Receiver for robust data extension for 8VSB signaling

In a communication system having a transmitter responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said trellis decoder further includes a selected Branch Metric signal, said receiver further including a normal/robust signal coupled to said trellis decoder to indicate when a normal encoded symbol or a robust encoded symbol, respectively, is being received, wherein said receiver further includes a symbol timing controller, a carrier control unit, an equalizer control unit and a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the updating of said plurality of filter coefficients of said decision feedback equalizer on a coefficient by coefficient basis, the receiver comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• a symbol timing controller responsive to said Path Metric Minimum Average and said normal/robust signal to control symbol timing recovery;
• a carrier recovery control unit, responsive to said Path Metric Minimum Average and said normal/robust signal to control carrier recovery;
• an equalizer control unit responsive to said Path Metric Minimum Average and said normal/robust signal to control said decision feedback equalizer;
• said equalizer control unit further including a Tap Control signal generator in said equalizer control unit coupled to said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• a Noise Enhancement signal generator in said decision feedback equalizer responsive to said Tap Control signal to generate a Noise Enhancement signal proportional to a level of noise in said receiver;
• said trellis decoder further including a Branch Metric signal modification circuit responsive to said Noise Enhancement signal to modify said selected Branch Metric signal in said trellis decoder to produce an adjusted selected Branch Metric signal;
• and
• said trellis decoder further being responsive to said adjusted selected Branch Metric signal and said normal/robust signal in said trellis decoder to generate said Path Metric Minimum Average.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver shaving a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, an improved method comprising:

• computing a Path Metric Minimum Average as an average of said Path Metric Minimum function wherein said Path Metric Minimum Average is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and
• multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, said improvement further comprising:
• decoding said encoded multiplexed data by a normal decoding method when said normal/robust signal indicates a normal data transmission and
• decoding said encoded multiplexed data by a robust decoding method when said normal/robust signal indicates a robust data transmission.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, an improved receiver apparatus comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, said improvement further comprising:
• a normal decoder coupled to said encoded multiplexed data when said normal/robust signal indicates a normal data transmission and
• a robust decoder coupled to said encoded multiplexed data when said normal/robust signal indicates a robust data transmission.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a symbol timing controller to control symbol timing recovery, an improved method comprising:

• computing a Path Metric Minimum Average as the average of said Path Metric Minimum function wherein said Path Metric Minimum Average is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• generating a symbol timing recovery loop bandwidth selection signal in said symbol timing controller responsive to said normal/robust signal and said Path Metric Minimum Average for selecting a loop bandwidth constant for the symbol timing recovery loop filter;
• selecting a Constant Modulus Algorithm (CMA) symbol timing recovery loop bandwidth constant if said symbol timing recovery loop bandwidth selection signal is a first value;
• and
• selecting a decision directed (DD) symbol timing recovery loop bandwidth constant if said symbol timing recovery loop bandwidth selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a symbol timing controller to control symbol timing recovery, a receiver improvement comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• a symbol timing recovery loop bandwidth selection signal generator in said symbol timing controller responsive to said normal/robust signal and said Path Metric Minimum Average;
• and
• a multiplexer (MUX) responsive to said symbol timing recovery loop bandwidth selection signal to select a Constant Modulus Algorithm (CMA) symbol timing recovery loop bandwidth constant when said symbol timing recovery loop bandwidth selection signal is a first value, and to select a decision directed (DD) symbol timing recovery loop bandwidth constant if said symbol timing recovery loop bandwidth selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a carrier control unit, an improved method comprising:

• computing a Path Metric Minimum Average as the average of said Path Metric Minimum function wherein said Path Metric Minimum Average is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• generating a carrier loop bandwidth selection signal in said carrier control unit responsive to said normal/robust signal and said Path Metric Minimum Average for selecting a loop bandwidth constant for the carrier recovery loop filter;
• selecting a Constant Modulus Algorithm (CMA) carrier loop bandwidth constant if said carrier loop bandwidth selection signal is a first value;
• and
• selecting a decision directed (CDD) carrier loop bandwidth constant if said carrier loop bandwidth selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a carrier control unit, an improved apparatus comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• a carrier loop bandwidth selection signal generator in said carrier control unit responsive to said normal/robust signal and said Path Metric Minimum Average;
• and
• a multiplexer (MUX) responsive to said symbol timing recovery loop bandwidth selection signal to select a Constant Modulus Algorithm (CMA) symbol timing recovery loop bandwidth constant when said symbol timing recovery loop bandwidth selection signal is a first value, and to select a decision directed (DD) symbol timing recovery loop bandwidth constant if said symbol timing recovery loop bandwidth selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, an improved method comprising:

