High speed indoor wireless systems with directional antennas

The consequences of designing indoor wireless systems with directional antennas at one or both ends of a line-of-sight link are investigated. The authors determine how narrow the beamwidth must be so that the maximum data rate is not limited by multipath effects. For such beamwidths, simple unequalized 2-level FSK or PSK modems can be used in place of the more costly and complex a `anti-multipath´ modems, and data rates above 1 Gbit/sec may be achieved. The channel impulse response in an empty room is estimated using geometrical optics, observing that with directional antennas, multipath rays must arrive from the same direction as the line of sight (LOS) ray. The link outage probability is then estimated as a function of antenna beamwidth, and guidelines are established for the selection of frequency band and antenna placement. Experiments using a 19-GHz 622-Mb/s BPSK link and 15 degree beamwidth horn antennas in an office building with plaster walls and large metallized windows have demonstrated error-free performance on both LOS and non-LOS links