18,560 research outputs found

    MAC Protocols for Wireless Mesh Networks with Multi-beam Antennas: A Survey

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    Multi-beam antenna technologies have provided lots of promising solutions to many current challenges faced in wireless mesh networks. The antenna can establish several beamformings simultaneously and initiate concurrent transmissions or receptions using multiple beams, thereby increasing the overall throughput of the network transmission. Multi-beam antenna has the ability to increase the spatial reuse, extend the transmission range, improve the transmission reliability, as well as save the power consumption. Traditional Medium Access Control (MAC) protocols for wireless network largely relied on the IEEE 802.11 Distributed Coordination Function(DCF) mechanism, however, IEEE 802.11 DCF cannot take the advantages of these unique capabilities provided by multi-beam antennas. This paper surveys the MAC protocols for wireless mesh networks with multi-beam antennas. The paper first discusses some basic information in designing multi-beam antenna system and MAC protocols, and then presents the main challenges for the MAC protocols in wireless mesh networks compared with the traditional MAC protocols. A qualitative comparison of the existing MAC protocols is provided to highlight their novel features, which provides a reference for designing the new MAC protocols. To provide some insights on future research, several open issues of MAC protocols are discussed for wireless mesh networks using multi-beam antennas.Comment: 22 pages, 6 figures, Future of Information and Communication Conference (FICC) 2019, https://doi.org/10.1007/978-3-030-12388-8_

    Performance Analysis of Concurrent Transmission with Reducing Handshakes in Multi-Hop Wireless Mesh Networks (WMNS)

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    The IEEE 802.11 Distributed Coordination Function (DCF) Medium Access Control (MAC) protocol continues to suffer from throughput degradation when directly applied in multi-hop Wireless Mesh Network (WMN). The Request-to-Send/Clear-to-Send (RTS/ CTS) signaling partially solved hidden node problems however the exposed node problems remain unaddressed. These exposed nodes lead to throughput degradation especially when the transmission in multi-hop networks is considered. The major reason for this poor performance is the restricted nature of the IEEE 802.11 MAC, which does not allow exposed nodes to initiates its transmission for the entire duration of ongoing transmission. Moreover, since multi-hop communication such as wireless mesh network transfer the data packet via intermediate nodes, the amount of control handshakes that take place at each intermediate node significantly reduce the throughput. This project proposes a set of enhancement to the existing IEEE 802.11 DCF MAC by enabling concurrent transmission by the exposed nodes and reduces the amount of handshakes required at every hop until the data packet reaches its destination. Analytical models are developed for analytical study of MAC protocols operating in multi-hop mesh networks and simulated over quasi-static Rayleigh fading channel. The multi-hop network performances are evaluated in terms of throughput and delay. The protocol outperforms the existing IEEE DCF MAC with more than 260% increase in overall throughput of multi-hop WM

    Adaptive secure network model for dynamic wireless mesh network

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    University of Technology Sydney. Faculty of Engineering and Information Technology.We as an advanced civilization rely on communication networks for a lot of important tasks. They are used to share information between vital systems, provide us with our pin-point location, access various digital resources and to stay connected with each other. Due to its necessity and enormity, maintaining and securing such a communication medium is an important task. As most communication networks rely on centralized systems, they are bound by the control of a central entity and are unable to keep up with the current growth of the network and advancements in electronic devices. The next step in an inter-connected world requires a decentralized distributed system that can also provide high levels of security. One possible solution is a dynamic distributed wireless mesh network as it provides all the features of a traditional network along with the flexibility of wireless communication and an infrastructure less distributed setup. The network can be created by connecting mobile or stationary devices together using wireless communication devices (such as smartphones, laptops, hot-spots, etc). As the network is created by multiple devices, it would not break-down if some of the devices were disabled. On the contrary, as the network uses hopping for message transmission using dynamic routes, it can self-heal by creating alternate routes if a device was to fail. As the workings and features of a dynamic mesh network differ from the traditional network, it also requires a modified security framework that can provide high levels of security whilst taking benefit of the dynamic mesh network’s unique features. This thesis investigates the problems and limitations linked to secure dynamic wireless mesh networks and how they can be improved upon. In addition to the routing protocols used and how they can be improved upon, the thesis also elaborates on the various security concerns with such networks. As distributed networks aren’t dependent on a central entity, enabling various security features such as authentication are a major challenge. In addition to the decentralized nature of the networks, a single security scheme would not be able to cover the various types of requirements a given scenario in the network might have. Along with authentication, providing end-to-end encryption is also an important component towards ensuring the data travelling through the network is secure and not tampered with. Encryption is also essential in a dynamic wireless mesh network as the data transmitted travels through multiple devices on the network before reaching the destination node and can be easily compromised if not secured. With such an importance of encryption, the network also requires a key management and distribution framework. As traditional network uses a centralized system for maintaining and distributing cryptographic keys in the network, it is a big challenge to implement the same in a distributed network with minimal dependence on a central entity. The key exchange must consider the nature of the network and accordingly incorporate improvements to be able to function in a distributed network. This thesis explores the above areas to propose a new network model for a secure dynamic wireless mesh network including a new routing scheme and a security framework comprising a hybrid encryption scheme, a hybrid authentication scheme and an improved key exchange and management scheme. This thesis demonstrates that our solutions not only strengthen and secure the dynamic wireless mesh networks but also significantly improve the performance and efficiency as compared to existing approaches

