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Scheduling for small delay in multirate multichannel wireless networks
 in INFOCOM
"... Abstract—This paper considers the problem of designing scheduling algorithms for multichannel (e.g., OFDMbased) wireless downlink systems. We show that the ServerSide Greedy (SSG) rule introduced in earlier papers for ONOFF channels performs well even for more general channel models. The key con ..."
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Abstract—This paper considers the problem of designing scheduling algorithms for multichannel (e.g., OFDMbased) wireless downlink systems. We show that the ServerSide Greedy (SSG) rule introduced in earlier papers for ONOFF channels performs well even for more general channel models. The key contribution in this paper is the development of new mathematical techniques for analyzing Markov chains that arise when studying general channel models. These techniques include a way of calculating the distribution of the maximum of a multidimensional Markov chain (note that the maximum does not have the Markov property on its own), and also a Markov chain stochastic dominance result using coupling arguments. Index Terms—Scheduling algorithms, large deviations, small buffer, Markov chain stochastic dominance I.
Lowcomplexity Scheduling Algorithms for Multichannel Downlink Wireless Networks
"... Abstract—This paper considers the problem of designing scheduling algorithms for multichannel (e.g., OFDM) wireless downlink networks with n users/OFDM subchannels. For this system, while the classical MaxWeight algorithm is known to be throughputoptimal, its bufferoverflow performance is very p ..."
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Abstract—This paper considers the problem of designing scheduling algorithms for multichannel (e.g., OFDM) wireless downlink networks with n users/OFDM subchannels. For this system, while the classical MaxWeight algorithm is known to be throughputoptimal, its bufferoverflow performance is very poor (formally, we show it has zero rate function in our setting). To address this, we propose a class of algorithms called iHLQF (iterated Heaviest matching with Longest Queues First) that is shown to be throughput optimal for a general class of arrival/channel processes, and also ratefunction optimal (i.e., exponentially small buffer overflow probability) for certain arrival/channel processes. iHLQF however has higher complexity than MaxWeight (n 4 vs. n 2 respectively). To overcome this issue, we propose a new algorithm called SSG (ServerSide Greedy). We show that SSG is throughput optimal, results in a much better peruser buffer overflow performance than the MaxWeight algorithm (positive rate function for certain arrival/channel processes), and has a computational complexity (n 2) that is comparable to the MaxWeight algorithm. Thus, it provides a nice tradeoff between bufferoverflow performance and computational complexity. These results are validated by both analysis and simulations. Index Terms—Scheduling algorithms, large deviations, small buffer, low complexity I.
Fundamental Lower Bound for Node Buffer Size in Intermittently Connected Wireless Networks
"... Abstract—We study the fundamental lower bound for node buffer size in intermittently connected wireless networks. The intermittent connectivity is caused by the possibility of node inactivity due to some external constraints. We find even with infinite network capacity and node processing speed, buf ..."
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Abstract—We study the fundamental lower bound for node buffer size in intermittently connected wireless networks. The intermittent connectivity is caused by the possibility of node inactivity due to some external constraints. We find even with infinite network capacity and node processing speed, buffer occupation in each node does not approach zero in a static random network where each node keeps a constant message generation rate. Given the condition that each node has the same probability p to be inactive during each time slot, there exists a critical value pc() for this probability from a percolationbased perspective. When p < pc(), the network is in the supercritical case, and there is an achievable lower bound for the occupied buffer size of each node, which is asymptotically independent of the size of the network. If p> pc(), the network is in the subcritical case, and there is a tight lower bound ( p n) for buffer occupation, where n is the number of nodes in the network. I.
On the Universality of AgeBased Scheduling in Wireless Networks
"... Abstract—It is wellknown that maximum weight scheduling, with link weights which are either functions of queue lengths or the ages of the HeadofLine (HoL) packets in each queue, maximizes the throughput region of wireless networks with persistent flows. In particular, with only persistent flows, ..."
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Abstract—It is wellknown that maximum weight scheduling, with link weights which are either functions of queue lengths or the ages of the HeadofLine (HoL) packets in each queue, maximizes the throughput region of wireless networks with persistent flows. In particular, with only persistent flows, it does not matter for throughput optimality whether one uses queue lengths or HoL ages as weights. In this paper, we show the following interesting result: when some flows in the network are dynamic (i.e., they arrive and depart from the network and are not persistent), then HoLagebased scheduling algorithms are throughputoptimal while it has previously been shown that queuelengthbased algorithms are not. This reveals that, agebased algorithms are universal in the sense that their throughput optimality does not depend on whether the arriving traffic is persistent or not. We also present a distributed implementation of the proposed agebased algorithm using CSMA techniques, where each flow only knows its own age and carrier sensing information. Finally, we support our analytical results through simulations. The proof of throughput optimality may be interesting in its own right: it uses a novel Lyapunov function which is the sum of the ages of all the packets in the network. I.
