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IEEE International Conference on computer-Aided Design

作者： James W. Fonda Maciej Zawodniok S. Jagannathan Steve E. Watkins Embedded Systems and Networking Laboratory Department of Electrical and Computer Engineering University of Missouri Rolla Rolla MO USA

The development and implementation of the optimized energy-delay sub-network routing (OEDSR) protocol for wireless sensor networks (WSN) is presented. This on-demand routing protocol minimizes a novel link cost factor which is defined using available energy, end-to-end (E2E) delay and distance from a node to the base station (BS), along with clustering, to effectively route information to the BS. Initially, the nodes are either in idle or sleep mode, but once an event is detected, the nodes near the event become active and start forming sub-networks. Formation of the inactive network into a sub-network saves energy because only a portion of the network is active in response to an event. Subsequently, the sub-networks organize themselves into clusters and elect cluster heads (CHs). The data from the CHs are sent to the BS via relay nodes (RNs) that are located outside the sub-networks in a multi-hop manner. This routing protocol improves the lifetime of the network and the scalability. This routing protocol is implemented over the medium access control (MAC) layer using UMR nodes. Experimental results illustrate that the protocol performs satisfactorily as expected

关键词： Routing protocols Wireless sensor networks Media Access Protocol Wireless application protocol Costs Delay effects Base stations Event detection Relays Scalability

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Optimal transmission range for cluster-based wireless sensor networks with mixed communication modes

Optimal transmission range for cluster-based wireless sensor...

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IEEE International Symposium on World of Wireless Mobile and Multimedia Networks (WoWMoM)

作者： Hang Su Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

Prolonging the network lifetime is one of the most important designing objectives in wireless sensor networks (WSN). We consider a heterogeneous cluster-based WSN, which consists of two types of nodes: powerful cluster-heads and basic sensor nodes. All the nodes are randomly deployed in a specific area. To better balance the energy dissipation, we use a simple mixed communication modes where the sensor nodes can communicate with cluster-heads in either single-hop or multi-hop mode. Given the initial energy of the basic sensor nodes, we derive the optimal communication range and identify the optimal mixed communication mode to maximize the WSN's lifetime through optimizations. Moreover, we also extend our model from 2-D space to 3-D space

关键词： Wireless sensor networks Spread spectrum communication Monitoring Upper bound Analytical models Information systems Laboratories Energy dissipation Wireless communication Signal processing

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QoS-Driven Power and Rate Adaptation for Multicarrier Communications Over Mobile Wireless Networks

QoS-Driven Power and Rate Adaptation for Multicarrier Commun...

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Annual Conference on Information Sciences and systems (CISS)

作者： Jia Tang Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

We propose a quality-of-service (QoS) driven power and rate adaptation scheme for multicarrier communications systems over mobile wireless networks. By integrating information theory with the concept of effective capacity, our proposed scheme aims at maximizing the system throughput subject to a given delay-QoS constraint. Under the framework of convex optimization, we develop the optimal adaptation algorithms. Our analytical analyses identify an important fact that when the QoS constraint becomes loose, the optimal power-control policy converges to the well-known water-filling scheme, where the Shannon capacity can be achieved. On the other hand, when the QoS constraint gets stringent, the optimal policy converges to the scheme which operates at a constant-rate, where, by using only a limited number of subchannels, the above constant-rate is close to the Shannon capacity. This observation implies that in contrast to single-channel transmission, which trades off the throughput for the QoS provisioning, the multicarrier communications can realize both the high throughput and the stringent QoS at the same time. For instance, our simulation results indicate that by using 64 independent subchannels, our proposed algorithms can achieve more than 99% of the Shannon capacity, while guaranteeing a constant-rate transmission.

关键词： Mobile communication Wireless networks Throughput Information theory Mobile computing Quality of service Delay effects Constraint theory Design optimization Information systems

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Power-Efficiency Data Gathering Schemes for Wireless Sensor Networks

Power-Efficiency Data Gathering Schemes for Wireless Sensor ...

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International Conference on computer Communications and Networks (ICCCN)

作者： Hang Su Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

We develop energy-efficiency data gathering schemes for wireless sensor networks (WSN), where the channel is characterized by the slow Rayleigh fading. We consider the homogeneous WSN which consists of a large number of sensor nodes equipped with the identical hardware. In the WSN, the sensor nodes are distributed randomly in a specific area. A mobile base station periodically stops by the area to collect the data from the senor nodes. Energy efficiency, which is the performance metric we adopt for our scheme design, is defined as the energy consumption by transmitting a bit sensing information. We develop analytical models to study the proposed data gathering schemes. First, we demonstrate that clustering and data-fusion technology can help improve the energy efficiency compared to the naive data gathering scheme where the sensor nodes send sensing data directly to the mobile base station. Second, we show that making full use of the channel state information (CSI) can further reduce the energy consumption for data gathering. Finally, we found that there is a tradeoff between the energy consumption and the data gathering delay.

