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103
CrossLayer Design for Wireless Networks
 IEEE Communications Magazine
, 2003
"... As the cellular and PCS world collides with Wireless LANs and Internetbased packet data, new networking approaches will support the integration of voice and data on the composite infrastructure of cellular base stations and Ethernetbased wireless access points. This paper highlights some of the pa ..."
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Cited by 155 (3 self)
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As the cellular and PCS world collides with Wireless LANs and Internetbased packet data, new networking approaches will support the integration of voice and data on the composite infrastructure of cellular base stations and Ethernetbased wireless access points. This paper highlights some of the past accomplishments and promising research avenues for an important topic in the creation of future wireless networks. In this paper, we address the issue of crosslayer networking, where the physical and MAC layer knowledge of the wireless medium is shared with higher layers, in order to provide efficient methods of allocating network resources and applications over the Internet. In essence, future networks will need to provide ”impedance matching ” of the instantaneous radio channel conditions and capacity needs with the traffic and congestion conditions found over the packetbased world of the Internet. Further, such matching will need to be coordinated with a wide range of particular applications and user expectations, making the topic of crosslayer networking an increasingly important one for the evolving wireless buildout. 1
Fair resource allocation in wireless networks using queuelengthbased scheduling and congestion control
 In Proceedings of IEEE Infocom
, 2005
"... We consider the problem of allocating resources (time slots, frequency, power, etc.) at a base station to many competing flows, where each flow is intended for a different receiver. The channel conditions may be timevarying and different for different receivers. It is wellknown that appropriately ..."
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Cited by 128 (22 self)
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We consider the problem of allocating resources (time slots, frequency, power, etc.) at a base station to many competing flows, where each flow is intended for a different receiver. The channel conditions may be timevarying and different for different receivers. It is wellknown that appropriately chosen queuelength based policies are throughputoptimal while other policies based on the estimation of channel statistics can be used to allocate resources fairly (such as proportional fairness) among competing users. In this paper, we show that a combination of queuelengthbased scheduling at the base station and congestion control implemented either at the base station or at the end users can lead to fair resource allocation and queuelength stability.
A tutorial on crosslayer optimization in wireless networks
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS
, 2006
"... This tutorial paper overviews recent developments in optimization based approaches for resource allocation problems in wireless systems. We begin by overviewing important results in the area of opportunistic (channelaware) scheduling for cellular (singlehop) networks, where easily implementable my ..."
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Cited by 128 (13 self)
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This tutorial paper overviews recent developments in optimization based approaches for resource allocation problems in wireless systems. We begin by overviewing important results in the area of opportunistic (channelaware) scheduling for cellular (singlehop) networks, where easily implementable myopic policies are shown to optimize system performance. We then describe key lessons learned and the main obstacles in extending the work to general resource allocation problems for multihop wireless networks. Towards this end, we show that a cleanslate optimization based approach to the multihop resource allocation problem naturally results in a “loosely coupled” crosslayer solution. That is, the algorithms obtained map to different layers (transport, network, and MAC/PHY) of the protocol stack are coupled through a limited amount of information being passed back and forth. It turns out that the optimal scheduling component at the MAC layer is very complex and thus needs simpler (potentially imperfect) distributed solutions. We demonstrate how to use imperfect scheduling in the crosslayer framework and describe recently developed distributed algorithms along these lines. We conclude by describing a set of open research problems.
A framework for opportunistic scheduling in wireless networks
 COMPUTER NETWORKS
, 2003
"... We present a method, called opportunistic scheduling, for exploiting the timevarying nature of the radio environment to increase the overall performance of the system under certain quality of service/fairness requirements of users. We first introduce a general framework for opportunistic scheduling ..."
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Cited by 127 (6 self)
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We present a method, called opportunistic scheduling, for exploiting the timevarying nature of the radio environment to increase the overall performance of the system under certain quality of service/fairness requirements of users. We first introduce a general framework for opportunistic scheduling, and then identify three general categories of scheduling problems under this framework. We provide optimal solutions for each of these scheduling problems. All the proposed scheduling policies are implementable online; we provide parameter estimation algorithms and implementation procedures for them. We also show how previous work by us and others directly fits into or is related to this framework. We demonstrate via simulation that opportunistic scheduling schemes result in significant performance improvement compared with nonopportunistic alternatives.
Scheduling Algorithms for a Mixture of RealTime and NonRealTime Data in HDR
 in Proceedings of 17th International Teletraffic Congress (ITC17
"... High Data Rate (HDR) technologz has recently been proposed as an overlay to CDMA... In this paper, we study various scheduling algorithms for a mixture of realtime and nonrealtime data over HDR/CDMA and compare their performance. We study the performance with respect to packet delays and also ave ..."
