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Full-Text Articles in Computer Engineering

On Privacy Of Encrypted Speech Communications, Ye Zhu, Yuanchao Lu, Anil Vikram Jul 2012

On Privacy Of Encrypted Speech Communications, Ye Zhu, Yuanchao Lu, Anil Vikram

Electrical Engineering & Computer Science Faculty Publications

Silence suppression, an essential feature of speech communications over the Internet, saves bandwidth by disabling voice packet transmissions when silence is detected. However, silence suppression enables an adversary to recover talk patterns from packet timing. In this paper, we investigate privacy leakage through the silence suppression feature. More specifically, we propose a new class of traffic analysis attacks to encrypted speech communications with the goal of detecting speakers of encrypted speech communications. These attacks are based on packet timing information only and the attacks can detect speakers of speech communications made with different codecs. We evaluate the proposed attacks with ...


Cache Invalidation Strategies For Internet-Based Vehicular Ad Hoc Networks, Sunho Lim, Chansu Yu, Chita R. Das Feb 2012

Cache Invalidation Strategies For Internet-Based Vehicular Ad Hoc Networks, Sunho Lim, Chansu Yu, Chita R. Das

Electrical Engineering & Computer Science Faculty Publications

Internet-based vehicular ad hoc network (Ivanet) is an emerging technique that combines a wired Internet and a vehicular ad hoc network (Vanet) for developing an ubiquitous communication infrastructure and improving universal information and service accessibility. A key design optimization technique in Ivanets is to cache the frequently accessed data items in a local storage of vehicles. Since vehicles are not critically limited by the storage/memory space and power consumption, selecting proper data items for caching is not very critical. Rather, an important design issue is how to keep the cached copies valid when the original data items are updated ...


Many-To-One Communication Protocol For Wireless Sensor Networks, Chansu Yu, Robert Fiske, Seungmin Park, Won-Tae Kim Jan 2012

Many-To-One Communication Protocol For Wireless Sensor Networks, Chansu Yu, Robert Fiske, Seungmin Park, Won-Tae Kim

Electrical Engineering & Computer Science Faculty Publications

This paper proposes a novel communication protocol, called Many-to-One Sensors-to-Sink (MOSS), tailored to wireless sensor networks (WSNs). It exploits the unique sensors-to-sink traffic pattern to realize low-overhead medium access and low- latency sensors-to-sink routing paths. In conventional schedule-based MAC protocols such as S-MAC, sensor nodes in the proximity of the event generate reports simultaneously, causing unreliable and unpredictable performance during a brief but critical period of time when an event of interest occurs. MOSS is based on time division multiple access (TDMA) that avoids energy waste due to collisions, idle listening and overhearing and avoids unreliable behavior mentioned above. A ...


Traffic Analysis Attacks On Skype Voip Calls, Ye Zhu, Huirong Fu Jul 2011

Traffic Analysis Attacks On Skype Voip Calls, Ye Zhu, Huirong Fu

Electrical Engineering & Computer Science Faculty Publications

Skype is one of the most popular voice-over-IP (VoIP) service providers. One of the main reasons for the popularity of Skype VoIP services is its unique set of features to protect privacy of VoIP calls such as strong encryption, proprietary protocols, unknown codecs, dynamic path selection, and the constant packet rate. In this paper, we propose a class of passive traffic analysis attacks to compromise privacy of Skype VoIP calls. The proposed attacks are based on application-level features extracted from VoIP call traces. The proposed attacks are evaluated by extensive experiments over different types of networks including commercialized anonymity networks ...


