Method and apparatus for filtering digital television signals

Abstract

A system for filtering digital television signals is provided. The system comprises a generator for providing a first data sequence to a private data packetizer, and a transmitter for transmitting the packetized first data sequence in a data channel of a digital television signal. The system further includes a receiver for receiving the digital television signal and recovering the first data sequence. The receiver includes a channel estimator for providing an estimate of channel characteristics, such as estimated channel impulse estimate and estimated noise variance. The receiver further includes an adaptive equalizer filter having an input for receiving the digital television signal and an input for receiving adaptive filter coefficients. The receiver further includes a coefficient processor for calculating adaptive filter coefficients based on the channel estimate, and providing the adaptive filter coefficients to the adaptive equalizer filter. The digital television signal is thus filtered to remove undesired channel effects.

1. A method of filtering a digital television transmission comprising the steps of:
 generating a plurality of packetized first data sequence  sequences distributed over a training interval at a transmitter;  
 transmitting through a channel, a digital television stream including said packetized first data sequence  sequences;  
 receiving said digital television stream at a receiver and recovering said first data sequence  sequences  from said digital television stream;  
 comparing ones of said first data sequence  sequences to a second data sequence, said second data sequence being locally generated, to provide a channel estimate;  
 applying said received television bit stream to an adaptive filter;  
 adaptively adjusting filter coefficients of said adaptive filter according to said channel estimate such that undesirable channel effects upon said received television stream are filtered from said received television stream, wherein the digital television transmission is a digital television signal and said data sequences are transmitted in a private channel of an MPEG (Motion Picture Expert Group) data channel.  
 
     
     
       2. The method of filtering a digital television transmission according to  claim 1  wherein the digital television transmission is a high definition television (HDTV) signal and said data sequences are transmitted in a private channel of an MPEG (Motion Picture Expert Group) data channel. 
     
     
       3. The method of filtering a digital television transmission according to  claim 1  wherein said first data sequence is corrupted by noise after passage through said channel to said receiver. 
     
     
       4. The method of filtering a digital television transmission to according to  claim 3  wherein said first data sequence corrupted by noise is used to compute an estimate of channel frequency response. 
     
     
       5. The method of filtering a digital television transmission according to  claim 4   A method of filtering a digital television transmission comprising the steps of:
   generating a packetized first data sequence at a transmitter;    
   transmitting through a channel, a digital television stream including said packetizing first data sequence;    
   receiving said digital television stream at a receiver and recovering said first data sequence from first data sequence from said digital television stream;    
   comparing said first data sequence to a second data sequence, said second data sequence being locally generated, to provide a channel estimate;    
   applying said received television bit stream to an adaptive filter;    
   adaptively adjusting filter coefficients of said adaptive filter according to said channel estimate such that undesirable channel effects upon said received television stream are filtered from said received television stream, wherein said first data sequence is corrupted by noise after passage through said channel to said receiver and is used to compute an estimate of channel frequency response, and  wherein the step of comparing comprises the steps of: 
 computing a Fast Fourier Transform (FFT) of said first data sequence corrupted by noise;    computing a FFT of said second data sequence; and    
 dividing the FFT of said first data sequence by the FFT of said second data sequence to provide said estimate of channel frequency response.  
 
     
     
       6. The method of filtering a digital television transmission according to  claim 5  further comprising the step of determining said channel impulse  frequency response using a quotient from said step of dividing. 
     
     
       7. The method of filtering a digital television transmission according to  claim 6  wherein the step of determining said channel impulse  frequency response comprises the step of windowing an Inverse FFT (IFFT) of said quotient of the dividing step. 
     
     
       8. The method of filtering a digital television transmission according to  claim 7  further comprising the step of estimating noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT, said first data sequence corrupted by noise and said second data sequence. 
     
     
       9. The method of filtering a digital television transmission according to  claim 8  wherein said step of estimating noise variance comprises the steps of:
 convolving said windowed IFFT with said second data sequence to generate an estimated noiseless output;  
 subtracting said estimated noiseless output from said first data sequence corrupted by noise to generate a difference signal; and  
 computing an average energy estimation from said difference signal.  
 
