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28
Joint Congestion Control and Media Access Control Design for Ad Hoc Wireless Networks
 In Proc. IEEE INFOCOM
, 2005
"... Abstract—We present a model for the joint design of congestion control and media access control (MAC) for ad hoc wireless networks. Using contention graph and contention matrix, we formulate resource allocation in the network as a utility maximization problem with constraints that arise from content ..."
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Cited by 120 (4 self)
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Abstract—We present a model for the joint design of congestion control and media access control (MAC) for ad hoc wireless networks. Using contention graph and contention matrix, we formulate resource allocation in the network as a utility maximization problem with constraints that arise from contention for channel access. We present two algorithms that are not only distributed spatially, but more interestingly, they decompose vertically into two protocol layers where TCP and MAC jointly solve the system problem. The first is a primal algorithm where the MAC layer at the links generates congestion (contention) prices based on local aggregate source rates, and TCP sources adjust their rates based on the aggregate prices in their paths. The second is a dual subgradient algorithm where the MAC subalgorithm is implemented through scheduling linklayer flows according to the congestion prices of the links. Global convergence properties of these algorithms are proved. This is a preliminary step towards a systematic approach to jointly design TCP congestion control algorithms and MAC algorithms, not only to improve performance, but more importantly, to make their interaction more transparent.
On Chromatic Sums and Distributed Resource Allocation
"... This paper studies an optimization problem that arises in the context of distributed resource allocation: Given a conflict graph that represents the competition of processors over resources, we seek an allocation under which no two jobs with conflicting requirements are executed simultaneously. Our ..."
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Cited by 65 (11 self)
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This paper studies an optimization problem that arises in the context of distributed resource allocation: Given a conflict graph that represents the competition of processors over resources, we seek an allocation under which no two jobs with conflicting requirements are executed simultaneously. Our objective is to minimize the average response time of the system. In alternative formulation this is known as the Minimum Color Sum (MCS) problem [24]. We show, that the algorithm based on finding iteratively a maximum independent set (MaxIS) is a 4approximation to the MCS. This bound is tight to within a factor of 2. We give improved ratios for the classes of bipartite, boundeddegree, and line graphs. The bound generalizes to a 4aeapproximation of MCS for classes of graphs for which the maximum independent set problem can be approximated within a factor of ae. On the other hand, we show that an n1 \Gamma fflapproximation is NPhard, for some ffl? 0. For some instances of the resource allocation problem, such as the Dining Philosophers, an efficient solution requires edge coloring of the conflict graph. We introduce the Minimum Edge Color Sum (MECS) problem which is shown to be NPhard. We show that a 2approximation to MECS(G) can be obtained distributively using compact coloring within O(log² n) communication rounds.
Fairness in Periodic RealTime Scheduling
, 1995
"... The issue of temporal fairness in periodic realtime scheduling is considered. It is argued that such fairness is often a desirable characteristic in realtime schedules. A concrete criterion for temporal fairness  pfairness  is described. The weightmonotonic scheduling algorithm, a static prio ..."
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Cited by 31 (3 self)
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The issue of temporal fairness in periodic realtime scheduling is considered. It is argued that such fairness is often a desirable characteristic in realtime schedules. A concrete criterion for temporal fairness  pfairness  is described. The weightmonotonic scheduling algorithm, a static priority scheduling algorithm for generating pfair schedules, is presented and proven correct. A feasibility test is presented which, if satisfied by a system of periodic tasks, ensures that the weightmonotonic scheduling algorithm will schedule the system in a pfair manner.
Throughputoptimal configuration of fixed wireless networks
 IEEE/ACM Trans. Netw
, 2007
"... Abstract—In this paper, we address the following two questions concerning the capacity and configuration of fixed wireless networks: (i) given a set of wireless nodes with arbitrary but fixed locations, and a set of data flows, what is the max–min achievable throughput? and (ii) how should the net ..."
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Cited by 16 (12 self)
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Abstract—In this paper, we address the following two questions concerning the capacity and configuration of fixed wireless networks: (i) given a set of wireless nodes with arbitrary but fixed locations, and a set of data flows, what is the max–min achievable throughput? and (ii) how should the network be configured to achieve the optimum? We consider these questions from a networking standpoint assuming pointtopoint links, and employ a rigorous physical layer model to model conflict relationships between them. Since we seek capacity results, we assume that the network is operated using an appropriate schedule of conflictfree link activations. We develop and investigate a novel optimization framework to determine the optimal throughput and configuration, i.e., flow routes, link activation schedules and physical layer parameters. Determining the optimal throughput is a computationally hard problem, in general. However, using a smart enumerative technique we obtain numerical results for several different scenarios of interest. We obtain several important insights into the structure of the optimal routes, schedules and physical layer parameters. Besides determining the achievable throughput, we believe that our optimizationbased framework can also be used as a tool, for configuring scheduled wireless networks, such as those based on IEEE 802.16. Index Terms—Capacity, fixed wireless networks, IEEE 802.16, mesh networks, optimal scheduling and routing. I.
Approximating Max–Min fair Rates via Distributed Local Scheduling with Partial Information
 In the proceedings of IEEE INFOCOM 1996. X. REFERENCES 173
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Congestion control in CSMAbased networks with inconsistent channel state
 in Proc. IEEE/ACM Int. Wireless Internet Conf. (WICON) 2006 (Invited Paper
, 2006
"... In this paper, we study the performance of utility maximization congestion control over multihop CSMAbased networks. We consider decoupled vs. joint design of congestion control and medium access and consider unmodified MAC protocols such as IEEE 802.11. Networks employing such MAC protocols incur ..."
