Enhanced decoder for a radio telephone

A method for identifying a bad GSM speech frame in digital mobile phone system, characterized in that the method comprises the steps of:

• receiving a signal;
• estimating the quality of the received signal using an estimated signal-to-noise ratio ESNR, where the ESNR is a vector comprising the estimated signal-to-noise ratio of each receiveg burst or a scalar describing their approximate signal-to-noise ratio, and a pseudo bit error rate PBER of a received and recorded speech frame, the ESNR and PBER being functionally related to a chosen threshold;
• and
• removing a speech frame if it fails to meet the threshold, and wherein
• f(a,b)=(C1*a)+(C2*b)
• is chosen for a function so that the speech frame is removed if
• (C1*ESNR)+(C2*PBER)>T
• wherein C1 and C2 are constants and the function is a linear combination of variables ESNR and PBER.

A method for identifying a bad GSM speech frame in digital mobile phone system, characterized in that the method is comprised of the steps of:

• receiving a signal;
• estimating the quality of the received signal using an estimated signal-to-noise ratio ESNR, where the ESNR is a vector comprising the estimated signal-to-noise ratio of each received burst or a scalar describing their approximate signal-to-noise ratio, and a pseudo bit error rate PBER of a received and recorded speech frame, the ESNR and PBER being functionally related by a function f to a chosen threshold;
• and
• removing a speech frame if it fails to meet the threshold, and wherein the function f and a threshold limit T are made adaptive.

A method for identifying a bad GSM speech frame in digital mobile phone system, characterized in that the method is comprised of the steps of:

• receiving a signal;
• estimating the quality of the received signal using an estimated signal-to-noise ratio ESNR, where the ESNR is a vector comprising the estimated signal-to-noise ratio of each received burst or a scalar describing their approximate signal-to-noise ratio, and a pseudo bit error rate PBER of a received and recorded speech frame, the ESNR and PBER being functionally related to a chosen threshold;
• and
• removing a speech frame if it fails to meet the threshold, wherein the speech frame is removed if
• f(ESNR, PBER)>T
• where f is a function of variables ESNR and PBER and T is a chosen threshold value, and wherein the threshold value is calculated
• BFI.sub.-- LIM=(SNR.sub.-- VAR)-C1)*C2+C3
• wherein SNR.sub.-- VAR is a variance of the values of the ESNR-vectors;
• and where the obtained result BFI.sub.-- LIM is limited in the following way
• C4.ltoreq.BFI.sub.-- LIM.ltoreq.C5
• so that the speech frame is removed if
• PBER>BFI.sub.-- LIM,
• where C1, C2, C3, C4 and C5 are constants defined by simulation.

A circuit for a radio telephone for providing speech frames from a modulated RF signal transmitted to the radio telephone as a plurality of digitally encoded bursts, comprising:

• an antenna for receiving said modulated RF signal;
• a demodulator for demodulating said received RF signal so as to extract digital information representing speech frames from said modulated RF signal;
• signal quality determination means having an input coupled to an output of said demodulator for providing, for each received burst, a first burst quality measure and a second burst quality measure, said first burst quality measure being indicative of a signal-to-noise ratio and said second burst quality measure being indicative of a bit error rate;
• and
• means, having inputs coupled to outputs of said signal quality determining means, and responsive to a function formed in accordance with a combination of said first and second burst quality measures, for rejecting the digital information of a burst having a function that fails to meet a burst quality threshold value.

A circuit for a radio telephone for providing speech frames from a modulated RF signal transmitted to the radio telephone as a plurality of digitally encoded bursts, comprising:

• an antenna for receiving said modulated RF signal;
• a demodulator for demodulating said received RF signal so as to extract digital information representing speech frames from said modulated RF signal;
• signal quality determination means having an input coupled to an output of said demodulator for providing, for each received burst, a first burst quality measure and a second burst quality measure, said first burst quality measure being indicative of a signal-to-noise ratio and said second burst quality measure being indicative of a bit error rate;
• and
• means, having inputs coupled to outputs of said signal quality determining means, and responsive to a comparison of said second burst quality measure with a burst quality threshold value, for rejecting the digital information of a burst having a second burst quality measure that fails to meet the burst quality threshold value;
• wherein said burst quality threshold value is derived at least in part from said first burst quality measure.