Patent ID: 7590419
Filing Date: 2009-09-15
Classification: H04B,H04W

Abstract:
1. In a Global System for Mobile Telephony (GSM) digital communication system, a method for single tone detection in a received signal, said method comprising the steps of: filtering a received signal, which contains one or more frequency tone signals, within a first pass band centered at a first center and containing the one or more frequency tone signals to generate a first filtered signal; filtering the received signal within a second pass band centered at a second center different than the first center to generate a second filtered signal, wherein the second pass band does not contain all of the one or more frequency tone signals; calculating an tone energy for the first filtered signal, wherein the estimated tone energy is a function of the amplitude of the first filtered signal; calculating an interference energy for the second filtered signal, wherein the interference energy is a function of the amplitude of the second filtered signal; and detecting presence of a single frequency tone signal in response to the tone energy being greater than the interference energy by a threshold amount for a threshold period of time.