Method and apparatus for capacity increase and enhanced communications performance in CATV networks

• US 6,647,069 B1
• Filed: 04/30/1999
• Issued: 11/11/2003
• Est. Priority Date: 05/01/1998
• Status: Expired due to Fees

• Current Assignee: Intel Corporation
• Original Assignee: Texas Instruments, Inc.
• Inventors: Shalvi, Ofir, Reznic, Zvi, Segal, Mordechai
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US09/302,872
• Time in Patent Office: 1,656 Days
• Field of Search: 375/219, 375/220, 375/222, 375/251, 375/260, 375/267, 375/262, 375/278, 375/284, 375/285, 375/296, 375/298, 375/324, 375/335, 375/340, 375/346, 375/350, 375/341, 455/50.1, 455/63, 455/67.3, 455/103, 455/133, 455/295, 455/296, 455/306, 348/6, 348/21, 370/282, 370/478, 370/464, 370/533, 370/535, 370/536, 370/539, 725/54, 725/67-68, 725/98, 725/118, 725/148, 725/151
• US Class Current: 375/278
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 7/102 Circuits therefor, e.g. noise reducers, equalisers, amplifiers H04N7/108 takes precedence

Abstract

In a cable television (CATV) data communication network, channel throughput and communications robustness are increased in a manner that improves speed of data transmission while maintaining compatibility with existing specifications and equipment. Enhanced throughput can be realized using the return channel of the CATV network. Alternatively, data retransmission and/or diversity techniques can be used to improve throughput.

Claims

1. A communication system for communicating a data signal using a cable television transmission medium, the communication arrangement comprising:

an encoder configured to encode an input data stream as an encoder output signal;

a transmission filter arrangement, responsive to the encoder output signal and configured to reduce adjacent channel interference in the encoder output signal and to generate a filter output signal;

a modulator, configured to modulate the filter output signal, generating a modulated radio frequency signal for transmission using the cable television transmission medium; and

a receiver arrangement coupled to receive the modulated radio frequency signal and configured to generate a stream of detected data based on the received modulated radio frequency signal, wherein the receiver arrangement comprises;

an analog front end arrangement, configured to sample a desired signal from the received modulated radio frequency signal at less than the Nyquist rate and to cause thereby a shift in a center frequency of the desired signal from an initial frequency to a lower frequency;

a modified matched filter configured to perform a convolution of a square-root raised cosine filter and a pre-calculated filter and to generate a modified matched filter output signal;

an adaptive equalizer, responsive to the modified matched filter output signal and configured to generate an equalizer output signal; and

a decoder, responsive to the equalizer output signal and configured to decode the equalizer output signal and to generate the stream of detected data.

2. A communication system, according to claim 1, wherein the analog front end arrangement comprises:

a plurality of band pass filters coupled to receive the modulated signal, each of the band pass filters centered around a different frequency;

a multiplexer coupled to receive output signals from the band pass filters and to couple a selected one of the band pass filter output signals to an output of the multiplexer;

an analog to digital converter, responsive to the output of the multiplexer and to an output of a clock signal generator and configured to provide a digital signal, generated as a function of the output of the multiplexer and the output of the clock signal generator, to a digital receiver.

3. A communication arrangement, according to claim 2, wherein the analog front end arrangement further comprises sample rate logic configured to provide, as a function of the center frequency, a select signal to the multiplexer, a rate parameter to the clock signal generator, and a spectrum inversion indication to the digital receiver.

4. A communication system, according to claim 1, wherein the adaptive equalizer comprises an adaptive decision feedback equalizer.

5. A communication system, according to claim 1, wherein the pre-calculated filter comprises

a pre-equalizer, configured to reduce interference attributable to at least one of ISI and ingress noise associated with a communication channel, and

a 1+α

z<sup>−

N</sup> filter, coupled to the output of the pre-equalizer and configured to generate a filter output signal;

and wherein the receiver arrangement comprises

a Viterbi decoder, configured to generate a Viterbi decoder output signal as a function of the filter output signal; and

a forward error correction decoder, configured to generate a corrected decoder output signal in response to the Viterbi decoder output signal.

6. A communication system, according to claim 1, further comprising a modified slicer arrangement configured to produce an estimate of an original transmitted symbol.

7. A communication system, according to claim 6, wherein the modified slicer arrangement comprises:

a slicer configured to estimate an output of the encoder;

a filter having a response of α

Z<sup>−

N</sup>;

a summing arrangement configured to add an output of the slicer to an output of the filter having a response of α

Z<sup>−

N</sup>;

a subtracting arrangement configured to subtract the output of the filter having a response of α

Z<sup>−

N</sup> from an input of the modified slicer;

an error estimation arrangement, coupled to both an input and the output of the slicer and configured to estimate a receiver error; and

a modified error estimation arrangement, coupled to both an input and the output of the modified slicer and configured to estimate the receiver error.

8. A communication system for communicating a data signal using a cable television transmission medium, the communication arrangement comprising:

an encoder configured to encode an input data stream as an encoder output signal;

a transmission filter arrangement, responsive to the encoder output signal and configured to reduce adjacent channel interference in the encoder output signal and to generate a filter output signal;

a modulator, configured to modulate the filter output signal, generating a modulated radio frequency signal for transmission using the cable television transmission medium;

an analog front end arrangement, configured to sample a desired signal from the modulated radio frequency signal at less than the Nyquist rate and thereby to cause a shift in a center frequency of the desired signal from an initial frequency to a lower frequency;

a modified matched filter configured to perform a convolution of a square-root raised cosine filter and a pre-calculated filter and to generate an modified matched filter output signal;

an adaptive equalizer, responsive to the modified matched filter output signal and configured to generate an equalizer output signal; and

a decoder, responsive to the equalizer output signal and configured to decode the equalizer output signal and to generate a stream of detected data.

9. A communication method for communicating a data signal using a cable television transmission medium, the communication method comprising:

encoding an input data stream as an encoder output signal;

filtering the encoder output signal to reduce adjacent channel interference in the encoder output signal, thereby generating a filter output signal;

modulating the filter output signal to generate a modulated radio frequency signal for transmission using the cable television transmission medium;

receiving the modulated radio frequency signal;

generating a stream of detected data based on the received modulated radio frequency signal;

sampling a desired signal from the received modulated radio frequency signal at less than the Nyquist rate and causing thereby a shift in a center frequency of the desired signal from an initial frequency to a lower frequency;

performing a convolution of a square-root raised cosine filter and a pre-calculated filter and to generate an modified matched filter output signal;

generating an equalizer output signal as a function of the modified matched filter output signal; and

decoding the equalizer Output signal to generate the stream of detected data.

10. A communication method, according to claim 9, further comprising:

providing a select signal to the multiplexer as a function of the center frequency;

providing a rate parameter as a function of the center frequency; and

providing a spectrum inversion indication as a function of the center frequency.