Fast symbol synchronization for use in conditioning a receiving modem

摘要

Modems at ends of a transmission line are synchronized with each other by a training procedure which initiates each of a plurality of communication sessions occurring while a connection between the modems is established. The initial communication session begins with a long training sequence. Ensuing communication sessions utilize a time-saving short training sequence which includes the following. A coarse timing algorithm establishes synchronization on a symbol boundary from two alternating elements transmitted in accordance with a standard and of which a plurality of amplitude samples are taken. A fine timing algorithm then quickly finds the peak point of the symbol so that the sampling instance can be adjusted accordingly. This is accomplished by identifying, which sample of an element represents the maximum amplitude between the elements. A comparison is made between the identified sample and its preceding one for that element, and the identified sample and its succeeding one for that element. The sampling instance is shifted based on such comparison to thereby adjust the synchronization.