2,560 research outputs found
Behavioural synthesis of an adaptive Viterbi decoder
No full textThe synthesis of a hardware implementation of a Viterbi decoder from a behavioural specification is discussed. This is applied to a parallelized version of a BCH decoder. A parameterizable high-level VHDL model of the parallel decoder has been developed. Scalability of the parallel decoder in hardware is demonstrated. An extension of this technique to an adaptive decoder is discussed
An Efficient Parallel Version of the Householder-QL Matrix Diagonalisation Algorithm
No full textIn this paper we report an effective parallelisation of the Householder routine for the reduction of a real symmetric matrix to tri-diagonal form and the QL algorithm for the diagonalisation of the resulting matrix. The Householder algorithm scales like and the QL algorithm like as the number of processors is increased for fixed problem size. The constant parameters , , and are obtained empirically. When the eigenvalues only are required the Householder method scales as above while the QL algorithm remains sequential. The code is implemented in c in conjunction with the Message Passing Interface (MPI) libraries and verified on a sixteen node IBM SP2 and for real matrices that occur in the simulation of properties of crystalline material
MP: An Application Specific Concurrent Language
No full textIn this paper we present the definition, and implementation of a concurrent language mp (Message Passer), which is aimed at programming embedded multi micro-processor systems. The novel features of the language includes the ability to program and develop the entire distributed system as a single unit, and the provision of simple restricted concurrency constructs that make such systems modular and deadlock free. mp programs are invariant with respect to the characteristics of a particular target machine, for instance, the number of processors, and their mutual connectivity. Programs written in mp can be transformed to a restricted set of Communicating Sequential Processes (CSP), in which particular specifications can be shown to be satisfied. The restricted model of concurrency, does not prevent the language being able to express all of the known course grained parallel programming paradigms. However, the structured nature of the code makes the model particularly attractive in concurrent embedded systems, where deadlock freedom and program correctness are prime issues. An mp program is a collection of objects which execute concurrently, maintain their own local state and connect with other objects via bound variables. Explicit communication between objects is totally transparent to the application programmer. A compiler for the language has been built and a multiprocessor run time environment has been established for any system with a C compiler and the message passing standard MPI library. Several applications have been tested, ranging from a clocked digital circuit simulation, to a simple event driven process controller
A TCP/IP Network Emulator
No full textIn this paper a Linux based framework of a TCP/IP emulator is introduced. Several advantages can be noted. Firstly, the maintenance of large numbers of processors is unnecessary. Secondly, compared with simulators constructed with conceptual codes, our emulator framework makes it possible to test the interaction and behaviour of TCP/IP in real Linux network environments. Thirdly, the wired network is fully controlled by a single processor enabling us to separate TCP/IP behaviour over the wireless network, which helps distinguish performance functions that occur due to noisy wireless links. The framework was tested on two Linux processors over an IEEE802.11b wireless link. The simulations show that the complex topology of the heterogeneous network was "realistically" constructed
A High Accurate and Component Based Network Emulator for the Simulation of Complex Heterogeneous Network Topology
No full textWired features like quick handover, radio jamming and dynamic data rates cannot be truthfully presented inside the simulator bue we concentrate on all layers above the physical layer. Previous network emulators were designed for wired networks or router related emulations. Complex network topologies can be constructed and integrated
Dynamic Threat Assessment for Prioritising Computer Network Security
No full textLarge corporations today consist of heterogeneous IT networks with many thousands of devices, which may use numerous physical and logical interfaces to communicate. Much effort has been applied in automating laborious, time-consuming and sometimes-repetitive security services such as patch management and event loggers for these networks. However such tasks can still take many hours and even days to successfully complete. Currently it is left to the systems administrators’ discretion to choose in which order to protect individual devices, which on larger networks can result in arbitrary security protection at best. In light of the rapidly decreasing time between vulnerabilities being discovered and maliciously exploited by malware, such an arbitrary method introduces an unacceptable level of risk to the security of those devices, which are critical to business processes. An information risk management approach needs to be adopted to ensure the protection of the network with a high likelihood; this can be achieved through the prioritisation of critical devices. In this introductory paper a generic prioritisation technique for individual devices in a network is described offering a methodical alternative to the current ambiguity of a systems administrators operations. The technique is based upon compromise path analysis, which identifies critical paths in a network from a security viewpoint and is relevant in a wide range of operations from the application of security services to analysing their results. The vulnerability period metric is introduced, as a mechanism to control the risk exposure to individual devices through prioritisation
Electronic Security Implications of NEC: A Tactical Battlefield Scenario
No full textIn [1] three principal themes are identified by the UK MoD (Ministry of Defence) in order to deliver the vision of NEC (Network Enabled Capability): Networks, People and Information. It is the security of information, which is discussed in this article. The drive towards NEC is due to many factors; one defining factor is to provide an increase in operational tempo in effect placing one ahead of their enemy in terms of acting within their OODA (Observe, Orient, Decide, Act) loop. However as technical and procedural systems are being advanced to achieve the vision of NEC, what impact does this have on the traditional information security triangle, of preserving the confidentiality, integrity and availability of information? And how does this influence current security engineering and accreditation practices, particularly in light of the proliferation problem? This article describes research conducted into answering these questions, building upon the findings of the NITEworks® [2] ISTAR (Intelligence, Surveillance, Target Acquisition and Reconnaissance) Theme studies and focusing on a tactical battlefield scenario. This scenario relates to the IFPA (Indirect Fire Precision Attack) [3] project where the efficient synchronisation of potentially numerous sources of information is required, providing real-time decisions and delivery of effects, in accordance with the requirements of NEC. It is envisaged that the IFPA systems will consist of numerous sub-systems each of which will provide a unique effecting capability to the UK army with differing levels of speed, accuracy and range
Improving TCP performance over wireless networks
No full textThis paper proposes a novel end-to-end congestion control mechanism called TCP NewZag. NewZag is simple and effective in dealing with random packet loss, so it can improve TCP performance in the wireless network. TCP NewZag proposes two new mechanisms: (1) a new end-to-end loss differentiation algorithm (LDA); (2) the adjustments of TCP NewReno multiplicative decrease algorithm. These two mechanisms only require the adjustment of TCP sender side, while the receiver side protocol remains the same. Based on experimental measurements of single link, it is shown that NewZag achieves significant throughput improvement when the wireless random packet losses occur. Compared with NewReno in 0.5% random packet loss rate, 20% throughput improvement can be demonstrated
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