Hub architecture for infra-red wireless networks in office environments

The paper describes a LOS system architecture that allows for a data rate of 155 Mbit/s on both down- and up-links. To achieve this, arrays of vertical cavity surface emitting lasers (VCSELs) are used that emit light of 850 nm and have an output power that is within eye-safety limits. Original theory is presented that permits calculation of the coverage area for a certain launch power and receiver sensitivity. Design equations are presented for the selection of the beam shaping/spreading lens placed in front of the laser arrays. Original results from an experimental testbed compare favorably with theoretical predictions. It is concluded that an 8 x 8 laser array will cover an area of 1 m by 1 m. The addition of a tracking system would permit multiuser operation with each individual user having access to the full bandwidth of the link.