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60
On the Complexity of Scheduling in Wireless Networks
 MOBICOM '06
, 2006
"... We consider the problem of throughputoptimal scheduling in wireless networks subject to interference constraints. We model the interference using a family of Khop interference models. We define a Khop interference model as one for which no two links within K hops can successfully transmit at the ..."
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Cited by 129 (3 self)
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We consider the problem of throughputoptimal scheduling in wireless networks subject to interference constraints. We model the interference using a family of Khop interference models. We define a Khop interference model as one for which no two links within K hops can successfully transmit at the same time (Note that IEEE 802.11 DCF corresponds to a 2hop interference model.). For a given K, a throughputoptimal scheduler needs to solve a maximum weighted matching problem subject to the Khop interference constraints. For K = 1, the resulting problem is the classical Maximum Weighted Matching problem, that can be solved in polynomial time. However, we show that for K> 1, the resulting problems are NPHard and cannot be approximated within a factor that grows polynomially with the number of nodes. Interestingly, we show that for specific kinds of graphs, that can be used to model the underlying connectivity graph of a wide range of wireless networks, the resulting problems admit polynomial time approximation schemes. We also show that a simple greedy matching algorithm provides a constant factor approximation to the scheduling problem for all K in this case. We then show that under a setting with singlehop traffic and no rate control, the maximal scheduling policy considered in recent related works can achieve a constant fraction of the capacity region for networks whose connectivity graph can be represented using one of the above classes of graphs. These results are encouraging as they suggest that one can develop distributed algorithms to achieve near optimal throughput in case of a wide range of wireless networks.
Joint congestion control, routing and MAC for stability and fairness in wireless networks
 IEEE Journal on Selected Areas in Communications
, 2006
"... In this work, we describe and analyze a joint scheduling, routing and congestion control mechanism for wireless networks, that asymptotically guarantees stability of the buffers and fair allocation of the network resources. The queue lengths serve as common information to different layers of the ne ..."
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Cited by 126 (23 self)
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In this work, we describe and analyze a joint scheduling, routing and congestion control mechanism for wireless networks, that asymptotically guarantees stability of the buffers and fair allocation of the network resources. The queue lengths serve as common information to different layers of the network protocol stack. Our main contribution is to prove the asymptotic optimality of a primaldual congestion controller, which is known to model different versions of TCP well.
Throughput guarantees through maximal scheduling in multihop wireless networks
, 2005
"... We address the question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time. We consider a simple distributed scheduling strategy, maximal scheduling, and prove that it attains a guaranteed fraction of the maximum throughput region in a ..."
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Cited by 111 (13 self)
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We address the question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time. We consider a simple distributed scheduling strategy, maximal scheduling, and prove that it attains a guaranteed fraction of the maximum throughput region in arbitrary wireless networks. The guaranteed fraction depends on “interference degree ” of the network which is the maximum number of sessions that interfere with any given session in the network and do not interfere with each other. Depending on the nature of communication, the transmission powers and the propagation models, the guaranteed fraction can be lower bounded by the maximum link degrees in the underlying topology, or even by constants that are independent of the topology. The guarantees also hold in networks with arbitrary number of frequencies. We prove that the guarantees are tight in that they can not be improved any further with maximal scheduling. I.
A Distributed Joint ChannelAssignment, Scheduling and Routing Algorithm for MultiChannel Ad Hoc Wireless Networks
 In Proceedings of IEEE INFOCOM
, 2007
"... Abstract — The capacity of ad hoc wireless networks can be substantially increased by equipping each network node with multiple radio interfaces that can operate on multiple nonoverlapping channels. However, new scheduling, channelassignment, and routing algorithms are required to fully utilize the ..."
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Cited by 81 (0 self)
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Abstract — The capacity of ad hoc wireless networks can be substantially increased by equipping each network node with multiple radio interfaces that can operate on multiple nonoverlapping channels. However, new scheduling, channelassignment, and routing algorithms are required to fully utilize the increased bandwidth in multichannel multiradio ad hoc networks. In this paper, we develop a fully distributed algorithm that jointly solves the channelassignment, scheduling and routing problem. Our algorithm is an online algorithm, i.e., it does not require prior information on the offered load to the network, and can adapt automatically to the changes in the network topology and offered load. We show that our algorithm is provably efficient. That is, even compared with the optimal centralized and offline algorithm, our proposed distributed algorithm can achieve a provable fraction of the maximum system capacity. Further, the achievable fraction that we can guarantee is larger than that of some other comparable algorithms in the literature. I.
Performance of Random Access Scheduling Schemes in Multihop Wireless Networks
"... The scheduling problem in multihop wireless networks has been extensively investigated. Although throughput optimal scheduling solutions have been developed in the literature, they are unsuitable for multihop wireless systems because they are usually centralized and have very high complexity. In ..."
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Cited by 74 (7 self)
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The scheduling problem in multihop wireless networks has been extensively investigated. Although throughput optimal scheduling solutions have been developed in the literature, they are unsuitable for multihop wireless systems because they are usually centralized and have very high complexity. In this paper, we develop a randomaccess based scheduling scheme that utilizes local information. The important features of this scheme include constanttime complexity, distributed operations, and a provable performance guarantee. Analytical results show that it guarantees a larger fraction of the optimal throughput performance than the stateoftheart. Through simulations with both singlehop and multihop traffics, we observe that the scheme provides high throughput, close to that of a wellknown highlyefficient centralized greedy solution called the Greedy Maximal Scheduler.
