Conference Paper

# Utility-optimal scheduling in time-varying wireless networks with delay constraints.

DOI: 10.1145/1860093.1860099 Conference: Proceedings of the 11th ACM Interational Symposium on Mobile Ad Hoc Networking and Computing, MobiHoc 2010, Chicago, IL, USA, September 20-24, 2010

Source: DBLP

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**ABSTRACT:**The optimal rate allocation problem with end-to-end delay constraints in wireless networks is highly challenging due to the dynamics incurred by delay related factors, such as traffic arrival pattern, queuing process, and wireless resource sharing mechanism. In this paper, we solve the problem through a utility maximization framework with two sets of constraints: (1) capacity and schedulability constraints and (2) end-to-end delay constraints. The end-to-end delay of a flow can be adjusted by controlling the per-link delays via a novel parameter called Virtual Link Capacity Margin (VLCM), which is the measurement of the gap between the schedulable link capacity and the maximum allowable flow rate over a link. This optimization problem can be solved via its dual decomposition through two prices derived with regard to the constraints: the link congestion price that reflects the relationship between the traffic load and the capacity of a link, and the flow delay price that reflects the margin between the average packet delay and the delay constraint of a flow. We prove that the algorithm converges to the optimal solution under the M/M/1 queuing model. We have also discussed using our algorithm under generalized traffic patterns, where we use link delay functions to formulate the relationship between VLCM and the average link delay. The algorithm is implemented distributedly via joint wireless link scheduling, VLCM adjustment and congestion control. Extensive experiments are conducted over diverse network topologies and traffic arrival models. The experimental results show that our algorithm is able to achieve optimal rate allocation while satisfying the end-to-end delay constraints.Ad Hoc Networks. 01/2014; 13:282–295. -
##### Conference Paper: On the performance of largest-deficit-first for scheduling real-time traffic in wireless networks

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**ABSTRACT:**This paper considers the problem of scheduling real-time traffic in wireless networks. We consider an ad hoc wireless network with general interference and general one-hop traffic. Each packet is associated with a deadline and will be dropped if it is not transmitted before the deadline expires. The number of packet arrivals in each time slot and the length of a deadline are both stochastic and follow certain distributions. We only allow a fraction of packets to be dropped. At each link, we assume the link keeps track of the difference between the minimum number of packets that need to be delivered and the number of packets that are actually delivered, which we call deficit. The largest-deficit-first (LDF) policy schedules links in descending order according to their deficit values, which is a variation of the largest-queue-first (LQF) policy for non-real-time traffic. We prove that the efficiency ratio of LDF can be lower bounded by a quantity that we call the real-time local-pooling factor (R-LPF). We further prove that given a network with interference degree β, the R-LPF is at least 1/(β+1), which in the case of the one-hop interference model translates into an R-LPF of at least 1/3.Proceedings of the fourteenth ACM international symposium on Mobile ad hoc networking and computing; 07/2013 - [Show abstract] [Hide abstract]

**ABSTRACT:**In this paper, optimal resource allocation policies are characterized for wireless cognitive networks under the spectrum leasing model. We propose cooperative schemes in which secondary users share the time-slot with primary users in return for cooperation. Cooperation is feasible only if the primary system's performance is improved over the non-cooperative case. First, we investigate a scheduling problem where secondary users are interested in immediate rewards. Here, we consider both infinite and finite backlog cases. Then, we formulate another problem where the secondary users are guaranteed a portion of the primary utility, on a long-term basis, in return for cooperation. Finally, we present a power allocation problem where the goal is to maximize the expected net benefit defined as utility minus cost of energy. Our proposed scheduling policies are shown to outperform non-cooperative scheduling policies, in terms of expected utility and net benefit, for a given set of feasible constraints. Based on Lyapunov optimization techniques, we show that our schemes are arbitrarily close to the optimal performance at the price of reduced convergence rate.IEEE/ACM Transactions on Networking 01/2013; 21(6):1708-1721. · 2.01 Impact Factor

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