Secure and Efficient Cross-Layer Techniques For Low-Power Wireless Embedded Systems

Title: Secure and Efficient Cross-Layer Techniques For Low-Power Wireless Embedded Systems
Authors: Onat, Ilker
Date: 2011
Abstract: Energy efficiency is playing a major role in the proliferation of low-power wireless sensing and identification systems. Hardware, firmware and communication protocol design processes of such systems are becoming increasingly adapt to low-power techniques enhancing the device lifetime, range, and efficiency. This thesis focuses on the cross-layer security and medium access techniques for low-power wireless embedded devices. Layer interactions in these systems are pointed out and algorithms taking advantage of these interactions are proposed. To improve the security of stationary systems, anomaly detection based algorithms can be used with various parameters at different layers. We introduce two distributed anomaly detection based security algorithms for wireless sensor networks, using the physical layer signal characteristics and network layer arrival patterns. By analyzing the received packet features at different layers, a node can effectively identify an intruder impersonating a legitimate neighbor. In a wireless sensor node, the radio is the main energy spending component. To limit energy consumption, wireless sensor nodes are periodically waken up and put to sleep. This duty-cycling operation still constitutes the major energy drain for battery powered wireless sensor architectures. Duty-cycling also imposes major constraints on the medium access and network layer operations of sensor nodes. We propose a hardware based solution in which an RFID wakeup system eliminates the duty-cycling completely from sensor operations using a boosting circuit and a low-threshold rectifier. This solution removes the burden of duty-cycling on the upper layers with a physical layer approach. Efficiency of RFID systems can be improved with smart slot selection algorithms in MAC layer for slotted ALOHA based MAC protocols. We introduce a MAC scheme where tags select their transmission slot based on their distance from the reader which is deduced by the received power levels. Slotted ALOHA based RFID MAC algorithms achieve smallest total reading time when, at each reading round, the frame length is set equal to the actual number of remaining unread tags. We present an a posteriori tag count estimation algorithm for these RFID MAC protocols from the collision statistics of the previous reading round.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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