     
     
       10. The method of filtering a digital television transmission according to  claim 9  wherein said channel impulse  frequency response and the estimate of noise variance are used to computer optimum equalizer coefficients for the step of adaptively adjusting filter coefficients. 
     
     
       11. The method of filtering a digital television transmission according to  claim 1  wherein said first transmitted data sequence is encrypted. 
     
     
       12. The method of filtering a digital television transmission according to  claim 1   A method of filtering a digital television transmission comprising the steps of:
   generating a packetized first data sequence at a transmitter;    
   transmitting through a channel, a digital television stream including said packetizing first data sequence;    
   receiving said digital television stream at a receiver and recovering said first data sequence from first data sequence from said digital television sequence;    
   comparing said first data sequence to a second data sequence, said second data sequence being locally generated, to provide a channel estimate;    
   applying said received television bit stream to an adaptive filter;    
   adaptively adjusting filter coefficients of said adaptive filter according to said channel estimate such that undesirable channel effects upon said received television stream are filtered from said received television stream,  wherein said first data sequence is transmitted in a dynamic or rolling frame/packet structure.  
 
     
     
       13. A system  An apparatus for filtering a digital television signal comprising:
 a generator for generating first data sequences at a transmitter and the transmitter for broadcasting said digital television signal including said first data sequences in a broadcast channel;  
 a receiver for receiving the digital television signal, said receiver including: 
 a channel estimator for comparing said  first data sequences to second data sequences, said second data sequences being locally generated, and for providing an estimate of the impulse response of said channel at an output of said channel estimator; and  
 an adaptive equalizer filter including an input for receiving said digital television signal, and filter taps in communication with said output of said channel estimator such that filter coefficients of said adaptive filter are adjusted according to said estimate of said impulse response of said channel, wherein the digital television signal comprises a high definition television ( HDTV )  signal and said first data sequences are transmitted in a private data stream of an MPEG  ( Motion Picture Expert Group )  channel .  
 
 
     
     
       14. The apparatus for filtering a digital television signal according to  claim 13  wherein the digital television signal comprises a high definition television (HDTV) signal and said first data sequences are transmitted in a private data stream of an MPEG (Motion Picture Expert Group) channel. 
     
     
       15. The apparatus for filtering a digital television signal according to  claim 13  wherein said first data sequences are corrupted by noise after passage through the channel to the receiver. 
     
     
       16. The apparatus for filtering a digital television signal according to  claim 15  wherein said first data sequences corrupted by noise are used to compute an estimate of the frequency response of said channel. 
     
     
       17. The apparatus for filtering a digital television transmission according to  claim 16   An apparatus for filtering a digital television signal comprising:
   a generator for generating first data sequences at a transmitter and the transmitter for broadcasting said digital television signal including said first data sequences in a broadcast channel;    
   a receiver for receiving the digital television signal, said receiving including;    
   a channel estimator for comparing said first data sequences to second data sequences, said second data sequences being locally generated, and for providing an estimate of the impulse response of said channel at an output of said channel estimator; and    
   an adaptive equalizer filter including an input for receiving said digital television signal, and filter taps in communication with said output of said channel estimator such that filter coefficients of said adaptive filter are adjusted according to said estimate of said impulse response of said channel, wherein the digital television signal comprises a high definition television  ( HDTV )  signal and said first data sequences are corrupted by noise after passage through the channel to the receiver, said first data sequences corrupted by noise being used to compute an estimate of the frequency response of said channel,  wherein said channel estimator comprises: 
 a first Fast Fourier Transform (FFT) processor for computing a FFT of said first data sequences corrupted by noise;    
 a generator for generating the second data sequences at the receiver;  
 a second FFT processor for computing a FFT of said second data sequences; and  
 a divider for dividing an output of said first FFT processor by an output of said second FFT processor to produce said estimate of channel frequency response.  
 
     
     
       18. The apparatus for filtering a digital television signal according to  claim 17  further comprising an estimator for estimating the channel impulse response using a quotient from said divider. 
     
