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Code reuse multiple access for satellite return linkRelated Patent Categories: Pulse Or Digital Communications, Spread SpectrumCode reuse multiple access for satellite return link description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070127553, Code reuse multiple access for satellite return link. Brief Patent Description - Full Patent Description - Patent Application Claims
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 Mark Dankberg, Mark Miller, Steve Hart, Kristi Jaska, and Bob Wilson for "Frequency Re-use for Service and Gateway Beams" (Attorney Docket No. 017018-008300US); [0005] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Satellite Architecture" (Attorney Docket No. 017018-008500US); [0006] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Piggy-back Satellite Architecture" (Attorney Docket No. 017018-008600US); [0007] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Placement of Gateways Away from Service Beams" (Attorney Docket No. 017018-008800US) [0008] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Multi-Service Provider Subscriber Authentication" (Attorney Docket No. 017018-007700US); [0009] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 "Large Packet Concatenation in Satellite Communication System" (Attorney Docket No. 017018-008200US); [0010] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 "Upfront Delayed Concatenation In Satellite Communication System" (Attorney Docket No. 017018-010500US); [0011] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Map-Trigger Dump Of Packets In Satellite Communication System" (Attorney Docket No. 017018-010600US); [0012] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Web/Bulk Transfer Preallocation Of Upstream Resources In A Satellite Communication System" (Attorney Docket No. 017018-010700US); [0013] U.S. Continuation in Part patent application Ser. No. ______, filed Oct. 3, 2006 for "Code Reuse Multiple Access For A Satellite Return Link" (Attorney Docket No. 017018-001212US); [0014] U.S. Continuation in Part patent application Ser. No. ______, filed Oct. 3, 2006 for "Method for Congestion Management" (Attorney Docket No. 017018-006110US); [0015] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Aggregate Rate Modem" (Attorney Docket No. 017018-008900US); [0016] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Packet Reformatting for Downstream Links" (Attorney Docket No. 017018-009000US); [0017] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Downstream Waveform Modification" (Attorney Docket No. 017018-009100US); [0018] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Upstream Resource Optimization" (Attorney Docket No. 017018-009200US); [0019] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Upstream MF-TDMA Frequency Hopping" (Attorney Docket No. 017018-009300US); [0020] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Downstream Virtual Channels Multiplexed on a Per Symbol Basis" (Attorney Docket No. 017018-009400US); [0021] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Modified Downstream Waveform" (Attorney Docket No. 017018-010800US); [0022] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Adapted DOCSIS Circuit for Satellite Media" (Attorney Docket No. 017018-009500US); [0023] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Satellite Downstream Virtual Channels" (Attorney Docket No. 017018-009700US); [0024] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Satellite Broadband with Less than One Country of Coverage" (Attorney Docket No. 017018-010300US); [0025] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Multi-User Detection in Satellite Return Link" (Attorney Docket No. 017018 [0026] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Multi-rate Downstreaming in Multiple Virtual Channel Enviroment" (Attorney Docket No. 017018-010200US); [0027] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Satellite Upstream Load Balancing" (Attorney Docket No. 017018-009900US); [0028] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Satellite Upstream/Downstream Virtual Channel Architecture" (Attorney Docket No. 017018-010000US); and [0029] U.S. Provisional Patent Application No. ______, filed Oct. 3, 2006 for "Virtual Downstream Channel Load Balancing" (Attorney Docket No. 017018-009800US). BACKGROUND OF THE INVENTION [0030] The present invention relates generally to communication techniques and in particular to a spread spectrum communication technique via a satellite communication network. [0031] A spread spectrum communication system is a system in which the transmitted signal is "spread" over a wide range of frequencies. Typically the bandwidth is much wider than the minimum bandwidth needed to transmit the information being sent. The underlying premise of this technique is that, in channels (typically wireless) with narrowband noise, an increase in the transmitted signal bandwidth produces a corresponding increase in the probability that the received information will be correct. [0032] Though inefficient in its use of bandwidth, an advantage of spread spectrum is its resistance to interference. Another advantage is that the technique can be combined with existing systems having narrower operating bandwidths that fall within the spread spectrum bandwidth. The presence of a spread spectrum signal only slightly increases the noise floor that the narrow band receivers see. [0033] Various spread spectrum techniques are known: In a frequency hopping system, the carrier frequency of the transmitter changes from among a pre-selected set of carrier frequencies in accordance with a pseudo-random code sequence. The frequencies selected from the list are dictated by the codes in the sequence. In a time hopping system, the period and duty cycle of the pulsed radio frequency ("RF") carrier are varied in a pseudo-random manner in accordance with the pseudo-random code sequence. In a pulsed frequency modulated ("FM") system, the RF carrier is modulated with a fixed period and fixed duty cycle sequence. During the transmission of each pulse, the carrier frequency is frequency modulated. Hybrid systems incorporate aspects of two or more other systems. [0034] Direct sequence ("DS") spread spectrum is a well known technique for transmitting digital data. The name direct sequence derives from the fact that the data sequence is directly multiplied by a high rate spreading sequence before it is transmitted over the channel. The spreading sequence is a sequence that transitions much faster than the data sequence. Instead of being called bits as in the data sequence, the individual states of the spreading sequence are called chips. The ratio of the chip rate to the data rate is commonly known as the spreading gain (or processing gain), since it is the ratio by which the bandwidth of the data sequence is increased once it is multiplied by the spreading sequence. [0035] Refer to FIG. 1 for an illustration of the operation of direction sequence signaling. The figure shows a time domain representation of a case in which the chip rate of spreading sequence signal C is four times the rate of the data sequence D; i.e. 1 t C = 4 .times. 