Apparatus and method for SCDMA digital data transmission using orthogonal codes and a head end modem with no tracking loops

• US 6,307,868 B1
• Filed: 07/16/1997
• Issued: 10/23/2001
• Est. Priority Date: 08/25/1995
• 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
• Primary Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/895,612
• Time in Patent Office: 1,560 Days
• Field of Search: 370/479, 370/480, 370/485, 370/486, 370/487, 370/498, 370/503, 370/516, 375/325, 375/326, 375/327, 375/371, 375/375, 375/376, 375/340, 455/3.1, 348/6, 348/8
• US Class Current: 370/485
• CPC Class Codes: H03M 13/256 with trellis coding, e.g. with convolutional codes and TCM
• CPC Class Codes: H03M 13/39 Sequence estimation, i.e. using statistical methods for the reconstruction of the original codes
• CPC Class Codes: H03M 13/41 using the Viterbi algorithm or Viterbi processors
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7087 Carrier synchronisation aspects
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04B 7/2668 Arrangements for Wireless Code-Division Multiple Access [CDMA] System Synchronisation, for code acquisition H04B1/7075, for code tracking H04B1/7085
• CPC Class Codes: H04H 20/77 using carrier waves
• CPC Class Codes: H04H 20/78 CATV [Community Antenna Television] systems
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 14/007 Orthogonal Optical Code Multiplex
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04J 3/0608 Detectors therefor, e.g. correlators, state machines
• CPC Class Codes: H04J 3/0638 Clock or time synchronisation among nodes; Internode synchronisation synchronization for ring networks H04L12/422; data switching networks with synchronous transmission H04L12/43
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 1/006 Trellis-coded modulation
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 2025/03414 : Multicarrier
• CPC Class Codes: H04L 2027/0083 : Signalling arrangements
• CPC Class Codes: H04L 2027/0087 : Out-of-band signals, (e.g. pilots)
• CPC Class Codes: H04L 25/03057 : with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 25/03343 : Arrangements at the transmitter end
• CPC Class Codes: H04L 25/4921 : using quadrature encoding, e.g. carrierless amplitude-phase coding
• CPC Class Codes: H04L 27/0014 : Carrier regulation of chaotic carriers H04L27/001; for multicarrier receivers H04L27/2657
• CPC Class Codes: H04L 27/2656 : Frame synchronisation, e.g. packet synchronisation, time division duplex [TDD] switching point detection or subframe synchronisation
• CPC Class Codes: H04L 27/2657 : Carrier synchronisation
• CPC Class Codes: H04L 27/2662 : Symbol synchronisation
• CPC Class Codes: H04L 27/362 : Modulation using more than one carrier, e.g. with quadrature carriers, separately amplitude modulated H04L27/366 takes precedence
• CPC Class Codes: H04L 5/023 : Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/026 : using code division
• CPC Class Codes: H04L 5/06 : the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04L 7/041 : using special codes as synchronising signal
• CPC Class Codes: H04N 21/2221 : being a cable television head-end CATV in broadcast systems H04H20/78
• CPC Class Codes: H04N 21/2408 : Monitoring of the upstream path of the transmission network, e.g. client requests monitoring data switching networks utilization H04L43/0876; scheduling or organising the servicing of application requests H04L67/60
• CPC Class Codes: H04N 21/4305 : Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/4383 : Accessing a communication channel
• CPC Class Codes: H04N 7/10 : Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/17309 : Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/54 : the signals being synchronous H04N21/23602, H04N21/23614, H04N21/2365, H04N21/2368, H04N21/4341, H04N21/4342, H04N21/4347, H04N21/4348 take precedence
• CPC Class Codes: H04W 24/00 : Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 48/16 : Discovering, processing access restriction or access information
• CPC Class Codes: H04W 56/00 : Synchronisation arrangements
• CPC Class Codes: H04W 74/0866 : using a dedicated channel for access

