First implementation of an operating 256 QAM 400 Mb/s microwave radio system

The design and performance of a 4, 5, 6-GHz, 400-Mb/s microwave radio system are described. The use of a 256-QAM (quadrature amplitude modulation) scheme in the system is discussed. An overall field test has been performed on the system for a 63.5-km overwater route. Results indicate that the outage probability of the 256-QAM system with SD, four-carrier transmission, a transversal equalizer (TRV-EQL), and a cross-polarization interference canceller (XPIC) is within the design objective. Based on these results, a 400-km-long commercial route was constructed and is currently in service.<>