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

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.

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.

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.

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.