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ABSTRACT: Deflection routing is an attractive scheme for resolving the burst contention problem in optical burst switching (OBS) networks and retransmission of rejected packets is widely accepted as a basic mechanism for guaranteeing the robust operation of IP networks. In this paper, we explore the potential benefits of combining the deflection routing and burst retransmission schemes in OBS networks. We first demonstrate that if these two schemes are not combined appropriately, the network performance may be significantly degraded. We then suggest a novel approach to combining deflection routing and burst retransmission, such that the resulting hybrid algorithm can always guarantee a better overall performance in terms of burst loss and end-to-end delay than that of both the conventional pure deflection routing and the pure retransmission scheme, as verified by the simulation results based on the ns-2 simulator and two typical network topologies
High Performance Switching and Routing, 2006 Workshop on; 01/2013
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ABSTRACT: Network coding has the potential to greatly improve the throughput of wireless networks. In the current proposals for wireless network coding, network nodes transmit packets at a fixed transmission rate. It is notable, however, that by dynamically selecting the rate, we can effectively improve the node transmission efficiency. In this paper, we study the application of a rate-adaptive transmission mechanism in network-coding-based multihop wireless networks. In such networks, whether a coding solution is satisfactory or not depends not only on the number of involved native packets but on the packet loss probabilities of its intended next hops and its transmission time as well, both of which depend on the transmission rate. Therefore, we aim to jointly design the coding operation and rate selection to maximize the transmission efficiency. Specifically, we first describe and mathematically formulate the optimal packet coding and rate-selection problem. Then, we prove the NP-completeness of this optimization problem. Finally, we propose an efficient algorithm for finding good combinations of the coding solution and the transmission rate. Simulation results demonstrate that compared with the rate-fixed transmission, the rate-adaptive transmission based on our algorithm can significantly improve the node transmission efficiency.
IEEE Transactions on Vehicular Technology 07/2010; · 1.92 Impact Factor
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ABSTRACT: The lack of optical buffer is still one of the main problems that hinder the development of all optical network. The current works on this topic mainly focus on the emulation of optical buffers by using bufferless switch fabric and fiber delay line (SDL). Recent advances have shown the feasibility of emulating many kinds of optical buffers, such as first in first out (FIFO) buffer, priority buffer etc. The last in first out (LIFO) buffer is another important network component that can be used for congestion control and providing quality of service guarantee in the network. In Huang et al. introduced a recursive construction of LIFO buffer with buffer size B by using no less than 9 log B delay lines. In this paper, we explore a more effective construction of optical LIFO buffer from SDL and the feedback switch architecture. Based on such an architecture, a scheduling algorithm is proposed to emulate the LIFO buffer of size B with 2 log B delay lines.
Communications, 2009. APCC 2009. 15th Asia-Pacific Conference on; 11/2009
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ABSTRACT: Designing optical buffer is still challenge for supporting all optical packet switching. The current practice is to emulate the optical buffer functions through a combination of switch and fiber delay lines (SDL). In this paper we introduce the recent progress on this line, in particular, the SDL-based emulation of optical queues, connectors and buffers.
Communications, 2009. APCC 2009. 15th Asia-Pacific Conference on; 11/2009
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ABSTRACT: Power is one of the most critical resources in wireless sensor networks and packet transmission is a very energy-consuming action for sensor nodes. Network coding has the potential to reduce the number of packets transmitted by encoding multiple packets together in transmission. To the best of our knowledge, little work applies the practical network coding for power saving in wireless sensor networks and AdapCode is by now the most promising one among them. However, AdapCode works based only on partial of all actual neighbors of a node in coding process, which may waste some potential coding opportunities. In this paper, thus, we enhance the AdapCode by deploying an energy efficient neighbor discovery protocol to find out all the neighbors of a node. Our objective is to develop a more efficient coding scheme for wireless sensor networks to achieve more power saving from using network coding.
Communications, 2009. APCC 2009. 15th Asia-Pacific Conference on; 11/2009
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ABSTRACT: An efficient voice-over-IP (VoIP) support at the wireless access point (AP) of a wireless LAN (WLAN) remains a challenge for the last-mile wireless coverage of IP networks with mobility support. Due to the limited bandwidth that is available in WLANs, an accurate analysis of the voice capacity in such networks is crucial for the efficient utilization of their resources. The available analytical models only provide the upper and lower bounds on voice capacity, which may significantly overestimate or underestimate the WLAN's capability of supporting VoIP and, thus, are not suitable for the mentioned purpose. In this paper, we focus on the voice capacity analysis of a wireless 802.11(a/b) AP running the distributed coordination function (DCF). In particular, we show that by incorporating the clients' spatial distribution into the analysis, we are able to develop a new analytical model for a much more accurate estimation of the average voice capacity. By properly exploring this spatial information, we further propose a new scheme for AP placement such that the overall voice capacity can be enhanced. The efficiency of the new voice capacity model and the new AP placement scheme is validated through both analytical and simulation studies.
