Distributed Contention-Aware Call Admission Control for IEEE 802.11 Multi-Radio Multi-Rate Multi-Channel Wireless Mesh Networks

In this paper, we focus on call admission control (CAC) in IEEE 802.11 multi-radio multi-rate multi-channel (MR²-MC) wireless mesh networks (WMNs). CAC is the key component of QoS routing protocols. The goal of CAC is to protect existing flows from QoS violations and fully utilize available radio resource on channels. We propose a CAC mechanism, called Contention-Aware Multi-channel Call Admission Control (CMC), for MR²-MC WMNs based on IEEE 802.11 DCF. CMC is fully distributed, relies on local information to estimate the residual bandwidth of a path, and can be integrated into existing routing protocols for MR²-MC WMNs to provide QoS. We evaluate the performance of CMC via ns-2 simulations. The results show that CMC can precisely predict the end-to-end residual bandwidths of paths, successfully protects existing flows from QoS violations, and fully utilizes the bandwidths on channels.     

Design and implementation of multicasting for multi-channel multi-interface wireless mesh networks

Multicasting is a useful communication method in wireless mesh networks (WMNs). Many applications in WMNs require efficient and reliable multicast communications, i.e., high delivery ratio with low overhead among a group of recipients. In spite of its significance, little work has been done on providing such multicast service in multi-channel WMNs. Traditional multicast protocols for wireless and multi-hop networks tend to assume that all nodes, each of which is equipped with a single interface, collaborate on the same channel. This single-channel assumption is not always true, as WMNs often provide nodes with multiple interfaces to enhance performance. In multi-channel and multi-interface (MCMI) WMNs, the same multicast data must be sent multiple times by a sender node if its neighboring nodes operate on different channels. In this paper, we try to tackle the challenging issue of how to design a multicast protocol more suitable for MCMI WMNs. Our multicast protocol builds multicast paths while inviting multicast members, and tries to allocate the same channel to neighboring members in a bottom-up manner. By unifying fixed channels of one-hop multicast neighbors, the proposed algorithm can improve the performance such as reducing multicast data transmission overhead and delay, while managing a successful delivery ratio. In order to prove such expectation on the performance, we have implemented and evaluated the proposed solution on the real testbed having the maximum 24 nodes, each of which is equipped with two IEEE 802.11a Atheros WLAN cards.     

A group-based channel assignment protocol for rate separation in IEEE 802.11-based multi-radio multi-rate ad hoc networks

Today’s IEEE 802.11 devices support multiple channels and data rates. Utilizing multiple channels and data rates can increase the performance of IEEE 802.11 networks. However, the multi-channel design to exploit available channels is one of the challenging issues. Moreover, performance anomaly occurs in IEEE 802.11 multi-rate networks when high-rate and low-rate links share a common channel, which degrades the overall network capacity significantly. In this paper, we introduce an extension of conflict graph, called rate conflict graph (RCG), to understand the performance anomaly problem in IEEE 802.11 multi-rate networks. Then, we propose a group-based channel assignment (GCA) protocol for IEEE 802.11-based multi-radio multi-rate single-hop ad hoc networks. In GCA, each node is equipped with multiple IEEE 802.11 interfaces, and links are subdivided into multiple groups, called component groups, by obeying the interface constraints. Then, GCA utilizes RCG and a heuristic algorithm to separate different data rate links via multiple channels so that the performance anomaly problem is addressed. Our extensive simulation results reveal that GCA achieves improved performance over existing channel assignment protocols designed to consider performance anomaly.     

