A link-state based on-demand routing protocol supporting real-time traffic for wireless mobile ad hoc networks

Ankara : The Department of Computer Engineering and the Institute of Engineering and Science of Bilkent University, 2007.Thesis (Master's) -- Bilkent University, 2007.Includes bibliographical references leaves 200-212.Wireless ad hoc networks have gained a lot of popularity since their introduction and as many wireless network interface cards provide support for ad hoc networking, such networks have also seen real-life deployment for non-specialized purposes. Wireless mobile ad hoc networks (MANETs) are currently the most common type of ad hoc networks, and such networks are especially esteemed for their mobility support and ease of deployment due to their ad hoc nature. As most common network applications, such as the Web, FTP, email, and instant messaging, are data-centric and do not operate under strict time constraints, MANETs have been deployed to enable such non-real-time applications in the past. However, with the increasing use of real-time applications over ad hoc networks, such as teleconferencing, VoIP, and security and tracking applications where timeliness is of importance, real-time traffic support in multi-hop wireless mobile ad hoc networks has become an issue. We propose an event-driven, link-state based, on-demand routing protocol to enable real-time traffic support in such multi-hop wireless mobile ad hoc networks. Our protocol, which is named Elessar, is based on link-state topology dissemination, but instead of the more common periodic link-state messaging scheme, we employ event-driven link-state messages in Elessar, where topology changes are the events of interest. Through such an approach, we aim to lower the overhead of our protocol, especially for low-mobility cases, which is currently the most commonly encountered case with ad hoc networks deployed with machines directly interacting with humans, such as PDAs and laptops. Due to its link-state nature, our protocol is able to support non-real-time traffic without any further action. In order to support real-time traffic, however, we employ a direct cost dissemination mechanism, which only operates on-demand when there are one or more real-time flows in the network. We aim to provide soft quality-of-service (QoS) guarantees to real-time flows through intelligent path selection, without any resource reservation. We also aim to provide such QoS guarantees throughout the lifetime of a real-time flow, even in the face of node failures and mobility, by dynamic path adaptation during the lifetime of the flow. Elessar is able to support real-time and non-real-time traffic concurrently, as well as various different types of concurrent real-time traffic, such as delay- and loss-sensitive traffic. Our protocol, therefore, does not aim to support a single type of real-time traffic, but rather a plethora of different types of real-time traffic. Elessar is completely distributed, dynamic and adaptive, and does not require the underlying MAC protocol to be QoS-aware. We analyse our design choices and the performance of our protocol through realistic simulation experiments conducted on the OMNeT++ discrete event simulation platform, using the INET framework. We have used the IEEE 802.11b MAC protocol during our simulations and have employed the random waypoint mobility model to simulate mobility. Our experimental results show that Elessar is able to efficiently provide real-time traffic support for different types of traf- fic flows, even in the face of mobility. Our protocol operates best for smallto-medium-sized networks where mobility rates are low-to-medium. Once the mobility rate exceeds a certain threshold, intelligent path selection cannot cope satisfactorily with the high dynamism of the environment and the overhead of Elessar exceeds acceptable levels due to its event-driven link-state nature.Görbil, GökçeM.S

An energy-aware and QOS assured wireless multi-hop transmission protocol

A thesis submitted in fulfillment of the requirements for the degree of Master of Science by researchThe Ad-hoc network is set up with multiple wireless devices without any pre-existing infrastructure. It usually supports best-effort traffic and occasionally some kinds of Quality of Service (QoS). However, there are some applications with real-time traffic requirements where deadlines must be met. To meet deadlines, the communication network has to support the timely delivery of inter-task messages. Furthermore, energy efficiency is a critical issue for battery-powered mobile devices in ad-hoc networks. Thus, A QoS guaranteed and energy-aware transmission scheme is one hot of research topics in the research area. The MSc research work is based on the idea of Real-Time Wireless Multi-hop Protocol (RT-WMP). RT-WMP is a well known protocol originally used in the robots control area. It allows wireless real-time traffic in relatively small mobile ad-hoc networks using the low-cost commercial IEEE 802.11 technology. The proposed scheme is based on a token-passing approach and message exchange is priority based. The idea of energy-aware routing mechanism is based on the AODV protocol. This energy-saving mechanism is analysed and simulated in our study as an extension of the RT-WMP. From the simulation results and analysis, it has been shown that adding energy-aware mechanism to RT-WMP is meaningful to optimise the performance of traffic on the network

Achieving Stable Throughput to Support QoS in IEEE 802.11 Wireless Networks

This paper investigates and describes a new provisioning technique for IEEE 802.11 based networks, focusing on the ad-hoc Distributed Coordination Function (DCF) to redefine stability of the network throughput to support QoS. This paper propose better techniques to achieve stable throughput in Wireless LAN networks by assigning new values to the Contention Window to high priority traffics which will guarantee better throughput to the selected network traffic. A simulation is done using Network Simulator 2 (NS-2) and findings are then presented. Results showed that stable throughput can be achieved to provide better traffic flows especially for real-time traffic and multimedia applications

A simulation environment for software defined wireless networks with legacy devices

