Claims
- 1. A method for decoding a received signal comprising at least one trellis coded modulated signal and a center-band pilot signal containing a Rayleigh-faded component, comprising the steps of:
- (a) filtering said received signal to extract said center-band pilot signal, thus providing an extracted center-band pilot signal;
- (b) applying said extracted center-band pilot signal to a frequency discriminator to provide a frequency discriminator output;
- (c) applying said frequency discriminator output to a soft limiter to provide a metric modifier ("s");
- (d) decoding said at least one trellis coded modulated signal using at least one Viterbi decoder whose metric ("m") is modified responsive to the formula:
- m=(1-s)d.sup.2
- where 1>s.gtoreq.0, and d is the Euclidian distance.
- 2. A radio having a decoder for decoding a received signal comprising at least one trellis coded modulated signal and a center-band pilot signal containing a Rayleigh-faded component, said decoder comprising:
- means for filtering said received signal to extract said center-band pilot signal, thus providing an extracted center-band pilot signal;
- means for applying said extracted center-band pilot signal to a frequency discriminator to provide a frequency discriminator output;
- means for applying said frequency discriminator output to a soft limiter to provide a metric modifier ("s");
- means for decoding said at least one trellis coded modulated signal using at least one Viterbi decoder whose metric ("m") is modified responsive to the formula:
- m=(1-s)d.sup.2
- where 1>s.gtoreq.0, and d is the Euclidian distance.
- 3. A radio having a trellis coded quadrature amplitude modulation (QAM) decoder for decoding a received signal comprising an upper QAM (UQAM) signal and a lower QAM (LQAM) signal and a center-band pilot signal containing a Rayleigh-faded component, said decoder comprising:
- means for filtering said received signal to extract said center-band pilot signal, thus providing an extracted center-band pilot signal;
- means for applying said extracted center-band pilot signal to a frequency discriminator to provide a frequency discriminator output;
- means for applying said frequency discriminator output to a soft limiter to provide a metric modifier ("s");
- means for decoding said UQAM signal using a first Viterbi decoder;
- means for decoding said LQAM signal using a second Viterbi decoder;
- said first and second Viterbi decoders each having a metric ("m") that is modified responsive to the formula:
- m=(1-s)d.sup.2
- where 1>s.gtoreq.0, and d is the Euclidian distance.
- 4. A method for decoding a received signal comprising a trellis coded modulated signal and a center-band pilot signal containing a Rayleigh-faded component, comprising the steps of:
- (a) low-pass filtering said received signal to extract said center-band pilot signal, thus providing an extracted center-band pilot signal;
- (b) applying said extracted center-band pilot signal to a frequency discriminator to provide a frequency discriminator output;
- (c) applying said frequency discriminator output to a soft limiter to provide a metric modifier ("s");
- (d) decoding said trellis coded modulated signal using a Viterbi decoder whose metric ("m") is modified responsive to the formula:
- m=(1-s)d.sup.2
- where 1>s.gtoreq.0, and d is the Euclidian distance.
- 5. A method for decoding a received signal (11) comprising a center-band pilot signal containing a Rayleigh-faded component, an upper side band trellis coded modulated signal and a lower side band trellis coded modulated signal, comprising the steps of:
- (a) low-pass filtering (13) said received signal to extract said center-band pilot signal (57), thus providing an extracted center-band pilot signal;
- (b) applying said extracted center-band pilot signal (57) to a frequency discriminator (59) to provide a frequency discriminator output;
- (c) applying said frequency discriminator output to a soft limiter (65) to provide a metric modifier ("s") (67,69);
- (d) using said metric modifier s to modify the metric ("m") of a first Viterbi decoder (53) and a second Viterbi decoder (55) responsive to the formula;
- m=(1-s)d.sup.2
- where 1>s.gtoreq.0, and d is the Euclidian distance;
- (e) decoding said upper side band trellis coded modulated signal using said first Viterbi decoder (53);
- (f) decoding said lower side band trellis coded modulated signal using said second Viterbi decoder (55);
- (g) combining (71) the results of step (e) and step (f) to form an output signal (73).
- 6. The method of claim 1 wherein s is defined by the following equation: ##EQU1## where the parameters A, B and C are optimized for the particular modulation and frequency discriminator used.
- 7. The radio of claim 2 wherein s is defined by the following equation: ##EQU2## where the parameters A, B and C are optimized for the particular modulation and frequency discriminator used.
- 8. The radio of claim 3 wherein s is defined by the following equation: ##EQU3## where the parameters A, B and C are optimized for the particular modulation and frequency discriminator used.
- 9. The method of claim 4 wherein s is defined by the following equation: ##EQU4## where the parameters A, B and C are optimized for the particular modulation and frequency discriminator used.
- 10. The method of claim 5 wherein s is defined by the following equation: ##EQU5## where the parameters A, B and C are optimized for the particular modulation and frequency discriminator used.
REFERENCE TO EARLIER-FILED U.S. PATENT APPLICATION
This is a continuation-in-part of Salomon Serfaty, "Improved Trellis Decoder," application Ser. No. 07/390,564, filed Aug. 7, 1989, now abandoned.
US Referenced Citations (1)
Number |
Name |
Date |
Kind |
4945549 |
Simon et al. |
Jul 1990 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
390564 |
Aug 1989 |
|