Jun Guo

University of New South Wales, Kensington, New South Wales, Australia

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Publications (19)10.55 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Overflow loss systems are an important class of teletraffic models. Evaluation of blocking probabilities in such systems involving mutual overflow effects is a difficult problem. In the literature, decoupling a given system into independent subsystems is typically regarded as a scalable, though non-robust, approach to the problem. This paper presents a new method that is based on a radically different idea from that of the conventional approach. Firstly a surrogate model that, in a systematic way, approximately captures the state dependencies due to the overflow model is designed. Secondly it is observed that approximation of the blocking probability of the surrogate model provides a good approximation to the blocking probability in the original model. We introduce important concepts underpinning this surrogate-based approximation method, and demonstrate its effectiveness by applying it to an overflow model that incorporates mutual overflow effects common to various applications of overflow loss systems. Unlike the conventional approach that requires a fixed-point solution of the blocking probability with no guarantee of the convergence and uniqueness, our new method provides a unique solution in a fixed number of iterations. Extensive and statistically reliable experiments demonstrate that the new method yields significantly and consistently better results compared to the conventional approach, improving the accuracy by orders of magnitude in many instances and yet requiring less computational effort.
    Teletraffic Congress (ITC), 2013 25th International; 01/2013
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    ABSTRACT: We present a cross-layer approach for enabling high-throughput routing in multi-hop wireless networks. This approach builds on a MAC-layer cooperative retransmission mechanism, which is explicitly designed to exploit the benefits of MAC-layer retransmission-based reliability, cooperative communications, and link-quality awareness. Based on this mechanism, we devise a routing metric, called the expected cooperative transmission count (ECTX), to capture the combined effects of MAC-layer cooperative retransmission and per-link estimates of packet delivery ratios. We show that, compared to conventional approaches using the well-known expected transmission count (ETX) metric, our approach has two advantages in principle: 1) with the cooperative retransmission mechanism, one can effectively reduce the expected total number of packet transmissions (including retransmissions) on the same path found by ETX; 2) with the ECTX metric, one may indeed identify a more effective path and further reduce the transmission count. We discuss modifications to IEEE 802.11 MAC to incorporate the cooperative retransmission mechanism, and implement ECTX-based routing using the DSR protocol. Extensive simulations on QualNet demonstrate that ECTX-based routing is significantly more efficient than ETX-based routing, in many instances reducing the transmission count by more than 30% and yet improving the network throughput by up to 80%.
    World of Wireless, Mobile and Multimedia Networks (WoWMoM), 2012 IEEE International Symposium on a; 01/2012
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    ABSTRACT: We propose a routing metric for enabling high- throughput reliable multicast in multi-rate wireless mesh net- works. This new multicast routing metric, called expected mul- ticast transmission time (EMTT), captures the combined effects of 1) MAC-layer retransmission-based reliability, 2) transmission rate diversity, 3) wireless broadcast advantage, and 4) link quality awareness. The EMTT of one-hop transmission of a multicast packet minimizes the amount of expected transmission time (including that required for retransmissions). This is achieved by allowing the sender to adapt its bit-rate for each ongoing transmission/retransmission, optimized exclusively for its next- hop receivers that have not yet received the multicast packet. We model the rate adaptation process as a Markov decision process (MDP) and derive an efficient procedure for computing EMTT from the theory of MDP. We present receiver-initiated algorithms and describe protocol implementation for the EMTT- based multicast routing problem. Numerical results are presented to demonstrate the accuracy of the proposed algorithms against optimal solutions to the multicast routing problem. Simulation experiments confirm that, in comparison with single-rate mul- ticast, multi-rate multicast using the EMTT metric effectively reduces the overall multicast transmission time while yielding higher packet delivery ratio and lower end-to-end latency.