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Cited by 6 (2 self)
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In this paper, we study the performance of utility maximization congestion control over multihop CSMAbased networks. We consider decoupled vs. joint design of congestion control and medium access and consider unmodified MAC protocols such as IEEE 802.11. Networks employing such MAC protocols incur flow starvation both without congestion control and with existing TCPbased congestion control. We develop a framework to study key issues in such networks that are not incorporated by prior models, yet are critical to the performance of congestion control algorithms. We study the role of data transmission capacity that is location dependent and, even more, unknown. We show that for the case of consistent channel state, a single globally optimal data transmission capacity does not exist. Moreover, for the case of inconsistent channel state that arises due to the carrier sense mechanism itself, a data transmission capacity that provides convergence to perfectly fair rates does not exist, i.e., the congestion control algorithm converges to incorrect rates. We study the impact of internode collaboration within a contention region, and show that collaboration can alleviate these problems and ensure convergence to fair rates. Finally, we compare the performance of congestion control in a collaborative network with the performance of TCP, and show that TCP starves some flows, whereas congestion control with collaboration removes starvation, provides significantly better fairness, and achieves 17 % higher aggregate throughput.
RealTime Mutable Broadcast Disks
, 1997
"... There is an increased interest in using broadcast disks to support mobile access to realtime databases. However, previous work has only considered the design of realtime immutable broadcast disks, the contents of which do not change over time. This paper considers the design of programs for real ..."
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Cited by 6 (0 self)
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There is an increased interest in using broadcast disks to support mobile access to realtime databases. However, previous work has only considered the design of realtime immutable broadcast disks, the contents of which do not change over time. This paper considers the design of programs for realtime mutable broadcast disks  broadcast disks whose contents are occasionally updated. Recent schedulingtheoretic results relating to pinwheel scheduling and pfair scheduling are used to design algorithms for the efficient generation of realtime mutable broadcast disk programs.
Minimizing Migrations in Fair Multiprocessor Scheduling of Persistent Tasks
"... Suppose that we are given n persistent tasks (jobs) that need to be executed in an equitable way on m processors (machines). Each machine is capable of performing one unit of work in each integral time unit and each job may be executed on at most one machine at a time. The schedule needs to specify ..."
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Cited by 5 (0 self)
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Suppose that we are given n persistent tasks (jobs) that need to be executed in an equitable way on m processors (machines). Each machine is capable of performing one unit of work in each integral time unit and each job may be executed on at most one machine at a time. The schedule needs to specify which job is to be executed on each machine in each time window. The goal is to find a schedule that minimizes job migrations between machines while guaranteeing a fair schedule. We measure the fairness by the drift d defined as the maximum difference between the execution times accumulated by any two jobs. Since jobs are persistent we measure the quality of the schedule by the ratio of the number of migrations to time windows. We show a tradeoff between the drift and the number of migrations. Let n = qm + r with 0 < r < m (the problem is trivial for n ≤ m and for r = 0). For any d ≥ 1, we show a schedule that achieves a migration ratio of r(m−r)/(n(q(d−1)+1))+o(1); namely, it asymptotically requires r(m−r) job migrations every n(q(d−1)+1) time windows. We show how to implement the schedule efficiently. We prove that our algorithm is almost optimal by proving a lower bound of r(m−r)/(nqd) on the migration ratio. We also give a more complicated schedule that matches the lower bound for a special case when 2q ≤ d and m = 2r. Our algorithms can be extended to the dynamic case in which jobs enter and leave the system over time. 1
A fair MAC protocol for IEEE 802.11based ad hoc networks: Design and implementation
 IEEE Transactions on Wireless Communications
, 2007
"... Abstract — In this paper, we model the problem of bandwidth sharing in wireless multihop networks as a general utility maximization problem with link bandwidth constraints. Lagrangean relaxation and duality are invoked to derive a gradientbased iterative algorithm to solve the problem. We then in ..."
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Cited by 5 (0 self)
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Abstract — In this paper, we model the problem of bandwidth sharing in wireless multihop networks as a general utility maximization problem with link bandwidth constraints. Lagrangean relaxation and duality are invoked to derive a gradientbased iterative algorithm to solve the problem. We then investigate the practical aspects of the problem and discuss how such theoretical framework can be used to design practical fair media access control frameworks that can be implemented in real systems based on the IEEE 802.11 distributed coordination function. Index Terms — IEEE 802.11, ad hoc networks, medium access control, fairness, backoff, convex programming, implementation. I.
CrossLayer Fair Bandwidth Sharing for MultiChannel Wireless Mesh Networks
, 2007
"... In a wireless mesh network (WMN) with a number of stationary wireless routers, the aggregate capacity can be increased when each router is equipped with multiple network interface cards (NICs) and each NIC is assigned to a distinct orthogonal frequency channel. In this paper, given the logical topol ..."
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Cited by 4 (0 self)
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In a wireless mesh network (WMN) with a number of stationary wireless routers, the aggregate capacity can be increased when each router is equipped with multiple network interface cards (NICs) and each NIC is assigned to a distinct orthogonal frequency channel. In this paper, given the logical topology of the network, we mathematically formulate a crosslayer fair bandwidth sharing problem as a nonlinear mixedinteger network utility maximization problem. An optimal joint design, based on exact binary linearization techniques, is proposed which leads to a global maximum. A nearoptimal joint design, based on approximate dual decomposition techniques, is also proposed which is practical for deployment. Performance is assessed through several numerical examples in terms of network utility, aggregate network throughput, and fairness index. Results show that our proposed designs can lead to multichannel WMNs which are more efficient and fair compared to their singlechannel counterparts. The performance gain on both efficiency and fairness increase as the number of available NICs per router or the number of available frequency channels increases.