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Cited by 111 (0 self)
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High Data Rate (HDR) technologz has recently been proposed as an overlay to CDMA... In this paper, we study various scheduling algorithms for a mixture of realtime and nonrealtime data over HDR/CDMA and compare their performance. We study the performance with respect to packet delays and also average throughput, where we use a token based mechanism to give minimum throughput guarantees. We nd that a rule which we call the exponential rule performs well with regard to both these criteria. (In a companion paper, we show that this rule is throughputoptimal, i.e., it makes the queues stable if it is feasible to do so with any other scheduling rule.) Our main conclusion is that intelligent scheduling algorithms in conjunction with token based rate control provide an ecient framework for supporting a mixture of realtime and nonrealtime data applications in a single carrier.
Stable scheduling policies for fading wireless channels
 IEEE/ACM TRANSACTIONS ON NETWORKING
, 2005
"... We study the problem of stable scheduling for a class of wireless networks. The goal is to stabilize the queues holding information to be transmitted over a fading channel. Few assumptions are made on the arrival process statistics other than the assumption that their mean values lie within the cap ..."
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Cited by 66 (15 self)
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We study the problem of stable scheduling for a class of wireless networks. The goal is to stabilize the queues holding information to be transmitted over a fading channel. Few assumptions are made on the arrival process statistics other than the assumption that their mean values lie within the capacity region and that they satisfy a version of the law of large numbers. We prove that, for any mean arrival rate that lies in the capacity region, the queues will be stable under our policy. Moreover, we show that it is easy to incorporate imperfect queue length information and other approximations that can simplify the implementation of our policy.
Exploiting Decentralized Channel State Information for Random Access
, 2002
"... We study the use of channel state information for random access in fading channels. Traditionally, random access protocols have been designed by assuming simple models for the physical layer where all users are symmetric and there is no notion of channel state. We introduce a reception model that ta ..."
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Cited by 60 (18 self)
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We study the use of channel state information for random access in fading channels. Traditionally, random access protocols have been designed by assuming simple models for the physical layer where all users are symmetric and there is no notion of channel state. We introduce a reception model that takes into account the channel states of various users. Under the assumption that each user has access to his channel state information (CSI), we propose a variant of Slotted ALOHA protocol for medium access control, where the transmission probability is allowed to be a function of the CSL The function is called the transmission control scheme. Assuming the finite user infinite buffer model we derive expressions for the maximum stable throughput of the system. We introduce the notion of asymptotic stable throughput (AST) that is the maximum stable throughput as the number of users goes to infinity. We consider two types of transmission control namely population independent transmission control (PITC) where the transmission control is not a function of the size of the network and population dependent transmission control where the transmission control is a function of the size of the network. We obtain expressions for the AST achievable with PITC. For population dependent transmission control, we introduce a particular transmission control that can potentially lead to significant gains in AST. For both PITC and PDTC, we show that the effect of transmission control is equivalent to changing the probability distribution of the channel state. The theory is then applied to CDMA networks with Linear Minimum Mean Square Error (LMMSE) receivers and Matched Filters (MF) to illustrate the effectiveness of utilizing channel state. It is shown that through the use of channel state, with an...
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 58 (8 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.
Pathwise optimality of the exponential scheduling rule for wireless channels
 Advances in Applied Probability
, 2004
"... We consider the problem of scheduling transmissions of multiple data users (flows) sharing the same wireless channel (server). The unique feature of this problem is the fact that the capacity (service rate) of the channel varies randomly with time and asynchronously for different users. We study a s ..."
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Cited by 48 (12 self)
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We consider the problem of scheduling transmissions of multiple data users (flows) sharing the same wireless channel (server). The unique feature of this problem is the fact that the capacity (service rate) of the channel varies randomly with time and asynchronously for different users. We study a scheduling policy called Exponential scheduling rule, which was introduced in an earlier paper. Given a system with N users, and any set of positive numbers {an},n = 1,2,...,N, we show that in a heavytraffic limit, under a nonrestrictive complete resource pooling condition, this algorithm has the property that, for each time t, it (asymptotically) minimizes maxn an˜qn(t), where ˜qn(t) is user n queue length in the heavy traffic regime.
Optimal Utility Based MultiUser Throughput Allocation subject to Throughput Constraints
 in Proceedings of IEEE INFOCOM ’05
, 2005
"... We consider the problem of scheduling multiple users sharing a timevarying wireless channel. (As an example, this is a model of scheduling in 3G wireless technologies, such as CDMA2000 3G1xEVDO downlink scheduling.) We introduce an algorithm which seeks to optimize a concave utility H i (R i ) o ..."
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Cited by 41 (10 self)
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We consider the problem of scheduling multiple users sharing a timevarying wireless channel. (As an example, this is a model of scheduling in 3G wireless technologies, such as CDMA2000 3G1xEVDO downlink scheduling.) We introduce an algorithm which seeks to optimize a concave utility H i (R i ) of the user throughputs R i , subject to certain lower and upper throughput bounds: R i R i i . The algorithm, which we call the Gradient algorithm with Minimum/Maximum Rate constraints (GMR) uses a token counter mechanism, which modifies an algorithm solving the corresponding unconstrained problem, to produce the algorithm solving the problem with throughput constraints. Two important special cases of the utility functions are log R i and R i , corresponding to the common Proportional Fairness and Throughput Maximization objectives.