Iterative decoding of joint data, time varying unknown symbol timing duration and phase tracking for wireless sensor networks and RFID systems

In this article a new class of receiver subsystems is introduced to enhance the performance of detection of signals in wireless sensor networks. The receiver design is applicable for detection of signals from any active or passive sensor, and ideal specifically for passive Radio Frequency Identification (RFID) tags. The system proposed herein employs iterative algorithms based on so called “Turbo Principle”. In this article, this theory is applied to sensory class of signals and waveforms. Iterative processing techniques with soft-input-soft-output (SISO) components is a novel approach to combine channel decoding with time varying symbol duration and phase tracking. This is achieved with exchange of probabilities or “soft information”. In presence of additive white Gaussian noise (AWGN) the performance of the receiver converge to the ideal coherent receiver. This class of digital packet radios is an essential ingredient to provide wide-area RFID reader systems, and gateways and access points for collecting data from new generation of emerging Internet of Things and sensor devices.