Code Reuse Multiple Access For Satellite Return Link

Abstract

This invention is a multiple access communication technique by which a multitude of transmitters communicate with receivers using direct sequence spread spectrum signaling. The direct sequence codes are reused by a large number of simultaneous transmitters, so the system is named Code Reuse Multiple Access (“CRMA”). This reuse method requires only a small number of codes relative to the number of simultaneous transmitters, and can use as few as one code for all the users. The direct sequence codes are not required to have special properties such as maximal length. The lengths of the spreading codes employed are not necessarily related to the bit or symbol interval. CRMA can be implemented on a Paired Carrier Multiple Access (“PCMA”) system with or without a novel receiver structure which is also described. In an environment having virtual channels, a clock is derived from the received signal in the uplink by sampling the signal to detect symbol edges.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS [0001] The present application is a Continuation-in-Part Application of Continuation application Ser. No. 11 / 431,228 filed May 9, 2006 of U.S. application Ser. No. 09 / 531,996, filed Mar. 20, 2000, now U.S. Pat. No. 7,065,125 issued Jun. 20, 2006, which in turn claims the benefit of U.S. Provisional Application No. 60 / 148,925, filed Aug. 13, 1999, all of which are incorporated by reference herein in their entirety for all purposes. [0002] The following U.S. provisional and continuation-in-part patent applications, including the present application, are being filed concurrently and the disclosure of every other application is incorporated by reference in the present application in its entirety for all purposes: [0003] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for “Adaptive Use of Satellite Uplink Bands” (Attorney Docket No. 017018-008000US); [0004] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 by Ma...

AI Technical Summary

Benefits of technology

The invention is a communication technique that uses direct sequence spread spectrum signaling for the access channel, called Code Reuse Multiple Access (CRMA). This technique improves collision performance compared to conventional multi-access techniques. The invention provides a small number of spreading codes, which are longer than the length of a data symbol and do not repeat during modulation of the data sequence. The coding technique can be combined with a Paired Carrier Multiple Access (PCMA) system, which provides a reverse channel without having to allocate an additional operating frequency range or provide a separate link. The invention also includes a multi-user receiver structure that efficiently processes a multitude of received signals by centralizing the header acquisition process. The invention exhibits improved multiple access collision performance as compared to SA / CDMA systems and reduces system complexity by eliminating some of the limitations of SA / CDMA. The invention can be used in a satellite ground station receiver system.

Problems solved by technology

The presence of a spread spectrum signal only slightly increases the noise floor that the narrow band receivers see.

While such first generation satellite systems may provide multi-gigabit per second (Gbps) per satellite overall capacity, the design of such systems inherently limits the number of customers that may be adequately served.

Moreover, the fact that the capacity is split across numerous coverage areas further limits the bandwidth to each subscriber.

While existing designs have a number of capacity limitations, the demand for such broadband services continues to grow.

Images