    INFOCOM 2011. 30th IEEE International Conference on Computer Communications, Joint Conference of the IEEE Computer and Communications Societies, 10-15 April 2011, Shanghai, China; 01/2011
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    ABSTRACT: We observe that an effect of ldquodisk resource sharingrdquo of multi-copy movie traffic has great impact on the blocking performance of a video-on-demand system. This observation leads us to establish a conjecture on how to balance the movie traffic load among ldquocombinationrdquo groups of disks to maximize the level of disk resource sharing. For a given file replication instance, the conjecture predicts in general an effective lower bound on the blocking performance of the system. It motivates the design of a numerical index that measures quantitatively the goodness of disk resource sharing on allocation of multi-copy movie files. It also motivates the design of a greedy file allocation method that decides a good quality heuristic solution for each feasible file replication instance. We further develop analytical formulas to obtain approximate results for the bound fast and accurately. These techniques can be utilized by an optimization program to find near-optimal file assignment solutions for the system computationally efficiently.
    IEEE Transactions on Circuits and Systems for Video Technology 08/2008; · 1.82 Impact Factor
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    ABSTRACT: This paper studies probabilistically reliable multicast in wireless mesh networks (WMNs), utilizing MAC layer re-transmission and wireless broadcast advantage to improve both the multicast throughput and the delivery rate. We first present a new multicast routing metric which we call the expected multicast transmissions (EMT). EMT captures the effect of link packet delivery ratio, MAC layer retransmission and wireless broadcast advantage at the same time. The EMT of a MAC layer multicast transmission is the expected number of data transmissions (including retransmissions) required for a packet to reach all the recipients. The EMT of a multicast tree is the sum over the EMT of each forwarding node. Then, we propose a probabilistically reliable on-demand (PROD) multicast protocol with the objective of minimizing the EMT of the multicast tree. Simulation results show that, in comparison with existing approaches, PROD reduces the end-to-end packet loss ratio by up to 30% and improves the multicast throughput by up to 25%. In addition, it reduces the number of transmissions per packet by up to 40% and thus significantly reduces the network overhead of the multicast session.
    World of Wireless, Mobile and Multimedia Networks, 2008. WoWMoM 2008. 2008 International Symposium on a; 07/2008
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    ABSTRACT: We present a genetic algorithm for tackling a file assignment problem for a large-scale video-on-demand system. The file assignment problem is to find the optimal replication and allocation of movie files to disks so that the request blocking probability is minimized subject to capacity constraints. We adopt a divide-and-conquer strategy, where the entire solution space of file assignments is divided into subspaces. Each subspace is an exclusive set of solutions sharing a common file replication instance. This allows us to utilize a greedy file allocation method for finding a good-quality heuristic solution within each subspace. We further design two performance indices to measure the quality of the heuristic solution on 1.) its assignment of multicopy movies and 2.) its assignment of single-copy movies. We demonstrate that these techniques, together with ad hoc population handling methods, enable genetic algorithms to operate in a significantly reduced search space and achieve good-quality file assignments in a computationally efficient way.
    IEEE Transactions on Knowledge and Data Engineering 07/2008; · 1.89 Impact Factor
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    Jun Guo, S. Jha
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    ABSTRACT: To support large-scale Internet-based broadcast of live streaming video efficiently in content delivery networks (CDNs), it is essential to implement a cost-effective overlay multicast mechanism by exploiting peer-to-peer distribution capabilities among end hosts. This way, the access bandwidth demand on CDN servers in the multicast overlay backbone can be largely reduced. Such a streaming infrastructure gives rise to an interesting host-aware routing problem (HARP). For a live streaming video broadcast event, each participating CDN server is made aware of the largest delay from it to end hosts within its service area. The problem is to optimize routing among CDN servers in the multicast overlay backbone such that the de facto maximal end-to-end latency from the origin server to all end hosts is minimized subject to access bandwidth constraints on CDN servers. In this paper, we frame HARP as a constrained spanning tree problem which is shown to be NP-hard. We present a distributed algorithm for HARP. Simulation experiments confirm that our proposed algorithm converges to good quality solutions that are close to the optimum.
    Network Operations and Management Symposium, 2008. NOMS 2008. IEEE; 05/2008
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    ABSTRACT: The designers of a large scale video-on-demand system face an optimization problem of deciding how to assign movies to multiple disks (servers) such that the request blocking probability is minimized subject to capacity constraints. To solve this problem, it is essential to develop scalable and accurate analytical means to evaluate the blocking performance of the system for a given file assignment. The performance analysis is made more complicated by the fact that the request blocking probability depends also on how disks are selected to serve user requests for multicopy movies. In this paper, we analyze several efficient resource selection schemes. Numerical results demonstrate that our analysis is scalable and sufficiently accurate to support the task of file assignment optimization in such a system.
