Fast and Efficient Adaptation Algorithms for Multi-Gigabit Wireless Infrared Systems

Multibeam angle adaptive systems (MBAAS) have been shown to offer performance improvements over traditional spot-diffusing optical wireless systems. However, an increase in the computational cost is incurred. This paper introduces a method to speed up the adaptation process through efficient use of a divide and conquer algorithm by recursively breaking down the scanning process and focusing it into a smaller region in each iteration. The new, fast and efficient angle adaptation algorithm offers the advantages of optimizing the number and pattern (positions) of the spots so as to maximize the receiver's signal-to-noise ratio (SNR), regardless of the transmitter's position, the receiver's orientation and its field of view. It can also adapt to environmental changes, providing a robust link against shadowing and signal blockage. Furthermore, a beam delay adaptation method is used to reduce the effect of multipath dispersion and inter-symbol interference. The combination of angle and delay adaptation adds a degree of freedom to the link design, resulting in a compact impulse response and a system that is able to achieve higher data rates (15 Gbit/s). Significant improvements in the SNR, with optical wireless channel bandwidths of more than 15 GHz are obtained, and eye safety is considered while operating at 15 Gbit/s with full mobility in a realistic environment where shadowing exists.