5138654
LISP: a link-indexed statistical traffic prediction approach to improving IEEE 802.11 PSM
We present a novel and complementary mechanism, called link-indexed statistical traffic predictor (LISP) to improve IEEE 802.11 power saving mechanism (PSM). LISP employs a simple, light-weight traffic prediction mechanism and enables each node to seek the inherent correlation between ATIM.ACKs and incoming traffic. Thereby nodes en route can stay awake in the BI in which a packet is anticipated to arrive, thus bridging a "freeway" for the packet to rapidly traverse the route. Meanwhile, the number of duty cycles is minimized and more energy is conserved. We conduct analytical and simulation studies and demonstrate the effectiveness of LISP.
14717474
A Novel Approach to Contention Control in IEEE 802.11e-Operated WLANs
In this paper, we devise, in compliance with the IEEE 802.11e protocol, a novel MAC-centric approach, called MAC contention control (MCC), to maximizing the bandwidth utilization and achieving proportional bandwidth allocation. We first show that approaches based on estimating the number of competing nodes and then setting the contention window size may not converge (and in some cases diverge) because of network dynamics. Then, by studying the optimality condition derived in our prior work, we identify two parameters (referred to as control references) that remain approximately constant when the network operates at the optimal operational point, regardless of the number of competing nodes in each AC. We instrument MCC to measure these control references, compare measurement results to their optimal control reference levels, and adjust the packet dequeuing rate from the interface queues in an additive-increase-multiplicative-decrease (AIMD) fashion and with respect to prespecified bandwidth allocation ratio associated with its AC. In some sense, MCC controls the rate of passing packets from the interface queues to to the MAC access function, and thus practically controls the effective number of competing nodes. We have conducted an extensive simulation study, and demonstrated the superiority of MCC to 802.11e in terms of both the achievable network throughput and the capability of achieving proportional bandwidth allocation. This, coupled with the fact that MCC does not require change in firmware and can be practically deployed, makes MCC a viable approach to contention control in IEEE 802.11e-operated WLANs.
5668129
A reactive channel model for expediting wireless network simulation
A major problem with leveraging event-driven, packet-level simulation environments, such as ns2[6], J-Sim[1], OpNet[2]), and QualNet[3]), in conducting wireless network simulation is the vast number of events generated, a majority of which are related to signal transmission in the PHY/MAC layers.In this extended abstract, we investigate the operations of signal transmission in the various stages: signal propagation, signal interference, and interaction with the PHY/MAC layers, and identify where events can be reduced without impairing the accuracy. We propose to leverage the MAC/PHY state information, and devise (from the perspective of network simulation) a reactive channel model (RCM) in which nodes explicitly register their interests in receiving certain events according to the MAC/PHY states they are in and the corresponding operations that should be performed. The simulation study indicates that RCM renders an order of magnitude of speed-up without compromising the accuracy of simulation results. An advantage of RCM with respect to the implementation is that there is no need to re-design the channel model for each specific MAC layer, and the modification made in the MAC/PHY layers is quite modest (e.g., a few API changes). This, coupled with the performance gain, suggests that RCM is an attractive, light-weight mechanism for expediting wireless network simulation.
14850039
Provisioning Quality Controlled Medium Access in UltraWideBand-Operated WPANs
Quality of service (QoS) provisioning is one of the most important criteria in newly emerging UWB-operated WPANs, as they are expected to support a wide variety of applica- tions from time-constrained, multimedia streaming to throughput- hungry, content transfer applications. As such, the Enhanced Distributed Coordinated Access (EDCA) mechanism has been adopted by MultiBand OFDM Alliance in its UWB MAC proposal. In this paper, we conduct a rigorous, comprehensive, theoretical analysis and show that with the currently recommended parame- ter setting, EDCA cannot provide adequate QoS. In particular, without responding to the system dynamics (e.g., taking into account of the number of active class-i stations), EDCA cannot allocate bandwidth in a deterministic proportional manner and the system bandwidth is under-utilized. After identifying the deficiency of EDCA, we propose, in compliance with the EDCA-incorporated UWB MAC protocol proposed in (15) (20), a framework, along with a set of theoretically grounded methods for controlling medium access with determin- istic QoS for UWB networks. We show that in this framework, 1) real-time traffic is guaranteed of deterministic bandwidth via a contention-based reservation access method; 2) best-effort traffic is provided with deterministic proportional QoS; and moreover, 3) the bandwidth utilization is maximized. We have also validated and evaluated the QoS provisioning capability and practicality of the proposed MAC framework both via simulation and empirically by leveraging the MADWifi (Multiband Atheros Driver for WiFi) Linux driver for Wireless LAN devices with the Atheros chipset.
