(12) United States Patent ao) Patent No.: us 6,639,939 Bi
Naden et al. (45) Date of Patent: Oct. 28,2003
(54) DIRECT SEQUENCE SPREAD SPECTRUM METHOD COMPUTER-BASED PRODUCT APPARATUS AND SYSTEM TOLERANT TO FREQUENCY REFERENCE OFFSET
(75) Inventors: Gary A. Naden, Mandeville, LA (US);
Robert E. Rouquette, Kenner, LA
(US); Dale E. Reiser, New Orleans, LA
(73) Assignee: Axonn L.L.C., New Orleans, LA (US)
( * ) Notice: Subject to any disclaimer, the term of this patent is extended or adjusted under 35 U.S.C. 154(b) by 0 days.
(21) Appl. No.: 09/359,441
(22) Filed: Jul. 22, 1999
Related U.S. Application Data
(62) Division of application No. 08/929,891, filed on Sep. 15,
1997, now Pat. No. 5,999,561. (60) Provisional application No. 60/047,128, filed on May 20,
1997, and provisional application No. 60/051,922, filed on
Jul. 8, 1997.
(51) Int. CI.7 H04B 1/707
(52) U.S. CI 375/140; 375/344; 375/355
(58) Field of Search 375/140, 142,
375/143, 145, 149, 150, 152, 316, 340, 355, 344, 346, 350
(56) References Cited
U.S. PATENT DOCUMENTS
A method, apparatus, computer-based product and system employs a digital receiver (or transceiver) to receive, digitize and process a direct sequence spread spectrum signal using efficient, low-cost digital signal processing components. A radio front end portion of the receiver receives and digitizes the signal, and a digital signal processing portion downconverts and despreads the signal by applying a pseudorandom noise (PN) code, used at a transmitter to spread a data signal contained in the direct sequence spread spectrum signal, to the received signal. In order to initially align, and maintain alignment of, the PN code with the direct sequence spread spectrum signal, a timing and state control mechanism is included that provides time reference correction information to the signal processing components of the receiver. This time reference correction information allows the receiver to be compatible with transmitters using inaccurate frequency references which impart a significant frequency ambiguity in the received signal. Additional features include computerbased synchronization methods and mechanisms suitable for use for low performance digital signal processors and employ power management mechanisms that enable longterm operation using battery power. The power management mechanisms enable the receiver to operate in a network setting, over the course of multiple years off battery power, with similar receivers, transmitters and transceiver that communicate with one another using direct sequence spread spectrum signals.
7 Claims, 75 Drawing Sheets