Indoor Radio Reception at 60 GHz: Fading Mitigation Using Diversity Techniques

Several radio propagation experiments have been conducted to analyze the propagation impairments in indoor scenarios at 60 GHz when mobile and portable terminals are used. The power variation with distance and the signal fading has been measured and characterized. Results show that the power decay with distance is similar for both types of terminals, while signal fading is more relevant in mobile reception, with fades up to 6 dB occurring as often as 1% of the time. Moreover, when a mobile terminal is considered, wideband measurements show that the coherence bandwidth is lower than the channel bandwidth, and that a wideband modulation scheme like COFDM should be adequate to reduce signal fading. Alternatively, the use of space diversity at the receiver has been considered to mitigate signal fading. The antenna separation needed to assure a low envelope correlation has been determined. Diversity gain, for an outage probability of 1%, has been calculated and ranges from 3 to 5 dB, depending on the combination technique used.