9059175
On thermal effects in deep sub-micron VLSI interconnects
This paper presents a comprehensive analysis of the thermal effects in advanced high performance interconnect systems arising due to self-heating under various circuit conditions, including electrostatic discharge. Technology (Cu, low-k etc.) and scaling effects on the thermal characteristics of the interconnects, and on their electromigration reliability has been analyzed simultaneously, which will have important implications for providing robust and aggressive deep sub-micron interconnect design guidelines. Furthermore, the impact of these thermal effects on the design (driver sizing) and optimization of the interconnect length between repeaters at the upper-level signal lines are investigated.
1743563
Toward an evaluation infrastructure for power and energy optimizations
Execution-driven simulators are often used for power/energy and performance evaluation. Simulators can provide semantic details but they provide insufficient speed and accuracy for compiler and OS research. Physical measurement is fast and objective but lacks a semantic connection between the measurement result and the evaluated program. The objective of our research is to bring together the advantages of simulation and physical measurement to build an infrastructure for power and energy optimization. Power and energy behavior is obtained through physical measurement. Simulation is used for observing the connection between power and energy behavior and the evaluated program. Our preliminary results demonstrate the ability of this infrastructure to capture detailed power behavior of any region of a program. To simplify the power/energy evaluation of programs with long execution times and overcome the limitation of physical devices, we propose using the SimPoints methodology developed by researchers at UC San Diego to find representative slices of a program. Through simulation, we validate the feasibility of the SimPoint idea in simplifying power/energy evaluation. We expect that this infrastructure will help researchers in OS/compiler power/energy optimization to evaluate their optimizations more efficiently and observe more optimization opportunities.
20310851
A mobile agent-based active network architecture for intelligent network control
The innovation and evolution of network technologies and services to enhance network functionality have traditionally encountered the problems of backward-compatibility and standardization. To resolve the related issues, active networks have been introduced to enable specific customization of network functionality without the lengthy standard-mediated committee processes. In this paper, we exploit the capability of mobile agent technology to construct an active network architecture. We argue that the mobile agent can be a building block for specific network customizations, and introduction of new network functionality. Both integrated and discrete operational models of network customizations can be supported in our prototype implementation. For the service development and deployment, an abstract service structure and a service loading mechanism are presented. Furthermore, we provide an agent management/control mechanism and devise a service management/control mechanism, which is either not available or incomplete in the other related work. The proposed architecture allows new service introduction, and as a result, achieves improved network functionality.
14245590
RED with optimized dynamic threshold deployment on shared buffer
Prior survey of RED algorithm deployment on multiqueue system with shared buffer was unfair and sensitive to congestion level by statically setting the parameters. In this paper, our goal is to deploy the Random Early Detection (RED) algorithm in routers on shared buffer and solve these problems. A novel buffer management scheme that dynamically adjusts the parameters of RED named RED-ODT is proposed. Simulations under uniform traffic load and nonuniform traffic load are given, the results of which ascertain and demonstrate the superiority of the proposed scheme in terms of low packet drop ratio, satisfying buffer utilization and fairness. Simulation also shows that RED-ODT is insensitive to congestion level.
146722
Adaptive dissemination of dynamic information services in an extended data broadcast environment
Considering that most information broadcast services generate data dynamically in practice, we devise in this paper an extended data broadcast mechanism which supports not only the original data broadcast scenario but also the dissemination of dynamic inforamtion services. Furthermore, we design an on-line loan-based slot allocation and feedback technique to tolerate the dynamic changes of broadcast traffic and accordingly perform the adaptation of service classification, bandwidth allocation and broadcast schedule so as to enhance the performance. Our experimental studies show that the extended data broadcast mechanism associated with the loan-based feedback technique is able to achieve a substantial saving in message traffic for dynamic information dissemination in wireless networks.