Results 1 - 10
of
338
Opportunistic Media Access for Multirate Ad Hoc Networks
, 2002
"... The IEEE 802.11 wireless media access standard supports multiple data rates at the physical layer. Moreover, various auto rate adaptation mechanisms at the medium access layer have been proposed to utilize this multi-rate capability by automatically adapting the transmission rate to best match the c ..."
Abstract
-
Cited by 332 (12 self)
- Add to MetaCart
The IEEE 802.11 wireless media access standard supports multiple data rates at the physical layer. Moreover, various auto rate adaptation mechanisms at the medium access layer have been proposed to utilize this multi-rate capability by automatically adapting the transmission rate to best match the channel conditions. In this paper, we introduce the Opportunistic Auto Rate (OAR) protocol to better exploit durations of high-quality channels conditions. The key mechanism of the OAR protocol is to opportunistically send multiple back-to-back data packets whenever the channel quality is good. As channel coherence times typically exceed multiple packet transmission times for both mobile and nonmobile users, OAR achieves significant throughput gains as compared to state-of-the-art auto-rate adaptation mechanisms. Moreover, over longer time scales, OAR ensures that all nodes are granted channel access for the same time-shares as achieved by single-rate IEEE 802.11. We describe mechanisms to implement OAR on top of any existing auto-rate adaptation scheme in a nearly IEEE 802.11 compliant manner. We also analytically study OAR and characterize the gains in throughput as a function of the channel conditions. Finally, we perform an extensive set of ns-2 simulations to study the impact of such factors as node velocity, channel conditions, and topology on the throughput of OAR.
Achieving MAC Layer Fairness in Wireless Packet Networks
, 2000
"... Link-layer fairness models that have been proposed for wireline and packet cellular networks cannot be generalized for shared channel wireless networks because of the unique characteristics of the wireless channel, such as location-dependent contention, inherent conflict between optimizing channel u ..."
Abstract
-
Cited by 242 (2 self)
- Add to MetaCart
Link-layer fairness models that have been proposed for wireline and packet cellular networks cannot be generalized for shared channel wireless networks because of the unique characteristics of the wireless channel, such as location-dependent contention, inherent conflict between optimizing channel utilization and achieving fairness, and the absence of any centralized control. In this paper, we propose a general analytical framework that captures the unique characteristics of shared wireless channels and allows the modeling of a large class of systemwide fairness models via the specification of per-flow utility functions. We show that system-wide fairness can be achieved without explicit global coordination so long as each node executes a contention resolution algorithm that is designed to optimize its local utility function. We present a general mechanism for translating a given fairness model in our framework into a corresponding contention resolution algorithm. Using this translation...
Opportunistic transmission scheduling with resource-sharing constraints in wireless networks
- IEEE Journal on Selected Areas in Communications
, 2001
"... We present an “opportunistic ” transmission scheduling policy that exploits time-varying channel conditions and maxi-mizes the system performance stochastically under a certain resource allocation constraint. We establish the optimality of the scheduling scheme, and also that every user experiences ..."
Abstract
-
Cited by 222 (9 self)
- Add to MetaCart
We present an “opportunistic ” transmission scheduling policy that exploits time-varying channel conditions and maxi-mizes the system performance stochastically under a certain resource allocation constraint. We establish the optimality of the scheduling scheme, and also that every user experiences a performance improvement over any non-opportunistic scheduling policy when users have independent performance values. We demonstrate via simulation results that the scheme is robust to es-timation errors, and also works well for nonstationary scenarios, resulting in performance improvements of 20–150 % compared with a scheduling scheme that does not take into account channel conditions. Last, we discuss an extension of our opportunistic scheduling scheme to improve “short-term ” performance.
Packet fair queueing algorithms for wireless networks with location-dependent errors
, 2000
"... ..."
(Show Context)
A framework for opportunistic scheduling in wireless networks,”
- Computer Networks,
, 2003
"... Abstract-Scheduling has been extensively studied in various disciplines in operations research and wireline networking. However, the unique characteristics of wireless communication systems -namely, timing-varying channel conditions and multiuser diversity -means that new scheduling solutions need ..."
Abstract
-
Cited by 167 (8 self)
- Add to MetaCart
(Show Context)
Abstract-Scheduling has been extensively studied in various disciplines in operations research and wireline networking. However, the unique characteristics of wireless communication systems -namely, timing-varying channel conditions and multiuser diversity -means that new scheduling solutions need to be developed that are specifically tailored for this environment. In this paper, we summarize various opportunistic scheduling schemes that exploit the time-varying nature of the radio environment to improve the spectrum efficiency while maintaining a certain level of satisfaction for each user. We also discuss the advantages and costs associated with opportunistic scheduling, and identify possible future research directions.
A New Model for Packet Scheduling in Multihop Wireless Networks
, 2000
"... The goal of packet scheduling disciplines is to achieve fair and maximum allocation of channel bandwidth. However, these two criteria can potentially be in conflict in a generic topology multihop wireless network where a single logical channel is shared among multiple contending ows and spatial reus ..."