关键词： Wireless sensor networks Energy efficiency Energy consumption Sensor phenomena and characterization Base stations Rayleigh channels Hardware Measurement Analytical models Channel state information

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QoS-Driven Adaptive Power and Rate Allocation for Multichannel Communications in Mobile Wireless Networks

QoS-Driven Adaptive Power and Rate Allocation for Multichann...

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IEEE International Symposium on Information Theory

作者： Jia Tang Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

ISBN: (纸本)142440505X

We propose a quality-of-service (QoS) driven power and rate adaptation scheme for multichannel communications systems over wireless links. In particular, we use multichannel communications to model either diversity or multiplexing systems, which play a fundamental role in physical-layer evolutions of mobile wireless networks. By integrating information theory with the concept of effective capacity, our proposed scheme aims at maximizing the multichannel-systems throughput subject to a given delay-QoS constraint. Under the framework of convex optimization, we develop the optimal adaptation algorithms. Our analyses show that when the QoS constraint becomes loose, the optimal power-control policy converges to the well-known water-filling scheme, where the Shannon (or ergodic) capacity can be achieved. On the other hand, when the QoS constraint gets stringent, the optimal policy converges to the scheme operating at a constant-rate (i.e., the zero-outage capacity), which, by using only a limited number of subchannels, approaches to the Shannon capacity. This observation implies that the optimal effective capacity function decreases from the ergodic capacity to the zero-outage capacity as the QoS constraint becomes more stringent. Furthermore, unlike the single-channel communications, which have to trade off the throughput for QoS provisioning, the multichannel communications can achieve both high throughput and stringent QoS at the same time

关键词： Mobile communication Wireless networks Throughput Quality of service Communication systems Wireless communication Power system modeling Information theory Delay effects Constraint theory

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Quality-of-Service Driven Power and Rate Control in Mobile Wireless Networks

Quality-of-Service Driven Power and Rate Control in Mobile W...

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IEEE International Conference on Communications (ICC)

作者： Jia Tang Xi Zhang Networking and Information Systems Laboratory Department of Electrical and Computer Engineering Texas A and M University College Station TX USA

We propose a Quality-of-Service (QoS) driven power- and rate-control scheme in mobile wireless networks. Specifically, the proposed scheme aims at maximizing the system throughput subject to a given delay QoS constraint. Over the block fading channel, we derive the optimal adaptation policy by integrating information theory with the concept of effective capacity. The analyses demonstrate that there exists a fundamental tradeoff between spectral efficiency and QoS provisioning. When the QoS constraint is loose, the optimal power control policy converges to the well-known water-filling scheme, where the Shannon capacity can be achieved. On the other hand, when the QoS constraint is stringent, the optimal policy converges to the total channel inversion such that the system operates with a constant service rate.

关键词： Quality of service Wireless networks Delay Information theory Fading Bandwidth Mobile computing Throughput Power control Control systems

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Adaptive Distributed Fair Scheduling and Its Implementation in Wireless Sensor Networks

Adaptive Distributed Fair Scheduling and Its Implementation ...

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IEEE International Conference on systems, Man and Cybernetics

作者： James W. Fonda Maciej Zawodniok S. Jagannathan Steve E. Watkins Networking Systems Laboratory and the Electrical and Computer Engineering Department University of Missouri Rolla Rolla MO USA Electrical and Computer Engineering Department University of Missouri Rolla Rolla MO USA

A novel adaptive and distributed fair scheduling (ADFS) scheme for wireless sensor networks is shown through hardware implementation. In contrast to simulation, hardware evaluation provides valuable feedback to protocol and hardware development process. The proposed protocol focuses on quality-of-service (QoS) issues to address flow prioritization. Thus, when nodes access a shared channel, the proposed ADFS allocates the channel bandwidth proportionally to the weight, or priority, of the packet flows. Moreover, ADFS allows for dynamic allocation of network resources with little added overhead. Weights are initially assigned using user specified QoS criteria. These weights are subsequently updated as a function of delay, enqueued packets, flow arrival rate, and the previous packet weight. The back-off interval is also altered using the weight update equation. The weight update and the back-off interval selection ensure that global fairness is attained even with variable service rates. The algorithm is implemented using UMR/SLU motes for an industrial monitoring application. Results the hardware implementation demonstrates improved performance in terms of fairness index, flow rate, and delay.

关键词： Adaptive scheduling Wireless sensor networks Hardware Job shop scheduling Access protocols Delay Adaptive systems Feedback Quality of service Bandwidth

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Wide-band electrooptic intensity modulator frequency response measurement using an optical heterodyne down-conversion technique

Wide-band electrooptic intensity modulator frequency respons...