• computing a Path Metric Minimum Average as the average of said Path Metric Minimum function wherein said Path Metric Minimum Average is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• generating an error selection signal in said equalizer control unit responsive to said normal/robust signal and said Path Metric Minimum Average for selecting an error function for said decision feedback equalizer;
• selecting function Constant Modulus Algorithm (CMA) error function Constant Modulus Algorithm (CMA) error function if said error selection signal is a first value;
• and
• selecting function decision directed (DD) error function decision directed (DD) error function if said error selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver having a trellis decoder for decoding said trellis encoded symbols, wherein said receiver includes stored path metrics for a plurality of state transition paths through said trellis decoder, and a receiver method including selecting the minimum path metric of said stored path metrics corresponding to the most likely path for each particular state of said trellis decoder, and selecting a survivor path corresponding to said selected minimum path metric and generating a Path Metric Minimum function, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, wherein said receiver further includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, an improved apparatus comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• an error selection signal generator in said equalizer control unit responsive to said normal/robust signal and said Path Metric Minimum Average for selecting an error function for said decision feedback equalizer;
• and
• a multiplexer (MUX) responsive to said error selection signal to select function Constant Modulus Algorithm (CMA) error function Constant Modulus Algorithm (CMA) error function when said error selection signal is a first value, and to select function decision directed (DD) error function decision directed (DD) error function when said error selection signal is a second value.

In a communication system having a transmitter providing trellis encoded symbols, wherein said communication system is responsive to first and second data, encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, and a receiver having a trellis decoder for decoding said trellis encoded symbols, an equalizer control unit and a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis, wherein said receiver includes the method of storing the path metrics for a plurality of state transition paths through said trellis decoder, selecting the minimum of said stored path metrics to generate the most likely path for each particular state of said trellis decoder and selecting a survivor path corresponding to said selected minimum path metric, and generating a Path Metric Minimum function and a selected Branch Metric signal, an improved receiver method comprising:

• computing a Path Metric Minimum Average as the average of said Path Metric Minimum function wherein said Path Metric Minimum Average is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• generating a Tap Control signal responsive to said Path Metric Minimum Average in said equalizer control unit for use in said decision feedback equalizer, wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• using said Tap Control signal in said decision feedback equalizer to generate a Noise Enhancement signal proportional to a level of noise in said receiver;
• using said Noise Enhancement signal to modify said selected Branch Metric signal to produce an adjusted selected Branch Metric signal;
• and
• using said adjusted selected Branch Metric signal in said trellis decoder to generate said Path Metric Minimum Average.

In a communication system having a transmitter providing trellis encoded symbols, wherein said communication system is responsive to first and second data, encoding said first data by a normal encoding method, encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, and a receiver having a trellis decoder for decoding said trellis encoded symbols, an equalizer control unit and a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis, wherein said receiver includes a method of storing the path metrics for a plurality of state transition paths through said trellis decoder, selecting the minimum of said stored path metrics to generate the most likely path for each particular state of said trellis decoder and selecting a survivor path corresponding to said selected minimum path metric, and generating a Path Metric Minimum function and a selected Branch Metric signal, an improved receiver apparatus comprising:

• a trellis decoder with a Path Metric Minimum Average generator wherein said Path Metric Minimum Average is an average of said Path Metric Minimum function and is an indication of the reliability of the survivor paths being selected by said trellis decoder;
• said equalizer control unit further including a Tap Control signal generator in said equalizer control unit coupled to said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• a Noise Enhancement signal generator in said decision feedback equalizer responsive to said Tap Control signal to generate a Noise Enhancement signal proportional to a level of noise in said receiver;
• said trellis decoder further including a Branch Metric signal modification circuit responsive to said Noise Enhancement signal to modify said selected Branch Metric signal in said trellis decoder to produce an adjusted selected Branch Metric signal;
• and
• said trellis decoder further being responsive to said adjusted selected Branch Metric and said normallrobust signal in said trellis decoder to generate said Path Metric Minimum Average.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, a method comprising:

• generating a Tap Control signal in said equalizer control unit for use in said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• updating said coefficients if said Tap control signal is at said first value;
• holding said coefficients at its current values if said Tap control signal is at said second value;
• wherein said decision feedback equalizer includes a decision directed (DD) mode and an hR mode, and a decision feedback equalizer error term, a method for updating said plurality of filter coefficients in decision directed mode, said method comprising:
• generating a Noise Enhancement signal proportional to a level of noise in said receiver;
• computing a Confidence factor from said Noise Enhancement Signal and a long average of channel noise (average noise), wherein said Confidence factor is a scaling factor proportional to the confidence in the received symbol at that time;
• and
• updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line using said decision feedback equalizer error term scaled by said Confidence factor.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, a method comprising:

• generating a Tap Control signal in said equalizer control unit for use in said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• updating said coefficients if said Tap control signal is at said first value;
• holding said coefficients at its current values if said Tap control signal is at said second value;
• wherein said decision feedback equalizer includes a decision directed (DD) mode and an IIR mode, and a decision feedback equalizer error term, a method for updating said plurality of filter coefficients in decision directed mode, said method comprising:
• generating a Noise Enhancement signal proportional to a level of noise in said receiver;
• computing a Confidence factor from said Noise Enhancement Signal and a long average of channel noise (average noise), wherein said Confidence factor is a scaling factor proportional to the confidence in the received symbol at that time;
• updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line using said decision feedback equalizer error term when said Tap Control signal is said first value;
• and
• updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line using said decision feedback equalizer error term scaled by said Confidence factor when said Tap Control signal is said second value.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, an apparatus comprising:

• said equalizer control unit further including a Tap Control signal generator in said equalizer control unit coupled to said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• a coefficient updating circuit responsive to said Tap Control signal to update said coefficients if said Tap Control signal is at said first value, and to hold said coefficients at its current values if said Tap Control signal is at said second value;
• wherein said decision feedback equalizer includes a decision directed (DD) mode and an IIR mode, and a decision feedback equalizer error term, an apparatus for updating said plurality of filter coefficients in decision directed mode, said apparatus comprising:
• a Noise Enhancement signal generator in said decision feedback equalizer responsive to said Tap Control signal to generate a Noise Enhancement signal proportional to a level of noise in said receiver;
• a Confidence factor computation circuit responsive to said Noise Enhancement Signal and a long average of channel noise (average noise), wherein said Confidence factor is a scaling factor proportional to the confidence in the received symbol at that time;
• and
• a filter coefficient updating circuit for updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line using said decision feedback equalizer error term scaled by said Confidence factor.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, an apparatus comprising:

• said equalizer control unit further including a Tap Control signal generator in said equalizer control unit coupled to said decision feedback equalizer wherein said Tap
• Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• a coefficient updating circuit responsive to said Tap Control signal to update said coefficients if said Tap Control signal is at said first value, and to hold said coefficients at its current values if said Tap Control signal is at said second value;
• wherein said decision feedback equalizer includes a decision directed (DD) mode and an IIR mode, and a decision feedback equalizer error term, an apparatus for updating said plurality of filter coefficients in decision directed mode, said apparatus comprising:
• a Noise Enhancement signal generator in said decision feedback equalizer to generate a Noise Enhancement signal proportional to a level of noise in said receiver;
• a Confidence factor signal generator responsive to said Noise Enhancement Signal and a long average of channel noise (average noise), wherein said Confidence factor is a scaling factor proportional to the confidence in the received symbol at that time;
• a filter coefficient updating circuit responsive to said Tap Control signal for updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line in said decision feedback equalizer error term when said Tap Control signal is said first value;
• and not updating corresponding ones of said plurality of filter coefficients at each tap position of said tapped delay line using said decision feedback equalizer error term scaled by said Confidence factor when said Tap Control signal is said second value.