IEEE Transactions on Vehicular Technology 07/2009; · 1.92 Impact Factor
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ABSTRACT: Interconnection networks play a crucial role in the performance of massively parallel computers. Hierarchical interconnection networks provide high performance at low cost by exploring the locality that exists in the communication patterns of massively parallel computer systems. The Tori-connected mESH (TESH) Network is a 2D-torus network of multiple basic modules, in which the basic modules are 2D-mesh networks that are hierarchically interconnected for higher level networks. In this paper, we present a deadlock-free routing algorithm for the TESH network using 2 virtual channels - 2 being the minimum number for dimension-order routing - and evaluate the network's dynamic communication performance under various nonuniform traffic patterns, using the proposed routing algorithm. We evaluate the dynamic communication performance of TESH, mesh, and torus networks by computer simulation. It is shown that the dynamic communication performance of the TESH network is better than that of the mesh and torus networks.
Computer and Information Technology, 2008. ICCIT 2008. 11th International Conference on; 01/2009
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ABSTRACT: Multi-log<sub>2</sub> N networks (or vertically stacked banyan networks) have been an attractive class of switching networks due to their small depth O(log N), absolute signal loss uniformity and good fault tolerance property. Recently, F.K.Hwang extended the study of multi-log<sub>2</sub> N networks to the general f-cast case, which covers the unicast case (f = 1) and multicast case (f = N) as special cases, and determined the conditions for these networks to be f-cast strictly nonblocking when the fan-out capability is available at both the input stage and middle banyan stage. In this paper, we study the rearrangeable f-cast multilog<sub>2</sub> N networks under both node-blocking scenario (relevant to photonic switches) and link-blocking scenario (relevant to electronic switches). In particular, we consider the following three fan-out cases in our study: (1) no restriction on fan-out capability; (2) input stage has no fan-out capability; (3) middle banyan stage has no fan-out capability. We determine the necessary conditions for the first two cases while obtaining the necessary and also sufficient condition for the third one.
IEEE Transactions on Communications 12/2008; · 1.68 Impact Factor
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ABSTRACT: The multicast capability and crosstalk issue need to be deliberately considered in the design of future high performance photonic switching networks. In this paper, we focus on the photonic switching networks built on the banyan-based architecture and directional coupler technology. We explore the capability of these networks to support general f-cast traffic, which covers the unicast traffic (f = 1) and multicast traffic (f = N) as special cases, and determine the conditions for these networks to be f-cast strictly nonblocking under various crosstalk constraints. In particular, we propose an optimization framework to determine the nonblocking condition of an f-cast photonic network when a general crosstalk constraint is imposed.
IEEE/ACM Transactions on Networking 07/2008; 16(3):732-745. · 2.03 Impact Factor
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ABSTRACT: We focus on the non-conflicting design of a multistage feedforward network with optical bufferless Switch and fiber Delay Lines (SDL) to emulate an N-to-1 output buffered multiplexer supporting variable length bursts. Y. T. Chen et al. presented a sufficient condition (a bound) to guarantee the non-conflicting and FIFO properties in such a design. In this paper, we first point out the upper bound can not rise infinitely with the increase of the maximum burst length. Then, we develop a framework to construct a case which can be used to achieve a lower bound. Through simulation and performance comparison, we find the new bounds can significantly decrease the hardware cost for constructing such a feedforward SDL multiplexer while still providing the same performance guarantee as that of the old one.
Parallel Architectures, Algorithms, and Networks, 2008. I-SPAN 2008. International Symposium on; 06/2008
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ABSTRACT: It is anticipated that a large amount of multicast traffic needs to be supported in future communication networks. The network coding technique proposed recently is promising for establishing multicast connections with a significantly lower bandwidth requirement than that of traditional Steiner-tree-based multicast connections. How to design multicast network topologies with the consideration of efficiently supporting multicast by the network coding technique becomes an important issue now. It is notable, however, that the conventional algorithms for network topology design are mainly unicast-oriented, and they cannot be adopted directly for the efficient topology design of network-coding-based multicast networks by simply treating each multicast as multiple unicasts. In this paper, we consider for the first time the novel topology design problem of network-coding-based multicast networks. Based on the characteristics of multicast and network coding, we first formulate this problem as a mixed-integer nonlinear programming problem, which is NP-hard, and then propose two heuristic algorithms for it. The effectiveness of our heuristics is verified through simulation and comparison with the exhaustive search method. We demonstrate in this paper that, in the topology design of multicast networks, adopting the network coding technique to support multicast transmissions can significantly reduce the overall topology cost as compared to conventional unicast-oriented design and the Steiner-tree-based design.