     
       19. The apparatus for filtering said digital television signal according to  claim 18  wherein said estimator includes a processor for windowing an Inverse FFT (IFFT) of the quotient of the divider. 
     
     
       20. The apparatus for filtering a digital television signal according to  claim 19  further comprising a channel estimator configured to provide an estimate of noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT, said first data sequences corrupted by noise and said second data sequences. 
     
     
       21. The apparatus for filtering a digital television signal according to  claim 20  wherein said noise variance estimator comprises:
 a convolver for convolving said windowed IFFT with said second data sequences to generate an estimated noiseless output;  
 a subtractor for subtracting said estimated noiseless output from said first data sequences corrupted by noise to generate a difference signal; and  
 a processor for computing an average energy estimation from said difference signal.  
 
     
     
       22. The apparatus for filtering a digital television signal according to  claim 20  wherein said channel impulse response and said estimate of noise variance are used to compute optimum equalizer coefficients for adaptively adjusting filter coefficients. 
     
     
       23. The apparatus for filtering a digital television signal according to  claim 13  wherein said first data sequences are encrypted. 
     
     
       24. The apparatus for filtering a digital television signal according to  claim 13   An apparatus for filtering a digital television signal comprising:
   a generator for generating first data sequences at a transmitter and the transmitter for broadcasting said digital television signal including said first data sequences in a broadcast channel;    
   a receiver for receiving the digital television signal, said receiver including:    
   a channel estimator for comparing said first data sequences to second data sequences, said second data sequences being locally generated, and for providing an estimate of the impulse response of said channel at an output of said channel estimator; and    
   an adaptive equalizer filter including an input for receiving said digital television signal, and filter taps in communication with said output of said channel estimator such that filter coefficients of said adaptive filter are adjusted according to said estimate of said impulse response of said channel,  wherein said first data sequences are transmitted in a dynamic or rolling frame/packet structure.  
 
     
     
       25. A method of processing a digital television stream including a plurality of first data sequences distributed over a training interval transmitted through a channel comprising the steps of:
   receiving said digital television stream at a receiver and recovering said first data sequence from said digital television stream;        comparing at least one of said first data sequences to a second data sequence, said second data sequence being locally generated;        applying said received television stream to an adaptive filter;        adaptively adjusting filter coefficients of said adaptive filter according to said comparing step such that undesirable channel effects upon said received television stream are filtered from said received television stream, wherein the digital television stream is a high definition television  ( HDTV )  signal and said first data sequences are transmitted in a channel of an MPEG  ( Motion Picture Expert Group )  data channel.     
     
     
       26. The method of processing a digital television stream according to  claim 25  wherein said first data sequences are corrupted by noise after passage through said channel to said receiver. 
     
     
       27. The method of processing a digital television stream to according to  claim 26  wherein said first data sequences corrupted by noise are used to compute an estimate of channel frequency response. 
     
     
       28. The method processing a digital television stream according to  claim 25  wherein said first data sequence is encrypted. 
     
     
       29. A method of processing a digital television stream including a packetized first data sequence transmitted through a channel comprising the steps of:
   receiving said digital television stream at a receiver and recovering said first data sequence from said digital television stream;        comparing said first data sequence to a second data sequence, said second data sequence being locally generated, to provide a channel estimate;        applying said received television stream to an adaptive filter;        adaptively adjusting filter coefficients of said adaptive filter according to said channel estimate such that undesirable channel effects upon said received television stream are filtered from said received television stream, wherein said first data sequence is corrupted by noise after passage through said channel to said receiver and is used to compute an estimate of channel frequency response, wherein the step of comparing comprises the steps of:      computing a Fast Fourier Transform  ( FFT )  of said first data sequence corrupted by noise;        computing a FFT of said second data sequence; and        dividing the FFT of said first data sequence by the FIT of said second data sequence to provide said estimate of channel frequency response.       
     
     
       30. The method of processing a digital television stream according to  claim 29  further comprising the step of determining said channel frequency response using a quotient from said step of dividing. 
     