Behavior-Based Mobility Prediction For Seamless Handoffs In Mobile Wireless Networks, Weetit Wanalertlak, Ben Lee, Chansu Yu, Myungchul Kim, Seung-Min Park, Won-Tae Kim Apr 2011

Behavior-Based Mobility Prediction For Seamless Handoffs In Mobile Wireless Networks, Weetit Wanalertlak, Ben Lee, Chansu Yu, Myungchul Kim, Seung-Min Park, Won-Tae Kim

Electrical Engineering & Computer Science Faculty Publications

The field of wireless networking has received unprecedented attention from the research community during the last decade due to its great potential to create new horizons for communicating beyond the Internet. Wireless LANs (WLANs) based on the IEEE 802.11 standard have become prevalent in public as well as residential areas, and their importance as an enabling technology will continue to grow for future pervasive computing applications. However, as their scale and complexity continue to grow, reducing handoff latency is particularly important. This paper presents the Behavior-based Mobility Prediction scheme to eliminate the scanning overhead incurred in IEEE 802.11 ...


A Cooperative Diversity-Based Robust Mac Protocol In Wireless Ad Hoc Networks, Sangman Moh, Chansu Yu Mar 2011

A Cooperative Diversity-Based Robust Mac Protocol In Wireless Ad Hoc Networks, Sangman Moh, Chansu Yu

Electrical Engineering & Computer Science Faculty Publications

In interference-rich and noisy environment, wireless communication is often hampered by unreliable communication links. Recently, there has been active research on cooperative communication that improves the communication reliability by having a collection of radio terminals transmit signals in a cooperative way. This paper proposes a medium access control (MAC) algorithm, called Cooperative Diversity MAC (CD-MAC), which exploits the cooperative communication capability of the physical (PHY) layer to improve robustness in wireless ad hoc networks. In CD-MAC, each terminal proactively selects a partner for cooperation and lets it transmit simultaneously so that this mitigates interference from nearby terminals, and thus, improves ...


Adaptive Multicast On Mobile Ad Hoc Networks Using Tree-Based Meshes With Variable Density Of Redundant Paths, Sangman Moh, Sang Jun Lee, Chansu Yu Nov 2009

Adaptive Multicast On Mobile Ad Hoc Networks Using Tree-Based Meshes With Variable Density Of Redundant Paths, Sangman Moh, Sang Jun Lee, Chansu Yu

Electrical Engineering & Computer Science Faculty Publications

Multicasting has been extensively studied for mobile ad hoc networks (MANETs) because it is fundamental to many ad hoc network applications requiring close collaboration of multiple nodes in a group. A general approach is to construct an overlay structure such as multicast tree or mesh and to deliver a multicast packet to multiple receivers over the overlay structure. However, it either incurs a lot of overhead (multicast mesh) or performs poorly in terms of delivery ratio (multicast tree). This paper proposes an adaptive multicast scheme, called tree-based mesh with k-hop redundant paths (TBM k ), which constructs a multicast tree ...


Failure Detectors For Wireless Sensor-Actuator Systems, Hamza A. Zia, Nigamanth Sridhar, Shivakumar Sastry Jul 2009

Failure Detectors For Wireless Sensor-Actuator Systems, Hamza A. Zia, Nigamanth Sridhar, Shivakumar Sastry

Electrical Engineering & Computer Science Faculty Publications

Wireless sensor-actuator systems (WSAS) offer exciting opportunities for emerging applications by facilitating fine-grained monitoring and control, and dense instrumentation. The large scale of such systems increases the need for such systems to tolerate and cope with failures, in a localized and decentralized manner. We present abstractions for detecting node failures and link failures caused by topology changes in a WSAS. These abstractions were designed and implemented as a set of reusable components in nesC under TinyOS. Results, which demonstrate the performance and viability of the abstractions, based on experiments on an 80 node testbed are presented. In the future ...


Proactive Service Migration For Long-Running Byzantine Fault-Tolerant Systems, Wenbing Zhao, H. Zhang Apr 2009

Proactive Service Migration For Long-Running Byzantine Fault-Tolerant Systems, Wenbing Zhao, H. Zhang

Electrical Engineering & Computer Science Faculty Publications

A proactive recovery scheme based on service migration for long-running Byzantine fault-tolerant systems is described. Proactive recovery is an essential method for ensuring the long-term reliability of fault-tolerant systems that are under continuous threats from malicious adversaries. The primary benefit of our proactive recovery scheme is a reduced vulnerability window under normal operation. This is achieved in two ways. First, the time-consuming reboot step is removed from the critical path of proactive recovery. Second, the response time and the service migration latency are continuously profiled and an optimal service migration interval is dynamically determined during runtime based on the observed ...


