Head end receiver for digital data delivery systems using mixed mode SCDMA and TDMA multiplexing

• US 7,050,419 B2
• Filed: 02/23/2001
• Issued: 05/23/2006
• Est. Priority Date: 02/23/2001
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Terayon Communications Systems Incorporated (Motorola Solutions, Inc.)
• Inventors: Azenkot, Yehuda, Rakib, Selim Shlomo, Lind, Paul Alan, Grimwood, Michael
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Ly, Anh-Vu
• Application Number:
  US09/792,815
• Publication Number:
  US 20020154620A1
• Time in Patent Office: 1,915 Days
• Field of Search: 370/441, 370/442, 370/478, 370/479, 370/480, 370/503, 370/204, 370/290, 370/292, 370/458, 370/535, 370/347
• US Class Current: 370/347
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 5/026 using code division

Abstract

A pipelined digital data receiver for a cable TV headend which is capable of receiving DOCSIS 1.0 or 1.1 or advanced PHY TDMA or SCDMA bursts having programmable symbol rates and programmable modulation types as well as a host of other burst parameters such at Trellis code modulation on or off, scrambling on or off, various values for Reed-Solomon T number and codeword length. The receiver has an RF section to filter and digitize incoming RF signals. It also has an input section to detect impulse noise and do match filtering and despread SCDMA bursts. A timing recovery section recovers the symbol clock and detects the start of bursts and collisions. A rotational amplifier and equalizer calculate and track gain, phase and frequency offsets and correct symbols and calculates equalization coefficients. A decoder section decodes TCM and non TCM bursts, and a Reed-Solomon decoder section reconstructs RS codewords and uses them to error correct the payload data.

Claims

1. A digital data receiver, comprising:

first means for suppressing frequencies in an input spectrum other than the frequency components of a desired carrier and digitizing at least said desired carrier;

second means for recovering data encoded in one or more burst type transmitted at different times on the same frequency subchannel, said bursts being any of a plurality of different burst types, and for recovering data encoded in two TDMA bursts transmitted at the same first symbol rate on two adjacent frequency channels during a first interval as well as the data from multiple services encoded in an SCDMA burst transmitted during a second interval that does not overlap said first interval and having a symbol rate which is twice as high as the symbol rate of said TDMA bursts and transmitted on a frequency channel having a center frequency approximately at the boundary frequency between said two adjacent frequency channels on which said TDMA bursts were transmitted, said burst types characterized by at least the following characteristics;

DOCSIS 1.0 or 1.1 time division multiplexed;

advanced PHY time division multiplexed or synchronous code division multiplexed, and any one of a plurality of different symbol rates and modulation types; and

having programmable interleaving depth and block size, and being or not being Trellis code modulated; and

means for controlling said first and second means to operate correctly to receive the particular type of burst or bursts being received on one or more selectable frequency channels.

2. An apparatus comprising:

a filtering, mixing and digitizing circuit for receiving a spectrum of radio frequency signals and suppressing unwanted frequencies to leave a band of frequencies including a desired carrier frequency modulated with digital data, and for altering the frequency of at least said desired carrier to the center frequency of the passband of a narrow passband bandpass filter having a passband bandwidth matched to the bandwidth of the highest symbol rate burst that can be received, and for filtering said band of frequencies to remove more unwanted frequencies, and for performing intermediate frequency sampling and analog to digital conversion in an analog to digital converter on the output signal from said narrow passband bandpass filter;

a demodulator circuit for recovering the data transmitted in one or more burst type transmitted at different times on the same frequency subchannel, said bursts being any of a plurality of different burst types characterized by a plurality of programmable characteristics, said demodulator including at least a decimation and programmable bandwidth, digital matched filter for filtering out frequencies outside the bandwidth of the burst based upon the symbol rate of the burst, and a despreader circuit which can be bypassed for despreading the spectrum of code division multiplexed bursts, and a timing recovery circuit to recover the upstream symbol clock of at least TDMA bursts, and a master upstream clock for use in receiving SCDMA bursts, and a start of burst detector for measuring the time offset of the start of TDMA training bursts from a specified reference time for use by transmitters which transmitted said training bursts to achieve frame synchronization, and including a rotational amplifier to calculate and track phase, amplitude and frequency correction factors from the preamble of at least training bursts and use the correction factors to correct phase, amplitude and frequency errors in received symbols, and including an adaptive equalizer circuitry to develop equalization coefficients from the preamble of training bursts, and including deinterleaver and slicer detector circuitry for detecting the bits encoded in each received symbol and including a Trellis code modulation Viterbi decoder which detects the coded and uncoded bits of each received symbol in Trellis code modulated bursts and which is bypassed for non Trellis code modulated bursts, and including circuitry to deinterleave and detect the data bits encoded in transmitted constellation points of Trellis encoded SCDMA bursts, and including a descrambler that can be bypassed to unscramble scrambled bursts, and including programmable Reed Solomon deinterleaver and decoder circuitry to deinterleave and error correct Reed Solomon codewords encoded in said received symbols; and

a computer coupled to said demodulator and to said filtering, mixing and digitizing circuit and programmed to read said timing offset and equalization coefficients for transmission to transmitters which transmitted said training bursts and programmed to generate downstream messages for transmission to said transmitters which control which burst types each transmitter can send and when, and programmed to control the configuration and operation of said demodulator and said filtering, mixing and digitizing circuits to correctly receive said bursts in accordance with the burst type being received.

