Verfahren und Vorrichtung zur Überprufung eines Übertragungskanals in einem Kommunikationssystem

摘要

The method involves determining the characteristics of the channel (105) with the aid of two test sequences transmitted by a calling modem (100). The pref. sequence (L1) is a periodic set of cosine waveforms spaced 150 Hz apart in 11 bands from 150 Hz to 3.75 kHz. At the receiver (14) a sampler (15) and digital signal processor (17) calculate the transfer function and the noise variance of the channel, and work out the best frequency band and bit rate for transmission, which are conveyed to the originating modem from the called modem (110).