Information Leakage As A Model For Quality Of Anonymity Networks, Ye Zhu, Riccardo Bettati Apr 2009

Information Leakage As A Model For Quality Of Anonymity Networks, Ye Zhu, Riccardo Bettati

Electrical Engineering & Computer Science Faculty Publications

Measures for anonymity in systems must be on one hand simple and concise, and on the other hand reflect the realities of real systems. Such systems are heterogeneous, as are the ways they are used, the deployed anonymity measures, and finally the possible attack methods. Implementation quality and topologies of the anonymity measures must be considered as well. We therefore propose a new measure for the anonymity degree, that takes into account these various. We model the effectiveness of single mixes or of mix networks in terms of information leakage, and we measure it in terms of covert channel capacity ...


Minimizing Spatial And Time Reservation With Collision-Aware Dcf In Mobile Ad Hoc Networks, Lubo Song, Chansu Yu Jan 2009

Minimizing Spatial And Time Reservation With Collision-Aware Dcf In Mobile Ad Hoc Networks, Lubo Song, Chansu Yu

Electrical Engineering & Computer Science Faculty Publications

Carrier sensing is widely adopted in wireless communication to protect data transfers from collisions. For example, distributed coordination function (DCF) in IEEE 802.11 standard renders a node to defer its communication if it senses the medium busy. For the duration of deferment, each frame carries, in its MAC header, a 16-bit number in microseconds during which any overhearing node must defer. However, even if the carrier signal is detected, both ongoing and a new communication can be simultaneously successful depending on their relative positions in the network or equivalently, their mutual interference level. Supporting multiple concurrent communications is important ...


Maximizing Communication Concurrency Via Link-Layer Packet Salvaging In Mobile Ad Hoc Networks, Chansu Yu, Kang G. Shin, Lubo Song Apr 2007

Maximizing Communication Concurrency Via Link-Layer Packet Salvaging In Mobile Ad Hoc Networks, Chansu Yu, Kang G. Shin, Lubo Song

Electrical Engineering & Computer Science Faculty Publications

Carrier-sense medium access control (MAC) protocols such as the IEEE 802.11 distributed coordination function (DCF) avoid collisions by holding up pending packet transmission requests when a carrier signal is observed above a certain threshold. However, this often results in unnecessarily conservative communication, thus making it difficult to maximize the utilization of the spatial spectral resource. This paper shows that a higher aggregate throughput can be achieved by allowing more concurrent communications and adjusting the communication distance on the fly, which needs provisions for the following two areas. On the one hand, carrier sense-based MAC protocols do not allow aggressive ...


End-To-End Latency Of A Fault-Tolerant Corba Infrastructure, Wenbing Zhao, Louise E. Moser, P. Michale Melliar-Smith May 2006

End-To-End Latency Of A Fault-Tolerant Corba Infrastructure, Wenbing Zhao, Louise E. Moser, P. Michale Melliar-Smith

Electrical Engineering & Computer Science Faculty Publications

This paper presents an evaluation of the end-to-end latency of a fault-tolerant CORBA infrastructure that we have implemented. The fault-tolerant infrastructure replicates the server applications using active, passive and semi-active replication, and maintains strong replica consistency of the server replicas. By analyses and by measurements of the running fault-tolerant infrastructure, we characterize the end-to-end latency under fault-free conditions. The main determining factor of the run-time performance of the fault-tolerant infrastructure is the Totem group communication protocol, which contributes to the end-to-end latency primarily in two ways: the delay in ...


