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111
DMesh: incorporating practical directional antennas in multichannel wireless mesh networks
 IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS SPECIAL ISSUE ON MULTIHOP WIRELESS MESH NETWORKS
, 2006
"... Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous lastmile broadband access. Three key factors that affect the usability of WMNs are high throughput, costeffectiveness, and ease of deployability. In this paper, we propose DMesh, a WMN architecture that combin ..."
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Cited by 28 (0 self)
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Wireless mesh networks (WMNs) have been proposed as an effective solution for ubiquitous lastmile broadband access. Three key factors that affect the usability of WMNs are high throughput, costeffectiveness, and ease of deployability. In this paper, we propose DMesh, a WMN architecture that combines spatial separation from directional antennas with frequency separation from orthogonal channels to improve the throughput of WMNs. DMesh achieves this improvement without inhibiting costeffectiveness and ease of deployability by utilizing practical directional antennas that are widely and cheaply available (e.g., patch and yagi) in contrast to costly and bulky smart beamforming directional antennas. Thus, the key challenge in DMesh is to exploit spatial separation from such practical directional antennas despite their lack of electronic steerability and interference nulling, as well as the presence of significant sidelobes and backlobes. In this paper, we study how such practical directional antennas can improve the throughput of a WMN. Central to our architecture is a distributed, directional channel assignment algorithm for mesh routers that effectively exploits the spatial and frequency separation opportunities in a DMesh network. Simulation results show that DMesh improves the throughput of WMNs by up to 231 % and reduces packet delay drastically compared to a multiradio multichannel omni antenna network. A DMesh implementation in our 16node 802.11b WMN testbed using commercially available practical directional antennas provides transmission control protocol throughput gains ranging from 31 % to 57%.
ContentAware Resource Allocation and Packet Scheduling for Video Transmission Over Wireless Networks
 IEEE J. Select. Areas Commun
, 2007
"... Abstract — A crosslayer packet scheduling scheme that streams preencoded video over wireless downlink packet access networks to multiple users is presented. The scheme can be used with the emerging wireless standards such as HSDPA and IEEE 802.16. A gradient based scheduling scheme is used in whi ..."
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Cited by 25 (5 self)
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Abstract — A crosslayer packet scheduling scheme that streams preencoded video over wireless downlink packet access networks to multiple users is presented. The scheme can be used with the emerging wireless standards such as HSDPA and IEEE 802.16. A gradient based scheduling scheme is used in which user data rates are dynamically adjusted based on channel quality as well as the gradients of a utility function. The user utilities are designed as a function of the distortion of the received video. This enables distortionaware packet scheduling both within and across multiple users. The utility takes into account decoder error concealment, an important component in deciding the received quality of the video. We consider both simple and complex error concealment techniques. Simulation results show that the gradient based scheduling framework combined with This work was supported by the Motorola Center for Seam
Opportunistic power scheduling for dynamic multiserver wireless systems
 IEEE Transactions on Wireless Communications
, 2006
"... In this paper, we present an opportunistic power scheduling scheme, i.e., a joint timeslot and power allocation scheme for downlink communication in wireless systems. Unlike past works, we allow multiple transmissions in a timeslot that could potentially interfere with each other. These multiple t ..."
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Cited by 25 (1 self)
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In this paper, we present an opportunistic power scheduling scheme, i.e., a joint timeslot and power allocation scheme for downlink communication in wireless systems. Unlike past works, we allow multiple transmissions in a timeslot that could potentially interfere with each other. These multiple transmissions are allowed to achieve high system efficiency. Hence, it is important to not only select the mobiles to be scheduled in a timeslot, but also to allocate an appropriate transmission power level to these scheduled mobiles. We model the timevarying wireless channel as a stochastic process and formulate a stochastic optimization problem that attempts to maximize the expected total system utility with general constraints on performance or fairness. The power scheduling algorithm is obtained by using stochastic duality and implemented via stochastic subgradient techniques. I.
Downlink power allocation for multiclass wireless systems,” submitted for publication
, 2002
"... In this paper we consider a power allocation problem in multiclass wireless systems. We focus on the downlink of the system. Each mobile has a utility function that characterizes its degree of satisfaction for the received service. The objective is to obtain a power allocation that maximizes the to ..."
