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United States Patent [w]
Jones et al.
US006108317A [ii] Patent Number:  Date of Patent:
 CYCLIC CODE PHASE MULTIPLE ACCESS FOR INBOUND SATELLITE COMMUNICATIONS
 Inventors: William W. Jones; James R. Luecke,
both of Mission Viejo, Calif.
 Assignee: STM Wireless, Inc., Irvine, Calif.
 Appl. No.: 08/742,907  Filed: Nov. 1, 1996
Related U.S. Application Data
 Provisional application No. 60/007,161, Nov. 1, 1995.
 Int. C I. I104J 13/02
 U.S. CI 370/320; 370/342; 375/208
 Field of Search 370/203, 206,
370/208, 319, 320, 342, 441, 479; 375/208,
 References Cited
U.S. PATENT DOCUMENTS
Scott L. Miller, "An Efficient Channel Coding Scheme for Direct Sequence CDMA Systems", MILCOM '91, IEEE, pp. 1249-1253, Sep. 1991.
F.A.B. Cercas et al., "Codes of Binary Length for LEO/ MEO CDMA Systems", ICUPC '93, IEEE, pp. 349-353, Aug. 1993.
A satellite communication system comprising of a central hub/gateway station and remote very small aperture terminal (VSAT) stations. VSAT inbound transmissions are spread in bandwidth using an assigned PN code sequence. This sequence is derived as a cyclic function of a base sequence for use by the group of VSATs. The gateway transmits a continuous outbound signal that functions as the network frequency and timing reference. In addition, the gateway periodically forms timing and frequency error estimates on each VSAT transmission and broadcasts these results over the outbound channel to the VSATs. Use of the outbound reference coupled with these time and frequency measurements enable all VSAT inbound transmissions within a group to be bit synchronized. Bit level synchronization enable the system to gain the full advantage of the correlation properties of the cyclic codes to improve multiple access performance as compared to asynchronous or chip synchronous code division multiple access (CDMA) techniques. N active users can be supported with an N length code in this system even for small values of N (N= 15). The synchronized, cyclic relationship of the inbound transmissions enables the gateway to receive and demodulate a group of channels using a single receiver. The gateway station includes a correlator receiver which is synchronized with the gateways outbound network reference and which contains all the cyclic PN code sequences to detect correlations between the pseudo-randomly modulated data bits corresponding to the cyclic PN sequence bits of the VSAT stations.
13 Claims, 21 Drawing Sheets
DaSilva, V.M. and Sousa, E.S., "Multicarrier Orthogonal
CDMA Signals for Quasi-Synchronous Communication
Systems", IEEE Journal on Selected Areas in Communica-
tions, Vol. 12, No. 5, Jun. 1994, pp. 842-852.
Fitz, M.P, "Further Results in the Fast Estimation of a
Single Frequency", IEEE Transactions on Communications,
Vol. 42, No. 2/3/4, Feb./Mar./Apr. 1994, pp. 862-864.
De Gaudenzi, R., et al., "Orthogonal CDMA Transmission
for Satellite-Based Mobile Communications Radio Net-
works", Proceedings of IEEE Globecom 1994, pp. 100-104.
De Gaudenzi, R., et al., "Bandlimited Quasi-Synchronous
CDMA: A Novel Satellite Access Technique for Mobile and
Personal Communication Systems", IEEE Journal on
Selected Areas in Communications, vol. 10, No.2, Feb.
1992, pp. 328-343.
Holmes, J.K., "Coherent Spread Spectrum Systems (Chapter
12)", John-Wiley, 1990, pp. 614-616.
Jones, W.W. and Lofquist, D.B., "Joint Time and Frequency
Estimation in TDM A Burst Receivers Using the Generalized
Semicoherent Statistic", IEEE Military Comm. Conf., San
Diego, CA, Nov. 5-8, 1995, pp. 793-797.
Kay, S., "A Fast and Accurate Single Frequency Estimator", IEEE Transactions on Acoustic, Speech and Signal Processing, vol. 37, No. 12, pp. 1987-1990, Dec. 1989. Lank, G., et al., "A Semicoherent Detection and Doppler Estimation Statistic", IEEE Transactions on Aerospace and Electronic Systems, vol. AES-9, No. 2, pp. 151-165, Mar. 1973.
Shah, B. and Hinedi, S., "The Split Symbol Moments SNR Estimator in Narrow-Band Channels", IEEE Transactions on Aerospace and Electronic Systems, vol. AES26, No. 5, Sep. 1990, pp. 737-747.
Simon, M.K., et al., "Spread Spectrum Communications Handbook", McGraw-Hill, Inc., 1994, pp. 1103-1108, 1180-1184.
Abramson, Norman, "Multiple Access in Wireless Digital Networks", Proceedings of the IEEE, vol. 82, No. 9, Sep. 1994, pp. 1360-1370.
Abramson, Norman, "VSAT Data Networks", Proceedings of the IEEE, vol. 78, No. 7, Jul. 1990, pp. 1267-1274. Simon, M.K., et al., "Digital Communication Techniques: Signal Design and Detection", PTR Prentice Hall, Englewood Cliffs, NJ, pp. 461-466.