Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1998-11-10
2002-08-27
Tse, Young T. (Department: 2634)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S133000, C375S135000, C375S146000
Reexamination Certificate
active
06442190
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the encoding of symbolic data, and more particularly is primarily a method of “self-encoding” data symbols for transmission over a spread-spectrum communication system such as code-division-multiple-access (CDMA) or frequency-division-multiple-acess (FDMA) communication systems. Said method comprises utilization of encountered data symbols in a sequence of data symbols, to develop data symbol energy spreading codes which are applied to encode subsequently encountered data symbols. Said method further includes decoding each encoded data symbol, after it is transmitted over a communications transmission system.
BACKGROUND
Both the telecommunications Industry and the military are very interested in efficient wireless electronic communication systems which maximize the number of users simultaneously served, in available bandwidth. For instance, the telecommunications industry has special interest in efficient wireless and mobile systems for application in multi-user cellular systems, and the military is particularly interested in wireless communication systems which are secure in hostile environments, have a low probability of detection, and which are not subject to being easily jammed.
Continuing, typical electronic communication systems provide a frequency bandwidth within which a multiplicity of individual communication signals are transmitted. Many well known communication systems utilize a frequency allocation approach such as frequency-division-multiplexed (FDM), wherein an available frequency bandwidth is divided into specific smaller bands, called channels, which channels are separated from one another by guard-bands. Likewise, time-division-multiplexed (TDMA) communication systems divide a period of time into a number of specific slots which sequentially carry different individual communications. In use each said channel typically carries a signal specific to a single user only. Alternative communication systems provide that a multiplicity of users simultaneously be provided access to an entire available bandwidth, and that each user's signal be somehow encoded so that it can be later selected out from all co-present signals. Such communications systems utilize an approach which is known as “Spread-Spectrum”, including for instance, code-division-multiple-access (CDMA)). It is well known then that spread spectrum communication systems operate by allowing many users to share a relatively large common bandwidth in an electronic communication system in conjunction with encoding techniques such as Code Division Multiple Access (CDMA), instead of providing many separate smaller bandwidth channels, each of which carries a single user's communication, as in (FDM).
It is noted at this point that the present invention finds primary, but not limiting, application in code-division-multiple-access (CDMA) based spread-spectrum communications systems. In that light, and as will be appreciated by those skilled in the art, it is noted that conventional wireless code-division-multiple-access (CDMA) spread spectrum electronic communication systems are designed according to the IS-95 standard for cellular telephony and personal communication services (PCS), and use Walsh Codes and m-sequences for mobile channels. Such systems presently provide that original data symbols input thereto be encoded by a method which is mediated by use of a pre-generated, determined, psuedo-random code, (rather than by a “self-encoding”approach), to encode original data symbols at a transmitter, and to decode spread spectrum data symbol chips, (which were encoded utilizing said pre-generated determined psuedo-random code) at a receiver. Said psuedo-random code generation is typically achieved by expansion of a same “data key” at both transmitter and receiver locations prior to use thereof. Said psuedo-random codes generated at the transmitter and receiver are, prior to use, synchronized, and said transmitter and receiver respectively serve to direct the conversion of each of M encountered data symbols into N encoded spread spectrum data symbol chips, and re-constitution of said N encoded spread spectrum data symbol chips into the M original data symbols.
With an eye to the present invention a Search of Patents was performed which focused on use of Data to encode itself in Spread Spectrum and particularly in CDMA communication system settings, with the result of said search being that very little was found.
U.S. Pat. No. 5,343,494 to Averst et al., describes a method for receiving and processing data in a portable transceiver which involves receiving at least one information signal; decoding the at least one information signal to recover information therein; generating a plurality of pseudo-noise (PN) sequences in accordance with the information wherein each of the plurality of PN sequences is indicative of a predetermined response. The Disclosure of the 494 Patent makes it clear that “generating a plurality of pseudo-noise (PN) sequences in accordance with the information” is to be interpreted in light of selecting one of a plurality of base station (PN) sequences so that lesser strength base station signals do not interfere. It is noted that the 494 Patent does not remotely describe reforming a transmitter spreading code with each new input symbol, to ready it for application in spreading a sequentially following data symbol, with a reverse operation applied at the receiver.
U.S. Pat. No. 5,757,853 to Tsujimoto describes using a plurality of spreading and de-spreading codes to the end that multipath fading and the like are overcome.
U.S. Pat. No. 5,467,368 to Takeuchi et al., (Col. 3, Line 67), alludes to the concept of using different spreading codes for different symbols in a sequence of symbols, however such is In the context of using a spreading code that is greater in length than the data symbols.
U.S. Patent No. 4,597,087 to Kadin describes producing first and second pseudo-noise (PN) code streams time displaced with respect to each other, and use thereof to encode data by groupings of randomly occurring frequencies and spacings therebetween. The 087 Patent also use of a frequency hopping rate equal to n times the rate of binary data being transmitted. Said 007 Patent, however, does not describe a technique of producing a (PN) code on a data symbol by symbol basis, for use in encoding subsequent data symbols.
U.S. Pat. No. 5,073,899 to Collier et al., (in Col. 3, Line 65 and thereafter), states that a pseudo-random code can be changed regularly or at irregular intervals. It describes application to pages of text. Said 899 Patent, however, provides for inclusion of a synchronization signal in a modulated signal as easily gleened from claim
1
therein.
U.S. Pat. No. 4,651,327 to Fujita describes a technique by which need for a synchronization signal can be avoided.
U.S. Pat. No. 5,495,509 to Lundquist et al., describes use of a short preamble (PN) code sequence to allow synchronization.
A lengthy Patent to Flammer, U.S. Pat. No. 5,130,987 focuses synchronization, but of information in a packet communication format on a plurality of frequencies without use of a central timing source.
U.S. Pat. No. 5,689,525 to Takeishi et al., describes generating a (PN) code based upon a delayed clock signal.
U.S. Pat. No. 5,745,522 to Heegard mentions a shift register and use of XOR to produce a pseudo-random noise sequence, operating on a byte by byte basis. Somewhat similar invention(s) is/are described in U.S. Pat. Nos. 5,410,586 & 5,260,967 to Schilling.
Additionally, a Patent to Gilhousen et al., (assigned to QUALCOMM), U.S. Pat. No. 4,901,307, was provided by the Searcher, as were Patents to Kadin, No. 4,606,041; Takeuchi et al., U.S. Pat. No. 5,467,368; U.S. Pat. No. 5,410,568 to Schilling; U.S. Pat. No. 5,260,967 to Schilling; U.S. Pat. No. 5,598,429 to Marshall; Patent U.S. Pat. No. 5,090,023 to Watanabe et al.; and U.S. Pat. No. 5,121,408 to Cai et al.
In addition, non-Patent references which are relevant and which are incorporated hereinto by reference
The Board of Regents of the University of Nebraska
Tse Young T.
Welch James D.
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