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Optimal Routing, Link Scheduling and Power Control in Multihop Wireless Networks
, 2003
"... In this paper, we study the problem of joint routing, link scheduling and power control to support high data rates for broadband wireless multihop networks. We first address the problem of finding an optimal link scheduling and power control policy that minimizes the total average transmission powe ..."
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Cited by 175 (0 self)
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In this paper, we study the problem of joint routing, link scheduling and power control to support high data rates for broadband wireless multihop networks. We first address the problem of finding an optimal link scheduling and power control policy that minimizes the total average transmission power in the wireless multihop network, subject to given constraints regarding the minimum average data rate per link, as well as peak transmission power constraints per node. Multiaccess signal interference is explicitly modeled. We use a duality approach whereby, as a byproduct of finding the optimal policy, we find the sensitivity of the minimal total average power with respect to the average data rate for each link. Since the minimal total average power is a convex function of the required minimum average data rates, shortest path algorithms with the link weights set to the link sensitivities can be used to guide the search for a globally optimum routing. We present a few simple examples that show our algorithm can find policies that support data rates that are not possible with conventional approaches. Moreover, we find that optimum allocations do not necessarily route traffic over minimum energy paths.
Optimal resource allocation in wireless ad hoc networks: A pricebased approach
 IEEE Transactions on Mobile Computing
, 2006
"... The sharedmedium multihop nature of wireless ad hoc networks poses fundamental challenges to the design of effective resource allocation algorithms that are optimal with respect to resource utilization and fair across different network flows. None of the existing resource allocation algorithms in ..."
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Cited by 70 (7 self)
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The sharedmedium multihop nature of wireless ad hoc networks poses fundamental challenges to the design of effective resource allocation algorithms that are optimal with respect to resource utilization and fair across different network flows. None of the existing resource allocation algorithms in wireless ad hoc networks have realistically considered endtoend flows spanning multiple hops. Moreover, strategies proposed in wireline networks are not applicable in the context of wireless ad hoc networks, due to their unique characteristics of locationdependent contention. In this paper, we propose a new pricebased resource allocation framework in wireless ad hoc networks to achieve optimal resource utilization and fairness among competing endtoend flows. We build our pricing framework on the notion of maximal cliques in wireless ad hoc networks, as compared to individual links in traditional widearea wireline networks. Based on such a pricebased theoretical framework, we present a twotier iterative algorithm. Distributed across wireless nodes, the algorithm converges to a global network optimum with respect to resource allocations. We further improve the algorithm towards asynchronous network settings, and prove its convergence. Extensive simulations under a variety of network environments have been conducted to validate our theoretical claims. ming
TCP with Adaptive Pacing for Multihop Wireless Networks
 in ACM MobiHoc
, 2005
"... In this paper, we introduce a novel congestion control algorithm for TCP over multihop IEEE 802.11 wireless networks implementing ratebased scheduling of transmissions within the TCP congestion window. We show how a TCP sender can adapt its transmission rate close to the optimum using an estimate o ..."
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Cited by 42 (5 self)
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In this paper, we introduce a novel congestion control algorithm for TCP over multihop IEEE 802.11 wireless networks implementing ratebased scheduling of transmissions within the TCP congestion window. We show how a TCP sender can adapt its transmission rate close to the optimum using an estimate of the current 4hop propagation delay and the coefficient of variation of recently measured roundtrip times. The novel TCP variant is denoted as TCP with Adaptive Pacing (TCPAP). Opposed to previous proposals for improving TCP over multihop IEEE 802.11 networks, TCPAP retains the endtoend semantics of TCP and does neither rely on modifications on the routing or the link layer nor requires crosslayer information from intermediate nodes along the path. A comprehensive simulation study using ns2 shows that TCPAP achieves up to 84 % more goodput than TCP NewReno, provides excellent fairness in almost all scenarios, and is highly responsive to changing traffic conditions.
Sufficient Rate Constraints for QoS Flows in AdHoc Networks
"... The capacity of an arbitrary adhoc network is difficult to estimate due to interference between the links. We use a conflict graph that models this interference relationship to determine if a set of flow rates can be accommodated. Using the cliques (complete subgraphs) of the conflict graph, we der ..."
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Cited by 31 (4 self)
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The capacity of an arbitrary adhoc network is difficult to estimate due to interference between the links. We use a conflict graph that models this interference relationship to determine if a set of flow rates can be accommodated. Using the cliques (complete subgraphs) of the conflict graph, we derive constraints that are sufficient for a set of flow rates to be feasible, yet are guaranteed to be within a constant bound of the optimal. We also compute an alternate set of sufficient constraints that can be easily derived from the rows of the matrix representation of the conflict graph. These two sets of constraints are particularly useful because their construction and verification may be distributed across the nodes of a network. We also extend the adhoc network model to incorporate variations in the interference range, and obstructions in the network.
Distributed flow control and medium access control in mobile ad hoc networks
 IEEE TRANSACTIONS ON MOBILE COMPUTING
, 2006
"... Recent studies have shown that the performance of wireless multihop ad hoc networks is very poor. In this paper, we first demonstrate that one important reason of the poor performance is the close coupling between medium contention and network congestion. Therefore, we present a framework of distri ..."