     
       31. The method of processing a digital television stream according to  claim 30  wherein the step of determining said channel frequency response comprises the step of windowing an Inverse FFT ( IFFT )  of said quotient of the dividing step.   
     
     
       32. The method of processing a digital television stream according to  claim 31  further comprising the step of estimating noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT, said first data sequence corrupted by noise and said second data sequence. 
     
     
       33. The method of processing a digital television stream according to  claim 32  wherein said step of estimating noise variance comprises the steps of:
   convolving said windowed IFFT with said second data sequence to generate an estimated noiseless output;    
   subtracting said estimated noiseless output from said first data sequence corrupted by noise to generate a difference signal; and    
   computing an average energy estimation from said difference signal.   
 
     
     
       34. The method of processing a digital television stream according to  claim 33  wherein said channel frequency response and the estimate of noise variance are used to compute optimum equalizer coefficients for the step of adaptively adjusting filter coefficients. 
     
     
       35. A method of processing a digital television stream including a packetized first data sequence transmitted through a channel comprising the steps of:
   receiving said digital television stream at a receiver and recovering said first data sequence from said digital television stream;        comparing said first data sequence to a second data sequence, said second data sequence being locally generated, to provide a channel estimate;        applying said received television stream to an adaptive filter;        adaptively adjusting filter coefficients of said adaptive filter according to said channel estimate such that undesirable channel effects upon said received television stream are filtered from said received television stream, wherein said first data sequence is transmitted in a dynamic or rolling frame/packet structure.     
     
     
       36. A method of transmitting a digital television stream through a channel comprising the steps of:
   generating a plurality of packetized first data sequences distributed over a training interval to be compared in a receiver coupled to said channel to a second data sequence, said second data sequence being locally generated, to adaptively adjust filter coefficients of an adaptive filter such that undesirable channel effects on a television stream received from said channel are filtered from said received television stream; and        transmitting through said channel, a digital television stream including said packetized first data sequences, wherein said first data sequences are transmitted in a private channel of an MPEG  ( Motion Picture Expert Group )  data channel.     
     
     
       37. The method of transmitting a digital television stream according to  claim 36  wherein said first data sequences are corrupted by noise after passage through said channel to said receiver. 
     
     
       38. The method of transmitting a digital television stream to according to  claim 37  wherein said first data sequences corrupted by noise are used to compute an estimate of channel frequency response. 
     
     
       39. The method of transmitting a digital television stream according to  claim 36  wherein said first transmitted data sequence is encrypted. 
     
     
       40. A method of transmitting a digital television stream through a channel comprising the steps of:
   generating a packetized first data sequence to be compared in a receiver coupled to said channel to a second data sequence, said second data sequence being locally generated, to provide a channel estimate for adaptively adjusting filter coefficients of an adaptive filter such that undesirable channel effects on a television stream received from said channel are filtered from said received television stream; and        transmitting through said channel, a digital television stream including said        packetized first data sequence, wherein said first data sequence is corrupted by noise after passage through said channel to said receiver, said first data sequence corrupted by noise being used to compute an estimate of channel frequency response, wherein the step of comparing comprises the steps of:      computing a Fast Fourier Transform  ( FFT )  of said first data sequence corrupted by noise;        computing; a FFT of said second data sequence; and        dividing the FFT of said first data sequence by the FFT of said second data sequence to provide said estimate of channel frequency response.       
     
     
       41. The method of transmitting a digital television stream according to  claim 40  further comprising the step of determining said channel frequency response using a quotient from said step of dividing. 
     
     
       42. The method of transmitting a digital television stream according to  claim 41  wherein the step of determining said channel frequency response comprises the step of windowing an Inverse FFT ( IFFT )  of said quotient of the dividing step.   
     
     
       43. The method of transmitting a digital television stream according to  claim 42  further comprising the step of estimating noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT said first data sequence corrupted by noise and said second data sequence. 
     
     
       44. The method of transmitting a digital television stream according to  claim 43  wherein said step of estimating noise variance comprises the steps of:
   convolving said windowed IFFT with said second data sequence to generate an estimated noiseless output;    
   subtracting said estimated noiseless output from said first data sequence corrupted by noise to generate a difference signal; and    
   computing an average energy estimation from said difference signal.   
 