In a communication system having a transmitter providing trellis encoded symbols, a dual phase trellis decoder method comprising:

• decoding a positive phase of a received signal in a first trellis decoder having stored path metrics for a plurality of state transition paths through said first trellis decoder the state of which is defined in accordance with said positive phase;
• decoding a negative phase of said received signal in a second trellis decoder having stored path metrics for a plurality of state transition paths through said second trellis decoder the state of which is defined in accordance with said negative phase,
• selecting a first Path Metric Minimum of said stored path metrics of said first trellis decoder corresponding to the most likely path for each particular state of said first trellis decoder, and a first survivor path corresponding to the selected a first Path Metric Minimum;
• selecting a second Path Metric Minimum of said stored path metrics of said second trellis decoder corresponding to the most likely path for each particular state of said second trellis decoder, and a second survivor path corresponding to the selected second Path Metric Minimum;
• and
• selecting one of said first or second survivor paths corresponding to the lower of said first Path Metric Minimum and said second Path Metric Minimum as the survivor path of said dual phase trellis decoder.

In a communication system having a transmitter providing trellis encoded symbols, a dual phase trellis decoder apparatus comprising:

• a first trellis decoder having stored path metrics for a plurality of state transition paths through said first trellis decoder the state of which is defined in accordance with a positive phase, said first trellis decoder adapted to select a first Path Metric Minimum of said stored path metrics corresponding to the most likely path for each particular state of said first trellis decoder, and a first survivor path corresponding to the selected first Path Metric Minimum;
• a second trellis decoder having stored path metrics for a plurality of state transition paths through said first trellis decoder the state of which is defined in accordance with a negative phase;
• said second trellis decoder adapted to select a second Path Metric Minimum of said stored path metrics of the second trellis decoder corresponding to the most likely path for each particular state of said second trellis decoder, and a second survivor path corresponding to the selected second Path Metric Minimum;
• and
• said dual phase trellis decoder further including a multiplexer (MUX) responsive to a Resolve Phase Ambiguity signal to select one of said first or second survivor paths corresponding to the lower of said first Path Metric Minimum and said second Path Metric Minimum as the survivor path of said dual phase trellis decoder.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver including a trellis decoder, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method and encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, a method comprising:

• storing a first plurality of constellation points corresponding to the constellation points of said normal encoded data:
• storing a second plurality of constellation points corresponding to the constellation points of said robust encoded data:
• receiving a channel symbol corresponding to said encoded multiplexed data;
• computing a first absolute minimum value of a difference between said channel symbol and the ideal value of the nearest constellation point of said first plurality of constellation points for that said channel symbol when said normal/robust signal indicates a normal data transmission as a first Branch Metric signal;
• computing a second absolute minimum value of the difference between said channel symbol and the ideal value of the nearest constellation point of said second plurality of constellation points for that said channel symbol when said normal/robust signal indicates a robust transmission as a second Branch Metric signal;
• modifying said first Branch Metric signal to provide an adjusted first Branch Metric signal;
• modifying said second Branch Metric signal to provide an adjusted second Branch Metric signal;
• adding a first stored path metric to said adjusted first Branch Metric signal to provide a first adjusted path metric;
• adding a second stored path metric to said adjusted second Branch Metric signal to provide a second adjusted path metric;
• selecting the minimum of said first adjusted path metric and said second adjusted path metric to provide a selected minimum path metric;
• and
• selecting a path metric value and survivor data corresponding to said selected minimum path metric.

In a communication system having a transmitter providing trellis encoded symbols, and a receiver including a trellis decoder, wherein said communication system is responsive to first and second data corresponding to respective first and second symbols, said transmitter encoding said first data by a normal encoding method and encoding said second data by a robust encoding method and multiplexing normal encoded data with robust encoded data, to form encoded multiplexed data, said receiver further including a normal/robust signal coupled to said trellis decoder, said receiver comprising:

• a first memory in which a first plurality of constellation points corresponding to the constellation points of said normal encoded data is stored:
• a second memory in which a second plurality of constellation points corresponding to the constellation points of said robust encoded data is stored:
• said receiver providing a channel symbol corresponding to said encoded multiplexed data;
• a first subtractor circuit generating a difference of said channel symbol and an ideal value of the nearest constellation point of said first plurality of constellation points stored in said first memory for that said channel symbol when said normal/robust signal indicates a normal data transmission as a first Branch Metric signal;
• a first absolute minimum value circuit responsive to said first subtractor circuit;
• a second subtractor circuit generating a difference of said channel symbol and an ideal value of the nearest constellation point of said second plurality of constellation points stored in said second memory for that said channel symbol when said normal/robust signal indicates a normal data transmission as a second Branch Metric signal;
• a second absolute minimum value circuit responsive to said second subtractor circuit;
• a first multiplier responsive to said first Branch Metric signal to provide an adjusted first Branch Metric signal;
• a second multiplier responsive to said second Branch Metric signal to provide an adjusted second Branch Metric signal;
• a first adder responsive to a first stored path metric and said adjusted first Branch Metric signal to provide a first adjusted path metric;
• a second adder responsive to a second stored path metric and said adjusted second Branch Metric signal to provide a second adjusted path metric;
• a comparator circuit responsive to said first adjusted path metric and said second adjusted path metric to provide a selected minimum path metric;
• and
• a selector circuit responsive to said selected minimum path metric to select a path metric value and survivor data corresponding to said selected minimum path metric.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and

