Multispot diffusing configuration for wireless infrared access

In order to combine the advantages and to overcome the drawbacks of a direc t 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 tran smitter ensures a more uniform signal power distribution. Improvements of a bout 2 dBo (optical decibels) can be achieved compared to a Lambertian patt ern illumination. The increased power path loss at the edges of the communi cation cell is accompanied with a decrease in the delay spread resulting in an extension of the coverage range. Utilization of angle diversity detecti on improves 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 combini ng. Use of a multibeam transmitter and an angle diversity receiver reduces the likelihood of shadowing of the receiver due to an obstacle standing alo ng the path between the receiver and the transmitter.