    IEEE Transactions on Multimedia 02/2008; · 1.75 Impact Factor
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    ABSTRACT: This paper proposes a novel transport network architecture for the next generation network (NGN) based on the optical burst switching technology. The proposed architecture aims to provide efficient delivery of various types of network traffic by satisfying their quality-of-service constraints. To this end, we have developed a soft-state bandwidth reservation mechanism, which enables NGN transport nodes to dynamically reserve bandwidth needed for active data burst flows. The performance of the proposed mechanism is evaluated by means of numerical analysis and NS2 simulation. Our results show that the packet delay is kept within the constraint for each traffic flow and the burst loss rate is remarkably improved.
    Etri Journal 01/2008; 30(2):216-226. · 0.74 Impact Factor
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    Jun Guo, Sanjay Jha
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    ABSTRACT: To support large-scale live Internet broadcasting services efficiently in content delivery networks (CDNs), it is essential to exploit peer-to-peer capabilities among end users. This way, the access bandwidth demand on CDN servers in the overlay backbone can be largely reduced. Such a streaming infrastructure gives rise to a challenging overlay backbone multicast routing problem (OBMRP) to optimize multicast routing among CDN servers in the overlay backbone. In this paper, we take a graph theoretic approach and frame OBMRP as a constrained spanning tree problem which is shown to be NP-hard. We present a lightweight distributed algorithm for OBMRP. Simulation experiments confirm that our proposed algorithm converges to good quality solutions and requires small control overhead.
    NETWORKING 2008, Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet , 7th International IFIP-TC6 Networking Conference, Singapore, May 5-9, 2008, Proceedings; 01/2008
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    Jun Guo, Sanjay Jha
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    ABSTRACT: Placing multicast proxies on the Internet can largely reduce the delivery delay of Internet live media streaming using overlay multicast mechanisms. In this paper, we propose a new approach to address the issue of proxy placement in an overlay multicast network. The task is to decide an optimal placement of multicast proxies in the overlay multicast network so as to minimize the average end-to-end delay of the overlay skeleton tree subject to out-degree balancing constraint and maximum delivery delay bound. We present two heuristic methods for this proxy placement problem. Experimental results demonstrate that proxy placement due to our proposed approach can greatly improve the overlay multicast routing performance. In comparison with an existing approach commonly used for replica placement in content distribution networks, our proposed approach significantly improves the end-to-end latency performance of overlay multicast networks, and is not much sensitive to network dynamics.
    Local Computer Networks, 2007. LCN 2007. 32nd IEEE Conference on; 11/2007
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    Jun Guo, Sanjay Jha
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    ABSTRACT: We consider the problem of constructing a proxy-based overlay skeleton tree (POST) in the backbone service domain of a two-tier overlay multicast infrastructure. Spanning all multicast proxies deployed in the overlay backbone, POST acts as an efficient resource sharing platform for supporting large numbers of concurrent multicast sessions, without the need of tree computation for each individual session. The problem is concerned with deciding an appropriate deployment of multicast proxies in the overlay backbone, upon which we wish to find an optimal POST solution so that the maximum end-to-end latency is minimized subject to degree balancing constraints. This problem is shown to be NP-hard. We present a simple heuristic method for deploying multicast proxies, and devise a low complexity greedy algorithm for optimizing the end-to-end latency and degree distribution of POST. Simulation experiments confirm that our proposed approach yields good quality approximate solutions that are close to the optimum.