IEEE Transactions on Parallel and Distributed Systems 06/2008; · 1.40 Impact Factor
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ABSTRACT: A new packet-forwarding architecture, COPE [1], was proposed recently to demonstrate that by properly exploiting the network coding and physical-layer broadcast properties, the throughput of multihop wireless networks may be significantly improved. However, the theoretical framework is not available yet for a rigorous throughput study of COPE. As the first step toward this direction, in this paper we conduct an analytical analysis on coding opportunities that COPE can create in a multihop wireless network. For a given node, we first derive the probability density function (pdf) of overhearing probability between its two neighbor nodes. Then, based on the pdf of overhearing probability we further analyze the probability of encoding multiple packets together at the node. This work not only provides a framework for the node-level performance analysis of COPE but also lays a foundation for the further network-level performance analysis of COPE.
Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE; 05/2008
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ABSTRACT: Effective support of VoIP over Wireless LAN (WLAN) remains a crucial challenge for the last-mile wireless coverage of IP networks with mobility support. Due to the limited bandwidth available in a WLAN, an accurate analysis of voice capacity in such a network is critical for the efficient usage of WLAN's resources. The available upper or lower bound models on voice capacity may significantly overestimate or underestimate a WLAN's capacity to support VoIP, thus they are not suitable for above purpose. In this paper, we focus on the voice capacity analysis of a single wireless 802.11(a/b) network cell running the distributed coordination function (DCF). In particular, by taking into account the spatial distribution of clients, we propose a more accurate analytical model to estimate the average voice capacity of such a network cell. We further show that by properly exploring the clients' spatial distribution information in allocating the access points, we may be able to increase the overall voice capacity. The efficiency of our new voice capacity model and new access point allocation scheme is validated through simulation and comparisons with available ones.
Wireless Communications and Networking Conference, 2008. WCNC 2008. IEEE; 05/2008
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ABSTRACT: Volunteer computing is very promising to build large scale parallel computing systems from enormous number of computers over the Internet. In a volunteer computing system, sabotage-tolerance is an important issue because there may be malicious users on the Internet who sabotage system by intentionally submitting erroneous results. In this paper, we consider the task scheduling problem of volunteer computing systems which implement sabotage-tolerance mechanism. Although existing sabotage-tolerance mechanisms can guarantee the requirement of credibility for computing results, however, such mechanisms always cause a high performance slowdown in terms of overall execution time. In this paper, we propose an efficient scheduling mechanism called Priority Round Robin (PRR) that takes into account the computing capacity of each volunteer computer. By grouping volunteer computers that have similar computing capacity, the PRR scheduling mechanism can help to reduce overall execution time in comparision with the conventional Round Robin (RR) scheduling, as shown by our extensive simulation results.
Advanced Information Networking and Applications, 2008. AINA 2008. 22nd International Conference on; 04/2008
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ABSTRACT: Shared-memory optical packet (SMOP) switch architecture is very promising for significantly reducing the amount of required optical memory, which is typically constructed from fiber delay lines (FDLs). The current reservation-based scheduling algorithms for SMOP switches can effectively utilize the FDLs and achieve a low packet loss rate by simply reserving the departure time for each arrival packet. It is notable, however, that such a simple scheduling scheme may introduce a significant packets out of order problem. In this paper, we first identify the two main sources of packets out of order in the current reservation-based SMOP switches. We then show that by introducing a "last-timestamp " variable and modifying the corresponding FDLs arrangement as well as the scheduling process in the current reservation-based SMOP switches, it is possible to keep packets in-sequence while still maintaining a similar delay and packet loss performance as the previous design.
Advanced Information Networking and Applications, 2008. AINA 2008. 22nd International Conference on; 04/2008
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ABSTRACT: Load balance (LB) switch architecture is attractive for building high speed switches since it does not require a centralized scheduler and still can guarantee 100% throughput under any admissible traffic. It is notable, however, that due to the multi-path property of LB switches, the packet out-of-sequence problem may happen in such switches. Several schemes have been proposed to tackle the above problem, but these schemes either require infinite central buffer or introduce a high average packet delay. In this paper, we propose a new LB switch architecture - central buffer one-packet-crosspoint (CBX-1). The key idea ofCBX-1 is to introduce a VIOQ (virtual input output queue) with capacity one (i.e., it can store only one packet) after the first stage of a LB switch to emulate a CIXB-1 switch (combined input-one-packet-crosspoint buffered switch). We show through both analysis and simulation that although our architecture requires only finite central buffer to tackle the packet out-of-sequence problem, it still guarantees 100% throughput and achieves a good delay performance.
