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International Conference on Broadband Networks (BroadNets)

作者： G. Sudha Anil Kumar G. Manimaran Z. Wang Real Time Computing and Networking Laboratory Department of Electrical and Computer Engineering Iowa State University Ames IA USA

ISBN: (纸本)9781424414321

In this paper, we address the problem of scheduling a set of periodic real-time messages in a wireless network with the objective of minimizing the total energy consumption while meeting deadline and reliability constraints. We formally prove that this problem is NP-hard and solve it in two stages. First, we consider a simple model that assumes that the wireless channel is completely reliable and the network is fully provisioned. Using the technique of employing multiple hop-by-hop transmissions instead of a single direct hop transmission as the basis, we prove that the strategy of choosing the hop distances such that they are equidistant is optimal in terms of energy consumption under the deadline constraint. Based on the intuition provided by the optimal strategy, we present heuristic scheduling algorithms for a more realistic wireless channel model and network condition. Our simulation results show that the proposed scheduling algorithms provide significant energy savings over the baseline algorithms

关键词： Wireless networks Energy consumption Scheduling algorithm Wireless application protocol Throughput Access protocols Streaming media Resource management Processor scheduling Computer network reliability

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Energy-Aware Scheduling of real-time Tasks in Wireless Networked Embedded Systems

Energy-Aware Scheduling of Real-Time Tasks in Wireless Netwo...

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real-time Systems Symposium (RTSS)

作者： G. Sudha Anil Kumar G. Manimaran Z. Wang Real-Time Computing and Networking Laboratory Department of Electrical and Computer Engineering Iowa State University Ames IA USA

Recent technological advances have opened up several distributed real-time applications involving battery-driven embedded devices with local processing and wireless communication capabilities. Energy management is the key issue in the design and operation of such systems. In this paper, we consider a single-hop networked real-time embedded system where each node supports both dynamic voltage scaling (DVS) and dynamic modulation scaling (DMS) power management techniques to tradeoff time for energy savings. In this model, we address the problem of scheduling periodic complex tasks where each task consists of several precedence constrained message passing sub-tasks. Our contributions towards this problem are twofold. First, we analyze the system level energy-time tradeoffs considering both the computation and communication workloads by defining a novel energy gain metric. We then present static (centralized) and dynamic (distributed) energy gain based slack allocation algorithms which reduce the total energy consumption, while guaranteeing the ready time, deadline and precedence constraints. We compare the performance of the proposed algorithms with several baseline algorithms through simulation studies. Our results show that the proposed algorithms perform significantly better than the baseline algorithms for the simulated conditions. Finally, we identify several interesting energy-aware research problems in the area of networked real-time embedded systems.

关键词： real time systems Embedded system Energy management Wireless communication Dynamic voltage scaling Voltage control Computer network management Power system management Power system modeling Processor scheduling

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An intra-task DVS algorithm exploiting program path locality for real-time embedded systems

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12th International Conference on High Performance computing, HiPC 2005

作者： Kumar, G. Sudha Anil Manimaran, G. Real-Time Computing and Networking Laboratory Dept. of Electrical and Computer Engineering Iowa State University Ames IA 50011 United States

ISBN: (纸本)3540309365

In this paper, we present a novel intra-task Dynamic Voltage Scheduling (DVS) algorithm based on the knowledge of frequently executed paths in the control flow graph for real-time embedded systems. The basic idea is to construct a common path composing all the frequently executed paths (hot-paths) and perform DVS scheduling based on this common path, rather than the most probable path. We compare the performance (energy consumption) of our algorithm with a recently proposed algorithm. Our simulation results show that the proposed algorithm performs better than the existing algorithm for most of the simulated conditions. We also identify interesting research problems in this context. © Springer-Verlag Berlin Heidelberg 2005.

关键词： Algorithms

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Spectrum agile radio: radio resource measurements for opportunistic spectrum usage

Spectrum agile radio: radio resource measurements for opport...

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IEEE Global Telecommunications Conference, 2004. GLOBECOM '04.