1 t D . The resulting spread signal S is the product of the two sequences. When the data bit in D is in a first logic state, signal S follows the spreading sequence C and when the data bit in D is in second logic state, signal S is the compliment of C. The spreading sequence signal shown in FIG. 1 does not repeat. In practice though, many conventional direct sequence spread spectrum techniques employ a spreading code that repeats once per data bit. Code representation 100 is the notational convention used in the disclosure of the present invention to represent a spreading sequence in explaining the operation of the invention. The top half of representation 100 contains an identifier for the code, in this case "Code C." The bottom half of representation 100 indicates the various chips in the spreading sequence and identifies them by number. [0036] These spreading sequences are generally referred to as codes, as in Code Division Multiple Access ("CDMA"). CDMA generally refers to a technique by which users are allocated different spreading codes to enable them to use the same channel without interfering with each other. Another technique, dubbed Spread ALOHA CDMA ("SA/CDMA"), uses a single maximal length code (or a small number of maximal length codes for different service classes) that repeats once per data symbol and relies on arrival time to separate the different incoming signals. A maximal length code is a code of length 2.sup.M-1, where M is an integer, and which has certain desirable autocorrelation properties. For more information on maximal length codes, refer to Pateros, Charles N., "An Adaptive Correlator Receiver for Spread Spectrum Communication," Ph. D. Thesis, Rensselaer Polytechnic Institute, Troy, N.Y., 1993. [0037] Various code spreading strategies are known: In U.S. Pat. No. 5,084,900 to Taylor, the technique described uses a slotted Aloha CDMA system, where each packet uses the same code for the first transmission. When a collision occurs on the first packet, the packet is retransmitted using randomly selected codes from a known pool of codes. No particular code type or relationship of code length to symbol interval is specified. [0038] Consumer broadband satellite services are gaining traction in North America with the start up of star network services using Ka band satellites. 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. [0039] While existing designs have a number of capacity limitations, the demand for such broadband services continues to grow. The past few years have seen strong advances in communications and processing technology. This technology, in conjunction with selected innovative system and component design, may be harnessed to produce a novel satellite communications system to address this demand. [0040] In U.S. Pat. No. 5,450,395, Hostetter et al. describe a single code system where data bit length codes are used and each user always transmits a data `one`. The data is encoded in the time position of each broadcast. The technique requires accurate time synchronization among all of the users. [0041] In U.S. Pat. No. 5,537,397, Abramson describes a spread ALOHA CDMA technique in which multiple users employ the same spreading code. The code is a maximal length code that repeats once per symbol. The users are time aligned at the chip level, but asynchronous at the data bit level. A subtractive multi-user receiver for this application is also described. In U.S. Pat. No. 5,745,485, Abramson extends his '397 patent to allow multiple codes to support different traffic types on the same channel. [0042] Dankberg, et al. describe, in U.S. Pat. No. 5,596,439, a technique for self-interference cancellation for a relay channel. The technique is referred to as Paired Carrier Multiple Access ("PCMA"), since it allows a pair of channels (one in each direction) to share the same relay channel. [0043] In U.S. Pat. No. 5,761,196, Ayerst, et al. describe a CDMA system employing re-use of spreading sequences. A central controller distributes seeds for maximal length codes as needed by users. [0044] What is needed is a communication method which improves upon the multiple access collision performance of the prior art communication techniques. What is needed is a system which can realize improved performance over prior art CDMA communication systems without further complication to the system. SUMMARY OF THE INVENTION [0045] The invention is a communication technique that employs direct sequence spread spectrum signaling for the access channel. Called Code Reuse Multiple Access ("CRMA"), the method is a novel and non-obvious extension of the Code Division Multiple Access ("CDMA") and Spread ALOHA CDMA ("SA/CDMA") multiple access techniques. The invention realizes an improvement in collision performance as compared to conventional multi-access techniques. [0046] In accordance with the invention, a small number of spreading codes relative to the number of simultaneous transmitters are provided. In one embodiment, only a single spreading code is used. In one embodiment, the length of the spreading code is longer than the length of a data symbol. In another embodiment, the length of the spreading code is such that the code does not repeat during modulation of the data sequence. To minimize the acquisition implementation complexity of the system, shortened codes are used in the preamble portion of a data burst. In one embodiment, the preamble is spread by using a code that repeats one or more times. [0047] Further in accordance with the invention, the coding technique can be combined with a Paired Carrier Multiple Access ("PCMA") system. This combination provides a reverse channel without having to allocate an additional operating frequency range or having to provide a separate link. [0048] Still further in accordance with the invention, a multi-user receiver structure efficiently processes a multitude of received signals by centralizing the header acquisition process. A header acquisition component tuned to a spreading code acquires received data bursts. A pool of demodulation components is provided. An individual user data transmission is then fed to a selected one of the demodulation components to process the data portion of the received data burst. Continue reading about Code reuse multiple access for satellite return link... 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