Power-Stepped Protocol: Enhancing Spatial Utilization In A Clustered Mobile Ad Hoc Network, Chansu Yu, Kang G. Shin, Ben Lee Sep 2004

Power-Stepped Protocol: Enhancing Spatial Utilization In A Clustered Mobile Ad Hoc Network, Chansu Yu, Kang G. Shin, Ben Lee

Electrical Engineering & Computer Science Faculty Publications

While most previous studies on mobile ad hoc networks (MANETs) rely on the assumption that nodes are randomly distributed in the network coverage area, this assumption is unlikely to hold, as nodes tend to be cluttered around hot spots like the site of an accident or disaster. We refer to this as a clustered layout. Intuitively, a MANET with the clustered layout may suffer from serious performance degradation due to the excessive collisions in congested hot spots and space underutilization of sparse areas. In this paper, we propose a power-controlled network protocol, called the power-stepped protocol (PSP), that maximizes the ...


Frequency-Hopped Multiple-Access Communications With Noncoherent M-Ary Ofdm-Ask, A. Al-Dweik, Fuqin Xiong Jan 2003

Frequency-Hopped Multiple-Access Communications With Noncoherent M-Ary Ofdm-Ask, A. Al-Dweik, Fuqin Xiong

Electrical Engineering & Computer Science Faculty Publications

A noncoherent, bandwidth-efficient modulation scheme is proposed for frequency-hopping multiple-access (FH-MA) networks. The proposed scheme is a combination of noncoherent M-ary amplitude-shift keying (NMASK) and orthogonal frequency-division multiplexing (OFDM). Using this scheme minimizes the required data bandwidth. The number of frequency slots available to the users increases significantly for a fixed spread-spectrum bandwidth (BWSS). The effect of the multiple-access interference is reduced. Simple and accurate bit error rate expressions have been derived for FH-OFDM-MASK in additive white Gaussian noise channels and for FH-OFDM-ASK in Rayleigh fading channels.


Training Radial Basis Neural Networks With The Extended Kalman Filter, Daniel J. Simon Oct 2002

Training Radial Basis Neural Networks With The Extended Kalman Filter, Daniel J. Simon

Electrical Engineering & Computer Science Faculty Publications

Radial basis function (RBF) neural networks provide attractive possibilities for solving signal processing and pattern classification problems. Several algorithms have been proposed for choosing the RBF prototypes and training the network. The selection of the RBF prototypes and the network weights can be viewed as a system identification problem. As such, this paper proposes the use of the extended Kalman filter for the learning procedure. After the user chooses how many prototypes to include in the network, the Kalman filter simultaneously solves for the prototype vectors and the weight matrix. A decoupled extended Kalman filter is then proposed in order ...


An Adaptive Scheme For Admission Control In Atm Networks, Saragur M. Srinidhi, William H. Thesling, Vijaya K. Konangi Apr 1997

An Adaptive Scheme For Admission Control In Atm Networks, Saragur M. Srinidhi, William H. Thesling, Vijaya K. Konangi

Electrical Engineering & Computer Science Faculty Publications

This paper presents a real time front-end admission control scheme for ATM networks. A call management scheme which uses the burstiness associated with traffic sources in a heterogeneous ATM environment to effect dynamic assignment of bandwidth is presented. In the proposed scheme, call acceptance is based on an on-line evaluation of the upper bound on cell loss probability which is derived from the estimated distribution of the number of calls arriving. Using this scheme, the negotiated quality of service will be assured when there is no estimation error. The control mechanism is effective when the number of calls is large ...


Navigation Satellite Selection Using Neural Networks, Daniel J. Simon, Hossny El-Sherief May 1995

Navigation Satellite Selection Using Neural Networks, Daniel J. Simon, Hossny El-Sherief

Electrical Engineering & Computer Science Faculty Publications

The application of neural networks to optimal satellite subset selection for navigation use is discussed. The methods presented in this paper are general enough to be applicable regardless of how many satellite signals are being processed by the receiver. The optimal satellite subset is chosen by minimizing a quantity known as Geometric Dilution of Precision (GDOP), which is given by the trace of the inverse of the measurement matrix. An artificial neural network learns the functional relationships between the entries of a measurement matrix and the eigenvalues of its inverse, and thus generates GDOP without inverting a matrix. Simulation results ...