International Journal of Sensors Wireless Communications and Control - Volume 1, Issue 2, 2011

Wireless Sensor Networks are often considered as low-rate asynchronous systems for distributed monitoring. However, there are several real-time and high data-rate applications where the traditional behavior of WSNs could give raise to channel sharing problems, thus limiting the usefulness of this technology for these emerging fields. This article proposes and discusses PRISM (Protocol for Real-tIme Synchronous Monitoring), a novel protocol for real-time synchronous acquisitions in single-hop and multi-hop wireless sensor networks. The PRISM protocol allows to define the maximum number of nodes, the requirements on the network synchronization and the data-rate in a flexible manner in order to accommodate for different types of acquisitions. Its performance has been studied theoretically through numerical simulations. Moreover, the protocol has been tested in a fully-working wireless monitoring system based on the IEEE 802.15.4 physical standard. Results show the effectiveness and the efficiency of the proposed protocol.

Recently, cross-layer routing design for cognitive radio networks (CRNs) has been studied widely. However, none of the previous literatures discuss multi-link interference (in routing protocol design), which results in queuing delay and backoff delay. A large queuing and backoff delay will reduce the transmission efficiency of a link and increase the cumulative end-to-end delay. In this paper, we first propose a multi-link interference model, and derive the transmission efficiency of a link. Then, in order to improve the transmission efficiency (thus the quality of service) under multi-link interference situation, we propose a source routing protocol based on on-demand routing and dynamic channel assignment. The channel assignment tries to maximize the transmission efficiency of links along the selected path. Hence, our proposed routing protocol can reduce the average cumulative end-to-end delay of all flows and increase the packet delivery ratio.

A definition for the measure of observability is introduced. It is illustrated by two examples of nonlinear systems defined by ordinary and partial differential equations. Using computational dynamic optimization, the concept of observability is numerically implementable for a wide spectrum of problems. Some topics addressed in this paper include the observability based on user-knowledge, the determination of strong observability vs. weak observability, the optimal sensor locations, and the partial observability of complex systems.

Opportunistic sensing can be used to obtain data from sensors that just happen to be present in the user’s surroundings. By harnessing these opportunistic sensor configurations to infer activity or context, ambient intelligence environments become more robust, have improved user comfort thanks to reduced requirements on body-worn sensor deployment and they are not limited to a predefined and restricted location, defined by sensors specifically deployed for an application. We present the OPPORTUNITY Framework and Data Processing Ecosystem to recognize human activities or contexts in such opportunistic sensor configurations. It addresses the challenge of inferring human activities with limited guarantees about placement, nature and run-time availability of sensors. We realize this by a combination of: (i) a sensing/context framework capable of coordinating sensor recruitment according to a high level recognition goal, (ii) the corresponding dynamic instantiation of data processing elements to infer activities, (iii) a tight interaction between the last two elements in an “ecosystem” allowing to autonomously discover novel knowledge about sensor characteristics that is reusable in subsequent recognition queries. This allows the system to operate in open-ended environments. We demonstrate OPPORTUNITY on a large-scale dataset collected to exhibit the sensor richness and related characteristics, typical of opportunistic sensing systems. The dataset comprises 25 hours of activities of daily living, collected from 12 subjects. It contains data of 72 sensors covering 10 modalities and 15 networked sensor systems deployed in objects, on the body and in the environment. We show the mapping from a recognition goal to an instantiation of the recognition system. We also show the knowledge acquisition and reuse of the autonomously discovered semantic meaning of a new unknown sensor, the autonomous update of the trust indicator of a sensor due to unforeseen deteriorations, and the autonomous discovery of the on-body sensor placement.

This paper shows an Incremental Redundancy Hybrid automatic repeat request (HARQ) scheme, based on rateless coding, for wireless sensor network (WSN) protocols. The proposed approach proved to be effective under energy consumption constraints, making it suitable for possible applications to WSNs. Moreover, the use of a rateless coding scheme increases the average throughput by limiting the length of retransmitted packets. Performance are evaluated through simulations in terms of average goodput and average energy consumption, comparing the presented solution with the traditional ARQ scheme employed in the IEEE 802.15.4 standard for WSNs. Results have been obtained using a novel network simulation model for rateless code transmissions based on information theoretic measures.

This paper proposes a common control method of three-dimension chaotic system by backstepping method. This method is applied to achieve chaos control for Lorenz, Chen and Lu systems. Based on Lyapunov stability theory and Jacobian matrix, control laws are derived. The greatest advantage of this method is that can be controlled effectively to be stable at any given point with a common linear controller. The results of numerical simulations by Matlab software show the control method is feasibility. And it might be expanded to higher dimension system in the future.

Wireless communications are highly error-prone due to inherent wireless channel effects, which include interference, multi-path fading, and noise. The conventional approach to reducing the effects of frequent channel errors is to attempt retransmitting the corrupted frames. This solution however introduces long end-to-end delay and channel usage inefficiency, especially in multi-hop wireless networks. In this work, we introduce the cooperative diversity-based opportunistic virtual MISO (Multiple-Input-Multiple-Output) approach to alleviate the problem and to improve the overall performance in multi-hop wireless networks. Our approach allows neighboring nodes to effectively share their available resources when there is an opportunity to participate. Our observation showed that multi-hop wireless networks consist of low and high quality links. In the low-quality links, we utilize spatial-diversity property that allows a wireless node with the highest delivery probability to relay data frames to the next hop. In the high-quality links, when there is more than one node successfully receiving the same data frame, we utilize space-time block codes (STBC) to extend the transmission range to deliver data frames up to two hops away. By proposing the approach described above, available network resources are always utilized to improve the overall performance. OVM provides an effective and simple design solution. Simulation results show that OVM is able to improve end-to-end network performance by up to eighty-six percent over previous works.

A solution of the pinball routing problem in a multihomed mobile network is proposed in the present work. All the communication to and from the mobile network node in a nested mobile network passes through the tunnel between mobile router and its home agent as mentioned in network mobility route optimization problem statement. Such problem is formally known as pinball routing problem. But in the present scheme the communication to and from the mobile network node may or may not pass through the home agents of mobile routers at the higher level of the nested network depending upon the network mobility. Such consideration helps to minimize delay due to pinball routing effect. Moreover in the present work direct communication is proposed if both the source node and the destination node lie inside the same nested mobile network. The proposed scheme is the combination of route optimization algorithm and pinball routing elimination algorithm in a nested multi-homed mobile network. The route optimization algorithm selects an optimal route inside the mobile network of the source node. The pinball routing elimination algorithm selects the pinball eliminated route from the mobile network to the destination node. The performance of the proposed scheme is evaluated on the basis of tunneling overhead, end to end packet delay and fragmentation using ENEMO_SIM simulator. Results based on a detailed performance evaluation study are also presented to demonstrate the efficacy of the proposed scheme.