     
     
       45. The method of transmitting a digital television stream according to  claim 44  wherein said channel frequency response and the estimate of noise variance are used to compute optimum equalizer coefficients for the step of adaptively adjusting filter coefficients. 
     
     
       46. A method of transmitting a digital television stream through a channel comprising the steps of:
   generating a packetized first data sequence to be compared in a receiver coupled to said channel to a second data sequence, said second data sequence being locally generated, to provide a channel estimate for adaptively adjusting filter coefficients of an adaptive filter such that undesirable channel effects on a television stream received from said channel are filtered from said received television stream; and        transmitting through said channel, a digital television stream including said packetized first data sequence, wherein said first data sequence is transmitted in a dynamic or rolling frame/packet structure.     
     
     
       47. An apparatus for processing a digital television signal including a plurality of first data sequences distributed over a training interval transmitted in a broadcast channel comprising:
   a receiver for receiving said digital television signal, said receiver including;        a comparator for comparing said first data sequences to second data sequences, said second data sequences being locally generated; and        an adaptive equalizer filter including an input for receiving said digital television signal, and being in communication with said output of said comparator such that filter coefficients of said adaptive filter are adjusted in response to comparator, wherein said first data sequences are transmitted in an MPEG Motion Picture Expert Group )  channel.     
     
     
       48. The apparatus for processing a digital television signal according to  claim 47  wherein said first data sequences are corrupted by noise after passage through said channel to said receiver. 
     
     
       49. The apparatus for processing a digital television signal according to  claim 48  wherein said first data sequences corrupted by noise are used to compute an estimate of the frequency response of said channel. 
     
     
       50. The apparatus for processing a digital television signal according to  claim 47  wherein said first data sequences are encrypted. 
     
     
       51. An apparatus for processing a digital television signal including first data sequences transmitted in a broadcast channel comprising:
   a receiver for receiving said digital television signal, said receiver including:      a channel estimator for comparing said first data sequences to second data sequences, said second data sequences being locally generated, and for providing an estimate of the impulse response of said channel at an output of said channel estimator; and        an adaptive equalizer filter including an input for receiving said digital television signal, and filter taps in communication with said output of said channel estimator such that filter coefficients of said adaptive filter are adjusted according to said estimate of said impulse response of said channel, wherein said first data sequences are corrupted by noise after passage through said channel to said receiver and wherein said first data sequences corrupted by noise are used to compute an estimate of the frequency response of said channel, wherein said channel estimator comprises:      a first Fast Fourier Transform  ( FFT )  processor for computing a FFT of said first data sequences corrupted by noise;        a generator for generating the second data sequences at the receiver;        a second FFT processor for computing a FFT of said second data sequences; and        a divider for dividing an output of said first FFT processor by an output of said second FFT processor to produce said estimate of channel frequency response.         
     
     
       52. The apparatus for processing a digital television signal according to  claim 51  further comprising; an estimator for estimating the channel impulse response using a quotient from said divider. 
     
     
       53. The apparatus for processing a digital television signal according to  claim 52  wherein said estimator includes a processor for windowing an Inverse FFT ( IFFT )  of the quotient of the divider.   
     
     
       54. The apparatus for processing a digital television signal according to  claim 53  further comprising a channel estimator configured to provide an estimate of noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT, said first data sequences corrupted by noise and said second data sequences. 
     
     
       55. The apparatus for processing a digital television signal according to  claim 54  wherein said noise variance estimator comprises:
   a convolver for convolving said windowed IFFT with said second data sequences to generate an estimated noiseless output;    
   a subtractor for subtracting said estimated noiseless output from said first data sequences corrupted by noise to generate a difference signal; and    
   a processor for computing average energy estimation from said difference signal.   
 
     
     
       56. The apparatus for processing a digital television signal according to  claim 55  wherein said channel impulse response and said estimate of noise variance are used to compute optimum equalizer coefficients for adaptively adjusting filter coefficients. 
     