• an equalizer control unit, a method for generating a Noise Enhancement signal proportional to a level of noise in said receiver, said method comprising:
• generating a Tap Control signal in said equalizer control unit for use in said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• inverting said Tap Control signal to form a negated Tap Control signal, wherein negating said Tap Control signal means substituting said first value for said second value and substituting said second value for said first value;
• multiplying said negated Tap Control signal by a corresponding coefficient of said decision feedback equalizer corresponding to said tap of said tapped delay line of said decision feedback equalizer to form a scaled coefficient for said tap;
• squaring each said scaled coefficient to form a squared scaled coefficient for each tap of said tapped delay line;
• and
• summing said squared scaled coefficient for each tap of said tapped delay line to form said Noise Enhancement signal.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, an apparatus for generating a Noise Enhancement signal proportional to a level of noise in said receiver, said apparatus comprising:

• generating a Tap Control signal in said equalizer control unit for use in said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• an inverter coupled to said Tap Control signal to form a negated Tap Control signal, wherein negating said Tap Control signal means substituting said first value for said second value and substituting said second value for said first value;
• a multiplier responsive to said negated Tap Control signal and a corresponding coefficient of said decision feedback equalizer corresponding to the tap of said tapped delay line of said decision feedback equalizer to form a scaled coefficient for said tap;
• a squaring circuit responsive to each said scaled coefficient to form a squared scaled coefficient for each tap of said tapped delay line;
• and
• an adder circuit responsive to said squared scaled coefficient for each tap of said tapped delay line to form said Noise Enhancement signal.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, further including a tapped delay line for storing past soft decision symbols (I), a method for generating a Noise Enhancement signal proportional to a level of noise in said receiver, said method comprising:

• generating a Tap Control signal in said equalizer control unit for use in said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• computing the difference term (I−I^) between past soft decision symbols (I) and hard decision symbols (I^);
• multiplying the difference term (I−I^) by a corresponding coefficient of said decision feedback equalizer corresponding to the tap of said tapped delay line of said decision feedback equalizer to form a scaled coefficient for said tap;
• squaring each said scaled coefficient to form a squared scaled coefficient for each tap of said tapped delay line;
• and
• summing said squared scaled coefficient for each tap of said tapped delay line to form said Noise Enhancement signal.

In a communication system having a transmitter and a receiver, wherein said receiver includes a decision feedback equalizer having a plurality of filter coefficients and a tapped delay line for controlling the coefficient updating of the coefficients of said decision feedback equalizer on a coefficient by coefficient basis and an equalizer control unit, further including a tapped delay line for storing past soft decision symbols (I), an apparatus for generating a Noise Enhancement signal proportional to a level of noise in said receiver, said apparatus comprising:

• said equalizer control unit further including a Tap Control signal generator in said equalizer control unit coupled to said decision feedback equalizer wherein said Tap Control signal at each tap position of said tapped delay line is a first value if the symbol at a tap is a symbol with a high reliability of being correct and a second value if the symbol at said tap is a symbol that could not be reliably predicted;
• a subtractor circuit coupled to I and I^, the output of said subtractor circuit being the difference term (I−I^) between past soft decision symbols (I) and hard decision symbols (I^);
• a multiplier coupled to said difference term (I−I^), the output of said multiplier being the difference term (I−I^) multiplied by a corresponding coefficient of said decision feedback equalizer corresponding to the tap of said tapped delay line of said decision feedback equalizer to form a scaled coefficient for said tap;
• a squaring circuit coupled to each said scaled coefficient to form a squared scaled coefficient for each tap of said tapped delay line;
• and
• an adder circuit responsive to said squared scaled coefficient for each tap of said tapped delay line to form said Noise Enhancement signal.