DIGITAL RADIO-RELAY SYSTEMS IN NTT

摘要

NTT has developed the first digital radio-relay system using 2GHz band in 1969. Since that time, a number of kinds of digital radio-relay systems in the 2GHz, 4/SGHz, 11/15GHz and 20GHz bands which operate at bit rates from 3Mb/s to 400Mb/s per one radio channel and use 4PSK, 8PSK, or 16QAM, have been introduced for short-haul and long-haul transmission lines. NTT is now concentrating its effort on construction of digital networks in order to realize its Information Network System (INS) in which digital radio systems are expected to play an important role in the economical and rapid construction of digital transmission routes.This paper describes the current status of NTT's digital radio routes and outlines these radio-relay systems, and the service performance of the newly developed 5GHz band 200Mb/s 16QAM digital radio-relay system.