197131
Multi-hop Cross-Layer Design in Wireless Sensor Networks: A Case Study
Cross-layer design has been proposed as a promising paradigm to tackle various problems of wireless communication systems. Recent research has led to a variety of protocols that rely on intensive interaction between different layers of the classical layered OSI protocol architecture. These protocols involve different layers and introduce new ideas how layers shall communicate and interact. In existing cross-layer approaches, the violation of the OSI architecture typically consists in passing information between different adjacent or non-adjacent layers of one single station's protocol stack to solve an optimization problem and exploiting the dependencies between the layers. This paper proposes to go a step further and to consider cross-layer information exchange across different layers of multiple stations involved in multi-hop communication systems. It outlines possible application scenarios of this approach, and trades off between advantages and disadvantages of the proposed \emph {multi-hop cross-layer design}. It examines an application scheme in a scenario of a wireless sensor network environment operating with a recent energy-efficient power saving protocol.
13946371
Self-Learning Disk Scheduling
Performance of disk I/O schedulers is affected by many factors, such as workloads, file systems, and disk systems. Disk scheduling performance can be improved by tuning scheduler parameters, such as the length of read timers. Scheduler performance tuning is mostly done manually. To automate this process, we propose four self-learning disk scheduling schemes: change-sensing Round-Robin, feedback learning, per-request learning, and two-layer learning. experiments show that the novel two-layer learning scheme performs best. It integrates the workload-level and request-level learning algorithms. It employs feedback learning techniques to analyze workloads, change scheduling policy, and tune scheduling parameters automatically. We discuss schemes to choose features for workload learning, divide and recognize workloads, generate training data, and integrate machine learning algorithms into the two-layer learning scheme. We conducted experiments to compare the accuracy, performance, and overhead of five machine learning algorithms: decision tree, logistic regression, naive Bayes, neural network, and support vector machine algorithms. Experiments with real-world and synthetic workloads show that self-learning disk scheduling can adapt to a wide variety of workloads, file systems, disk systems, and user preferences. It outperforms existing disk schedulers by as much as 15.8% while consuming less than 3%-5% of CPU time.
17509795
Collaborative attacks in WiMAX networks
Summary In this paper, we discuss security problems, with a focus on collaborative attacks, in the Worldwide Interoperability for Microwave Access (WiMAX) scenario. The WiMAX protocol suite, which includes but is not limited to DOCSIS, DES, and AES, consists of a large number of protocols. We present briefly the WiMAX standard and its vulnerabilities. We pinpoint the problems with individual protocols in the WiMAX protocol suite, and discuss collaborative attacks on WiMAX systems. We present several typical WiMAX attack scenarios, including: bringing a large number of attackers to increase their computation power and break WiMAX protocols; assembling a sufficient number of attackers to influence the decision-making of core machines, which includes routing attacks and Sybil attacks; and exploiting implementations that do not conform to the WiMAX specification completely, causing interoperability problems among various protocols, including the ones in typical WiMAX/WiFi/LAN deployment scenarios. We present theoretical models and practical solutions to profile, model, and analyze collaborative attacks in WiMAX. We employ attack graphs to do vulnerability analysis. Experimental results verify our models and validate our analysis. Copyright © 2009 John Wiley & Sons, Ltd.
6059000
Preserving User Location Privacy in Mobile Data Management Infrastructures
Location-based services, such as finding the nearest gas station, require users to supply their location information. However, a user's location can be tracked without her consent or knowledge. Lowering the spatial and temporal resolution of location data sent to the server has been proposed as a solution. Although this technique is effective in protecting privacy, it may be overkill and the quality of desired services can be severely affected. In this paper, we suggest a framework where uncertainty can be controlled to provide high quality and privacy-preserving services, and investigate how such a framework can be realized in the GPS and cellular network systems. Based on this framework, we suggest a data model to augment uncertainty to location data, and propose imprecise queries that hide the location of the query issuer and yields probabilistic results. We investigate the evaluation and quality aspects for a range query. We also provide novel methods to protect our solutions against trajectory-tracing. Experiments are conducted to examine the effectiveness of our approaches.
15016600
Addressing Collaborative Attacks and Defense in Ad Hoc Wireless Networks
Since ad hoc networks rely on nodes cooperation to establish communication, malicious nodes can compromise the entire network. If they collaborate the devastation is even worse. Collaborative attacks may cause more devastating impacts on wireless environments than single and uncoordinated groups of attacks, as they combine efforts of more than one attacker against the target victim. In this paper, we present the most important forms of attacks,discuss possible collaborations among attackers, show how machine learning techniques and signal processing techniques can be used to detect and defend against collaborative attacks in such environments, and discuss implementation issues.