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作者： Lam, Alfred K. M. Fairburn, Mark Jaeger, Nicolas A. F. IEEE Department of Electrical and Computer Engineering University of British Columbia Vancouver BC V6T 1Z4 Canada Tantalus Systems Corporation Vancouver BC V5M 4X6 Canada Electro-Optics Laboratory Electrical and Computer Engineering Department UBC Tantalus Systems Corporation Vancouver BC Canada Department of Electrical and Computer Engineering UBC

This paper describes a novel system for measuring the frequency response of electrooptic intensity modulators at millimeter-wave frequencies. The system measures |S21| in decibels electrical. In it, the electrical input signal to the modulator is generated by heterodyning two tunable lasers. The output of the modulator is then down-converted to a microwave frequency at which the output is easily measured. Measurements have been made up to 78 GHz using a 55-GHz photodiode as the mixer for the two lasers. In addition, our system tracks any frequency variations in the outputs of the lasers. Our system can also measure the linear response of the modulator if it is operated in nonlinear regions since it can reject higher order harmonics, due to nonlinearities, generated in the modulator © 2006 IEEE.

关键词： Frequency response

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Enhancing /spl epsiv/-approximation algorithms with the optimal linear scaling factor

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IEEE Transactions on Communications 2006年第9期54卷 1624-1632页

作者： Gang Cheng N. Ansari Li Zhu VPI Systems Inc. Holmdel NJ USA Advanced Networking Laboratory Electrical and Computer Engineering Department New Jersey Institute of Technology Newark NJ USA

Finding a least-cost path subject to a delay constraint in a network is an NP-complete problem and has been extensively studied. Many works reported in the literature tackle this problem by using epsiv-approximation schemes and scaling techniques, i.e., by mapping link costs into integers or at least discrete numbers, a solution which satisfies the delay constraint and has a cost within a factor of the optimal one, that can be computed with pseudopolynomial computational complexity. In this paper, having observed that the computational complexities of the epsiv-approximation algorithms using the linear scaling technique are linearly proportional to the linear scaling factor, we investigate the issue of finding the optimal (the smallest) linear scaling factor to reduce the computational complexities, and propose two algorithms, the optimal linear scaling algorithm (OLSA) and the transformed OLSA. We analytically show that the computational complexities of our proposed algorithms are very low, as compared with those of epsiv-approximation algorithms. Therefore, incorporating the two algorithms can enhance the epsiv-approximation algorithms by granting them a practically important capability: self-adaptively picking the optimal linear scaling factors in different networks. As such, epsiv-approximation algorithms become more flexible and efficient

关键词： Routing Computational complexity Delay Cost function Laboratories computer networks NP-complete problem Algorithm design and analysis Telecommunication traffic

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An efficient approach for the reliability analysis of phased-mission systems with dependent failures

An efficient approach for the reliability analysis of phased...

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8th International Conference on Probabilistic Safety Assessment and Management, PSAM 2006

作者： Xing, Liudong Meshkat, Leila Donohue, Susan K. Electrical and Computer Engineering Department University of Massachusetts-Dartmouth United States Jet Propulsion Laboratory California Institute of Technology United States Department of Systems and Information Engineering University of Virginia United States

ISBN: (纸本)0791802442

We consider the reliability analysis of phased-mission systems with dependent common-cause failures in this paper. A phased-mission system (PMS) is a system supporting a mission characterized by multiple, consecutive, and non-overlapping phases of operation. System components may be subject to different stresses as well as different reliability requirements throughout the course of the mission. As a result, component behavior and relationships may need to be modeled differently from phase to phase when performing a system-level reliability analysis. This consideration poses unique challenges to existing analysis methods. The challenges increase when common-cause failures (CCF) are considered in the analysis. CCF are multiple dependent component failures within a system that are a direct result of a shared root cause, such as sabotage, flood, earthquake, power outage, or human errors. It has been shown by many reliability studies that CCF tend to increase a system's joint failure probabilities and thus contribute significantly to the overall unreliability of systems subject to CCF. We propose a separable phase-modular approach for the solution of fault trees, our chosen formalism, as one way to meet the above challenges in an efficient and elegant manner. Our methodology is twofold: first, we separate the effects of CCF from the base PMS analysis using the Total Probability Theorem and the concept of a common-cause event space based on elementary common-causes;next, we apply an efficient phase-modular approach to determine the reliability of the PMS. The phase-modular approach employs both combinatorial and Markov-chain solution methods as appropriate, based on the characterization of a given phase module. We use the example of a hypothetical system subject to CCF to illustrate the basic steps of our proposed methodology. © 2006 by ASME.

关键词： Reliability analysis

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