The adoption of Software Defined Networks (SDNs) in a Mobile ad-hoc network (MANET) could present several benefits, such as adaptability and performance increase. However, to assess this possibility, a simulation tool may be necessary to test new protocols and solutions in a large combination of scenarios and traffic patterns, without the need of real equipment. Unfortunately, few tools are available for wireless SDNs, and none have the ability to also support MANETs with multiple radio access technologies. While NS-3 has the ability to simulate heterogeneous MANETs, it does not support wireless OpenFlow capable devices or wireless OpenFlow channels. In this work we present a simulation environment that, besides creating an ad-hoc data plane, enables the possibility of creating wireless hybrid SDN devices capable of connecting to legacy devices, alongside with an LTE OpenFlow channel connected to an external SDN Controller (RYU). Results show that the simulation environment supports large networks with both legacy and SDN devices, although these will bear an effective running time higher than their simulation time. Moreover, when comparing to an OLSR-only network, the proposed network (with a basic path search metric) has the same or higher performance.info:eu-repo/semantics/publishedVersio

Distributed Medium Access Control for QoS Support in Wireless Networks

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

Mobile Crowd Sensing for Traffic Prediction in Internet of Vehicles.

The advances in wireless communication techniques, mobile cloud computing, automotive and intelligent terminal technology are driving the evolution of vehicle ad hoc networks into the Internet of Vehicles (IoV) paradigm. This leads to a change in the vehicle routing problem from a calculation based on static data towards real-time traffic prediction. In this paper, we first address the taxonomy of cloud-assisted IoV from the viewpoint of the service relationship between cloud computing and IoV. Then, we review the traditional traffic prediction approached used by both Vehicle to Infrastructure (V2I) and Vehicle to Vehicle (V2V) communications. On this basis, we propose a mobile crowd sensing technology to support the creation of dynamic route choices for drivers wishing to avoid congestion. Experiments were carried out to verify the proposed approaches. Finally, we discuss the outlook of reliable traffic prediction

Quality of Service-Based Medium Access Control Mechanism for Multimedia Traffic in Mobile Ad Hoc Networks

This thesis describes an investigation on the problem of quality of service (QoS) support in mobile ad hoc networks (MANETs). The decentralized nature of wireless ad hoc networks makes them suitable for a variety of applications where central nodes cannot be relied on. This thesis presents a medium access control (MAC) QoS mechanism for multimedia applications in IEEE 802.11e based MANETs. IEEE 802.11e standard draft includes new features to facilitate and promote the provision of QoS guarantees in wireless networks with a long-term solution based on QoS-architectures. The motivation is driven by the need to support increasing demand of time-sensitive applications such as Voice over IP (VoIP) and video conferencing applications. IEEE 802.11e enhances the Distributed Coordination Function (DCF) and the Point Coordination Function (PCF) of the legacy IEEE 802.11, through a new coordination function: the Hybrid Coordination Function (HCF). Within the HCF, there are two methods of channel access: HCF Controlled Channel Access (HCCA) and Enhanced Distributed Channel Access (EDCA). EDCA operates in infrastructure-less ad hoc mode and is widely used in MANETs, unlike HCCA, which further assures QoS provisioning operates in infrastructure mode in the presence of access points (AP). Recent researches showed that EDCA lacks QoS support of real-time traffic in MANETs due to its contention based medium access method. This thesis takes HCCA QoS provisioning potentials to MANETs by implementing a MAC mechanism in which HCCA is employed on top of EDCA to work in infrastructure-less environment like MANET with the help of multiple channels. The mechanism dedicates a unique receiver-based channel to every mobile node. It will act as virtual hybrid coordinator (VHC) to exercise control over the channel in contention-free manner while maintaining a common channel in which all mobile nodes can exchange broadcast and routing related messages. The mechanism can be easily integrated with existing 802.11 systems without modification to existing protocols while ensuring a level of admission control and resource reservation over the medium. Simulation results indicate that the mechanism significantly improves the overall network throughput by 20% at the saturation point and improves average delay by 20% at the saturation point compared to pure EDCA with or without multiple channels. Even with multi-channel EDCA, our mechanism guarantees better performance in terms of throughput and MAC delay for high priority traffic in MANET. The research contribution on MAC layer can be integrated into a larger framework for QoS support in MANETs, which opens a wide range of further research in QoS provisioning in MANETs and solve QoS multi-layer design and implementation issues

Two-stage wireless network emulation

Testing and deploying mobile wireless networks and applications are very challenging tasks, due to the network size and administration as well as node mobility management. Well known simulation tools provide a more flexible environment but they do not run in real time and they rely on models of the developed system rather than on the system itself. Emulation is a hybrid approach allowing real application and traffic to be run over a simulated network, at the expense of accuracy when the number of nodes is too important. In this paper, emulation is split in two stages : first, the simulation of network conditions is precomputed so that it does not undergo real-time constraints that decrease its accuracy ; second, real applications and traffic are run on an emulation platform where the precomputed events are scheduled in soft real-time. This allows the use of accurate models for node mobility, radio signal propagation and communication stacks. An example shows that a simple situation can be simply tested with real applications and traffic while relying on accurate models. The consistency between the simulation results and the emulated conditions is also illustrated