Low cost DSSS communication system

• US 6,563,857 B1
• Filed: 12/21/2001
• Issued: 05/13/2003
• Est. Priority Date: 12/21/2001
• Status: Expired due to Fees

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Shi, Qicai, OʼDea, Robert J.
• Primary Examiner(s): Ghayour, Mohammad H.
• Application Number:
  US10/036,554
• Time in Patent Office: 508 Days
• Field of Search: 375/140, 375/145, 375/147, 375/149, 375/130, 370/335, 370/342, 370/441
• US Class Current: 375/140
• CPC Class Codes: H04B 1/70718 with asynchronous demodulation, i.e. not requiring code synchronisation

Abstract

A method and apparatus for direct sequence spread spectrum communication having low complexity. In the transmitter, the data bit is spreaded by a code sequence, a reference code is interleaved with the code sequence, and together they are transmitted by the transmitter. The corresponding receiver recovers the data signal from the received signal by transforming the received signal to a complex base band signal and differentially decoding the base band signal at the chip level. The spreaded signal is despreaded by the chip-level differential operation, thus eliminating the decorrelation operation, and so significantly reducing the cost of the overall system. Furthermore, this system is very robust to any carrier frequency drift since the chip-level differential operation is used, thus releasing the reference clock or crystal requirements, and so further reducing the cost of the system.

Claims

1. A method for recovering a data value from a received signal in a direct sequence spread spectrum receiver, said received signal having a chip period T_c, a bit period T_b and being modulated by first code sequence C_a or second code sequence C_b generated by interleaving groups of M chips from a pseudo-noise sequence C=(C₁, C₂, C₃, . . . , C_N) of length N with elements C_i=±

1, said first code sequence C_a having elements

2. A method as in claim 1, wherein M=1, C_a=(C₁, C₁, C₂, C₂, C₃, C₃, . . . , C_N, C_N) and C_b=(C₁, −

C₁, C₂, −

C₂, C₃, −

C₃, . . . , C_N, −

C_N).

3. A method as in claim 1, wherein said determining comprises comparing said integrated value to a predetermined threshold value.

4. A method as in claim 1, further comprising sampling said baseband complex signal using an analog-to-digital converter.

5. A direct sequence spread spectrum receiver for recovering a data value from a received signal in a direct sequence spread spectrum receiver, said received signal having a chip period T_c, a bit period T_b and being modulated by first code sequence C_a or second code sequence C_b generated by interleaving groups of M chips from a pseudo-noise sequence C=(C₁, C₂, C₃, . . . , C_N) of length N with elements C_i=±

1, said second code sequence C_b having elements

6. A direct sequence spread spectrum receiver as in claim 5, wherein said first code sequence C_a has length 2N and elements

7. A direct sequence spread spectrum receiver as in claim 5, wherein said first code sequence C_a is C and has length N.