Browsing by Author "Sharafkandi, Sarah"
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Item DECOR: Distributed and Energy Efficient Collection of Raw Data in Sensor Networks(2010-02-23) Sharafkandi, Sarah; DuHung-Chang, David; Razavi, AlirezaIn wireless sensor networks, collection of raw sensor data at a base station provides the flexibility to perform offline detailed analysis on the data which may not be possible with in-network data aggregation. However, lossless data collection consumes considerable amount of energy for communication while sensors usually have limited energy. In this paper, we propose a Distributed and Energy Efficient algorithm for collection of Raw data in sensor networks called DECOR. DECOR exploits spatial correlation to reduce the communication energy in sensor networks with highly correlated data. In our approach, at each neighborhood, one sensor shares its raw data as a reference with the rest of sensors without any suppression or compression. Other sensors use this reference data to compress their observations by representing them in the forms of mutual differences. In a highly correlated network, transmission of reference data consumes significantly more energy than transmission of compressed data. Thus, we first attempt to minimize the number of reference transmissions. Then, we try to minimize the size of mutual differences. We derive analytical lower bounds for both these phases and based on our theoretical results, we propose a two-step distributed data collection algorithm which reduces the communication energy significantly compared to existing methods. In addition, we modify our algorithm for lossy communication channels and we evaluate its performance through simulation.Item Energy-Aware Scheduling with Quality of Surveillance Guarantee in Wireless Sensor Networks(2006-06-21) Jeong, Jaehoon; Sharafkandi, Sarah; DuHung-Chang, DavidWe propose and evaluate an energy-efficient scheduling algorithm for detection of mobile targets in wireless sensor networks. We consider a setting where the sensors are deployed for both road surveillance and mobile target tracking. A typical example would be where some sensors are deployed along the entrance roads of a city to detect the vehicles entering the city and other sensors can wake up and track the vehicles after detection. We show that there exists a tradeoff between overall energy consumed by the sensors and the average detection time of a target, both of which are very critical aspects in our problem. To this end, we define the quality of surveillance (QoSv) as the reciprocal value of the average detection time for vehicles. We propose an optimal scheduling algorithm that guarantees the detection of every target with specified QoSv and at the same time minimizes the overall energy consumed by the sensor nodes. By minimizing the energy consumed, we maximize the lifetime of the sensor network and by the quality of surveillance guarantee we ensure that no target goes undetected. We theoretically derive the upper bound on the lifetime of the sensor network for a given QoSv guarantee and prove that our method can always achieve this upper bound. Our simulation results validate the claims made on the algorithm optimality and QoSv guarantee.Item On QoS provisioning for vehicular safety communication(2013-09) Sharafkandi, SarahThis dissertation studies the problem of safety communication in vehicular networks. Despite advances in automative safety during the past decades, still thousand of injuries and fatalities happen yearly in vehicle-related accidents. Dedicated Short Range Communication (DSRC) technology enables vehicles to communicate to each other through wireless medium, so they can inform each other of a potential danger on the road. Two important applications of vehicular network technology are collision avoidance and collecting traffic information. Collision avoidance relies on periodic sharing of safety messages to avoid accidents. Each vehicle that receives these safety messages from its neighbors, uses them to determine if any of the neighbors poses a collision threat. If a vehicle determines that this is the case, the onboard unit will warn the driver. For collision avoidance it is important that the status data of the vehicles be delivered on time and so the Medium Access Control (MAC) protocol design is very important. This dissertation studies two different approaches to the MAC design protocol: First, we use the QoS mechanism of IEEE 802.11 to reduce the collision rate among safety packets when IEEE 802.11p is used which is the likely scenario in United States. Then, we introduce a new contention-free TDMA-based MAC protocol tuned for vehicular communication which can guarantee an upper bound on the delivery delay of safety messages. Finally, we propose a strategy for collecting safety information of vehicles in a Road Side Units (RSU). This information can be used for analysis on the road traffic condition which can be then shared through a disseminating strategy with the vehicles on the road.