3. The apparatus of claim 2 wherein said computer is programmed to control said demodulator and said filtering, mixing and digitizing circuit to correctly receive any burst having predetermined combinations of the following characteristics:

DOCSIS 1.0 or 1.1 time division multiplexed;

advanced PHY time division multiplexed or synchronous code division multiplexed, and

any one of a plurality of different symbol rates and modulation types; and

having programmable interleaving depth and block size; and

being or not being Trellis code modulated; and

being differentially encoded or not for predetermined TDMA bursts; and

being Trellis code modulated or not; and

having a programmable preamble length and programmable preamble type; and

having a programmable Reed Solomon T value, and a programmable Reed Solomon codeword length; and

having a programmable scrambler seed value and being scrambled or not scrambled; and

having a programmable maximum burst length in minislots, and a

programmable guardtime in symbols between different intervals and having a

programmable last codeword length; and

having a programmable byte interleave depth, and a programmable byte interleaver block size; and

having a programmable number of codes per subframe for SCDMA bursts and a programmable SCDMA interleaver step size.

4. The apparatus of claim 2 or 3 wherein said computer is programmed to control said demodulator and said filtering, mixing and digitizing circuit to also correctly receive data encoded in two TDMA bursts transmitted at the same first symbol rate on two adjacent frequency channels during a first interval as well as the data from multiple services encoded in an SCDMA burst transmitted during a second interval that does not overlap said first interval and having a symbol rate which is twice as high as the symbol rate of said TDMA bursts and transmitted on a frequency channel having a center frequency approximately at the boundary frequency between said two adjacent frequency channels on which said TDMA bursts were transmitted.

5. The apparatus of claim 2 or 3 wherein said Trellis code modulation Viterbi decoder is structured to use a soft output Viterbi algorithm and outputs both the coded and uncoded bits of each received symbol as well as an erasure indication for said coded bits indicating the degree of confidence in the decoding of said coded bits, and wherein said Reed Solomon deinterleaving and decoding circuitry is coupled to receive said erasure indications for said coded bits from said Viterbi decoder and functions to use said erasure indications as well as Reed Solomon parity symbols added to each codeword to detect errors therein and correct at least some of said errors.

6. The apparatus of claim 2 or 3 wherein said slicer detector outputs the bits encoded in each received symbol as well as an erasure indication for said coded bits indicating the degree of confidence in the decoding of said bits, and wherein said Reed Solomon deinterleaving and decoding circuitry is coupled to receive said erasure indications from said slicer and functions to use said erasure indications as well as Reed Solomon parity symbols added to each codeword to detect errors therein and correct at least some of said errors.

7. The apparatus of claim 2 or 3 wherein said adaptive equalizer circuitry is structured to perform a coarse and fine filter coefficient convergence process with programmable step size.

8. The apparatus of claim 2 or 3 wherein said adaptive equalizer circuitry is structured to perform a coarse and fine filter coefficient convergence process such that during coarse equalization, the adaptive equalizer uses the known preamble symbols of a training burst using a relatively larger step size to adapt only a subset of the most significant feed forward tap coefficients of an FFE filter and a subset of the most significant feedback equalization filter tap coefficients of an FBE filter during the coarse equalization and then iteratively passes at least the preamble symbols of said training burst through said equalization circuitry to do a fine adaptive equalization convergence using a smaller step size to adapt all the tap coefficients of said FFE and FBE filters.

9. The apparatus of claim 2 or 3 wherein said adaptive equalizer circuitry is structured to perform a coarse and fine filter coefficient convergence process using programmable step size such that during a coarse equalization convergence, the adaptive equalizer uses the known preamble symbols of a training burst that includes known preamble symbols prepended to a data portion that identifies the transmitter that sent said training burst, said coarse equalization convergence performed using a relatively larger step size to adapt only a subset of the most significant feed forward tap coefficients of an FFE filter and a subset of the most significant feedback equalization filter tap coefficients of an FBE filter and then filters the data portion of said training burst using the coarse coefficients and forwards the filtered data portion of the training burst to other circuitry in said demodulator for detection, and then, automatically switches to a fine equalization convergence wherein said equalization circuitry iteratively passes at least the preamble symbols of said training burst through said equalization circuitry to do a fine adaptive equalization convergence using a smaller step size than was used during said coarse equalization convergence so as to adapt all the tap coefficients of said FFE and FBE filters to the final equalization tap coefficients to be sent to the transmitter which transmitted said training burst.