Polynomial complexity algorithms for full utilization of multihop wireless networks
"... In this paper, we propose and study a general framework that allows the development of distributed mechanisms to achieve full utilization of multihop wireless networks. In particular, we develop a generic randomized routing, scheduling and flow control scheme that is applicable to a large class o ..."
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Cited by 58 (15 self)
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In this paper, we propose and study a general framework that allows the development of distributed mechanisms to achieve full utilization of multihop wireless networks. In particular, we develop a generic randomized routing, scheduling and flow control scheme that is applicable to a large class of interference models. We prove that any algorithm which satisfies the conditions of our generic scheme maximizes network throughput and utilization. Then, we focus on a specific interference model, namely the twohop interference model, and develop distributed algorithms with polynomial communication and computation complexity. This is an important result given that earlier throughputoptimal algorithms developed for such a model relies on the solution to an NPhard problem. To the best of our knowledge, this is the first polynomial complexity algorithm that guarantees full utilization in multihop wireless networks. We further show that our algorithmic approach enables us to efficiently approximate the capacity region of a multihop wireless network.
Throughput and fairness guarantees through maximal scheduling in wireless networks
 IEEE Transactions on Information Theory
, 2008
"... We address the question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time. We consider a simple distributed scheduling strategy, maximal scheduling, and prove that it attains a guaranteed fraction of the maximum throughput region in a ..."
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Cited by 56 (2 self)
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We address the question of providing throughput guarantees through distributed scheduling, which has remained an open problem for some time. We consider a simple distributed scheduling strategy, maximal scheduling, and prove that it attains a guaranteed fraction of the maximum throughput region in arbitrary wireless networks. The guaranteed fraction depends on the “interference degree ” of the network, which is the maximum number of transmitterreceiver pairs that interfere with any given transmitterreceiver pair in the network and do not interfere with each other. Depending on the nature of communication, the transmission powers and the propagation models, the guaranteed fraction can be lower bounded by the maximum link degrees in the underlying topology, or even by constants that are independent of the topology. We prove that the guarantees are tight in that they can not be improved any further with maximal scheduling. Our results can also be generalized to endtoend multihop sessions. Finally, we enhance maximal scheduling to guarantee fairness of rate allocation among different sessions. I.
Control for intersession network coding
 in Proc. Workshop on Network Coding, Theory & Applications
, 2007
"... Abstract — We propose a dynamic routingschedulingcoding strategy for serving multiple unicast sessions when linear network coding is allowed across sessions. Noting that the set of stabilizable throughput levels in this context is an open problem, we prove that our strategy supports any point in t ..."
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Cited by 44 (5 self)
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Abstract — We propose a dynamic routingschedulingcoding strategy for serving multiple unicast sessions when linear network coding is allowed across sessions. Noting that the set of stabilizable throughput levels in this context is an open problem, we prove that our strategy supports any point in the nontrivial region of achievable rates recently characterized by Traskov et al. [1]. This work also provides a theoretical framework in which the gains of intersession network coding and pure routing can be compared. I.
A distributed optimization algorithm for multihop cognitive radio networks
 IEEE INFOCOM
, 2008
"... Cognitive radio (CR) is a revolution in radio technology and is viewed as an enabling technology for dynamic spectrum access. This paper investigates how to design distributed algorithm for a multihop CR network, with the objective of maximizing data rates for a set of user communication sessions. ..."
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Cited by 44 (1 self)
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Cognitive radio (CR) is a revolution in radio technology and is viewed as an enabling technology for dynamic spectrum access. This paper investigates how to design distributed algorithm for a multihop CR network, with the objective of maximizing data rates for a set of user communication sessions. We study this problem via a crosslayer optimization approach, with joint consideration of power control, scheduling, and routing. For the centralized problem, we show that this optimization problem is in the form of mixed integer nonlinear program (MINLP), which cannot be solved in polynomial time. To develop a performance benchmark for the distributed optimization algorithm, we first develop a tight upper bound on the objective function via relaxation on the MINLP problem. Subsequently, we develop a distributed optimization algorithm that iteratively increases the data rate among user communication sessions. During each iteration, there are two separate processes, a Conservative Iterative Process (CIP) and an Aggressive Iterative Process (AIP). Both CIP and AIP incorporates routing, minimalist scheduling, and power control/scheduling modules. Via simulation results, we compare the performance of the distributed optimization algorithm with the upper bound and validate its efficacy.
On Constructive Network Coding for Multiple Unicasts
"... We consider the problem of network coding across multiple unicasts. We develop, for wired and wireless networks, offline and online back pressure algorithms for finding approximately throughputoptimal network codes within the class of network codes restricted to XOR coding between pairs of flows. ..."
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Cited by 42 (1 self)
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We consider the problem of network coding across multiple unicasts. We develop, for wired and wireless networks, offline and online back pressure algorithms for finding approximately throughputoptimal network codes within the class of network codes restricted to XOR coding between pairs of flows. Our online algorithm incorporates realtime control signaling with delays, and random exploration approaches for reducing computation.