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Cited by 24 (1 self)
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In this paper we consider a power allocation problem in multiclass wireless systems. We focus on the downlink of the system. Each mobile has a utility function that characterizes its degree of satisfaction for the received service. The objective is to obtain a power allocation that maximizes the total system utility. Typically, natural utility functions for each mobile are nonconcave. Hence, we cannot use existing convex optimization techniques to derive a global optimal solution. We develop a simple (distributed) algorithm to obtain a power allocation that is asymptotically optimal in the number of mobiles. The algorithm is based on dynamic pricing and consists of two stages. At the mobile selection stage, the basestation selects mobiles to which power is allocated. At the power allocation stage, the basestation allocates power to the selected mobiles. We provide numerical results that illustrate the performance of our scheme. In particular, we show that our algorithm results in system performance that is close to the performance of a global optimal solution in most cases. Index Terms Power allocation, downlink, wireless networks, and nonconvex optimization.
Opportunistic Packet Scheduling and Media Access Control for Wireless LANs and Multihop Ad Hoc Networks
 in Proc. of IEEE Wireless Communications and Networking Conference (WCNC’04
, 2004
"... In the wireless LANs or mobile ad hoc networks, a node with multipackets in its queue waiting for delivery to several neighboring nodes may choose to schedule a candidate receiver with good channel condition for transmission. By choosing a receiver with good channel condition, the HeadofLine (HOL ..."
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Cited by 22 (3 self)
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In the wireless LANs or mobile ad hoc networks, a node with multipackets in its queue waiting for delivery to several neighboring nodes may choose to schedule a candidate receiver with good channel condition for transmission. By choosing a receiver with good channel condition, the HeadofLine (HOL) blocking problem can be alleviated and the overall system throughput can be increased. Motivated by this observation, we introduce the Opportunistic packet Scheduling and Media Access control (OSMA) protocol to exploit high quality channel condition under certain fairness constraints. We base our design on CSMA/CA so that it can be simply incorporated into the 802.11 standard.The key mechanisms of OSMA protocol are multicast RTS and prioritybased CTS. In the OSMA protocol, RTS includes a list of candidate receivers. Among those who are qualified to receive data, the one with the highest order would be granted to catch the channel by replying CTS in the first place. The ordering list will be updated dynamically according to certain scheduling policy such as Round Robin (RR) and Earlier timestamp First (ETF), so other performance metrics, e.x., fairness and timeliness, can be enhanced. To the best of our knowledge, this is the first paper to exploit the multiuser diversity in the CSMA/CA based wireless networks. We evaluate the OSMA using ns2 and our simulation results show that this protocol can improve the network throughput significantly.
REFIM: A practical interference management in heterogeneous wireless access networks
 IEEE Journal on Sel. Areas in Communic
, 2011
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Joint Scheduling and Resource Allocation in CDMA Systems
 Proc. of 2nd Workshop on Modeling and Optimization in Mobile, Ad Hoc, and Wireless Networks (WiOpt ’04
, 2004
"... Abstract. We consider scheduling and resource allocation for the downlink in a CDMA based wireless network. The scheduling and resource allocation problem is to select a subset of the users for transmission and for each of the users selected, to choose the modulation and coding scheme, transmission ..."
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Cited by 18 (3 self)
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Abstract. We consider scheduling and resource allocation for the downlink in a CDMA based wireless network. The scheduling and resource allocation problem is to select a subset of the users for transmission and for each of the users selected, to choose the modulation and coding scheme, transmission power, and number of codes used. We refer to this combination as the physical layer operating point (PLOP). Each PLOP consumes different amounts of code and power resources. The resource allocation task to pick the “optimal ” PLOP taking into account both systemwide and individual user resource constraints that can arise in a practical system. In this paper, we tackle this problem as part of a utility maximization problem framed in earlier papers that includes both scheduling and resource allocation. Using an information theoretic model for the achievable rate per code results in a tractable convex optimization problem. By exploiting the structure of this problem, we give algorithms for finding the optimal solution with geometric convergence. We also use insights obtained from the optimal solution to construct low complexity near optimal algorithms that are easily implementable. Numerical results comparing these algorithms are also given. 1
A Fluid Analysis of a Utilitybased Wireless Scheduling Policy
 IEEE TRANS. ON INFORMATION THEORY
, 2006
"... We consider packet scheduling for the downlink in a wireless network, where each packet’s service preferences are captured by a utility function that depends on the total delay incurred. The goal is to schedule packet transmissions to maximize the total utility. In this setting, we examine a simple ..."