    NETWORKING 2007. Ad Hoc and Sensor Networks, Wireless Networks, Next Generation Internet, 6th International IFIP-TC6 Networking Conference, Atlanta, GA, USA, May 14-18, 2007, Proceedings; 01/2007
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    ABSTRACT: To support reliable multicast routing in wireless mesh networks, it is important to protect multicast sessions against link or node failures. The issue of protecting multicast sessions in wireless mesh networks is a new problem to the best of our knowledge. In this paper, we propose a resilient forwarding mesh approach for protecting a multicast session in wireless mesh networks. Utilizing the wireless broadcast advantage, a resilient forwarding mesh effectively establishes two node disjoint paths for each source-destination pair. This allows a multicast session to be immune from any single link or intermediate node failure. We introduce four heuristic algorithms to obtain approximate solutions that seek to minimize the number of required broadcast transmissions. We evaluate the performance of these heuristic algorithms against the optimal resilient forwarding mesh (ORFM) obtained by solving an integer linear programming (ILP) formulation of the problem. Experimental results demonstrate that one of these heuristic algorithms, which we call the minimal disjoint mesh algorithm (MDM), performs sufficiently close to ORFM. Besides, we find that the resilient forwarding mesh approach provides efficient 1+ 1 protection (Pioro and Medhi, 2004) to the multicast session without incurring much additional overhead on a single minimal cost multicast tree
    Local Computer Networks, Proceedings 2006 31st IEEE Conference on; 12/2006
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    [Show abstract] [Hide abstract]
    ABSTRACT: To support reliable multicast routing in wireless mesh networks, it is important to protect multicast sessions against link or node failures. In this paper, we propose a resilient forwarding mesh approach for protecting a multicast session. Utilizing the wireless broadcast advantage, a resilient forwarding mesh effectively establishes two node disjoint paths for each source-destination pair. This allows a multicast session to be immune from any single link or intermediate node failure. An integer linear programming (ILP) formulation is presented to find the optimal resilient forwarding mesh (ORFM) that minimizes the number of broadcast transmissions. In comparison with the existing optimal path-pair (OPP) approach proposed in [1] for wired mesh networks, our experimental results demonstrate that ORFM outperforms OPP in wireless scenarios.
    01/2006;
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    ABSTRACT: We obtain detailed analytic formulas for the density and probability distribution of the waiting time in a time-division multiple-access (TDMA) model with a finite buffer and state-dependent service. On successive intervals of length equal to the duration of a slot, the density is expressed as a linear combination of beta densities with positive coefficients. A recursive scheme, obtained by a matrix-analytic derivation, allows for the highly efficient computations of the coefficient sequences. An expression for the mean waiting time is derived using the classical queueing formula L=λW. We also demonstrate that our methodology provides a concise treatment of various special cases that have been studied over the past half century.
    IEEE Transactions on Communications 10/2005; · 1.75 Impact Factor
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    IEEE Transactions on Communications 01/2005; 53:1522-1533. · 1.75 Impact Factor
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    ABSTRACT: We consider a video-on-demand system in which multiple copies of each movie file are kept in separate disks. Various schemes for file allocation and retrieval are considered and compared. We have introduced a certain easy-to-implement scheme that requires 15% more storage than another certain harder-to-implement scheme.
    Multimedia and Expo, 2003. ICME '03. Proceedings. 2003 International Conference on; 08/2003
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    ABSTRACT: This paper provides and efficient for the derivation of the delay distribution for a TDMA system with a finite buffer. Assuming successive intervals of length equal to the duration of a slot, the density is expressed as (finite) linear combinations of gamma densities and beta densities with positive coefficients. The results are verified by simulations. Comparison with a previously proposed solution demonstrates that the solution presented here is more efficient.
    Communications, 2003. ICC '03. IEEE International Conference on; 06/2003
  • Marcel Neuts, Jun Guo
    [Show abstract] [Hide abstract]
    ABSTRACT: In simulation studies, the distributional properties of random variables associated witharbitrary events in point processes, queues, and other stochastic models are to be understood as appropriate averages over long simulation runs. We caution against trying to generate arbitrary events explicitly by some randomized selection. Because of the likelihood of hidden selection biases, that easily results in significant errors. The point is illustrated by an example for which explicit formulas yield computational results that allow comparisons with the simulation estimates.
    Top 02/2003; 11(1):131-140. · 0.84 Impact Factor

Publication Stats

72 Citations
10.55 Total Impact Points

Institutions

  • 2006–2011
    • University of New South Wales
      • School of Computer Science and Engineering
      Kensington, New South Wales, Australia
  • 2003–2005
    • The University of Arizona
      • Department of Systems & Industrial Engineering
      Tucson, AZ, United States
    • University of Melbourne
      • Department of Electrical and Electronic Engineering
      Melbourne, Victoria, Australia