Sebnem Baydere

Robust Image Transmission Over Wireless Sensor Networks

Robust image and video communications have become more imperative due to the ubiquitous proliferation of multimedia applications over wireless sensor networks. In this work, the transmission distortions on the image data induced by both channel and instant node failures for Wireless Sensor Networks (WSN) are considered. The effect of two techniques and their integration with multipath transmission are investigated to compensate the multimedia distortions at the expense of incurring additional energy consumption and/or wasting bandwidth resources. First technique is watermarking based error concealment utilizing discrete wavelet transform for embedding downsized replicas of original image into itself. The other is conventional Reed–Solomon (RS) coding utilizing additional information bits to correct bit/symbol errors. Performance results obtained from extensive simulations utilizing a communication and energy model applicable to WSN show that error concealment (EC) integrated schemes, especially EC with multipath fusion (ECMF), are more promising to compensate losses than RS-coding-integrated and pure multipath transmission techniques in WSN.

Lifetime Analysis of Reliable Wireless Sensor Networks

A wireless sensor network is comprised of a large number of battery-limited sensor nodes communicating with unreliable radio links. The nodes are deployed in an ad hoc fashion and a reverse multicast tree is formed in the target domain. The sink node disseminates a query and collects responses from the sensors over pre-established links. Survivability in wireless sensor networks reflects the ability of the network to continue to detect events in the case of individual node failures. We present a sender initiated path switching algorithm that enables the immediate sender to change the packets route dynamically when its parent on the reverse path is down. The overall effect of path switching on the survivability is analyzed as a measure of reliable event delivery. Using independent battery capacities, an analytical model of a multihop network is derived. The model is used to predict the maximum network lifetime in terms of total transmitted messages; which is in turn used to verify the correctness of our simulations. The results have revealed that dynamic path switching has a better performance than static multipath routing and salvaging schemes. It has also been shown that the proposed approach enhances reliability up to 30% in some topologies.

FireSenseTB: a wireless sensor networks testbed for forest fire detection

Wireless sensor networks promise great success in many areas from environmental monitoring to medical and military applications. Forest fire detection is one of these areas where many of the ongoing WSN research is focused today. Unfortunately, most of these studies choose simulating their proposed solutions instead of doing experiments in real testbed environments, since that kind of setup exposes additional difficulties. Our previous work, named FireSense, proposed a fire detection algorithm, which was shown to be successful in terms of simulation results. In this study, we take FireSense to a real outdoor testbed for further analysis of its effectiveness in terms of various parameters such as link and node failures, topology and physical configuration changes, wind direction, ignition point position and sampling period variations.

Quality aware image transmission over underwater multimedia sensor networks

With the recent advances in Micro Electro-Mechanical Systems (MEMS) and underwater imaging sensors, and cameras, underwater multimedia sensor networks (UMSNs) have been proposed and drawn the immediate attention of the research community. Underwater multimedia sensor networks enable several new applications, such as target tracking, advanced coastal multimedia surveillance, undersea explorations, image acquisition and classification, environmental monitoring, and disaster prevention. However, the practical realization of these currently designed and envisioned applications directly depends on reliable and quality-aware communication capabilities of the deployed UMSNs. This paper presents a comprehensive performance evaluation of error concealment and error correction algorithms for quality-aware image transmission over UMSNs. Specifically, different combinations of multipath transport,watermarking-based error concealment (EC), forward error correction (FEC) and adaptive retransmission mechanisms have been evaluated to combat underwater channel impairments and mitigate packet losses due to node failures and intrinsic underwater acoustic channel characteristics. In addition, two novel image quality assessment metrics have been proposed to obtain the predicted quality of the image depending on the channel and node failures. Comparative performance evaluations show that the EC approach reconstructs the distorted image as closely as the original one while avoiding the burden of retransmissions and consequent delay.

Image Quality Estimation in Wireless Multimedia Sensor Networks: An Experimental Study

Multimedia applications in wireless sensor networks (WMSN) have stringent quality of service (QoS) requirements. In this paper, we study image quality distortions due to packet losses in multi hop WMSN. An experimental simulation and real testbed environment has been setup to estimate the quality of the test images over 30,000 transmissions. Two scenarios are considered: in the first scenario, images are watermarked with their replicas at the source node and an error concealment (EC) algorithm is employed at the sink. In the second scenario, raw images are transmitted without any encoding. The empirical results have revealed that there is a strong correlation between Peak-Signal-To-Noise-Ratio (PSNR) values of the distorted images and packet loss rate of the transmission route (PER). Moreover, the relationship is linear when EC technique is used with an achievement over 25dB PSNR for PER less than 0.6. This correlation is useful when designing QoS based transport schemes.

