OFDM. COFDM: Rohde&Schwarz GN2130 digital voice modem

Rohde&Schwarz GN2130 digital voice modem

OFDM, Ch - 48, Sh - 56.25, Br - 44.4(4), QAM-16/PSK-4, k = 17/64

Author: SergUA6 

Band Width ~ 2700 Hz

Low Range ~ 360 Hz

Baud Rate 44.4(4) Hz

n-Ary (PSK/MPSK) Mixed QAM-16/PSK-4

Count of Carriers 48

Step between carriers 56.25 Hz

ACF Typical ~ 45 ms

RX mode  SSB

The record of GN2130 is here.

Sonorgams:

pic.1  General view

Diagrams:

pic.2 General quantity of the channels

pic.3 The constellation in the channel

R&S GN2130 - is the The voice modem, optionaly delivered to HF transceiver XK200 of R&S corporation. It is used for a speech transmission after conversions into a digital form, closing of the data by means of internal cryptoprocessor is possible. In this example, 48 channel OFDM signal is orginized, with standard enough parametres. 


Modulation in the channels is mixed QAM-16/PSK-4.  Features: it is necessary to mark presence of the auxiliary/pilot-symbols , in every second symbol through every one channel for synchronisation and customisation/fine tuning of the adaptive corrector the special signals are transmitted. Also there is a presence of the preamble with duration about 600 msec. Maximum common technical speed for QAM-16 is ~ 8533 bps.