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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
First Claim
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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.

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