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Ultra wide band (UWB) is a promising technology for short-range wireless networks. In this paper we present our efforts on investigating the impact of the multipath delay spread on the MAC layer performance of time-hopped impulse-based UWB ad hoc networks. We discuss a simplified channel model for the multipath delay spread and we simulate a single-band MAC protocol which employs binary pulse position...
High-speed optical networking infrastructures such as National LambdaRail promise to revolutionize the way that we approach grid computing. With optical-fiber speeds doubling every 9 months and computing speeds doubling only every 18-24 months over the past few decades, we have finally reached a crossroads where network speeds have outstripped the ability of processors to keep up. Thus, we may be...
One-way links are an unavoidable reality in wireless channels. The detrimental effects of one way links on many routing strategies, including the dynamic source routing protocol (DSR), have been investigated by many researchers. Apart from reducing the efficiency of DSR, we point out that disregarding possible one-way links also has some implications on the security of secure DSR extensions. Most...
We propose several relay selection strategies for distributed space-time cooperative systems, in which the Alamouti scheme is used. Our strategies select the best two nodes among the source and all relays to assist the packet transmissions from the source to the destination. In the amplify-and-forward mode, we develop an efficient algorithm to select the optimal cooperative nodes which can maximize...
Core stateless packet scheduling systems have received considerable attention in recent years because of their scalability in supporting per-flow quality of services guarantees. In such a system core routers do not need to maintain per-flow state and do not need to perform per-flow operations such as per-flow classification, per-flow queueing, and per-flow scheduling. On the other hand, existing core...
IEEE 802.11 is the most important standard for wireless local area networks (WLANs). In the IEEE 802.11 WLANs, distributed coordination function (DCF) is a fundamental medium access control (MAC) protocol, whose performance has been studied analytically in the literature. However, there is no research work that takes into account various incoming traffic load, network size, and the influence of transmission...
The border gateway protocol (BGP) has been known to suffer from large convergence delays after failures. We have also found that the impact of a failure rises sharply with the size of the failure. In this paper we present and evaluate a speculative route invalidation scheme aimed at reducing the convergence delays for large-scale failures. Our scheme collects statistics from BGP updates received at...
The prosperity of various real-time applications triggers significant challenges for the Internet to meet the critical end-to-end delay requirements. This paper investigates the feasibility and practical issues of using overlay routing to improve end-to-end delay performance, with the analysis of round trip time data collected over three months by the all pairs pings project between each pair of hundreds...
Traditional IP multicast in a network domain is likely to imply a huge burden of storage and forwarding for routers and it's hard to support quality of service. The recent proposed application layer multicast is more scalable but increases traffic load and end-to-end delay. In the paper, we make multicast supporting comparable multi-class services on the overlay network comprising only edge routers...
Geocast, which allows for forwarding messages to hosts residing at specified geographic areas, is a promising communication paradigm with a wide range of applications. Geocast target areas can be specified either by geometric figures or symbolic addresses, such as /usa/f 1/miami/market-street. In this paper, we present a novel geocast routing protocol for symbolically addressed messages. Compared...
Parallel disk systems, which have been widely used in building networked and data intensive applications, are highly scalable and can alleviate the problem of disk I/O bottleneck. Although a number of parallel disk systems have been developed, the systems lack a means to optimize quality of security for dynamically changing networked environments. We remedy this situation by proposing an adaptive...
This paper studies how to assign radio interfaces to work on multiple channels in multi-channel and multi-interface wireless networks. Different from previous studies that focused on the MAC layer, we study this problem from a global perspective. We use a layered graph to model multi-channel wireless networks, and develop effective interface assignment and routing path computation algorithms based...
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