Intelligent wireless mesh path selection algorithm using fuzzy decision making

Wireless mesh networks (WMNs) are expected to be widely deployed due to their ability to provide ubiquity, convenience, cost-efficiency, and simplicity for both service providers and end-users. Recently, the IEEE 802.11s standard introduces the hybrid wireless mesh protocol (HWMP) which is inspired by a combination of on-demand and tree-based pro-active routing algorithms. In this paper, we argue that the proposed unimetric path selection algorithm in the standard is not reliable. We introduce and examine a novel multimetric wireless mesh path selection algorithm using fuzzy decision making under realistic wireless channel conditions. The proposed path selection algorithm is designed to improve the performance of both re-active and pro-active routing protocols of HWMP for not only single-channel but also multi-channel WMNs. The reported results show the superior performance of the proposed path selection algorithm in terms of delay and packet delivery ratio without increasing overhead significantly. Although some fuzzy-based routing algorithms have been defined in literature recently, to the best of our knowledge, this paper is the first one to introduce and examine the use of fuzzy logic in the path selection of single- and multi-channel wireless local area network-based WMNs under realistic wireless channel conditions.     

Joint multi-radio multi-channel assignment, scheduling, and routing in wireless mesh networks

The IEEE 802.11 DCF and EDCA mechanisms based on CSMA/CA are the most widely used random channel access mechanisms in wireless mesh networks (WMNs), but unfortunately these cannot effectively eliminate hidden terminal and exposed terminal problems in multi-hop scenarios. In this paper, we propose a set of efficient multi-radio multi-channel (MRMC) assignment, scheduling and routing protocols based on Latin squares for WMNs with MRMC communication capabilities, called “M4”, i.e., the Multiple access scheduling in Multi-radio Multi-channel Mesh networking. M4 uses nodal interference information to form cliques for inter-cluster and intra-cluster inWMNs, and then applies Latin squares to map the clique-based clustering structure to radios and channels for communication purposes. Then, M4 again applies Latin squares to schedule the channel access among nodes within each cluster in a collision-free manner. From a systematic view, we also design the corresponding MRMC routing to support M4 communication. Extensive simulation results show that M4 achieves much better performance than IEEE 802.11 standards and other channel access control protocols.     

A Cooperative Channel Assignment protocol for multi-channel multi-rate wireless mesh networks

Wireless mesh networks (WMNs) are considered as one of the outstanding technologies that provide cost-effective broadband Internet accesses to users. The off-the-shelf IEEE 802.11 PHY and MAC specifications support both multi-channel and multi-rate capabilities. However, designing an efficient channel assignment protocol that exploits both available channels and data rates is a critical issue to overcome the network performance degradation. In multi-rate wireless networks, high-rate links may severely suffer from throughput degradation due to the presence of low-rate links. This problem is often referred to as performance anomaly. In this paper, we design a Cooperative Channel Assignment (CoCA) protocol to consider the performance anomaly problem in multi-channel multi-rate WMNs. Based on the proposed family architecture, CoCA exploits the Estimated Delivery Time (EDT) metric and an efficient balancing algorithm. Using the EDT metric, CoCA performs channel assignments to form Multi-channel Multi-hop Paths (MMPs) so that CoCA separates high-rate links from low-rate links over different channels and increases the channel diversity. In addition, CoCA considers the performance anomaly problem and throughput fairness during channel assignments by utilizing the balancing algorithm. We evaluated the performance of CoCA through extensive simulations and found that CoCA outperforms existing well-known channel assignment protocols for WMNs.     

An MAC protocol supporting multiple traffic over mobile ad hoc networks

This letter presents the design and performance of a multi-channel MAC protocol that supports multiple traffics for IEEE 802.11 mobile ad-hoc networks.The dynamic channel selection scheme by receiver decision is implemented and the number of the data channel is independent of the network topology.The priority for real-time traffic is assured by the proposed adaptive back off algorithm and different IFS.The protocol is evaluated by simulation and the results have shown that it can support multiple traffics and the performance is better than the performance that IEEE 802.11 standard provides.     