Abstract

A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

Claims

1. An apparatus comprising:

a central unit transmitter having an input to receive downstream digital data, and having an input for receiving a master clock signal and an input for receiving a master carrier signal, said transmitter transmitting one or more signals from which said master clock and master carrier signals can be recovered and from which said downstream data can be recovered;

a transmission media coupled to said central unit transmitter through which signals from said central unit transmitter propagate;

a remote unit receiver coupled to said transmission media to receive said signals transmitted from said central unit transmitter and having a local clock reference input for receiving a local clock reference signal and a local carrier reference input for receiving a local carrier reference signal, said remote unit receiver for recovering and outputting said downstream data;

synchronization means in said remote unit receiver coupled to drive said local clock reference input with said local clock reference signal and coupled to drive said local carrier reference input with said local carrier reference signal said synchronization means functioning to use one or more signals transmitted by said central unit transmitter to synchronize said local clock reference signal to said master clock signal and synchronize said local carrier reference signal to said master carrier signal so that said local clock reference signal is phase coherent with said master clock signal and said local carrier reference signal is phase coherent with said master carrier signal;

a remote unit transmitter coupled to said transmission media and having an input for receiving upstream digital data and having an input coupled to receive an upstream carrier reference signal which is phase coherent with said local carrier reference signal generated by said synchronization means, and having an input coupled to receive an upstream clock reference signal which is phase coherent with said local clock reference signal generated by said synchronization means, said remote unit transmitter including means for using said upstream carrier reference signal and said upstream clock reference signals for transmitting known preamble data for an interval preceding transmission of said upstream data, and then for using said upstream clock and upstream carrier reference signals for transmitting upstream signals modulated by said upstream data;

a central unit receiver coupled to said transmission media and having means for using said preamble data transmitted by each said remote unit transmitter to derive phase and amplitude correction factors such that said master carrier and master clock signals can be used to recover said upstream data transmitted by each said remote unit transmitter.

2. A process of bidirectionally communicating digital data comprising:

in a central unit modem, using a master clock signal to modulate downstream digital data onto a master carrier signal, and transmitting signals through a transmission media from which said downstream digital data and said master clock signal and said master carrier signal can be recovered;

in each of a plurality of remote unit modems, receiving said signals propagating through said transmission media, and recovering said master carrier and master clock signals and using said master carrier and master clock signals to generate local master clock reference and local master carrier reference signals which are phase coherent with said recovered master clock signal and said recovered master carrier signals, respectively, and using said local master clock reference and local master carrier reference signals to recover said downstream digital data;

using said local master clock reference and local master carrier reference signals in each of said plurality of remote unit modems to modulate known preamble data followed by upstream digital data received by each said remote unit transmitter onto at least one upstream carrier signal which is in phase coherent with said local master carrier reference signal;

in said central unit modem, receiving said signals bearing said upstream digital data information including said preamble data, and receiving said master clock signal and said master carrier signal and using said preamble data transmitted upstream by each said remote unit modem to develop correction factors used in a rotational amplifier and a G2 amplifier to correct for phase and amplitude errors created by propagation of said upstream data from each remote unit modem to said central unit modem to allow recovery of said upstream digital data from each said remote unit modem transmitter correctly.

3. A system comprising:

a central unit transceiver which uses a master clock signal and master carrier signal to transmit downstream payload data and transmits said master clock downstream;

a plurality of remote unit transceivers each coupled to said central unit transceiver through a transmission media, and each having a receiver section including means for recovering said master clock signal and generating therefrom a phase coherent local clock signal and a phase coherent local carrier signal, and means for using said local clock and local carrier signals to recover said downstream payload data and to transmit upstream payload data, each said remote unit transceiver including circuitry to transmit known preamble data preceding upstream payload data for use by said central unit transceiver;

and wherein said central unit transceiver includes circuitry for using said preamble data transmitted by each said remote unit transceiver to generate amplitude and phase correction factors for the remote unit transceiver that transmitted said preamble data and for using said amplitude and phase correction factors so determined for each remote unit transceiver and a rotational amplifier and a G2 amplifier to recover said upstream payload data transmitted by that particular remote unit transceiver.