10. An apparatus comprising:

a broad passband bandpass filter;

a mixer having one input coupled to said bandpass filter and a local oscillator input for receiving a local oscillator signal, and having an output;

a local oscillator having an output frequency signal coupled to said local oscillator input;

a narrow passband filter coupled to said output of said mixer for outputting at least a desired signal;

an analog to digital converter coupled to digitize the output of said narrow passband filter for generating digital data samples of at least said desired signal;

a configurable demodulator capable of recovering data transmitted in said desired signal in bursts, said bursts being any one of the following types on the same or different frequency channels;

DOCSIS 1.0 or 1.0 time division multiplexed (TDMA) bursts or advanced PHY time division multiplexed or advanced PHY synchronous code division multiplexed (SCDMA) bursts;

and wherein each burst can have a predetermined one of a plurality of different symbol rates and a predetermined one of a plurality of different modulation types;

and wherein each burst may be Trellis code modulated or not; and

a computer coupled to said demodulator and programmed to configure said demodulator properly to receive the particular type of burst to be received by writing burst parameters into a burst parameter memory, said configurable demodulator having a timing and control circuit which uses said burst parameters in said burst parameter memory to control and configure said demodulator properly to receive the type of burst being received.

11. The apparatus of claim 10 wherein said local oscillator is frequency agile and has a frequency control input for receiving a frequency control signal which controls what frequency the local oscillator outputs, and wherein said computer is coupled to said frequency control input and is programmed to generate a frequency control signal at said frequency control input which causes said receiver to tune to the desired carrier frequency.

12. The apparatus of claim 10 wherein said demodulator is further structured so as to be capable of receiving different type bursts defined by the following burst parameters:

scrambled or not and scrambler seed;

variable byte interleaver depth and block size;

differential encoding on or off;

programmable preamble length, programmable preamble value offset, programmable preamble type, programmable Reed Solomon error correction T value between 0 to 16;

programmable Reed Solomon codeword length;

programmable maximum burst length in minislots;

programmable guardtime for TDMA and SCDMA bursts;

programmable last codeword length;

a programmable number of spreading codes per subframe; and

programmable SCDMA interleaver step size.

13. The apparatus of claim 10 further comprising a narrowband excision circuit coupled to process the digital data output by said analog to digital converter to remove narrowband interference and supply the processed data to said demodulator.

14. The apparatus of claim 10 further comprising a transmitter coupled to said computer for transmitting downstream data and messages to transmitters which transmit said bursts, and wherein said demodulator comprises:

a burst parameter memory for storing burst parameters, channel characteristics and MAP messages stored therein by said computer;

a timing and control circuit coupled to use said information in said burst parameter memory to control the circuits of said demodulator;

a decimation and matched filter circuit that is configured by said computer to have a bandwidth for the matched filter which matches the bandwidth of the burst to be received;

a despreader that is configured by said computer to be bypassed for TDMA bursts;

a code hopping circuit that is configured by said computer to be bypassed for TDMA bursts;

a sample buffer for storing data of at least one burst;

a timing recovery circuit that is configured by said computer to recover the sample clock from the data symbols of TDMA bursts, said receiver using a master upstream symbol clock in said receiver to receive data symbols of SCDMA bursts;

a start of burst detector that is configured by said computer to receive the preamble of at least training bursts and at least measure a time offset thereof from a reference time for transmission downstream to the transmitter which sent said training burst;

a preamble processor that is configured by said computer to deinterleave the preamble symbols if necessary and process the preamble symbols of at least some of said bursts to develop initial gain, phase and frequency offset correction factors;

a rotational amplifer that is configured by said computer to receive the data symbols of each burst following the preamble symbols and coupled to receive said initial gain, phase and frequency offset correction factors and functioning to fine tune said initial gain, phase and frequency offset correction factors and track said correction factors as said data symbols are received and use said correction factors to receive said data symbols;

an equalizer means that is controlled by data output by said computer to receive the preamble symbols of at least one training burst from a transmitter and functioning to use said preamble symbols of said training burst to iteratively converge in coarse and fine equalization convergence intervals on equalization filter coefficients that correct for channel impairments that affect transmissions from the transmitter which transmitted said training burst, and wherein said computer is programmed to control said transmitter to transmit the final equalization coefficients to said transmitter for use in deriving new equalization coefficients;

a burst buffer that is configured by said computer to receive corrected data symbols output by said rotational amplifer;

an inner deinterleaver that is configured by said computer to receive at least the data of advanced PHY SCDMA and TDMA Trellis coded modulation bursts including training bursts and deinterleave the uncoded and coded bits to undo the interleaving of said coded bits performed by the transmitter prior to Trellis encoding said coded and uncoded bits when the received SCDMA burst is Trellis code modulated, and is configured by said computer to be bypassed for non Trellis code modulated bursts;

a differential decoder coupled to receive the output from said inner deinterleaver that is configured by said computer to decode differentially encoded TDMA bursts but is bypassed for all other bursts;

a Trellis coded modulation decoder/slicer that is configured by said computer to decode the coded and uncoded bits of Trellis coded constellation points of advanced PHY TDMA and SCDMA TCM bursts and is configured by said computer to determine which constellation point corresponds to each received symbol in non TCM bursts and output the data bits that correspond to each said constellation point;

an uncoded bit interleaver that is configured by said computer to interleave the uncoded bits output by said Trellis coded modulation decoder to undo the effects of said inner deinterleaver on said uncoded bits and outputting the coded and uncoded bits, and is configured by said computer to be bypassed for non Trellis code modulated bursts;

