Co-channel Interference Assessment for Line-of-Sight and Nearly Line-of-Sight Millimeter-Waves Cellular LMDS Architecture

Behavior of co-channel interference in fixed wireless cellular systems, such as millimeter-waves Local Multipoint Distribution Service (LMDS), is different compared to what has been established for mobile microwave systems. This is due to utilization of a high-gain antenna for the subscriber. In this paper, first the analysis of signal-to-interference ratio (SIR) is presented for line-of-sight and nearly line-of-sight LMDS architecture. In this analysis, the effects of precipitation and foliage attenuation and depolarization have been considered. These two parameters have negligible effect on the microwave mobile systems but in millimeter-wave range are among the most important factors in the link budget. To mitigate the fading due to shadowing by buildings and trees, a highly overlapped architecture and macro-diversity are proposed. After analysis of downlink SIR in previously proposed cellular systems, a cellular architecture is proposed based on polarization interleaving and frequency segmentation which has a much higher SIR yield. The statistical assessment of SIR is accomplished by assuming lognormal distribution for the received signals.