A review of scalability and topological stability issues in IEEE 802.11s wireless mesh networks deployments

Scalability and topological stability are two of the most challenging issues in current wireless mesh networks (WMNs) deployments. In the literature, both the scalability and the topological stability of WMNs are described as likely to suffer from poor performance due to the ad hoc nature of the underlying IEEE 802.11 mechanisms. The main contribution of this article is a comprehensive review of the main topological stability and scalability‐related issues in IEEE 802.11s‐based networks. Moreover, the most relevant proposed solutions are surveyed, where both the drawbacks and the merits of each proposal are highlighted. At the end of the article, some open research challenges are presented and discussed. It is expected that this work may serve as motivation for more and deeper research on these issues to allow the design of future more stable and scalable IEEE 802.11s mesh networks deployments. Copyright © 2015 John Wiley & Sons, Ltd.     

Indoor deployment of IEEE 802.11s mesh networks: Lessons and guidelines

Emerging wireless mesh networks (WMNs) are known for their fast and low cost deployment. Conventional mesh deployment focuses on the outdoor environment, which regards the WMNs as backbone networks. This study deploys and measures indoor IEEE 802.11s mesh networks to extend WLAN capabilities with extensive experiment configurations. The testbed is constructed in a laboratory and a field crossing three floors of a building. Disagreeing with previous research, the results of this study indicate that RTS/CTS can improve throughput by up to 87.5%. Moreover, compared with the IEEE 802.11b/g, 802.11n achieves better fairness for multi-stream or multi-hop communications. Experimental results also suggest that a longer beacon interval, e.g. 500 ms, can improve channel efficiency for a denser deployment. On the other hand, sparser deployments should use a shorter beacon interval, e.g. 100 ms, to enhance link stability.     

Improving Delay and Jitter Performance in Wireless Mesh Networks for Mobile IPTV Services

Wireless mesh networking has recently emerged as a promising technology for the next-generation wireless networks. In wireless mesh networks (WMNs), it is practically attractive to support the low-cost quality-of-service (QoS) guaranteed mobile TV service. To meet this need, our study addresses how to improve the delay and jitter performance of mobile IPTV services over IEEE 802.11 based WMN. Particularly, we first discuss the adaptation of IEEE 802.11 MAC layer to construct a WMN with emphasis on mobile IPTV service; we then develop an enhanced version of Guaranteed-Rate (GR) packet scheduling algorithm, namely virtual reserved rate GR (VRR-GR), to further reduce the delay and suppress the jitter in multiservice network environment. Simulation results show that our proposed approach can satisfyingly prioritize mobile IPTV services in WMN, while providing non-IPTV services with what they need as well.      

A taxonomy and evaluation for developing 802.11‐based wireless mesh network testbeds

The definition of wireless mesh networks (WMNs) has been used in the literature to connote and epitomize the ideal, ubiquitous, pervasive, and autonomic networking technology. An increasing interest has been emerging on the development of 802.11‐based WMN testbeds to test the new ideas and approaches more realistically as opposed to relying solely on simulations. Although the developed testbeds have provided several insights to researchers for furthering the technology, there are still several issues that need to be addressed, particularly, with the approval of new standards, such as IEEE 802.11s, IEEE 802.11n, and IEEE 802.16, and upcoming protocols, such as IEEE 802.11ac, 802.11ad, 802.11ah, and 802.11af TV White Space efforts. In this paper, our goal is to provide a taxonomy and insightful guidelines for the creation of 802.11‐based WMN testbeds as well as to identify several features that future WMN testbeds should possess. Utilizing these features, we evaluate the existing WMN testbeds. Finally, in addition to the existing WMN testbed experiments conducted at several layers of the protocol stack, we provide a list of open future research issues that can benefit from experiments on WMN testbeds. Copyright © 2011 John Wiley & Sons, Ltd.     