an Reed Solomon degrouper controlled by said computer to receive the coded and uncoded bits and controlled by said computer to reverse the mapping of some bits from each Reed Solomon codeword byte to the uncoded bits and coded bits inputs of a Trellis coded modulator in the transmitter so as to output a Reed Solomon byte stream of codewords;

a descrambler that is configured by said computer to unscramble the data of bursts that are scrambled but to not affect the data of bursts that are not scrambled;

a Reed Solomon deinterleaver that is configured by said computer to correctly deinterleave said byte stream of Reed Solomon codewords;

a Reed Solomon decoder to receive said Reed Solomon codewords and use the error detection and correction bits therein to correct the payload bits thereof; and

a MAC interface for transmitting said payload bit data output from said Reed Solomon decoder to a MAC process, and for transmitting measurements made by said demodulator to said MAC process and for receiving control information from said MAC process and storing at least some of said control information in said burst parameter memory.

15. The apparatus of claim 14 wherein said Trellis coded modulation decoder/slicer is a SOVA TCM decoder which outputs erasure indications along with the coded and uncoded bits corresponding to each received symbol and a slicer which outputs erasure indications with the bits that correspond to each received symbol, and wherein said Reed Solomon decoder includes an erasure indication input coupled to receive said erasure indications, and is structured to use said erasure indications along with Reed Solomon parity bits appended to each Reed Solomon codeword transmitted in a burst to detect and correct at least some of the errors in said codewords.

16. A process carried out in a digital data receiver comprising:

filtering out unwanted radio frequency signals and digitizing the radio frequency components of a desired radio frequency carrier that remain;

storing burst parameters of one or more bursts encoded into said radio frequency carrier in a burst parameter memory and using said burst parameters to select and configure circuitry that carry out the processing steps necessary to recover the payload data encoded in said burst;

despreading the spectrum of synchronous spread spectrum multiplexed (SCDMA) bursts but skipping this step for DOCSIS 1.0 and DOCSIS 1.1 and advanced PHY time division multiplexed (TDMA) bursts and TDMA training bursts;

storing sample data for said despread SCDMA bursts and said TDMA bursts in a sample buffer so as to keep the data of each burst separate;

recovering the symbol clock of TDMA bursts and using a symbol clock synchronized to said recovered symbol clock to receive at least TDMA bursts, and using a master upstream symbol clock to receive SCDMA bursts from transmitters that have performed at least a ranging process, and resampling the received symbols at the correct timing using the recovered symbol clock or said master upstream symbol clock and storing the re sampled samples in a frame buffer;

detecting the time of arrival of a preamble of each burst and measuring the time offset between said time of arrival and a reference time in a contention interval for at least training bursts;

deinterleaving the preamble symbols if the preamble symbols are interleaved and processing the preamble symbols of at least training bursts to calculate and track gain, phase and frequency offset coefficients, and using said offset coefficients to correct the received symbols of at least some bursts and storing the corrected data symbols in a burst buffer and storing the corrected preamble symbols of at least training bursts in an equalizer buffer;

processing said received preamble symbols of at least training bursts to develop equalization coefficients for use in developing new equalization coefficients by the transmitter which sent said training bursts;

deinterleaving Trellis coded modulated (TCM) TDMA and SCDMA bursts but bypassing this step for non TCM bursts;

differentially decoding differentially encoded bursts but bypassing this step for all other bursts;

using a Viterbi decoder to detect the coded and uncoded bits of received symbols of TCM bursts, and using a slicer to detect the bits encoded in constellation points that correspond to each received symbol of non TCM bursts and outputting the bits mapped to said constellation points;

receiving the bits encoded in each received symbol of TCM and non TCM bursts and reversing the mapping of said payload bits of bytes of Reed Solomon codewords to constellation points to output a byte stream of Reed Solomon codewords;

descrambling said codewords of bursts that are scrambled, but bypassing this step is a burst is not scrambled;

deinterleaving said byte stream of Reed Solomon codewords;

decoding said Reed Solomon codewords by using error detection and correction bits therein to correct the data bits therein.

17. The process of claim 16 wherein said step of processing the preamble symbols to develop equalization coefficients comprises performing a coarse equalization convergence using a relatively larger step size to converge a subset of the most significant equalization filter taps and then performing a fine equalization convergence using a relatively smaller step size to adapt all the equalization filter coefficients by iteratively passing said preamble symbols through equalization filter circuitry.

18. The process of claim 16 wherein said step of using a Viterbi decoder comprises using a SOVA Viterbi decoder to detect and output the coded and uncoded bits of received symbols of TCM bursts along with an erasure indication and wherein said step of decoding said Reed Solomon codewords comprising using said erasure indication from said SOVA Viterbi decoder along with Reed Solomon parity bits appended to each Reed Solomon codeword to detect and correct at least some of the errors in said codewords.

19. The process of claim 16 further comprising the steps of performing a narrowband excision process to remove narrowband interference before the step of despreading.

20. The process of claim 16 further comprising the steps of performing impulse noise detection and erasing any samples from portions of bursts that have been corrupted by impulse noise before the step of despreading.

21. The process of claim 19 further comprising the steps of performing impulse noise detection and erasing any samples from portions of bursts that have been corrupted by impulse noise before the step of despreading.

