Backoff as Performance improvements Algorithms - A Comprehenssive Review

As a significant part of the Media Access Control protocol, the backoff algorithm purpose is to minimize number of collisions if not totally avoid any collision in Mobile Ad Hoc Networks, in the case of contention between nodes to access a channel. Researchers have proposed many algorithms for backoff to enhance the network performance and improve it. This paper aims at exploring the main and most studied backoff algorithms and how do these algorithms lead to an enhancement of the MANETs performance. This paper also compares between the algorithms proposed in the literature and evaluates to what extent they have affected the performance and enhance it

Towards End-to-End QoS in Ad Hoc Networks

http://citi.insa-lyon.fr/wons2006/index.htmlIn this paper, we address the problem of supporting adaptive QoS resource management in mobile ad hoc networks, by proposing an efficient model for providing proportional endto- end QoS between classes. The effectiveness of our proposed solution in meeting desired QoS differentiation at a specific node and from end-to-end are assessed by simulation using a queueing network model implemented in QNAP. The experiments results show that the proposed solution provides consistent proportional differentiation for any service class and validates our claim even under bursty traffic and fading channel conditions

Adaptive Medium Access Control for Internet-of-Things Enabled Mobile Ad Hoc Networks

An Internet-of-Things (IoT) enabled mobile ad hoc network (MANET) is a self organized distributed wireless network, in which nodes can randomly move making the network traffic load vary with time. A medium access control (MAC) protocol, as a most important mechanism of radio resource management, is required in MANETs to coordinate nodes’ access to the wireless channel in a distributed way to satisfy their quality of service (QoS) requirements. However, the distinctive characteristics of IoT-enabled MANETs, i.e., distributed network operation, varying network traffic load, heterogeneous QoS demands, and increased interference level with a large number of nodes and extended communication distances, pose technical challenges on MAC. An efficient MAC solution should achieve consistently maximal QoS performance by adapting to the network traffic load variations, and be scalable to an increasing number of nodes in a multi-hop communication environment. In this thesis, we develop comprehensive adaptive MAC solutions for an IoT-enabled MANET with the consideration of different network characteristics. First, an adaptive MAC solution is proposed for a fully-connected network, supporting homogeneous best-effort data traffic. Based on the detection of current network traffic load condition, nodes can make a switching decision between IEEE 802.11 distributed coordination function (DCF) and dynamic time division multiple access (D-TDMA), when the network traffic load reaches a threshold, referred to as MAC switching point. The adaptive MAC solution determines the MAC switching point in an analytically tractable way to achieve consistently high network performance by adapting to the varying network traffic load. Second, when heterogeneous services are supported in the network, we propose an adaptive hybrid MAC scheme, in which a hybrid superframe structure is designed to accommodate the channel access from delay-sensitive voice traffic using time division multiple access (TDMA) and from best-effort data traffic using truncated carrier sense multiple access with collision avoidance (T-CSMA/CA). According to instantaneous voice and data traffic load conditions, the MAC exploits voice traffic multiplexing to increase the voice capacity by adaptively allocating TDMA time slots to active voice nodes, and maximizes the aggregate data throughput by adjusting the optimal contention window size for each data node. Lastly, we develop a scalable token-based adaptive MAC scheme for a two-hop MANET with an increasing number of nodes. In the network, nodes are partitioned into different one-hop node groups, and a TDMA-based superframe structure is proposed to allocate different TDMA time durations to different node groups to overcome the hidden terminal problem. A probabilistic token passing scheme is adopted for packet transmissions within different node groups, forming different token rings. An average end-to-end delay optimization framework is established to derive the set of optimal MAC parameters for a varying network load condition. With the optimal MAC design, the proposed adaptive MAC scheme achieves consistently minimal average end-to-end delay in an IoT-based two-hop environment with a high network traffic load. This research on adaptive MAC provides some insights in MAC design for performance improvement in different IoT-based network environments with different QoS requirements

