Kronecker-Based Fusion Rule for Cooperative Spectrum Sensing with Multi-Antenna Receivers

This paper considers a novel fusion rule for spectrum sensing scheme for a cognitive radio network with multi-antenna receivers. The proposed scheme exploits the fact that when any primary signal is present, measurements are spatially correlated due to presence of inter-antenna and inter-receiver spatial correlation. In order to exploit this spatial structure, the generalized likelihood ratio test (GLRT) operates with the determinant of the sample covariance matrix. Therefore, it depends on the sample size N and the dimensionality of the received data (i.e., the number of receivers K and antennas L). However, when the dimensionality fK; Lg is on the order, or larger than the sample size N, the GLRT degenerates due to the ill-conditioning of the sample covariance matrix. In order to circumvent this issue, we propose two techniques that exploit the inner spatial structure of the received observations by using single pair and multi-pairs Kronecker products. The performance of the proposed detectors is evaluated by means of numerical simulations, showing important advantages with respect to the traditional (i.e., unstructured) GLRT approach

Design and implementation of application-specific medium access control protocol for scalable smart home embedded systems

Thesis (M.S.) University of Alaska Fairbanks, 2016By incorporating electrical devices, appliances and house features in a system that is controlled and monitored either remotely or on-site, smart home technologies have recently gained an increasing popularity. There are several smart home systems already available, ranging from simple on-site home monitoring to self-learning and Wi-Fi enabled systems. However, current systems do not fully make use of recent technological advancement and synergy among a variable number of sensors for improved data collection. For a synergistic system to be provident it needs to be modular and scalable to match exact user needs (type of applications and adequate number of sensors for each application). With an increased number of sensors intelligently placed to optimize the data collection, a wireless network is indispensable for a flexible and inexpensive installation. Such a network requires an efficient medium access control protocol to sustain a reliable system, provide flexibility in design and to achieve lower power consumption. This thesis brings to light practical ways to improve current smart home systems. As the main contribution of this work, we introduce a novel application-specific medium access control protocol able to support suggested improvements. In addition, a smart home prototype system is implemented to evaluate the protocol performance and prove concepts of recommended advances. This thesis covers the design of the proposed novel medium access protocol and the software/hardware implementation of the prototype system focusing on the monitoring and data analysis side, while providing inputs for the control side of the system. The smart home system prototype is Wi-Fi and Web connected, designed and implemented to emphasize system usability and energy efficiency

Efficient and Secure Network Services in Wireless Sensor Networks.

Wireless sensor networks (WSNs) have been deployed for environment monitoring and surveillance. A message delivery service is one of the most fundamental services for WSNs, thus making its efficiency and effectiveness important. A widely-adopted protocol for message delivery in WSNs is a geographic forward routing (GFR), in which messages are greedily forwarded to their destinations. In this thesis, we develop network services complementary to the existing GFR for efficient and secure message delivery in WSNs. We first develop a distributed location service protocol (DLSP) for message delivery to mobile nodes. Since GFR represents destinations of messages with destinations' geographic locations, the knowledge of location of mobile nodes is necessary to ensure correct message delivery. In DLSP, mobile nodes select some sensor nodes as their location servers, and publish the mobiles' location information to the location servers. Sensor nodes contact those location servers to retrieve the current location of mobile nodes when needed. DLSP provides systematic methods for mobile nodes to select location servers and publish their location to those servers, and for sensor nodes to query mobiles' location. We then design an algorithm called Traverse for hole boundary detection and geographic forward routing with hole avoidance (GFRHA) for efficient message routing. Traverse identifies boundaries of holes, i.e., areas without any functioning sensor node. GFRHA then utilizes the identified hole information to route messages around holes while being forwarded before they encounter holes. This way, the message path lengths, and subsequently the message delay and energy consumption, can be significantly reduced, depending on hole shapes and source and destination locations. We also develop attack-resilient collaborative message authentication (ARCMA) for message delivery. ARCMA is designed to tolerate node-capture attacks, in which attackers obtain valid keys by compromising physically-exposed sensor nodes, and use the keys to generate forged messages. To defend against such attacks, in ARCMA, messages are collaboratively authenticated by a set of sensor nodes rather than by one node. The security of ARCMA does not degrade unless attackers simultaneously compromise more than a certain number of sensor nodes.Ph.D.Computer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/64831/1/mgcho_1.pd