4. A process comprising:

in a central unit modem, transmitting downstream payload data from a central unit modem using a master clock and master carrier and transmitting at least said master clock downstream;

recovering at least said master clock in each of a plurality of remote unit modems physically spread throughout a distributed system and using said recovered master clock to generate local clock and carrier signals which are phase coherent with said master clock, and using said local clock and carrier signals to recover downstream data in each remote unit modem, and using said local clock and carrier signals in each said remote unit modem to transmit upstream data preceded by preamble data;

using said preamble data from each particular remote unit modem in said central unit modem to generate phase and amplitude correction factors for said remote unit modem for use in recovering upstream data transmitted thereby; and

using said amplitude and phase correction factors developed for each said remote unit modem with said master clock and master carrier signals to recover in said central unit modem the upstream payload data transmitted by that particular remote unit modem.

5. A distributed communication system having a central unit transceiver coupled by a shared transmission media to a plurality of remote unit transceivers wherein said remote unit transceivers and said central unit transceiver include circuitry to bidirectionally communicate digital data using any form of multiplexing and any form of modulation using a single master clock and a single master carrier, both said master clock and said master carrier being synthesized in said central unit transceiver from a single crystal controlled oscillator, said master clock and master carrier signals being transmitted downstream to said remote unit transceivers and recovered there and used by each remote unit transceiver to transmit data upstream to said central unit transceiver, each said remote unit transceiver transmitting its upstream data after transmitting at least some preamble data, said central unit transceiver including circuitry to use said preamble data from each remote unit transceiver to determine amplitude and phase correction factors for use in receiving data from said remote unit transceiver by correcting for phase and amplitude errors caused by channel impairments and the transmission delay between said remote unit transceiver and said central unit transceiver.

6. A distributed bidirectional digital data communication system having a shared transmission medium, comprising:

central unit transmitter means having any encoder and a master clock oscillator generating a master clock signal, for receiving downstream data, encoding said downstream data in any way and transmitting said encoded downstream data over said shared transmission medium using any type of digital passband modulator and a master carrier signal generated separately or from said master clock, and transmitting downstream data from which said master clock and master carrier signals can be recovered in any way;

remote unit receiver means having any demodulator and any detector compatible with the type of modulation and encoding used, for using any form of clock and carrier recovery circuitry to generate local clock and carrier signals that are phase coherent with said master clock and master carrier signals transmitted downstream by said central unit transmitter and for using said phase coherent local clock and carrier signals and said demodulator and detector to recover said downstream data;

a plurality of remote unit transmitter means, each having any encoder and any digital passband modulator, for receiving upstream digital data and transmitting known preamble data upstream on said shared transmission medium followed by transmitting said upstream data using said local clock and carrier signals and said encoder and modulator; and

a central unit receiver means having any detector compatible with the type of transmissions from said remote unit transmitter means and any decoder compatible with the type of encoding of upstream data performed in said remote unit transmitters, for using said master clock and master carrier and said preamble data transmitted by each said remote unit transmitter means for recovering said upstream data transmitted by each said remote unit transmitter.

7. A process of bidirectionally communicating digital data comprising:

in a central unit modem, using a master clock signal to modulate downstream digital data onto a master carrier signal, and transmitting signals through a transmission media from which said downstream digital data and said master clock signal and said master carrier signal can be recovered;

in each of a plurality of remote unit modems, receiving said signals propagating through said transmission media, and recovering said master carrier and master clock signals and using said master carrier and master clock signals to generate local master clock reference and local master carrier reference signals which are phase coherent with said recovered master clock signal and said recovered master carrier signals, respectively, and using said local master clock reference and local master carrier reference signals to recover said downstream digital data;

in each of a plurality of remote unit modems, using said local master clock reference signal to receive and encode upstream digital data and using said local master clock and carrier reference signals to modulate first known preamble data and then said encoded upstream digital data onto said local master carrier reference signal to generate an output signal, and transmitting said output signal to said central unit modem;

in said central unit modem, receiving said preamble data from each said remote unit modem and generating correction factors for each said remote unit modem for use in receiving upstream data transmitted by that remote unit modem, and using said master clock signal and said master carrier signal and said correction factors for a particular remote unit modem when upstream data from said remote unit modem is being processed so as to receive said upstream digital data transmitted by each said remote unit modem.