Abstract
-
Cited by 153 (8 self)
- Add to MetaCart
The goal of packet scheduling disciplines is to achieve fair and maximum allocation of channel bandwidth. However, these two criteria can potentially be in conflict in a generic topology multihop wireless network where a single logical channel is shared among multiple contending ows and spatial reuse of the channel bandwidth is possible. In this paper, we propose a new model for packet scheduling that addresses this conflict. The main results of this paper are the following: (a) a two-tier service model that provides a minimum "fair" allocation of the channel bandwidth for each packet flow and additionally maximizes spatial reuse of bandwidth, (b) an ideal centralized packet scheduling algorithm that realizes the above service model, and (c) a practical distributed backoff-based channel contention mechanism that approximates the ideal service within the framework of the CSMA/CA protocol.
INSIGNIA: An IP-Based Quality of Service Framework for Mobile ad Hoc Networks
- Journal of Parallel and Distributed Computing
, 2000
"... this paper, we present the design, implementation, and evaluation of the INSIGNIA QOS Framework that supports the delivery of adaptive services in mobile ad hoc networks. A key component of our QOS framework is the INSIGNIA signaling system, an in-band signaling system that supports fast reservation ..."
Abstract
-
Cited by 150 (6 self)
- Add to MetaCart
(Show Context)
this paper, we present the design, implementation, and evaluation of the INSIGNIA QOS Framework that supports the delivery of adaptive services in mobile ad hoc networks. A key component of our QOS framework is the INSIGNIA signaling system, an in-band signaling system that supports fast reservation, restoration, and adaptation algorithms that are specifically designed to deliver adaptive service. The signaling system is designed to be lightweight and highly responsive to changes in network topology, node connectivity, and end-to-end quality of service conditions. The structure of the paper is as follows. We discuss our framework in the context of the related work and present the main design considerations that have influenced our thinking in Sections 2 and 3, respectively. Section 4 presents an overview of the INSIGNIA QOS framework. The detailed design of the INSIGNIA signaling system is given in Section 5. We evaluate our QOS framework in Section 6, paying particular attention to the performance of the signaling system under a variety of network conditions. Our simulation results show the benefit of the INSIGNIA QOS framework under diverse mobility, traffic, and channel conditions in support of fast reservation, restoration, and adaptation. Finally, we present our conclusion in Section 7
Distributed multi-hop scheduling and medium access with delay and throughput constraints
, 2001
"... Providing quality of service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypotheti ..."
Abstract
-
Cited by 110 (3 self)
- Add to MetaCart
(Show Context)
Providing quality of service in random access multi-hop wireless networks requires support from both medium access and packet scheduling algorithms. However, due to the distributed nature of ad hoc networks, nodes may not be able to determine the next packet that would be transmitted in a (hypothetical) centralized and ideal dynamic priority scheduler. In this paper, we develop two mechanisms for QoS communication in multi-hop wireless networks. First, we devise distributed priority scheduling, a technique that piggybacks the priority tag of a node’s head-of-line packet onto handshake and data packets; e.g., RTS/DATA packets in IEEE 802.11. By monitoring transmitted packets, each node maintains a scheduling table which is used to assess the node’s priority level relative to other nodes. We then incorporate this scheduling table into existing IEEE 802.11 priority back-off schemes to approximate the idealized schedule. Second, we observe that congestion, link errors, and the random nature of medium access prohibit an exact realization of the ideal schedule. Consequently, we devise a scheduling scheme termed multi-hop coordination so that downstream nodes can increase a packet’s relative priority to make up for excessive delays incurred upstream. We next develop a simple analytical model to quantitatively explore these two mechanisms. In the former case, we study the impact of the probability of overhearing another packet’s priority index on the scheme’s ability to achieve the ideal schedule. In the latter case, we explore the role of multi-hop coordination in increasing the probability that a packet satisfies its end-to-end QoS target. Finally, we perform a set of ns-2 simulations to study the scheme’s performance under more realistic conditions. 1.
Scheduling algorithms for broadband wireless networks
- Proc. IEEE
, 2001
"... Scheduling algorithms that support quality of service (QoS) dif-ferentiation and guarantees for wireless data networks are crucial to the development of broad-band wireless networks. Wireless com-munication poses special problems that do not exist in wireline net-works, such as time-varying channel ..."
Abstract
-
Cited by 109 (5 self)
- Add to MetaCart
(Show Context)
Scheduling algorithms that support quality of service (QoS) dif-ferentiation and guarantees for wireless data networks are crucial to the development of broad-band wireless networks. Wireless com-munication poses special problems that do not exist in wireline net-works, such as time-varying channel capacity and location-depen-dent errors. Although many mature scheduling algorithms are avail-able for wireline networks, they are not directly applicable in wire-less networks because of these special problems. This paper pro-vides a comprehensive and in-depth survey on recent research in wireless scheduling. The problems and difficulties in wireless sched-uling are discussed. Various representative algorithms are exam-ined. Their themes of thoughts and pros and cons are compared and analyzed. At the end of the paper, some open questions and future research directions are addressed. Keywords—Broad-band wireless networks, QoS, scheduling. I.