Parallel and Distributed Computing, Applications and Technologies, 2007. PDCAT '07. Eighth International Conference on; 01/2008
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ABSTRACT: Current implementations of multi-hop wireless networks suffer from a severe throughput limitation and do not scale well with an increasing number of nodes. A promising architecture COPE [12], which exploits the physical-layer broadcast property and network coding technique, was recently proposed to significantly improve the throughput of multi-hop wireless networks. In this paper, we will improve the packet coding scheme in COPE to further reduce the number of bytes transmitted by a network node for forwarding its incoming packets to the respective neighbors. We first propose a more general packet coding framework, which covers the one in COPE as a special case and can offer us more coding opportunities. We then formulate the optimal packet coding problem under this general coding framework as an integer programming problem, and prove that it is NP-complete. Finally, we present an efficient algorithm to find the optimal coding solution for the proposed general packet coding framework.
Global Telecommunications Conference, 2007. GLOBECOM '07. IEEE; 12/2007
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ABSTRACT: Active restoration (AR) is a novel lightpath restoration scheme proposed recently to guarantee a certain degree of survivability in wavelength-division multiplexing (WDM) optical networks with a reasonable trade-off between capacity requirement and restoration time. In this paper, we conduct a comprehensive performance analysis for AR-based optical networks. In particular, we propose a novel analytical framework for modeling the restoration probability of a connection (the probability that the connection can be successfully restored in case of a failure) when the possible correlation among its multiple backup routes is incorporated. Although theoretically, we need to consider all the possible correlations between as many as Q) pairs of backup routes to analyze the restoration probability in a network with N nodes, and this high computation complexity may obscure the practicality of an approach, considering all the possible correlations among backup routes, our analysis in this paper indicates that by considering at most the possible correlations among any three successive backup routes of a connection, we can achieve a very good approximation to the simulated restoration probability of the connection, as verified by extensive simulation results upon two typical network topologies under various workloads. We find that the proposed framework can deeply investigate into the inherent relationship among restoration probability, wavelength channel utilization ratio, number of wavelengths per fiber, routes hop length, and wavelength conversion capability. As a result, the framework significantly contributes to the related areas by providing network designers with a quantitative tool to evaluate the restoration probability and, thus, the survivability of AR-based optical networks.
IEEE Transactions on Parallel and Distributed Systems 12/2007; · 1.40 Impact Factor
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ABSTRACT: This paper presents and evaluates an approach for defect isolation of DNA self-assembled networks made of a large number of processing nodes. A previous framework based on a broadcast algorithm isolates defective nodes by using no redundancy (for the nodes) and an external defect map. Its disadvantage is the limited scalability, thus making it unsuitable for extremely large scale networks built through DNA self-assembly. Our framework improves upon the previous framework by involving three algorithmic tiers; namely, 1-hop wave expansion, efficient via placement, and unsafe node defection. The efficiency of the proposed framework is evaluated and compared with the original framework by considering large scale networks (up to 1000 times 1000 nodes), and a novel gross defect model (as well as the conventional random defect model assumed in previous manuscripts). Simulation results indicate that the proposed framework outperforms the original framework in broadcast latency and coverage, and shows excellent scalability features for DNA self-assembled nano-scale networks.
Defect and Fault-Tolerance in VLSI Systems, 2007. DFT '07. 22nd IEEE International Symposium on; 10/2007
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ABSTRACT: Voice over Internet protocol service (VoIP) is growing fast during the last few years. Unlike the usual best effort traffic, the voice traffic is delay and delay jitter sensitive. The current scheduling schemes meet the voice traffic delay constraint by assigning its packets with the highest priority. This behavior is acceptable as long as the volume of voice traffic is relatively very small in comparison with other competitor traffic. With the notable increase of voice traffic volume, the current scheduling will not be able to handle the voice packets with the same behavior otherwise a forceful unfair resource sharing, to other traffic, will rise up. In this paper, we introduce a new flexible scheduling architecture which is capable of satisfying the voice traffic delay constraint while providing a fair resource sharing to the rest of the traffic, as verified by both analytical analysis and an extensive experimental simulation study under various traffic workloads.
Parallel Processing Workshops, 2007. ICPPW 2007. International Conference on; 10/2007
