Patent ID: 6954493
Filing Date: 2005-10-11
Classification: H04L

Abstract:
1. A modem apparatus comprising: a demodulator configured to demodulate a received symbol subjected to quadrature amplitude modulation; a memory configured to store the demodulated symbol; and a controller configured to detect coordinates of the demodulated symbols on a signal space diagram, to calculate a cross product of two vectors from the origin of the signal space diagram to the detected coordinates of two consecutive demodulated symbols, to obtain a polarity array of the calculation result over a plurality of consecutive demodulated symbols, and to determine a rotation direction of the demodulated symbol, based on the obtained polarity array, the controller being further configured to determine that the received symbol is a Sh signal when positive polarity appears at least two times consecutively in the polarity array after a communication in compliance with Recommendation V.34 begins through a control channel.