. A cognitive radio network is composed of wireless users, referred to as secondary users, which are allowed to use a given licensed spectrum band as long as there are no primary, licensed, users occupying this band in their vicinity. This restricted spectrum access strategy leads to heterogeneity in channel availability among secondary users. Heterogeneity in channel availability forms a significant source of performance degradation for cognitive radio networks, and poses a great challenge on protocol design. In this dissertation, we propose spectrum allocation algorithms that take this heterogeneity property and its effect on the network performance into consideration. The spectrum allocation solutions proposed in this dissertation address three major objectives in cognitive radio mesh networks. The first objective is maximizing the network coverage, in terms of the total number of served clients, and at the same time simplifying the communication coordination function. To address this objective, we proposed a received based channel allocation strategy that alleviates the need for a common control channel, thus simplifying the coordination function, and at the same time maximizes the number of clients served with link reliability guarantees. We show the superiority of the proposed allocation strategy over other existing strategies. The second objective is improving the multicast throughput to compensate for the performance degradation caused by the heterogeneity in channel availability. We proposed a

With the advanced physical layer techniques such as multiple-input and multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM), transmission real-time 2D/3D contents and applications becomes more and more necessary in wireless networks for the amazing growing in demand of customers. However, the low efficiency of medium access control (MAC) protocol degrades the performance of real-time traffic greatly in multihop, wireless and mobile environment. Focusing on supporting real-time multimedia traffic in cognitive wireless mesh networks (WMNs), an enhanced MAC protocol is proposed. And the contribution of this paper is twofold: (1) An efficient carrier sense multiple access with collision avoidance (CSMA/CA) compatible time division multiple access (TDMA)-like MAC protocol called T-MAC is proposed, which aims to improve the system performance by allocating more channel access time in centralized manner and decreasing overhead. (2) An optimal adaptive scheduling scheme is proposed to support real-time multimedia applications and guarantee QoS for different priority traffic, which aims to find the optimized schedule among all possible sequences of concurrent transmissions by minimizing the occupied resources. Detailed simulation results and comparison with IEEE 802.11e MAC scheme show that the proposed T-MAC can effectively improve quality of service (QoS) for multimedia traffic in terms of throughput, end-to-end delay and packet loss rate, which also manifests that T-MAC is an efficient multimedia applications transmission scheme for mobile terminals and MAPs in cognitive WMNs.

Nowadays there are inexpensive WiFi devices that have fostered the deployment of wireless communities. Well known routing protocols used in the Internet do not fit well to time varying characteristic of wireless networks. This has motivated an intensive research on routing protocols for wireless mesh networks. At this time there are a number of mature and stable implementations that are being deployed in production networks. In this paper we focus on the experimental evaluation of a production Wireless Mesh network being deployed in a testbed at Universitat Politecnica de Catalunya (UPC) and a quarter of the city of Barcelona, Spain. To our best knowledge, this is the first paper where a production community wireless network using 802.11an is analyzed.

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.