ContentAware Caching and Traffic Management in Content Distribution Networks
"... Abstract—The rapid increase of content delivery over the Internet has led to the proliferation of content distribution networks (CDNs). Management of CDNs requires algorithms for request routing, content placement, and eviction in such a way that user delays are small. We abstract the system of fron ..."
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Abstract—The rapid increase of content delivery over the Internet has led to the proliferation of content distribution networks (CDNs). Management of CDNs requires algorithms for request routing, content placement, and eviction in such a way that user delays are small. We abstract the system of frontend source nodes and backend caches of the CDN in the likeness of the input and output nodes of a switch. In this model, queues of requests for different pieces of content build up at the source nodes, which route these requests to a cache that contains the requested content. For each request that is routed to a cache, a corresponding data file is transmitted back to the requesting source across links of finite capacity. Caches are of finite size, and the content of the caches can be refreshed periodically. Our objective is to design policies for request routing, content placement and content eviction with the goal of small user delays. Stable policies ensure the finiteness of the request queues, while good polices also lead to short queue lengths. We first design a throughputoptimal algorithm that solves the routingplacementeviction problem. The design yields insight into the impact of different cache refresh policies on queue length, and we construct throughput optimal algorithms that engender short queue lengths. We illustrate the potential of our approach through simulations on different CDN topologies. I.
1Fundamental Lower Bound for Node Buffer Size in Intermittently Connected Wireless Networks
"... Abstract—We study the fundamental lower bound for node buffer size in intermittently connected wireless networks. The intermittent connectivity is caused by the possibility of node inactivity due to some external constraints. We find even with infinite channel capacity and node processing speed, bu ..."
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Abstract—We study the fundamental lower bound for node buffer size in intermittently connected wireless networks. The intermittent connectivity is caused by the possibility of node inactivity due to some external constraints. We find even with infinite channel capacity and node processing speed, buffer occupation in each node does not approach zero in a static random network where each node keeps a constant message generation rate. Given the condition that each node has the same probability p of being inactive during each time slot, there exists a critical value pc() for this probability from a percolationbased perspective. When p < pc(), the network is in the supercritical case, and there is an achievable lower bound for the occupied buffer size of each node, which is asymptotically independent of the size of the network. If p> pc(), the network is in the subcritical case, and there is a tight lower bound ( p n) for buffer occupation, where n is the number of nodes in the network. 1
Particle Swarm Optimization With Composite Particles in Dynamic Environments
 IEEE TRANSACTIONS ON SYSTEMS, MAN, AND CYBERNETICS—PART B: CYBERNETICS
, 2010
"... In recent years, there has been a growing interest in the study of particle swarm optimization (PSO) in dynamic environments. This paper presents a new PSO model, called PSO with composite particles (PSOCP), to address dynamic optimization problems. PSOCP partitions the swarm into a set of composi ..."
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In recent years, there has been a growing interest in the study of particle swarm optimization (PSO) in dynamic environments. This paper presents a new PSO model, called PSO with composite particles (PSOCP), to address dynamic optimization problems. PSOCP partitions the swarm into a set of composite particles based on their similarity using a “worst first ” principle. Inspired by the composite particle phenomenon in physics, the elementary members in each composite particle interact via a velocityanisotropic reflection scheme to integrate valuable information for effectively and rapidly finding the promising optima in the search space. Each composite particle maintains the diversity by a scattering operator. In addition, an integral movement strategy is introduced to promote the swarm diversity. Experiments on a typical dynamic test benchmark problem provide a guideline for setting the involved parameters and show that PSOCP is efficient in comparison with several stateoftheart PSO algorithms for dynamic optimization problems.
Utility Maximization Scheduling in Multichannel Wireless Networks
"... This paper considers the problem of designing utility maximization scheduling algorithms for multichannel(e.g, OFDMbased) wireless downlink systems. We extend Lyapunov Optimization to design a throughpututility maximizing algorithm that uses a queuebased and delaybased Lyapunov functions, wher ..."
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This paper considers the problem of designing utility maximization scheduling algorithms for multichannel(e.g, OFDMbased) wireless downlink systems. We extend Lyapunov Optimization to design a throughpututility maximizing algorithm that uses a queuebased and delaybased Lyapunov functions, where the delay uses explicit delay information from the headofline packet destined to each user. Our approach provably achieves the maximum utility, and empirically outperforms the previous solution.