Modelling and performance analysis of mobile ad hoc networks

PhD ThesisMobile Ad hoc Networks (MANETs) are becoming very attractive and useful in many kinds of communication and networking applications. This is due to their efficiency, relatively low cost, and flexibility provided by their dynamic infrastructure. Performance evaluation of mobile ad hoc networks is needed to compare various architectures of the network for their performance, study the effect of varying certain network parameters and study the interaction between various parameters that characterise the network. It can help in the design and implementation of MANETs. It is to be noted that most of the research that studies the performance of MANETs were evaluated using discrete event simulation (DES) utilising a broad band of network simulators. The principle drawback of DES models is the time and resources needed to run such models for large realistic systems, especially when results with a high accuracy are desired. In addition, studying typical problems such as the deadlock and concurrency in MANETs using DES is hard because network simulators implement the network at a low abstraction level and cannot support specifications at higher levels. Due to the advantage of quick construction and numerical analysis, analytical modelling techniques, such as stochastic Petri nets and process algebra, have been used for performance analysis of communication systems. In addition, analytical modelling is a less costly and more efficient method. It generally provides the best insight into the effects of various parameters and their interactions. Hence, analytical modelling is the method of choice for a fast and cost effective evaluation of mobile ad hoc networks. To the best of our knowledge, there is no analytical study that analyses the performance of multi-hop ad hoc networks, where mobile nodes move according to a random mobility model, in terms of the end-to-end delay and throughput. This work ii presents a novel analytical framework developed using stochastic reward nets and mathematical modelling techniques for modelling and analysis of multi-hop ad hoc networks, based on the IEEE 802.11 DCF MAC protocol, where mobile nodes move according to the random waypoint mobility model. The proposed framework is used to analysis the performance of multi-hop ad hoc networks as a function of network parameters such as the transmission range, carrier sensing range, interference range, number of nodes, network area size, packet size, and packet generation rate. The proposed framework is organized into several models to break up the complexity of modelling the complete network and make it easier to analyse each model as required. This is based on the idea of decomposition and fixed point iteration of stochastic reward nets. The proposed framework consists of a mathematical model and four stochastic reward nets models; the path analysis model, data link layer model, network layer model and transport layer model. These models are arranged in a way similar to the layers of the OSI protocol stack model. The mathematical model is used to compute the expected number of hops between any source-destination pair; and the average number of carrier sensing, hidden, and interfering nodes. The path analysis model analyses the dynamic of paths in the network due to the node mobility in terms of the path connection availability and rate of failure and repair. The data link layer model describes the behaviour of the IEEE 802.11 DCF MAC protocol. The actions in the network layer are modelled by the network layer model. The transport layer model represents the behaviour of the transport layer protocols. The proposed models are validated using extensive simulations

Recursive analytical performance evaluation of broadcast protocols with silencing: application to VANETs

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Mobile Ad-Hoc Networks

Being infrastructure-less and without central administration control, wireless ad-hoc networking is playing a more and more important role in extending the coverage of traditional wireless infrastructure (cellular networks, wireless LAN, etc). This book includes state-of-the-art techniques and solutions for wireless ad-hoc networks. It focuses on the following topics in ad-hoc networks: quality-of-service and video communication, routing protocol and cross-layer design. A few interesting problems about security and delay-tolerant networks are also discussed. This book is targeted to provide network engineers and researchers with design guidelines for large scale wireless ad hoc networks

Secure Routing and Medium Access Protocols inWireless Multi-hop Networks

While the rapid proliferation of mobile devices along with the tremendous growth of various applications using wireless multi-hop networks have significantly facilitate our human life, securing and ensuring high quality services of these networks are still a primary concern. In particular, anomalous protocol operation in wireless multi-hop networks has recently received considerable attention in the research community. These relevant security issues are fundamentally different from those of wireline networks due to the special characteristics of wireless multi-hop networks, such as the limited energy resources and the lack of centralized control. These issues are extremely hard to cope with due to the absence of trust relationships between the nodes. To enhance security in wireless multi-hop networks, this dissertation addresses both MAC and routing layers misbehaviors issues, with main focuses on thwarting black hole attack in proactive routing protocols like OLSR, and greedy behavior in IEEE 802.11 MAC protocol. Our contributions are briefly summarized as follows. As for black hole attack, we analyze two types of attack scenarios: one is launched at routing layer, and the other is cross layer. We then provide comprehensive analysis on the consequences of this attack and propose effective countermeasures. As for MAC layer misbehavior, we particularly study the adaptive greedy behavior in the context of Wireless Mesh Networks (WMNs) and propose FLSAC (Fuzzy Logic based scheme to Struggle against Adaptive Cheaters) to cope with it. A new characterization of the greedy behavior in Mobile Ad Hoc Networks (MANETs) is also introduced. Finally, we design a new backoff scheme to quickly detect the greedy nodes that do not comply with IEEE 802.11 MAC protocol, together with a reaction scheme that encourages the greedy nodes to become honest rather than punishing them

A Simple and Robust Dissemination Protocol for VANETs

Several promising applications for Vehicular Ad-hoc Networks (VANETs) exist. For most of these applications, the communication among vehicles is envisioned to be based on the broadcasting of messages. This is due to the inherent highly mobile environment and importance of these messages to vehicles nearby. To deal with broadcast communication, dissemination protocols must be defined in such a way as to (i) prevent the so-called broadcast storm problem in dense networks and (ii) deal with disconnected networks in sparse topologies. In this paper, we present a Simple and Robust Dissemination (SRD) protocol that deals with these requirements in both sparse and dense networks. Its novelty lies in its simplicity and robustness. Simplicity is achieved by considering only two states (cluster tail and non- tail) for a vehicle. Robustness is achieved by assigning message delivery responsibility to multiple vehicles in sparse networks. Our simulation results show that SRD achieves high delivery ratio and low end-to-end delay under diverse traffic conditions