22. The process of claim 16 wherein said step of filtering out unwanted radio frequency signals and digitizing the radio frequency components that remain, comprises the steps of:

using a broadband passband filter to filter out some unwanted frequency components;

using a frequency agile local oscillator and mixer combination to alter the center frequency of the band of frequency coming out of said broadband passband filter to the center frequency in the passband of a surface acoustic wave (SAW) passband filter that has its passband set wide enough to receive the bandwidth of the highest symbol rate burst to be received;

performing intermediate frequency sampling in an A/D converter to digitize the output band of frequency components output from said SAW filter;

performing narrowband excision to remove narrowband interference from said samples output from said A/D converter;

detecting impulse noise in said samples output by said narrowband excision filter and marking as erased any samples possibly corrupted by impulse noise;

performing decimation to remove excess samples not necessary for the symbol rate of the burst being received; and

performing digital matched filtering using a digital filter having its filter coefficients set to establish a filter that matches the burst being received.

23. The process of claim 16 wherein said step of filtering out unwanted radio frequency signals and digitizing the radio frequency components that remain, comprises the steps of:

using a broadband passband filter to filter out some unwanted frequency components;

using a frequency agile local oscillator and mixer combination to alter the center frequency of the band of frequency coming out of said broadband passband filter to the center frequency in the passband of a surface acoustic wave (SAW) passband filter that has its passband set wide enough to receive the bandwidth of the highest symbol rate burst to be received;

down converting the signal output by said SAW filter to an intermediate frequency;

low pass filtering to remove all radio frequency components above a predetermined frequency;

digitizing the output signal of said low pass filter in an A/D converter;

performing narrowband excision to remove narrowband interference from said samples output from said A/D converter;

detecting impulse noise in said samples output by said narrowband excision filter and marking as erased any samples possibly corrupted by impulse noise;

performing decimation to remove excess samples not necessary for the symbol rate of the burst being received; and

performing digital matched filtering using a digital passband filter having its filter coefficients set to establish a filter that matches the bandwidth of the burst to be received.

24. The process of claim 16 wherein said step of filtering out unwanted radio frequency signals and digitizing the radio frequency components that remain, comprises the steps of:

using a selected filter from a bank of passband filters with overlapping passbands to filter out some unwanted frequency components and leave generally a band of frequency components including the frequency components of a desired radio frequency carrier;

performing intermediate frequency sampling in an A/D converter to digitize the output band of frequency components output from said bank of passband filters so as to output a band of frequencies that depends on the radio frequency carrier to be received;

digitally mixing the signals represented by the samples output from said A/D converter with a quadrature, frequency agile local oscillator signal to mix the signals down to a lower fixed intermediate frequency signal that is independent of the center frequency of the radio frequency carrier to be received;

performing decimation and matched filtering on the output from the previous step to remove unnecessary samples for the symbol rate of the burst to be received and to passband filter the signal using a passband matched to the symbol rate of the symbol to be received;

performing narrowband excision to remove narrowband interference from said samples output from said A/D converter; and

detecting impulse noise in said samples output by said narrowband excision filter and marking as erased any samples possibly corrupted by impulse noise.

25. The process of claim 16 wherein said step of filtering out unwanted radio frequency signals and digitizing the radio frequency components that remain, comprises the steps of:

using a frequency agile low resolution frequency synthesizer to down convert the desired radio frequency carrier to a signal having a frequency which is approximately at a fixed intermediate frequency;

digitizing said intermediate frequency signal at a fast sample rate high enough to correctly represent even the highest symbol rate burst to be received;

using a high resolution frequency synthesizer to digitally down convert the intermediate frequency signal to a digital intermediate frequency having the exact, desired intermediate frequency;

performing narrowband excision to remove narrowband interference from said samples output from said A/D converter; and

detecting impulse noise in said samples output by said narrowband excision filter and marking as erased any samples possibly corrupted by impulse noise;

performing decimation to remove excess samples not necessary for the symbol rate of the burst being received; and

performing digital matched filtering using a digital passband filter having its filter coefficients set to establish a passband for said filter that matches the bandwidth caused by the symbol rate of the burst to be received.

26. The process of claim 16 further comprising the step of cancelling intersymbol interference by processing data in said frame buffer using time offset information derived in the step of recovering said symbol clock.

27. The process of claim 16 further comprising the step of adjusting the gain of the received radio frequency signals and/or the sample data derived therefrom appropriately depending upon the application to which said receiver is put.