作者： S. Mangold Zhun Zhong K. Challapali Chun-Ting Chou Wireless Communication and Networking Department Philips Research Briarcliff Manor NY USA Real-Time Computing Laboratory University of Michigan Ann Arbor MI USA

Radio spectrum allocation is undergoing radical rethinking. Regulators, government agencies, industry, and the research community have recently established many initiatives for new spectrum policies and seek approaches to more efficiently manage the radio spectrum. In this paper, we examine new approaches, namely, spectrum agile radios, for opportunistic spectrum usage. Spectrum agile radios use parts of the radio spectrum that were originally licensed to other radio services. A spectrum agile radio device seeks opportunities, i.e. unused radio resources. Devices communicate using the identified opportunities, without interfering with the operation of licensed radio devices. The identification of spectrum opportunities is coordinated by policies, which are defined by, and under the control of, the radio regulator. Our approach is motivated by the publications of the next generation communications, XG, research project of the USA-based Defense Advanced Research Projects Agency, DARPA. We focus on IEEE 802.11k for radio resource measurements as an approach to facilitate the development of spectrum agile radios.

关键词： Frequency Resource management Computer networks Regulators Radio spectrum management Radio control Consumer electronics Radio communication Wireless communication USA Councils

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Energy-efficient PCF operation of IEEE 802.11a wireless LAN

Energy-efficient PCF operation of IEEE 802.11a wireless LAN

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IEEE Annual Joint Conference: INFOCOM, IEEE Computer and Communications Societies

作者： Daji Qiao Sunghyun Choi A. Soomro K.G. Shin Real-Time Computing Laboratory University of Michigan Ann Arbor MI USA Wireless Communications and Networking Philips Research USA Briarcliff Manor NY USA

In this paper, we demonstrate the energy-efficient point coordination function (PCF) operation of IEEE 802.11a wireless LAN (WLAN) via both transmit power control (TPC) and physical layer (PHY) rate adaptation. First, we derive the energy-consumption performance analytically for uplink data transmissions under the PCF. From the evaluation results, we observe that significant energy savings can be achieved by combining TPC with adaptive PHY rate selection. A key requirement for a transmitter to select the most energy-efficient combination of transmit power level and PHY rate is the knowledge of the path loss between the receiver and itself. We present a novel scheme for accurate path loss estimation in 802.11 WLAN. Results and conclusions presented in this paper can serve as a valuable guidance or reference for the design of future 5 GHz 802.11 WLAN systems.

关键词： Energy efficiency Wireless LAN Physical layer Power control Data analysis Performance analysis Data communication Diversity reception Transmitters Propagation losses

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Load-sensitive routing of long-lived IP flows 99

Load-sensitive routing of long-lived IP flows

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Proceedings of the conference on Applications, technologies, architectures, and protocols for computer communication

作者： Anees Shaikh Jennifer Rexford Kang G. Shin Real-Time Computing Laboratory Department of EECS University of Michigan Ann Arbor MI Network Mathematics Research Networking and Distributed Systems AT&T Labs - Research Florham Park NJ

ISBN: (纸本)9781581131352

Internet service providers face a daunting challenge in provisioning network resources, due to the rapid growth of the Internet and wide fluctuations in the underlying traffic patterns. The ability of dynamic routing to circumvent congested links and improve application performance makes it a valuable traffic engineering tool. However, deployment of load-sensitive routing is hampered by the overheads imposed by link-state update propagation, path selection, and signaling. Under reasonable protocol and computational overheads, traditional approaches to load-sensitive routing of IP traffic are ineffective, and can introduce significant route flapping, since paths are selected based on out-of-date link-state information. Although stability is improved by performing load-sensitive routing at the flow level, flapping still occurs, because most IP flows have a short duration relative to the desired frequency of link-state updates. To address the efficiency and stability challenges of load-sensitive routing, we introduce a new hybrid approach that performs dynamic routing of long-lived flows, while forwarding short-lived flows on static preprovisioned paths. By relating the detection of long-lived flows to the timescale of link-state update messages in the routing protocol, route stability is considerably improved. Through simulation experiments using a one-week ISP packet trace, we show that our hybrid approach significantly outperforms traditional static and dynamic routing schemes, by reacting to fluctuations in network load without introducing route flapping.

