Maximum length linearly occurring code sequence generator in a spread spectrum communication system

• US 4,847,861 A
• Filed: 08/13/1987
• Issued: 07/11/1989
• Est. Priority Date: 10/09/1986
• Status: Expired due to Term

• Current Assignee: Clarion Co., Ltd. (Faurecia SA)
• Original Assignee: Clarion Co., Ltd. (Faurecia SA)
• Inventors: Mori, Masaharu, Hamatsu, Masahiro
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/084,956
• Time in Patent Office: 698 Days
• Field of Search: 375/1, 380/48
• US Class Current: 375/142
• CPC Class Codes: G06F 2207/581 Generating an LFSR sequence, e.g. an m-sequence; sequence may be generated without LFSR, e.g. using Galois Field arithmetic
• CPC Class Codes: G06F 7/584 using finite field arithmetic, e.g. using a linear feedback shift register
• CPC Class Codes: H04B 1/707 using direct sequence modulation

Abstract

A method for determining the initial state of shift registers constituting a modular type or simple construction type maximum length linearly occurring code sequence generator used in a spread spectrum communication system is disclosed, by which it is determined by the following equation; ##EQU1## where yj(0) is the j-th element of Y (0), and

X=P X (0).

Claims

1. A spread spectrum communication system, by which demodulation of necessary information is effected by correlation output between signals for which spectrum of information signals is spread by using a maximum length linearly occurring code sequence on the sender side and a maximum length linearly occurring code sequence generated on the receiver side, wherein the initial state of shift registers constituting the maximum length linearly occurring code sequence generator is determined by the following equation;

##EQU11## j=1, . . . , n where

yj(0) is the j-th element of Y(O),

X is the j-th row,

and

X=PX(O).

2. A spread spectrum communication system according to claim 1, wherein said maximum length linearly occurring code sequence generator includes a plurality of flip-flops which each have a data input and a data output, and a plurality of exclusive OR gates which each have first and second data inputs and a data output, a first of said flip-flops having its data output coupled to said first data input of each said gate and to the data input of a second of said flip-flops, each said gate having its second data input coupled to the data output of a respective said flip-flop other than said first flip-flop, and each said gate having its data output coupled to the data input of a respective said flip-flop other than said second flip-flop.

3. A spread spectrum communication system according to claim 1, wherein said maximum length linearly occurring code sequence generator includes a plurality of flip-flops which each have a data input and a data output, and a plurality of exclusive OR gates which each have first and second data inputs and a data output, a first said flip-flop having its data output coupled to the first data input of a first said gate, a second said gate having its data output coupled to the data input of a second said flip-flop, each said flip-flop other than said first flip-flop having its data output coupled to the second data input of a respective one of said gates and coupled to the data input of a respective one of said flip-flops other than said second flip-flop, and each said gate other than said second gate having its data output coupled to the first data input of a respective one of said gates other than said first gate.