Multispot diffusing configuration for wireless infrared access

• Published in: IEEE transactions on communications 2000-06, Vol.48 (6), p.970-978
• Main Authors: Jovkova, S.T., Kavehard, M.
• Format: Article
• Language: English
• Subjects: Arrays; Delay; Diffusion; Diversity reception; Holographic optical components; Holography; Infrared; Lighting; Noise levels; Optical losses; Optical receivers; Optical transmitters; Power distribution; Receivers; Signal to noise ratio; Spreads; Transmitters
• ISSN: 0090-6778; 1558-0857
• DOI: 10.1109/26.848558

In order to combine the advantages and to overcome the drawbacks of a direct line-of-sight or a diffuse configuration for wireless infrared access, a multispot diffusing concept utilizing a holographic spot array generator is presented. Simulation results are presented and compared with those for a pure diffuse configuration in terms of link characteristics, when a single-element or a multibranch composite receiver is employed. The multispot transmitter ensures a more uniform signal power distribution. Improvements of about 2 dBo (optical decibels) can be achieved compared to a Lambertian pattern illumination. The increased power path loss at the edges of the communication cell is accompanied with a decrease in the delay spread resulting in an extension of the coverage range. Utilization of angle diversity detection improves the signal-to-noise ratio by more than 7 dB when selecting the best receiver branch and more than 10.5 dB in the case of maximal-ratio combining. Use of a multibeam transmitter and an angle diversity receiver reduces the likelihood of shadowing of the receiver due to an obstacle standing along the path between the receiver and the transmitter.