1039556
Indexing Noncrashing Failures: A Dynamic Program Slicing-Based Approach
Recent software systems usually feature an automated failure reporting component, with which a huge number of failures are collected from software end-users. With a proper support of failure indexing, which identifies failures due to the same fault, the collected failure data can help developers prioritize failure diagnosis, among other utilities of the failure data. Since crashing failures can be effectively indexed by program crashing venues, current practice has seen great success in prioritizing crashing failures. A recent study of bug characteristics indicates that as excellent memory checking tools are widely adopted, semantic bugs and the resulting noncrashing failures have become dominant. Unfortunately, the problem of how to index non-crashing failures has not been seriously studied before. In previous study, two techniques have been proposed to index noncrashing failures, and they are T-Proximity and R-Proximity. However, as T-Proximity indexes failures by the profile of the entire execution, it is generally not effective because most information in the profile is fault-irrelevant. On the other hand, although R-Proximity is more effective than T-Proximity, it relies on a sufficient number of correct executions that may not be available in practice. In this paper, we propose a dynamic slicing-based approach, which does not require any correct executions, and is comparably effective as R-Proximity. A detailed case study with gzip is reported, which clearly strates the advantages of the proposed approach.
5001846
Propagation characteristics of wideband MIMO channel in urban micro- and macrocells
The wideband channel measurements at 580 MHz, 2.35 GHz and 4.90 GHz have been performed in the urban micro- and macrocell scenarios in the cities of China with multiple-input multiple-output (MIMO) channel sounder. The measured cases include line-of-sight (LOS) and non-line-of-sight (NLOS) propagation. Statistical results and comparative analysis for both scenarios are presented in this paper, including path loss (PL), root mean square (rms) delay spread (DS) and maximum excess delay (maxED), and angular spread (AS). In NLOS case, the frequency dependent factor (FDF) is observed as 32.1 by fitting the PL model of 2.35 GHz and 4.90 GHz. Moreover, a larger rms DS in urban microcell and AS at both base station (BS) and mobile subscriber (MS) are found for the denser and higher buildings in the cities of China. As the frequency varying from 580 MHz to 4.90 GHz, the median rms DS is decreased from 330 ns to 130 ns for NLOS case.
44610157
A New Robust Bandpass Sampling Scheme for Multiple RF Signals in SDR System
Software defined radio (SDR) technology has been widely applied for its powerful universality and flexibility in the past decade. To address the issue of bandpass sampling of multiband signals, a novel and efficient method of finding the minimum valid sampling frequency is proposed. Since there are frequency deviations due to the channel effect and hardware instability in actual systems, we also consider the guard-bands between downconverted signal spectra in determining the minimum sampling frequency. In addition, the case that the spectra within the sampled bandwidth are located in inverse placement can be avoided by our proposed method, which will reduce the complexity of the succeeding digital signal process significantly. Simulation results illustrate that the proper minimum sampling frequency can be determined rapidly and accurately.
6114653
Alignment of Optical Maps
An adjustable device that provides a secure anchor in a crevice or other irregularity. The anchor may be used to assist rock climbers, rescue groups, military personnel, construction workers, etc. The device is comprised of a spring loaded sleeve mounted on a first end of a threaded shaft and limited in its movement on the shaft by a pin and slot arrangement. The sleeve provides a means for adjusting the length of the device. A first locking means releasably secures the sleeve in a retracted position, and a second locking means secures the sleeve at the desired extended position. A lever assembly is provided at the second end of the device in such a manner that a force applied to an attachment point of the assembly will be translated along the longitudinal axis of the device.
2899555
Scalable Video Transmission over the IEEE 802.11e Networks Using Cross-Layer Rate Control
This paper presents a novel cross-layer rate control scheme for optimizing 3D wavelet scalable video transmission over the IEEE 802.11e wireless local area networks. The proposed scheme consists of a macro and a micro rate control schemes residing at the application layer and the network sublayer respectively. The macro rate control uses bandwidth estimation to achieve optimal bit allocation with minimum distortion. The micro rate control employs an adaptive mapping of packets using video classifications. This prioritizes appropriately the video traffic to maximize the transmission protection to the important video packets. The performance is investigated by simulations showing advantages of our cross-layer design.
24687403
A synthesis scheme for simultaneous scheduling, binding, partitioning and placement with resources operating at multiple voltages
One promising technique to reduce power consumption is to power a chip with multiple supply voltages. However, as noticed by M.C. Johnson and K. Roy (see ACM Trans. Design Auto. Electronic Syst., vol.2, p.227-48, 1997), multiple voltage designs can cause a number of serious layout problems. We have shown that the layout problems can be partially solved by the addition of a partitioning step into the synthesis flow. A more subtle solution to solve the layout problems requires placement also to be included in the design flow. We present a synthesis scheme, following a simulated annealing engine, to minimize power consumption and area with resources operating at multiple voltages under timing constraints. The scheme simultaneously considers many correlated factors, such as scheduling, binding, partitioning and placement, to reduce power consumption due to both functional units and interconnections between and among them. Experiments with a number of DSP benchmarks show that the proposed algorithm can achieve significant reduction in power and area.