[show abstract][hide abstract] 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
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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.
[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  for wired mesh networks, our experimental results demonstrate that ORFM outperforms OPP in wireless scenarios.
[show abstract][hide abstract] 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
[show abstract][hide abstract] 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