    Distributed Medium Access Control for QoS Support in Wireless Networks

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    With the rapid growth of multimedia applications and the advances of wireless communication technologies, quality-of-service (QoS) provisioning for multimedia services in heterogeneous wireless networks has been an important issue and drawn much attention from both academia and industry. Due to the hostile transmission environment and limited radio resources, QoS provisioning in wireless networks is much more complex and difficult than in its wired counterpart. Moreover, due to the lack of central controller in the networks, distributed network control is required, adding complexity to QoS provisioning. In this thesis, medium access control (MAC) with QoS provisioning is investigated for both single- and multi-hop wireless networks including wireless local area networks (WLANs), wireless ad hoc networks, and wireless mesh networks. Originally designed for high-rate data traffic, a WLAN has limited capability to support delay-sensitive voice traffic, and the service for voice traffic may be impacted by data traffic load, resulting in delay violation or large delay variance. Aiming at addressing these limitations, we propose an efficient MAC scheme and a call admission control algorithm to provide guaranteed QoS for voice traffic and, at the same time, increase the voice capacity significantly compared with the current WLAN standard. In addition to supporting voice traffic, providing better services for data traffic in WLANs is another focus of our research. In the current WLANs, all the data traffic receives the same best-effort service, and it is difficult to provide further service differentiation for data traffic based on some specific requirements of customers or network service providers. In order to address this problem, we propose a novel token-based scheduling scheme, which provides great flexibility and facility to the network service provider for service class management. As a WLAN has small coverage and cannot meet the growing demand for wireless service requiring communications ``at anywhere and at anytime", a large scale multi-hop wireless network (e.g., wireless ad hoc networks and wireless mesh networks) becomes a necessity. Due to the location-dependent contentions, a number of problems (e.g., hidden/exposed terminal problem, unfairness, and priority reversal problem) appear in a multi-hop wireless environment, posing more challenges for QoS provisioning. To address these challenges, we propose a novel busy-tone based distributed MAC scheme for wireless ad hoc networks, and a collision-free MAC scheme for wireless mesh networks, respectively, taking the different network characteristics into consideration. The proposed schemes enhance the QoS provisioning capability to real-time traffic and, at the same time, significantly improve the system throughput and fairness performance for data traffic, as compared with the most popular IEEE 802.11 MAC scheme

    A GA-based simulation system for WMNs: comparison analysis for different number of flows, client distributions, DCF and EDCA functions

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    In this paper, we compare the performance of Distributed Coordination Function (DCF) and Enhanced Distributed Channel Access (EDCA) for normal and uniform distributions of mesh clients considering two Wireless Mesh Network (WMN) architectures. As evaluation metrics, we consider throughput, delay, jitter and fairness index metrics. For simulations, we used WMN-GA simulation system, ns-3 and Optimized Link State Routing. The simulation results show that for normal distribution, the throughput of I/B WMN is higher than Hybrid WMN architecture. For uniform distribution, in case of I/B WMN, the throughput of EDCA is a little bit higher than Hybrid WMN. However, for Hybrid WMN, the throughput of DCF is higher than EDCA. For normal distribution, the delay and jitter of Hybrid WMN are lower compared with I/B WMN. For uniform distribution, the delay and jitter of both architectures are almost the same. However, in the case of DCF for 20 flows, the delay and jitter of I/B WMN are lower compared with Hybrid WMN. For I/B architecture, in case of normal distribution the fairness index of DCF is higher than EDCA. However, for Hybrid WMN, the fairness index of EDCA is higher than DCF. For uniform distribution, the fairness index of few flows is higher than others for both WMN architectures.Peer ReviewedPostprint (author's final draft

    Scalability of broadcast performance in wireless network-on-chip

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    Networks-on-Chip (NoCs) are currently the paradigm of choice to interconnect the cores of a chip multiprocessor. However, conventional NoCs may not suffice to fulfill the on-chip communication requirements of processors with hundreds or thousands of cores. The main reason is that the performance of such networks drops as the number of cores grows, especially in the presence of multicast and broadcast traffic. This not only limits the scalability of current multiprocessor architectures, but also sets a performance wall that prevents the development of architectures that generate moderate-to-high levels of multicast. In this paper, a Wireless Network-on-Chip (WNoC) where all cores share a single broadband channel is presented. Such design is conceived to provide low latency and ordered delivery for multicast/broadcast traffic, in an attempt to complement a wireline NoC that will transport the rest of communication flows. To assess the feasibility of this approach, the network performance of WNoC is analyzed as a function of the system size and the channel capacity, and then compared to that of wireline NoCs with embedded multicast support. Based on this evaluation, preliminary results on the potential performance of the proposed hybrid scheme are provided, together with guidelines for the design of MAC protocols for WNoC.Peer ReviewedPostprint (published version

    Wireless industrial monitoring and control networks: the journey so far and the road ahead

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    While traditional wired communication technologies have played a crucial role in industrial monitoring and control networks over the past few decades, they are increasingly proving to be inadequate to meet the highly dynamic and stringent demands of today’s industrial applications, primarily due to the very rigid nature of wired infrastructures. Wireless technology, however, through its increased pervasiveness, has the potential to revolutionize the industry, not only by mitigating the problems faced by wired solutions, but also by introducing a completely new class of applications. While present day wireless technologies made some preliminary inroads in the monitoring domain, they still have severe limitations especially when real-time, reliable distributed control operations are concerned. This article provides the reader with an overview of existing wireless technologies commonly used in the monitoring and control industry. It highlights the pros and cons of each technology and assesses the degree to which each technology is able to meet the stringent demands of industrial monitoring and control networks. Additionally, it summarizes mechanisms proposed by academia, especially serving critical applications by addressing the real-time and reliability requirements of industrial process automation. The article also describes certain key research problems from the physical layer communication for sensor networks and the wireless networking perspective that have yet to be addressed to allow the successful use of wireless technologies in industrial monitoring and control networks
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