MrFair: Misbehavior-resistant fair scheduling in wireless mesh networks

It is a critical issue to ensure that nodes and/or flows have fair access to the network bandwidth in wireless mesh networks (WMNs). However, current WMNs based on IEEE 802.11 exhibit severe unfairness. Several scheduling schemes have been proposed to ensure fairness in WMNs. Unfortunately, all of them implicitly trust nodes in the network, and thus are vulnerable to the misbehavior of nodes participating in scheduling. In this paper, we address the threats to fair scheduling in WMNs resulting from node misbehavior and present a generic verification framework to detect such misbehavior. Moreover, we develop two verification schemes based on this framework for distributed and centralized authentication environments, respectively. We validate our approach by extending an existing fair scheduling scheme and evaluating it through simulation. The results show that our approach improves misbehavior detection with light performance overhead.     

Performance evaluation of multihop ad hoc WLANs

Ongoing technological advances in portable devices, coupled with the need for continuous connectivity while mobile, have made ad hoc networks a compelling research and development topic, particularly in a challenging multimedia multihop scenario. The ability of IEEE 802.11's ad hoc mode of operation, as a dominating wireless local area network (WLAN) protocol, to serve multihop networks requires thorough investigation. In this article, through considering crucial real-life physical phenomena and avoiding as many confining assumptions as possible, system performance measures such as delay and packet failure rate are evaluated. As a result, the importance of adequate selection of the system parameters toward performance improvement is underscored. Moreover, the simulation results imply that by complementing through priority provisions, coordination, route reservation, clustering, and optimum channel coding considerations, the IEEE 802.11 medium access control (MAC) protocol can survive in a multihop scenario. The custom simulation environment developed features modularity, comprising traffic generator, mobility, wireless channel, and IEEE 802.11 protocol modules, and is capable of accommodating many more of the physical phenomena involved.     

Enhancing IEEE 802.11n WLANs using group-orthogonal code-division multiplex

The definition of the next generation of wireless networks is well under way within the IEEE 802.11 High Throughput Task Group committee. The resulting standard, to be called IEEE 802.11n, is expected to be a backward-compatible evolution of the successful IEEE 802.11a/g systems also based on multicarrier techniques. It can be anticipated that 802.11n systems will outperform its predecessors in terms of transmission rate and/or performance, mainly, due to the use of multiple antennae technology for transmission and reception. In this paper we propose to incorporate group-orthogonal (GO) code division multiplex (CDM) into the IEEE 802.11n specifications to further enhance its performance. It is shown how GO-CDM can take full advantage of the diversity offered by the multiple antennae and multicarrier transmission by using an iterative maximum likelihood (ML) joint detector. Furthermore, the use of GO-CDM does not compromise the backward compatibility with legacy systems.     

Interference Evaluation of Bluetooth and IEEE 802.11b Systems

The emergence of several radio technologies, such as Bluetooth and IEEE 802.11, operating in the 2.4 GHz unlicensed ISM frequency band, may lead to signal interference and result in significant performance degradation when devices are colocated in the same environment. The main goal of this paper is to evaluate the effect of mutual interference on the performance of Bluetooth and IEEE 802.11b systems. We develop a simulation framework for modeling interference based on detailed MAC and PHY models. First, we use a simple simulation scenario to highlight the effects of parameters, such as transmission power, offered load, and traffic type. We then turn to more complex scenarios involving multiple Bluetooth piconets and WLAN devices.     

