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Wireless direct-sequence spread spectrum TDMA communications system

  • US 5,488,631 A
  • Filed: 10/31/1994
  • Issued: 01/30/1996
  • Est. Priority Date: 10/31/1994
  • Status: Expired due to Term
First Claim
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1. A method of direct-sequence spread spectrum (DSSS) digital communication between a transmitter and a receiver within a frequency band including a predetermined lower limit frequency, a predetermined center frequency, and a predetermined upper limit frequency, said method at the transmitter comprising the steps of:

  • generating continuously and repetitively at a predetermined chip-clock rate about one-half of the predetermined frequency bandwidth, a pseudorandom digital sequence (PRDS) code comprising a multiplicity of bits and having a bit sequence length equal to the product of a first integer and a second integer, each complete sequence of the code generated over a predetermined time interval;

    intermittently modulating onto the PRDS code, in accordance with protocol for repetitively determining whether, when, and over what duration the transmitter may transmit, the protocol common to the transmitter and the receiver, a plurality of data signals, each signal comprising a plurality of digital symbols, wherein the number of chips encoding a symbol is a third integer, the number of bits included in a symbol is a fourth integer, and the number of bits included in a digital byte is a fifth integer;

    intermittently transmitting the data-modulated PRDS code, each transmission of a code segment beginning at a time determined by the protocol and initialized at a preselected and identifiable bit position in the PRDS code, the bit position selected from among the multiplicity of bits comprising the code, each transmission comprising a predetermined number of data bytes and terminating at a time determined by the protocol, each transmission beginning and ending at a position in the PRDS code coinciding with one of a multiplicity of symbol boundaries;

    transmitting each transmission of the data-modulated PRDS code at a signal center frequency about equal to the center frequency of the frequency band;

    said method at the receiver comprising the steps of;

    generating continuously and repetitively, at the chip-clock rate of the transmitter PRDS code, a PRDS code identical to the transmitter PRDS code, each complete sequence of the receiver-generated code generated over said predetermined time interval;

    receiving from the transmitter, when the transmitter is transmitting, the data-modulated PRDS code;

    synchronizing a bit sequence in the receiver-generated PRDS code with a corresponding bit sequence in the transmitter PRDS code segment;

    demodulating the data signals modulated onto the received code segment.

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