Sectorized antennas are a promising class of antennas for enabling direction-of-arrival (DoA) estimation and successive transmitter localization. In contrast to antenna arrays, sectorized antennas do not require multiple transceiver branches and can be implemented using a single RF front-end only, thus reducing the overall size and cost of the devices. However, for good localization performance the underlying DoA estimator is of uttermost importance. In this paper, we therefore propose a novel high performance DoA estimator for sectorized antennas that does not require cooperation between the transmitter and the localizing network. The proposed DoA estimator is broadly applicable with different sectorized antenna types and signal waveforms, and has low computational complexity. Using computer simulations, we show that our algorithm approaches the respective Cramer-Rao lower bound for DoA estimation variance if the signal-to-noise ratio (SNR) is moderate to large and also outperforms the existing estimators. Moreover, we also derive analytical error models for the underlying DoA estimation principle considering both free space as well as multipath propagation scenarios. Furthermore, we also address the fusion of the individual DoA estimates into a location estimate using the Stansfield algorithm and study the corresponding localization performance in detail. Finally, we show how to implement the localization in practical systems and demonstrate the achievable performance using indoor RF measurements obtained with practical sectorized antenna units.

Authentication schemes based on wireless physical layer channel information have gained significant attention in recent years. It has been shown in recent studies, that the channel based authentication can either cooperate with existing higher layer security protocols or provide some degree of security to networks without central authority such as sensor networks. We propose a Gaussian Mixture Model based semi-supervised learning technique to identify intruders in the network by building a probabilistic model of the wireless channel of the network users. We show that even without having a complete apriori knowledge of the statistics of intruders and users in the network, our technique can learn and update the model in an online fashion while maintaining high detection rate. We experimentally demonstrate our proposed technique leveraging pattern diversity and show using measured channels that miss detection rates as low as 0.1% for false alarm rate of 0.3% can be achieved.

Increasing chip power density has brought application specific accelerator architectures to the forefront as an energy and area efficient solution. While GPGPU systems take advantage of specialized hardware to perform computationally intensive tasks faster than chip multiprocessor (CMP) systems, accelerators are hardware units that are designed to execute a specific application efficiently. Real-time ultrasound imaging applications require the removal of multiplicative noise while maintaining a steady frame-rate, and are good candidates to explore accelerator-based systems. In this paper, we propose and evaluate the architecture of an accelerator designed to improve performance of SRAD image enhancing algorithm. We compare the projected performance of the SRAD accelerator to software implementations on a multi-core CPU and a CPU+GPU system. The proposed architecture achieves higher throughput by eliminating redundant fetches from memory and by storing intermediate data locally. The speedup of the GPU is found to be 3.2x over the CPU, while the accelerator achieved a speedup of 24x. The area efficiency of the GPU and accelerator is up to 1.6x and 370x better than the CPU, respectively. In comparison with the CPU, we find that the energy consumed for operation on a single frame is found to be 1.5x lesser on the GPU and upto 580x lesser on the accelerator.