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Cited by 17 (3 self)
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We consider packet scheduling for the downlink in a wireless network, where each packet’s service preferences are captured by a utility function that depends on the total delay incurred. The goal is to schedule packet transmissions to maximize the total utility. In this setting, we examine a simple gradientbased scheduling algorithm called the ˙ URrule, which is a type of generalized cµrule (Gcµ) that takes into account both a user’s channel condition and derived utility when making scheduling decisions. We study the performance of this scheduling rule for a draining problem, where there is a given set of initial packets and no further arrivals. We formulate a “large system” fluid model for this draining problem where the number of packets becomes large while the packetsize decreases to zero, and give a complete characterization of the behavior of the UR scheduling rule in this limiting regime. Comparison with simulation results show that the fluid limit accurately predicts the corresponding behavior of finite systems of interest. We then give an optimal control formulation for finding the optimal scheduling policy for the fluid draining model. Using Pontryagin’s minimum principle, we show that, when the user rates are chosen from a TDMtype of capacity region, the ˙ UR rule is in fact optimal in many cases. Sufficient conditions for optimality are also given. Finally, we consider a general capacity region and show that the ˙ UR rule is optimal only in special cases. This work was supported by the NorthwesternMotorola Center for Communications, and by NSF under grants CCR
Downlink joint basestation assignment and packet scheduling algorithm for cellular CDMA/TDMA networks
 in IEEE ICC
"... Abstract — In this paper using a utilitybased approach, downlink packet transmission in a CDMA/TDMA cellular network is formulated as an optimization problem. A utility function corresponds to each packet served by a basestation that is an increasing function of the packet experienced delay and th ..."
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Abstract — In this paper using a utilitybased approach, downlink packet transmission in a CDMA/TDMA cellular network is formulated as an optimization problem. A utility function corresponds to each packet served by a basestation that is an increasing function of the packet experienced delay and the channel gain, and a decreasing function of the basestation load. Unlike previous works, in this paper, the optimization objective is to maximize the total network utility instead of the basestation utility. We show that this optimization results in joint basestation assignment and packet scheduling. Therefore, in addition to multiuser diversity, the proposed method also exploits multiaccesspoint diversity and soft capacity. A polynomial time heuristic algorithm is then proposed to solve the optimization problem. Simulation results indicate a significant performance improvement in terms of packetdropratio and achieved throughput. I.
A Channel and Rate Assignment Algorithm and a Layer2.5 Forwarding Paradigm for MultiRadio Wireless Mesh Networks
"... Abstract—The availability of costeffective wireless network interface cards makes it practical to design network devices with multiple radios which can be exploited to simultaneously transmit/receive over different frequency channels. It has been shown that using multiple radios per node increases ..."
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Cited by 13 (2 self)
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Abstract—The availability of costeffective wireless network interface cards makes it practical to design network devices with multiple radios which can be exploited to simultaneously transmit/receive over different frequency channels. It has been shown that using multiple radios per node increases the throughput of multihop wireless mesh networks. However, multiradios create several research challenges. A fundamental problem is the joint channel assignment and routing problem, i.e., how the channels can be assigned to radios and how a set of flow rates can be determined for every network link in order to achieve an anticipated objective. This joint problem is NPcomplete. Thus, an approximate solution is developed by solving the channel assignment and the routing problems separately. The channel assignment problem turns out to be the problem to assign channels such that a given set of flow rates are schedulable and itself is shown to be also NPcomplete. This paper shows that not only the channels but also the transmission rates of the links have to be properly selected to make a given set of flow rates schedulable. Thus, a greedy heuristic for the channel and rate assignment problem is developed. Algorithms to schedule the resulting set of flow rates have been proposed in the literature, which require synchronization among nodes and hence modified coordination functions. Unlike previous work, in this paper a forwarding paradigm is developed to achieve the resulting set of flow rates while using a standard MAC. A bidimensional Markov chain model of the proposed forwarding paradigm is presented to analyze its behavior. Thorough performance studies are conducted to: a) compare the proposed greedy heuristic to other channel assignment algorithms; b) analyze the behavior of the forwarding paradigm through numerical simulations based on the Markov chain model; c) simulate the operations of the forwarding paradigm and evaluate the achieved network throughput. Index Terms—Multiradio wireless mesh networks, channel assignment, physical model of interference, layer2.5 forwarding paradigm.