28. A pipelined digital data receiver comprising:

a filtering and digitizing circuit;

a pipelined demodulator that can process 5 different bursts simultaneously in different stages of the pipeline, comprised of the following five sections;

(1) an input processing circuit for marking samples that have been corrupted with impulse noise, performing decimation and matched bandpass filtering based upon the sample rate of each burst, despreading the spectrum of any synchronous code division multiplexed bursts and storing the processed sample data in a sample buffer;

(2) a timing recovery circuit for recovering the symbol clock of at least some bursts and detecting the timing offset of the start of at least training bursts from a time reference and detecting collisions in other bursts and resampling the received symbols of each burst at the correct timing, and storing the re sampled samples in a frame buffer;

(3) a rotational amplifier and equalizer circuit for processing the preambles of at least training bursts to calculate and track gain, phase and frequency correction factors and correct the preamble symbols of at least training bursts using said correction factors and store the corrected symbols in an equalizer buffer, and for correcting the data symbols of at least some bursts and storing the corrected symbols in a burst buffer, and for calculating upstream equalization coefficients from said corrected preamble symbols in said equalization buffer and making them available for transmission to the transmitter which transmitted said training burst;

(4) a deinterleaving and decoding circuit for deinterleaving Trellis code modulated (TCM) bursts and detecting the payload bits mapped to every constellation point corresponding to a TCM burst symbol and for detecting the payload bits mapped to the constellation point corresponding to each symbol of non TCM bursts; and

(5) Reed Solomon error correcting circuitry for reconstructing Reed Solomon codewords from said payload bits and error correcting said codewords to generate payload data for output; and

a computer programmed to control a transmitter to send messages downstream to upstream transmitters to control what type of bursts they transmit and when they transmit them and for storing burst parameters that define said bursts and MAP messages that define when the bursts are supposed to be transmitted in a burst parameter memory; and

a timing and control circuit for using said burst parameters of each burst and said MAP data to control each section of said pipeline.

29. A process for receiving multiple types of DOCSIS bursts of radio frequency carrier signals modulated with constellation points each of which corresponds to a transmitted symbol including time division multiplexed (TDMA) bursts and synchronous code division multiplexed (SCDMA) bursts, said bursts having programmable symbol rates and modulation types comprising:

filtering out unwanted carrier signals and digitizing a desired carrier signal;

performing symbol timing recovery and tracking to recover a symbol clock;

performing carrier recovery and tracking;

performing burst acquisition and measuring timing offset of at least some bursts for transmission to a transmitter which transmitted said burst for using in achieving and maintaining frame synchronization and time alignment to minislot boundaries;

despreading the spectrum of any received SCDMA bursts using the proper codes but bypassing the despreading step for TDMA bursts;

processing a known, prepended preamble of each burst to determine gain, phase and frequency correction factors and using said correction factors to correct the received symbols prior to detection of the data bits encoded in each symbol;

developing equalization coefficients from a known preamble prepended to each burst, and providing said equalization coefficients for transmission to a transmitter which transmitted said burst for use in developing new equalization filter coefficients for subsequent transmissions;

deinterleaving received symbols if necessary;

detecting the data bits represented by each symbol including, if necessary, detecting both coded and uncoded bits for Trellis coded bursts;

receiving the bits of each burst including coded and uncoded bits of each constellation point of Trellis coded bursts and unmapping them back into a byte stream of Reed Solomon codewords;

descrambling the byte stream of Reed Solomon codewords derived from said received symbols if necessary;

deinterleaving the Reed Solomon codeword byte stream, and error correcting the byte stream into data for output.

30. The process of claim 29 wherein said symbol timing recovery step is only performed when receiving TDMA bursts and a master clock in the receiver is used for symbol timing when receiving SCDMA bursts, and wherein said step of developing equalization coefficients comprises the steps:

iteratively passing known preamble symbols of a training burst through equalization filtering circuitry and using a relatively larger step size to converge a subset of the most significant filter tap coefficients of an FFE and an FBE filter on coarse equalization coefficient values

using said coarse equalization coefficient values to filtering the data symbols of said training burst in said FFE and FBE filters and passing the corrected data symbols to detecting circuitry to perform said detecting step; and

iteratively passing at least said preamble symbols of said training burst through said FFE and FBE filters and using a relatively smaller step size to converge all the tap coefficients of said FFE and FBE filter on fine equalization coefficient values; and

further comprising the steps of reading said fine equalization coefficient values and preparing a message which includes said fine equalization coefficient values for transmission to the transmitter which sent said training burst.

31. The process of claim 29 wherein the step of detecting the data bits comprises the steps of using a SOVA TCM Viterbi decoder to detect and output the coded and uncoded bits of each received symbol along with an erasure indication indicating the degree of confidence in the accuracy of said coded bits, and wherein the step of error correcting the Reed Solomon codewords comprises using said erasure indication output by said Viterbi decoder along with Reed Solomon parity symbols appended to each said codeword to detect and correct at least some errors.

32. The process of claim 29 wherein said bursts may have 16 QAM for TDMA bursts, Gray coded QPSK and 8 QAM to 64 QAM for TDMA and SCDMA bursts and Trellis encoded QPSK and 8 QAM through 128 QAM for SCDMA bursts, each modulation type having a predetermined symbol constellation, and wherein said bursts may have symbol rates of 160, 320, 640, 1280, 2560 and 5120 kilosymbols per second.

33. The process of claim 29 further comprising the steps of detecting impulse noise in the received bursts and marking data that may be corrupted by impulse noise as erased.

34. The process of claim 29 further comprising the steps of excising narrowband interference from the digitized data before demodulating it and detecting the transmitted bits.

35. The process of claim 29 further comprising the steps of amplifying the received radio frequency carriers by an appropriate gain level prior to digitization so as to allow said receiving process to be used in wireless as well as wired and other cable modem applications.

