This thesis researches mitigations for BLE relay attacks. A design for a timebased distance bounding protocol using the Bluetooth channel sounding feature introduced in the new Bluetooth 6.0 core specification is presented. Bluetooth channel sounding is compromised of two distance measurement techniques: Phase-Based Ranging (PBR) and Round Trip Tim (RTT). The proposed protocol requires consistent channel sounding distance measurements in order to minimize the likelihood of succesfull relay attacks. Single-antenna channel sounding measurements have shown poor spatial and sequential consistency in a complex multipath office environment. In order to overcome inaccuracies that arise due to multipath propagation, this thesis investigates the optimal antenna configuration for Bluetooth channel sounding using multiple antennas. A comparison
between the root-mean-square error and maximum error of the single-antenna baseline and the proposed multi-antenna solution for both spatial and sequential consistency in a complex multipath office environment shows that there is, on average, a 58% reduction in error metrics when the optimal multi-antenna setup is used. The performance of the optimal multi-antenna channel sounding setup
in the complex environment approaches the single-antenna baseline performance
in an ideal outdoor environment. This shows that the added antenna diversity
successfully overcomes the negative effects due to multipath propagation.

This paper describes the design of an adaptable, low-cost, and energy efficient gesture detection system. The system leverages the ambient light available in the environment to perform Visible Light Sensing (VLS) using powerful Convolutional Neural Networks. The focus lies on designing a system that is capable of robust gesture detection in any environment while only utilizing a limited number (3) of photodiode sensors. The research conducted in this paper contributes to two crucial aspects of VLS gesture recognition systems. First, it shows how the photodiode sensors can be automatically fine-tuned using four resistors to achieve excellent sensing performance in a wide range of lighting environments from 50 Lux up to 150k Lux. Secondly it is shown that a photodiode arrangement consisting of an equilateral triangle with sides of 5cm facilitates the highest performance and robustness using Dynamic Time Warping for general and user-friendly gestures.