     
       57. An apparatus for processing a digital television signal including first data sequences transmitted in a broadcast channel comprising:
   a receiver for receiving said digital television signal, said receiver including;      a channel estimator for comparing said first data sequences to second data sequences, said second data sequences being locally generated, and for providing an estimate of the impulse response of said channel at an output of said channel estimator; and        an adaptive equalizer filter including an input for receiving said digital television signal, and filter taps in communication with said output of said channel estimator such that filter coefficients of said adaptive filter are adjusted according to said estimate of said impulse response of said channel, wherein said first data sequences are transmitted in a dynamic or rolling frame/packet structure.       
     
     
       58. An apparatus for transmitting a digital television signal through a channel comprising:
   a generator for generating a plurality of first data sequences distributed over a training interval to be compared in a receiver to at least one second data sequence, said second data sequence being locally generated to adjust filter coefficients of an adaptive filter; and        a transmitter for transmitting a digital television signal including said first data sequences through said channel, wherein said first data sequences are transmitted in an MPEG  ( Motion Picture Expert Group )  channel.     
     
     
       59. The apparatus for transmitting a digital television signal according to  claim 58  wherein said first data sequences are corrupted by noise after passage through the channel to said receiver. 
     
     
       60. The apparatus for transmitting a digital television signal according to  claim 59  wherein said first data sequences corrupted by noise are used to compute an estimate of the frequency response of said channel. 
     
     
       61. The apparatus for transmitting a digital television transmission according to  claim 60  wherein said channel estimator comprises:
   a first Fast Fourier Transform  ( FFT )  processor for computing a FFT of said first data sequences corrupted by noise;    
   a generator for generating said second data sequences at the receiver;    
   a second FFT processor for computing a FFT of said second data sequences; and    
   a divider for dividing an output of said first FFT processor by an output of said second FFT processor to produce said estimate of channel frequency response.   
 
     
     
       62. The apparatus for transmitting a digital television signal according to  claim 61  further comprising an estimator for estimating the channel impulse response using a quotient from said divider. 
     
     
       63. The apparatus for transmitting a digital television signal according to  claim 62  wherein said estimator includes a processor for windowing an Inverse FFT ( IFFT )  of the quotient the divider.   
     
     
       64. The apparatus for transmitting a digital television signal according to  claim 63  further comprising a channel estimator configured to provide an estimate of noise variance by computing average energy of channel estimation error sequence as a function of said windowed IFFT, said first data sequences corrupted by noise and said second data sequences. 
     
     
       65. The apparatus for transmitting a digital television signal according to  claim 64  wherein said noise variance estimator comprises:
   a convolver for convolving said windowed IFFT with said second data sequences to generate an estimated noiseless output;    
   a subtractor for subtracting said estimated noiseless output from said first data sequences corrupted by noise to generate a difference signal; and    
   a processor for computing average energy estimation from said difference signal.   
 
     
     
       66. The apparatus for transmitting a digital television signal according to  claim 64  wherein said channel impulse response and said estimate of noise variance are used to compute optimum equalizer coefficients for adaptively adjusting, filter coefficients. 
     
     
       67. An apparatus for transmitting a digital television signal through a channel comprising:
   a generator for generating first data sequences to be compared in a receiver to second data sequences, said second data sequences being locally generated to provide an estimate of the impulse response of said channel for adjusting filter coefficients of an adaptive filter; and        a transmitter for transmitting a digital television signal including said first data sequences through said channel, wherein the digital television signal comprises a high definition television  ( HDTV )  signal and said first data sequences are transmitted in a private data stream of an MPEG  ( Motion Picture Expert Group )  channel, wherein said first data sequences are encrypted.     
     
     
       68. An apparatus for transmitting a digital television signal through a channel comprising:
   a generator for generating first data sequences to be compared in a receiver to second data sequences, said second data sequences being locally generated to provide an estimate of the impulse response of said channel for adjusting filter coefficients of an adaptive filter; and        a transmitter for transmitting a digital television signal including said first data sequences through said channel, wherein said first data sequences are transmitted in a dynamic or rolling frame/packet structure.