36. The process of claim 29 wherein said filtering step is performed by using a decimation and programmable passband digital filter and adjusting said passband of said filter digitally to match the bandwidth of bursts at various symbol rates.

37. The process of claim 36 wherein said filtering step is performed in a matched filter.

38. The process of claim 29 wherein said process of despreading the spectrum of SCDMA bursts includes the process of matching the codes used to despread said bursts so as to match a code hopping algorithm used in the transmitter which transmitted said burst.

39. The process of claim 29 wherein said step of burst acquisition is performed using a start of burst detector and further comprising the step of detecting collisions in bursts using said start of burst detector.

40. The process of claim 29 further comprising the step of performing intersymbol interference cancellation prior to detection of the bits that were sent.

41. An apparatus comprising:

a downstream transmitter;

an upstream receiver comprising;

a radio frequency filtering and digitizing circuit for filtering out undesired radio frequency components and digitizing a desired carrier;

a demodulator circuit capable of processing the digitized data to recover payload data transmitted in any of the following type bursts on the same or different frequency channels;

DOCIS 1.0 or DOCSIS 1.1 or advanced PHY TDMA or SCDMA bursts, said bursts having programmable symbol rates and programmable modulation types, and including a start of burst detector to measure the time offset of the start of a training burst from a reference time, and including a preamble processor for developing phase, gain and frequency offset correction factors from known preamble symbols prepended to at least training bursts and for using said correction factors to correct received symbols, and including equalization circuitry to develop equalization coefficients from said prepended preamble symbols; and

a computer programmed to control said downstream transmitter to send messages downstream to multiple transmitters telling them what type of burst to send and when to send them, and programmed to control said radio frequency filtering and digitizing circuit and said demodulator so as to know the type of burst that each received burst is so as to control these circuits to properly receive the burst, said computer programmed to read said time offset factor and said equalization coefficients developed from each training burst and to send said time offset and said equalization coefficients to the transmitter that sent said training burst via said downstream transmitter.

42. The apparatus of claim 41 wherein said radio frequency filtering and digitizing circuit comprises:

a gain controlled amplifier circuit either with a fixed gain or with a gain control input to receive a signal that controls the gain;

a wideband bandpass filter coupled to filter the output of said amplifier so as to pass a band of frequencies that includes the desired carrier frequency;

a frequency agile frequency synthesizer coupled to be controlled by said computer for generating a local oscillator signal;

a second bandpass filter in the form of a surface acoustic wave bandpass filter or other bandpass filter with suitable sharp rolloff and adequately linear passband to filter out most unwanted radio frequency signals outside a bandwidth selected to match the spectrum of the fastest symbol rate burst to be received, and having an input;

a mixer to receive the output of said wideband bandpass filter and mix it up to a predetermined frequency in the middle of the passband of said second bandpass filter using said local oscillator signal and couple the resulting signal to said input of said second bandpass filter;

an analog to digital converter coupled to receive the output signal from said second bandpass filter and functioning to IF sample said signal down to an intermediate frequency; and

and wherein said demodulator circuit includes a digital bandpass filter with a programmable bandwidth set to match the bandwidth of each burst as said burst is received.

43. The apparatus of claim 41 wherein said demodulator circuit has five piplined sections which comprise:

input processing circuitry for removing impulse noise and filter at a bandwidth appropriate to the symbol rate and despread the spectrum of any SCDMA bursts;

timing recovery circuitry for at least recovering the symbol clock of at least TDMA bursts and detecting the start time of at least TDMA bursts;

rotational amplifier/equalization circuitry for deriving phase, amplitude and frequency correction factors and equalization coefficients from a preamble of known data prepended to every burst and using said correction factors to correct the constellation points of said burst; and

detector circuitry including a Trellis code modulation detector for determining the bits encoded in each symbol included the coded and uncoded bits of each Trellis coded constellation point and circuitry to deinterleave and decode Reed Solomon code words encoded by said bits to correct any errors therein.

44. An apparatus comprising:

a first filter to filter out most of the unwanted signals;

an analog to digital converter;

a digital matched filter with programmable filter coefficients which are altered so as to filter the output of the first filter using a passband matched to the bandwidth of each burst being received;

an SCDMA burst despreader which can be bypassed for TDMA bursts and functioning to despread the spectrum of received SCDMA bursts;

clock recovery circuitry to recover symbol clocks of TDMA bursts and to use a master clock for receiving SCDMA bursts;

a rotational amplifier to develop correction factors from known preambles of training bursts and use said correction factors to correct received symbols;

a ranging processor to determine a ranging offset for training bursts from each upstream transmitter for transmission to transmitters which transmitted said training bursts so that said transmitters can transmit bursts with timing such that the bursts arrives at said receiver with their boundaries aligned in time with the boundaries of assigned minislots;

a equalizer to develop equalization coefficients from said known preamble of training bursts;

a deinterleaver and Trellis decoder/slicer to detect the bits that are encoded into each SCDMA or TDMA burst constellation point, as appropriate;

a descrambler to reverse the effects of scrambling in the transmitter that transmitted each burst; and

a Reed Solomon decoder to correct errors in transmitted bits using error correction bits added to the bits by a Reed Solomon encoder at the transmitter which transmitted a burst.