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Cited by 19 (6 self)
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Recent studies have shown that the performance of wireless multihop ad hoc networks is very poor. In this paper, we first demonstrate that one important reason of the poor performance is the close coupling between medium contention and network congestion. Therefore, we present a framework of distributed flow control and medium access control to address both medium contention and network congestion. The proposed scheme utilizes the MAC layer control frames to efficiently conduct the network layer’s flow control function and only allows the upstream nodes to forward enough packets to make it possible for the downstream nodes to fully utilize the shared channel but never introduce severe MAC collisions and network congestion. Extensive simulations illustrate that the proposed scheme well controls congestion and greatly alleviates medium collisions. It achieves up to 12 times the endtoend throughput of IEEE 802.11, maintains a short delay and a low control overhead, and improves the fairness regardless of the hop count and the traffic load.
Approximating maximal cliques in adhoc networks
 in Proc. of PIMRC’04
, 2004
"... Abstract The capacity of an adhoc network is severely affected by interference between links, and several efforts to model this effect make use of ‘clique ’ structures in the adhoc graphs. We propose a fully distributed heuristic algorithm to approximate cliques in such networks. We further propo ..."
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Cited by 17 (1 self)
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Abstract The capacity of an adhoc network is severely affected by interference between links, and several efforts to model this effect make use of ‘clique ’ structures in the adhoc graphs. We propose a fully distributed heuristic algorithm to approximate cliques in such networks. We further propose methods to shrink the generated set of cliques to a set of maximal cliques. Simulation results verify the efficacy of the heuristic algorithms and also analyze their computation time.
Endtoend fair bandwidth allocation in multihop wireless ad hoc networks
 in IEEE ICDCS
"... The sharedmedium multihop nature of wireless ad hoc networks poses fundamental challenges to the design of an effective resource allocation algorithm to maximize spatial reuse of spectrum, while maintaining basic fairness among multiple flows. When previously proposed scheduling algorithms have be ..."
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Cited by 16 (0 self)
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The sharedmedium multihop nature of wireless ad hoc networks poses fundamental challenges to the design of an effective resource allocation algorithm to maximize spatial reuse of spectrum, while maintaining basic fairness among multiple flows. When previously proposed scheduling algorithms have been shown to perform well in providing fair shares of bandwidth among singlehop wireless flows, they do not consider multihop flows with an endtoend perspective when maximizing spatial reuse of spectrum. Instead, previous work attempts to break each multihop endtoend flow into multiple singlehop flows for scheduling purposes. While this may be sufficient for maintaining basic fairness properties among singlehop subflows with respect to bandwidth, we show that, due to the intraflow correlation between upstream and downstream hops, it may not be appropriate for maximizing spatial reuse of bandwidth. In this paper, we analyze the issue of increasing such spatial reuse of bandwidth from an endtoend perspective of multihop flows. Through analysis and simulation results, we show that our proposed algorithm is able to appropriately distribute resources among multihop flows, so that endtoend throughput may be maximized in wireless ad hoc networks, while still maintaining basic fairness across the multihop flows. I.
Bandwidth Guaranteed Routing for AdHoc Networks with Interference Consideration
"... The problem of computing bandwidth guaranteed paths for given flow requests in an adhoc network is complicated because neighboring links share the medium. We define the path width on top of the conflict graph based interference model, and present the AdHoc Shortest Widest Path (ASWP) routing prob ..."
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Cited by 15 (3 self)
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The problem of computing bandwidth guaranteed paths for given flow requests in an adhoc network is complicated because neighboring links share the medium. We define the path width on top of the conflict graph based interference model, and present the AdHoc Shortest Widest Path (ASWP) routing problem in an adhoc network context. We propose a distributed algorithm to address the ASWP problem. Adopting the BellmanFord architecture and the kshortestpath approach, the proposed algorithm achieves a performance close to the optimum. Numerical simulations demonstrate the performance of the algorithm, and also analyze gains achieved over prevalent shortestpath algorithms.
Can CSMA/CA networks be made fair
 In MobiCom
, 2008
"... We demonstrate that CSMA/CA networks, including IEEE 802.11 networks, exhibit severe fairness problem in many scenarios, where some hosts obtain most of the channel’s bandwidth while others starve. Most existing solutions require nodes to overhear transmissions made by contending nodes and, based o ..."
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Cited by 15 (1 self)
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We demonstrate that CSMA/CA networks, including IEEE 802.11 networks, exhibit severe fairness problem in many scenarios, where some hosts obtain most of the channel’s bandwidth while others starve. Most existing solutions require nodes to overhear transmissions made by contending nodes and, based on the overheard information, adjust local rates to achieve fairness among all contending links. Their underlying assumption is that transmissions made by contending nodes can be overheard. However, this assumption holds only when the transmission range is equal to the carrier sensing range, which is not true in reality. As our study reveals, the overhearingbased solutions, as well as several nonoverhearing AIMD solutions, cannot achieve MAClayer fairness in various settings. We propose a new rate control protocol, called PISD (Proportional Increase Synchronized multiplicative Decrease). Without relying on overhearing, it provides fairness in CSMA/CA networks, particularly IEEE 802.11 networks, by using only local information and performing localized operations. It combines several novel rate control mechanisms, including synchronized multiplicative decrease, proportional increase, and background transmission. We prove that PISD converges and achieves (weighted) fairness.