Results of a 140 Mbit/s co-frequency cross-polarised 16 QAM trial

The results of a two-year trial of a cofrequency cross-polarized 16-QAM (quadrature amplitude modulation) system are discussed. A major subrefractive event in the first phase of the experiment that produced considerable median level fading which lasted for several hours, causing approximately 1200 s of outage, is described. After reducing FM interference and improving the flat fade margin from 32 to 42 dB, a cross-polarization interference channel was added. The second phase of the experiment showed that 140-Mb/s cochannel 16-QAM operation is a practical method for providing 140-Mb/s transmission to CCIR performance objectives without cross-polarization interference cancellers.<>