45. The apparatus of claim 44 wherein said Trellis decoder/slicer are a SOVA TCM Viterbi decoder which is used to detect TDMA or SCDMA TCM bursts and output erasure indications and a slicer which detects non TCM bursts and outputs erasure indications, and wherein said Reed Solomon decoder is of a type which can use said erasure indications along with Reed Solomon parity bits to detect and correct errors in Reed Solomon codewords.

46. A digital data receiver, comprising:

first means for suppressing frequencies in an input spectrum other than the frequency components of a desired carrier and digitizing at least said desired carrier;

second means for recovering the payload data from any of a plurality of different burst types transmitted on the same frequency channel or two or more different burst types transmitted during different non overlapping intervals on the same frequency channel, said burst types having the following characteristics;

multiplexing is DOCSIS 1.0 or 1.1 TDMA or advanced PHY TDMA or SCDMA; and

any one of a plurality of different symbol rates and modulation types; and

programmable interleaving depth and block size; and

being or not being Trellis code modulated; and

means for controlling said first and second means to operate correctly to receive the particular type of burst or bursts being received on a selectable frequency channel.

47. A digital data receiver, comprising:

first means for suppressing frequencies in an input spectrum other than the frequency components of a desired carrier and digitizing at least said desired carrier;

second means for recovering the payload data from a plurality of different bursts transmitted at different times on the same frequency subchannel, each said bursts being any of a plurality of different burst types, said burst types having the following characteristics;

multiplexing is DOCSIS 1.0 or 1.1 TDMA or advanced PHY

TDMA or SCDMA; and

any one of a plurality of different symbol rates and modulation types; and

programmable interleaving depth and block size; and

being or not being Trellis code modulated; and

means for controlling by transmission of downstream messages which transmitters can send which burst types at which times and for controlling said first and second means to operate correctly to receive the particular type of burst being received at any particular time.

48. A two stage equalizer circuit for a digital data receiver, comprising:

first means in a DOCSIS compatible Cable Modem Termination System for processing known preamble data of only a training burst sent by a first DOCSIS compatible cable modem to said DOCSIS compatible Cable Modem Termination System to perform a coarse equalization convergence using a relatively larger step size to converge on a subset of coarse filter tap coefficients for a digital equalization filter by iteratively passing said known preamble data of a training burst through Feed Forward Equalization (hereafter FFE) and Feedback Equalization (hereafter FBE) digital filters of a two stage equalizer;

second means for filtering a data portion of a training burst sent by said first DOCSIS compatible cable modem using said Feed Forward and Feedback Equalization fitters having taps programmed with said coarse filter tap coefficients to correct said data symbols of said data portion of said training burst and for decoding said corrected data symbols to determine the identity of a cable modem which sent said training burst;

means for iteratively passing said known preamble data of said training burst sent by said first DOCSIS compatible cable modem through said first means and performing a fine equalization convergence using a relatively smaller step size so as to adjust all the tap coefficients of said FFE and FBE filters to converge on final equalization coefficients, and for sending said final equalization coefficients to said first DOCSIS compatible cable modem which transmitted said training burst and initializing said tap coefficients of said FFE and FBE filters to initial values to ready said FFE and FBE filters to process a training burst from a second DOCSIS compatible cable modem and for not filtering subsequent data bursts from said first DOCSIS compatible cable modem in said two stage equalization circuit.

49. An transceiver for transmitting a variety of different kinds of bursts, comprising:

a transmitter comprising;

a Reed Solomon encoder means for encoding bits to be transmitted into Reed Solomon codewords;

interleaver means for interleaving said codewords;

a scrambler means for scrambling said interleaved codewords;

a mapper for mapping bits output by said scrambler into constellation points of non Trellis code modulated bursts;

a Trellis code modulator for convolutionally encoding some bits of each scrambled codeword of bursts to be TCM modulated and mapping said convolutionally encoded bits plus one or more redundant bits into constellation points of TCM bursts;

a framer means for mapping bursts onto minislots for TDMA bursts and for mapping bursts onto minislots and codes for SCDMA bursts;

an SCDMA spreader means for spreading the spectrum of SCDMA bursts;

a transmit equalizer means for receiving equalization coefficients developed by a CMTS receiver and for convolving said coefficients with existing equalization coefficients to develop new equalization coefficients and for using said new equalization coefficients in an equalization filter which filters the output of said SCDMA spreader for SCDMA bursts or the output of said mapper means for TDMA bursts;

shaping filter means for shaping the resulting spectrum of the symbols to be transmitted;

modulator means for encoding the filtered spectrum output by said shaping filter means onto one or more radio frequency carriers; and

control circuitry coupled to said transmitter and having an input to receive downstream message data, and programmed to control all of the above transmitter circuitry appropriately to transmit the type of burst specified in said downstream message data; and

a receiver to receive downstream messages including MAP and UCD messages and ranging offset data and equalization coefficients and for coupling said downstream message data to said input of said control circuitry, and including a ranging processor to control said transmitter to transmit training bursts including a known preamble and the identity of said transceiver.