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日本电报电话公司横须贺研究所为进一步降低远距离数字微波系统的成本和提高频率利用率,研究了能在现用频带内进行大容量传输的新的超多值调制技术,用256QAM调解器成功地进行了所内的传输实验。 256QAM方式与己往的16QAM比较,在同一频带内可传二倍的容量,为409Mb/s,折合电话是5760路;因此,频率利用率提高了一倍,达10b/s/Hz。为实现这种方式,需研制精度为已往5倍的256QAM超多值调制器(组合载波的相位与振幅,形成256个信号状态)。它的实现与F-400M光传输
Yokosuka Institute of the Nippon Telegraph and Telephone Corporation In order to further reduce the cost and improve the frequency utilization rate of long-distance digital microwave systems, a new supermodulation modulation technique capable of high-capacity transmission in the active frequency band was studied. The 256QAM modem was successfully used Conducted the transmission experiment. Compared with the previous 16QAM, the 256QAM method can transmit twice the capacity of 409Mb / s in the same frequency band and the 5760-equivalent telephony; therefore, the frequency utilization rate is doubled to 10b / s / Hz. In order to do this, it is necessary to develop a 256QAM supermodulation modulator (combining the phase and amplitude of the carrier to form 256 signal states) with a resolution of 5 times in the past. It’s realized with F-400M optical transmission