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Load-sensitive routing of long-lived IP flows

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Computer Communication Review 1999年第4期29卷 215-226页

作者： Shaikh, Anees Rexford, Jennifer Shin, Kang G. Real-Time Computing Laboratory Department of EECS University of Michigan Ann Arbor MI 48109-2122 United States Netwk. Math. Res. Networking/D. S. AT and T Labs - Research Florham Park NJ 07932-0971 United States

关键词： Internet

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realizing services for guaranteed-QoS communication on a microkernel operating system

Realizing services for guaranteed-QoS communication on a mic...

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real-time Systems Symposium (RTSS)

作者： A. Mehra A. Shaikh T. Abdelzaher Zhiqun Wang K.G. Shin Real-Time Computing Laboratory University of Michigan Ann Arbor MI USA Server and Enterprise Networking IBM Thomas J. Watson Research Center Yorktown Heights NY USA

Provision of end-to-end QoS guarantees on communication necessitates appropriate support in the end systems (i.e., hosts) and network routers that form the communication fabric. The paper focuses on the architectural and implementation challenges involved in realizing QoS sensitive host communication subsystems on contemporary microkernel operating systems with limited real time support. We motivate and describe the components constituting our integrated service architecture that together ensure QoS sensitive handling of network traffic at both sending and receiving hosts and demonstrate a communication framework that can implement alternative QoS models by applying appropriate policies. An experimental evaluation in a controlled configuration demonstrates the efficacy with which QoS guarantees are maintained despite limitations imposed by the underlying operating system.

关键词： Operating systems Network servers real time systems Resource management Computer networks Laboratories Microwave integrated circuits Intserv networks Design optimization Electrical capacitance tomography

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Scalable hardware priority queue architectures for high-speed packet switches

Scalable hardware priority queue architectures for high-spee...

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3rd IEEE real-time Technology and Applications Symposium

作者： Moon, SW Shin, KG Rexford, J Real-Time Computing Laboratory Dept. of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI 48109 United States Network Mathematics Research Networking and Distributed Systems ATandT Labs Research Murray Hill NJ 07974 United States

ISBN: (纸本)0818680164

In packet-switched networks, queueing of packets at the switches can result when multiple connections share the same physical link. To accommodate a large number of connections, a switch can employ link-scheduling algorithms to prioritize the transmission of the queued packets. Due to the high-speed links and small packet sizes, a hardware solution is needed for the priority queue in order to make the link schedulers effective. But for good performance, the switch should also support a large number of priority levels (P) and be able to buffer a large number of packets (N). So a hardware priority queue design must be both fast and scalable (with respect to N and P) in order to be implemented effectively. In this paper, we first compare four existing hardware priority queue architectures, and identify scalability limitations on implementing these existing architectures for large N and P. Based on our findings, we propose two new priority queue architectures, and evaluate them using simulation results from Verilog HDL and Epoch implementations.

关键词： Computer architecture

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Scalable hardware priority queue architectures for high-speed packet switches

Scalable hardware priority queue architectures for high-spee...

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real-time Technology and Applications Symposium

作者： S.-W. Moon K.G. Shin J. Rexford Real-Time Computing Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor MI USA Network Mathematics Research Networking and Distributed Systems AT and T Research Laboratories Murray Hill NJ USA

In packet-switched networks, queueing of packets at the switches can result when multiple connections share the same physical link. To accommodate a large number of connections, a switch can employ link-scheduling algorithms to prioritize the transmission of the queued packets. Due to the high-speed links and small packet sizes, a hardware solution is needed for the priority queue in order to make the link schedulers effective. But for good performance, the switch should also support a large number of priority levels (P) and be able to buffer a large number of packets (N). So a hardware priority queue design must be both fast and scalable (with respect to N and P) in order to be implemented effectively. In this paper we first compare four existing hardware priority queue architectures, and identify scalability limitations on implementing these existing architectures for large N and P. Based on our findings, we propose two new priority queue architectures, and evaluate them using simulation results from Verilog HDL and Epoch implementations.

关键词： Packet switching Switches Traffic control Scheduling algorithm Asynchronous transfer mode Hardware design languages Communication system traffic control Computer architecture Moon real time systems

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