A MAC-Layer QoS Provisioning Protocol for Cognitive Radio Networks

Due to the proliferation of diverse network devices with multimedia capabilities, there is an increasing need for Quality of Service (QoS) provisioning in wireless networks. The MAC layer protocol with enhanced distributed channel access (EDCA) in the IEEE 802.11-2007 is able to provide differentiated QoS for different traffic types in wireless networks through varying the Arbitration Inter-Frame Spaces (AIFS) and contention window sizes. However, the performance of high priority traffic can be seriously degraded in the presence of strong noise over the wireless channels. Schemes utilizing adaptive modulation and coding (AMC) technique have also been proposed for the provisioning of QoS. They can provide limited protection in the presence of noise but are ineffective in a high noise scenario. Although multiple non-overlapped channels exist in the 2.4 and 5?GHz spectrum, most IEEE 802.11-based multi-hop ad hoc networks today use only a single channel at anytime. As a result, these networks cannot fully exploit the aggregate bandwidth available in the radio spectrum provisioned by the standards. By identifying vacant channels through the use of cognitive radios technique, the noise problem can be mitigated by distributing network traffic across multiple vacant channels to reduce the node density per transmission channel. In this paper, we propose the MAC-Layer QoS Provisioning Protocol (MQPP) for 802.11-based cognitive radio networks (CRNs) which combines adaptive modulation and coding with dynamic spectrum access. Simulation results demonstrate that MQPP can achieve better performance in terms of lower delay and higher throughput.     

Resource Allocation in High Data Rate Mesh WPAN: A Survey Paper

IEEE 802.15.3 High data rate wireless personal area networks (HDR WPANs) have been developed to communicate with devices within 10 m at high speed. A mesh network made up of a parent piconet and several child piconets can support multi-hop communications. Wireless mesh networks (WMNs) have been expected to be the ultimate solution for the next decade wireless networking, showing rapid progress and many new inspiring applications. The international standardization organizations formed working groups to address the problem of standardization for WMNs. These groups were the IEEE 802.15.5 (mesh extensions for WPANs),the IEEE 802.11s (mesh extensions for WLANs), and the IEEE 802.16a (mesh extensions for WiMAX). The IEEE 802.15.5 standard is the standard which defines specifications for including multi-hop functionality in the legacy 802.15.3 and 802.15.4 low data rate (LDR) WPAN networks. The impetus for a WPAN to operate in a mesh topology is to increase the network coverage without increasing the transmit power, to increase the route reliability via route redundancy, self-configuration, and efficient use of device battery life. In the case of meshed WPANs, multiple WPAN clusters compete for channel time in a shared superframe. Therefore, it is essential to determine the channel time requirements of each cluster with a certain number of devices and to determine how these clusters can compete to the shared channel time. In this paper, we investigate the different resource allocation mechanisms related to the meshed HDR WPANs for the 802.15.3 and the 802.15.5 standards. We introduce the single hop and the multi-hop IEEE 802.15.3 WPAN architectures. This is followed by the introduction of the IEEE 802.15.5 standard that provides the mesh capabilities for extending the coverage area of HDR WPANs. The current on-going research issues for resource allocation, including beacon interference, reservation collision etc., in both meshed 802.15.3 and 802.15.5 are alluded to.     

A hybrid multi-channel MAC protocol for wireless ad hoc networks

In a regular wireless ad hoc network, the Medium Access Control (MAC) protocol coordinates channel access among nodes, and the throughput of the network is limited by the bandwidth of a single channel. The multi-channel MAC protocols can exploit multiple channels to achieve high network throughput by enabling more concurrent transmissions. In this paper, we propose a hybrid and adaptive protocol, called H-MMAC, which utilizes multi-channel resources more efficiently than other multi-channel MAC protocols. The main idea is to adopt the IEEE 802.11 Power Saving Mechanism and to allow nodes to transmit data packets while other nodes try to negotiate the data channel during the Ad hoc Traffic Indication Message window based on the network traffic load. The analytical and simulation results show that the proposed H-MMAC protocol improves the network performance significantly in terms of the aggregate throughput, average delay, fairness and energy efficiency.     

基于干扰图的无线自组织网络MAC协议

由于IEEE802．11MAC协议采用了简单的干扰模型，因此产生了隐藏终端和暴露终端这两个严重影响无线自组织网络性能的问题。文章提出了一种新的基于干扰图（Conflict Graph）的MAC协议——CG-MAC来提高无线自组织网络的吞吐量。通过仿真实验，该协议能够同时解决隐藏终端和暴露终端问题．很大程度地提高了网络性能。