Design Considerations for LMDS

CT&T has demonstrated that the Cellular Vision System¿ produces a video S/N of at least 45dB, even under rain faded conditions at the edge of a cell. Under these conditions, a Q of approximately 4 is obtainable. A Q of 5 id obtainable under the vast majority of cases (all but 8 hours per year for 99.9% availability in fringe areas). The Cellular Vision System¿ has show that the combination of spatial separation of cells, frequency interleaving, polarization isolation, and antenna discrimination effects suppress co-channel interference between LMDS transmitters such that a Q of 5 is obtainable in 100% of receiver locations. Should receiver sites suffer from co-channel interference for any reason after these methods are applied, exploitation of the FM threshold characteristic by receiver level control and the effects of path blockage and earth curvature will likely eliminate any remaining co-channel interference. Accordingly, it is clear that the CT&T Cellular Vision System¿ for cellular LMDS affords the spectral efficiency benefits of frequency reuse within each and every cell without cell-to-cell interference. Further, it is clear that the use of polarization isolation and frequency interleaving are essential to achieve the desired cell-to-cell interference ratios.