A hybrid packet loss recovery technique in wireless ad hoc networks

TCP utilization in wireless networks poses certain problems due to its inability to distinguish packet losses caused by congestion from those caused by frequent wireless errors, leading to degraded network performance. To avoid these problems and to minimize the effect of intensive channel contention in wireless networks, this work presents a new Hybrid ARQ technique for reliable and efficient packets transfer in static wireless ad hoc network. It is a combination of recent FEC based Raptor coding technique with ARQ based selective retransmission method, which outperforms purely ARQ based method. In contrast to most Hybrid ARQ techniques, which usually employ a byte level FEC, we mostly use packet level FEC in our simulations for the data transfer, on top of less frequent ARQ to recover the residual errors. Existing packet level FEC methods are mostly based on simple parity check codes or Reed Solomon codes with erasure decoding; in this work we use the recent raptor codes. We also introduce the notion of adaptive redundancy which helps to achieve better average network performance and to further improve the redundancy efficiency

Implications and Limitations of Securing an InfiniBand Network

The InfiniBand Architecture is one of the leading network interconnects used in high performance computing, delivering very high bandwidth and low latency. As the popularity of InfiniBand increases, the possibility for new InfiniBand applications arise outside the domain of high performance computing, thereby creating the opportunity for new security risks. In this work, new security questions are considered and addressed. The study demonstrates that many common traffic analyzing tools cannot monitor or capture InfiniBand traffic transmitted between two hosts. Due to the kernel bypass nature of InfiniBand, many host-based network security systems cannot be executed on InfiniBand applications. Those that can impose a significant performance loss for the network. The research concludes that not all network security practices used for Ethernet translate to InfiniBand as previously suggested and that an answer to meeting specific security requirements for an InfiniBand network might reside in hardware offload

Reliable data delivery in wireless sensor networks

Wireless sensor networks (WSN) have generated tremendous interest among researchers these years because of their potential usage in a wide variety of applications. Sensor nodes are inexpensive portable devices with limited processing power and energy resources. Sensor nodes can be used to collect information from the environment, locally process this data and transmit the sensed data back to the user. This thesis proposes a new reliable data delivery protocol for general point-to-point data delivery (unicasting) in wireless sensor networks. The new protocol is designed that aims at providing 100% reliability when possible as well as minimizing overhead and network delay. The design of the new protocol includes three components. The new protocol adopts a NACK-based hop-by-hop loss detection and recovery scheme using end-to-end sequence numbers. In order to solve the single/last packet problem in the NACK-based approach, a hybrid ACK/NACK scheme is proposed where an ACK-based approach is used as a supplement to the NACK-based approach to solve the single/last packet problem. The proposed protocol also has a new queue management scheme that gives priority to new data. By introducing the idea of a Ready_Bit and newer packet first rule in the transmission queue, nodes can detect and recover lost packets in parallel with the normal data transmission process. The performance of the new protocol is tested in a Crossbow MicaZ testbed. Experimental results show that the new protocol performs well under various system and protocol parameter settings

Reowolf 1.0

This document serves as the documentation and specification of the Reowolf project, aiming to provide connectors as a generalization of BSD-sockets for multi-party communication over the Internet

Scalable Video Streaming with Prioritised Network Coding on End-System Overlays

PhDDistribution over the internet is destined to become a standard approach for live broadcasting of TV or events of nation-wide interest. The demand for high-quality live video with personal requirements is destined to grow exponentially over the next few years. Endsystem multicast is a desirable option for relieving the content server from bandwidth bottlenecks and computational load by allowing decentralised allocation of resources to the users and distributed service management. Network coding provides innovative solutions for a multitude of issues related to multi-user content distribution, such as the coupon-collection problem, allocation and scheduling procedure. This thesis tackles the problem of streaming scalable video on end-system multicast overlays with prioritised push-based streaming. We analyse the characteristic arising from a random coding process as a linear channel operator, and present a novel error detection and correction system for error-resilient decoding, providing one of the first practical frameworks for Joint Source-Channel-Network coding. Our system outperforms both network error correction and traditional FEC coding when performed separately. We then present a content distribution system based on endsystem multicast. Our data exchange protocol makes use of network coding as a way to collaboratively deliver data to several peers. Prioritised streaming is performed by means of hierarchical network coding and a dynamic chunk selection for optimised rate allocation based on goodput statistics at application layer. We prove, by simulated experiments, the efficient allocation of resources for adaptive video delivery. Finally we describe the implementation of our coding system. We highlighting the use rateless coding properties, discuss the application in collaborative and distributed coding systems, and provide an optimised implementation of the decoding algorithm with advanced CPU instructions. We analyse computational load and packet loss protection via lab tests and simulations, complementing the overall analysis of the video streaming system in all its components

Fountain codes: performance analysis and optimization

The fountain coding principle provides a framework for efficient and reliable data transmission techniques over erasure channels, such as file transmission over the Internet. This thesis presents topics related to the optimisation and performance analysis for different settings where fountain coding methods are applied. We start by reviewing the fountain coding principle on which our own contributions are based. Strategies for both elastic and streaming traffic are considered. The coding schemes are typically modelled as stochastic processes and we analyse them using well-known tools, such as Markov chains and fixed-point iteration. Some of the schemes realise the principles of an ideal digital fountain, while the other sacrifice some characteristics, such as time-independence and the statistical equivalence of the encoded packets. The description of our own work is divided into two parts. The first part begins by addressing the optimisation of the degree distribution of LT coding, the first universal fountain coding method, for small file sizes. We present exact analysis for LT codes of very small size with some novel results. A simulation based method is presented for the analysis and optimisation of longer codes, up to hundreds of source blocks. We further present a method in which a random linear fountain code is divided into parts and conduct a performance analysis of the system. We propose and analyse two different strategies to overcome the performance degradation caused by the division. The first part ends with the description and optimisation of a systematic, sequential coding scheme in which the sender makes greedy choices concerning the repair packet structure on the basis of his belief about the state of the receiver. We present repair packet degree sequences which result in a low required overhead. In the second part we will address the problem of achieving a low residual erasure probability for streaming traffic using packet erasure correction. The methods are based on a sliding window. Four different methods are presented differing in how the repair packets are constructed. These codes further differ in the repair packet sending strategy; one code always sends a repair packet deterministically after a window movement, while the others send the repair packets probabilistically. We conclude that methods inspired by fountain coding provide efficient, yet simple, coding strategies for implementing data transfer in many settings

