Channel estimation and transmit power control in wireless body area networks

Wireless body area networks have recently received much attention because of their application to assisted living and remote patient monitoring. For these applications, energy minimisation is a critical issue since, in many cases, batteries cannot be easily replaced or recharged. Reducing energy expenditure by avoiding unnecessary high transmission power and minimising frame retransmissions is therefore crucial. In this study, a transmit power control scheme suitable for IEEE 802.15.6 networks operating in beacon mode with superframe boundaries is proposed. The transmission power is modulated, frame-by-frame, according to a run-time estimation of the channel conditions. Power measurements using the beacon frames are made periodically, providing reverse channel gain and an opportunistic fade margin, set on the basis of prior power fluctuations, is added. This approach allows tracking of the highly variable on-body to on-body propagation channel without the need to transmit additional probe frames. An experimental study based on test cases demonstrates the effectiveness of the scheme and compares its performance with alternative solutions presented in the literature

Adaptive Windowed Sinc Filter for Image Interpolation

In this thesis, an image interpolation scheme using an adaptive windowed sinc, which varies in length and frequency response guided by the Laplacian operator, is proposed to improve quality and accuracy. First, an optimization is performed to minimize the squared error for each sliding window by sweeping a range of windowed sinc filters with varying filter lengths. The relationship between the windows, filter length, and edge intensity is analyzed to determine the optimal beta value and filter length. This analysis inspires an image interpolation approach that uses the Laplacian of each sliding window to choose the optimal beta and filter length. The performance of the proposed approach is compared with the optimized result, as well as traditional interpolation methods such as bilinear and bicubic, in terms of PSNR, SSIM, and a subjective visual test. The findings demonstrate the effectiveness of the proposed method in enhancing the resolution of images, contributing to a deeper understanding of adaptive windowed sinc filters and their potential applications in image interpolation