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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.