Achieving reliable and enhanced communication in vehicular ad hoc networks (VANETs)

A thesis submitted to the University of Bedfordshire in partial fulfilment of the requirement for the degree of Doctor of PhilosophyWith the envisioned age of Internet of Things (IoTs), different aspects of Intelligent Transportation System (ITS) will be linked so as to advance road transportation safety, ease congestion of road traffic, lessen air pollution, improve passenger transportation comfort and significantly reduce road accidents. In vehicular networks, regular exchange of current position, direction, speed, etc., enable mobile vehicle to foresee an imminent vehicle accident and notify the driver early enough in order to take appropriate action(s) or the vehicle on its own may take adequate preventive measures to avert the looming accident. Actualizing this concept requires use of shared media access protocol that is capable of guaranteeing reliable and timely broadcast of safety messages. This dissertation investigates the use of Network Coding (NC) techniques to enrich the content of each transmission and ensure improved high reliability of the broadcasted safety messages with less number of retransmissions. A Code Aided Retransmission-based Error Recovery (CARER) protocol is proposed. In order to avoid broadcast storm problem, a rebroadcasting vehicle selection metric η, is developed, which is used to select a vehicle that will rebroadcast the received encoded message. Although the proposed CARER protocol demonstrates an impressive performance, the level of incurred overhead is fairly high due to the use of complex rebroadcasting vehicle selection metric. To resolve this issue, a Random Network Coding (RNC) and vehicle clustering based vehicular communication scheme with low algorithmic complexity, named Reliable and Enhanced Cooperative Cross-layer MAC (RECMAC) scheme, is proposed. The use of this clustering technique enables RECMAC to subdivide the vehicular network into small manageable, coordinated clusters which further improve transmission reliability and minimise negative impact of network overhead. Similarly, a Cluster Head (CH) selection metric ℱ(\u1d457) is designed, which is used to determine and select the most suitably qualified candidate to become the CH of a particular cluster. Finally, in order to investigate the impact of available radio spectral resource, an in-depth study of the required amount of spectrum sufficient to support high transmission reliability and minimum latency requirements of critical road safety messages in vehicular networks was carried out. The performance of the proposed schemes was clearly shown with detailed theoretical analysis and was further validated with simulation experiments

End-to-end reliable communication in data networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1993.Includes bibliographical references (p. 207-209).Supported by the National Science Foundation. NCR 8802991 Supported by the Defense Advanced Research Projects Agency. MDA972-92-J-1038 Supported by ATT Bell Laboratories.Jane Marie Simmons

Modulating application behaviour for closely coupled intrusion detection

Includes bibliographical references.This thesis presents a security measure that is closely coupled to applications. This distinguishes it from conventional security measures which tend to operate at the infrastructure level (network, operating system or virtual machine). Such lower level mechanisms exhibit a number of limitations, amongst others they are poorly suited to the monitoring of applications which operate on encrypted data or the enforcement of security policies involving abstractions introduced by applications. In order to address these problems, the thesis proposes externalising the security related analysis functions performed by applications. These otherwise remain hidden in applications and so are likely to be underdeveloped, inflexible or insular. It is argued that these deficiencies have resulted in an over-reliance on infrastructure security components

Quality of Service Controlled Multimedia Transport Protocol

PhDThis research looks at the design of an open transport protocol that supports a range of services including multimedia over low data-rate networks. Low data-rate multimedia applications require a system that provides quality of service (QoS) assurance and flexibility. One promising field is the area of content-based coding. Content-based systems use an array of protocols to select the optimum set of coding algorithms. A content-based transport protocol integrates a content-based application to a transmission network. General transport protocols form a bottleneck in low data-rate multimedia communicationbsy limiting throughpuot r by not maintainingt iming requirementsT. his work presents an original model of a transport protocol that eliminates the bottleneck by introducing a flexible yet efficient algorithm that uses an open approach to flexibility and holistic architectureto promoteQ oS.T he flexibility andt ransparenccyo mesi n the form of a fixed syntaxt hat providesa seto f transportp rotocols emanticsT. he mediaQ oSi s maintained by defining a generic descriptor. Overall, the structure of the protocol is based on a single adaptablea lgorithm that supportsa pplication independencen, etwork independencea nd quality of service. The transportp rotocol was evaluatedth rougha set of assessmentos:f f-line; off-line for a specific application; and on-line for a specific application. Application contexts used MPEG-4 test material where the on-line assessmenuts eda modified MPEG-4 pl; yer. The performanceo f the QoSc ontrolledt ransportp rotocoli s often bettert hano thers chemews hen appropriateQ oS controlledm anagemenatl gorithmsa re selectedT. his is shownf irst for an off-line assessmenwt here the performancei s compared between the QoS controlled multiplexer,a n emulatedM PEG-4F lexMux multiplexers chemea, ndt he targetr equirements. The performanceis also shownt o be better in a real environmentw hen the QoS controlled multiplexeri s comparedw ith the real MPEG-4F lexMux scheme