A Bayesian approach for indoor human activity monitoring

Activity monitoring plays a crucial role in ambient living environments for assessing changes in the normal behavioral pattern of elderly people. In this paper, we present a composite action description and detection model for activity monitoring. The model accomplishes real time continuous monitoring of composite actions by detecting the transitions from one simple action to another and determining the types of those actions. It utilizes a wearable TI Chronos watch with a built-in tri-axial accelerometer for data acquisition and uses naive Bayes classifier for the classification of simple actions; walk, sit stand and lie. The unique feature of these actions is that the transition between walk, sit and lie are the most likely causes of fall event in a home environment for elderly people. The early results of an experimental study conducted for the detection of the composite actions; walk-after-sit and sit-after-lie are very encouraging in terms of detection success rates.

QoSMOS: cross-layer QoS architecture for wireless multimedia sensor networks

Wireless multimedia sensor networks (WMSNs), having inherent features and limited resources, require new quality of service (QoS) protocols for real-time and multimedia applications. In this paper, we present a cross-layer QoS architecture (QoSMOS), that unifies network and link layers into a single communication module for QoS provisioning. Based on QoSMOS architecture, we developed an example reference cross-layer protocol, named cross-layer communication protocol (XLCP), enabling scalable service differentiation in WMSNs. Comprehensive analysis of simulation results indicate that the proposed architecture successfully differentiates service classes in terms of soft delay, reliability and throughput domains. A comparative analysis of XLCP and its counterparts is also given to show the superiority of the cross-layer protocol.

Perceptual quality‐based image communication service framework for wireless sensor networks

Wireless multimedia sensor networks (WMSNs) have an increasing variety of multimedia-based applications including image and video transmission. In these types of applications, multimedia sensor nodes should ideally maximize perceptual quality and minimize energy expenditures in communication. For the required perceptual quality to be obtained, quality-aware routing is a key research area in WMSNs. However, mapping the system parameters to the end users perceptual quality-of-service measures is a challenging task because of incomplete identification metrics. Unfortunately, unless disputable assumptions and simplifications are made, optimal routing algorithm is not tractable. In this paper, we propose a novel image transmission framework to optimize both perceptual quality and energy expenditure in WMSNs. Our framework aims to provide acceptable perceptual quality at the end user by using an analytical distortion prediction model that is able to predict the image distortion resulting from any given error pattern. The innovation of the proposed scheme lies in the combined use of a content-aware packet prioritization with an energy-aware and quality-aware routing protocol, named as image quality-aware routing. Additionally, it does not only propose an energy-efficient route selection policy but also manages the network load according to the energy residues of nodes, thus leading to a great energy economy. The results reveal that the framework is capable of identifying true metrics for mapping required image quality to network parameters. Copyright (c) 2011 John Wiley & Sons, Ltd.

RH+: A Hybrid Localization Algorithm for Wireless Sensor Networks

Today, localization of nodes in Wireless Sensor Networks (WSNs) is a challenging problem. Especially, it is almost impossible to guarantee that one algorithm giving optimal results for one topology will give optimal results for any other random topology. In this study, we propose a centralized, range- and anchor-based, hybrid algorithm called RH+ that aims to combine the powerful features of two orthogonal techniques: Classical Multi-Dimensional Scaling (CMDS) and Particle Spring Optimization (PSO). As a result, we find that our hybrid approach gives a fast-converging solution which is resilient to range-errors and very robust to topology changes. Across all topologies we studied, the average estimation error is less than 0.5m. when the average node density is 10 and only 2.5% of the nodes are beacons.

IQAR: Image quality aware routing for Wireless Multimedia Sensor Networks

Wireless Multimedia Sensor Networks (WMSN) have an increasing variety of multimedia based applications including image and video transmission. In these types of applications, multimedia sensor nodes should ideally maximize perceptual quality and minimize energy expenditures in communication. To obtain the required perceptual quality, quality of service (QoS) support is needed at the network level. However, mapping the network parameters to the end-users perceptual quality measures during building paths is a challenging task due to incomplete identification metrics. In this paper, we propose Image Quality Aware Routing (IQAR) for WMSN that introduces the concept of image quality awareness by considering energy issue. The proposed approach employs intra-image prioritization and an adaptive path selection scheme that adjusts reliability level during image transmission using a distortion prediction model.