Trw Limited

Jean A Develet, Jr

Oliver W Saunders

Eldad Perahia

Eric R Wiswell

A communications system (100) is disclosed for processing at least one uplink channel contained in at least one uplink beam (112) transmitted to a satellite (106). The communications system (100) includes at least one user terminal (110) that extracts a system clock, a synchronization word, and timing correction information from a downlink beam transmitted by a satellite. The user terminal includes a timing controller (226) that aligns uplink channel transmissions by generating a system clock based on the downlink symbol clock, said synchronization word, and said timing correction information. The user terminal includes at least one spread-spectrum spreader (254) for encoding at least one uplink channel, and a transmitter connected to the spread-spectrum spreader (254) for transmitting said at least one uplink channel in an uplink beam (112). The system also includes a satellite (106) which generates the synchronization word, downlink symbol clock, and the timing correction information needed by the user terminal. The satellite also includes a wideband FFT processor (322) that extracts uplink channels from the uplink beam (112) in bulk, and a despreader (326) connected to the FFT processor (322) for simultaneously despreading user signals contained in said uplink channels.

Bulk despreading of multiple independent CDMA sources

A satellite communications technique is disclosed that synchronizes the reception of numerous OFDM uplink signals (108, 110) at a satellite (106) receiver and bulk processes them in the satellite (106). In operation, the satellite (106) receives an OFDM uplink signal (110) transmitted by a CPE (104). The satellite 106 then compares the reception timing of the symbols in the received OFDM uplink signal (110) with a satellite timing reference, and generates a timing correction. The satellite (106) provides a downlink symbol clock as inherent structure in a downlink beam to the CPE (104) and also transmits the timing correction in the downlink beam. The CPE (104) uses the downlink symbol clock in conjunction with the timing correction to generate an uplink clock. The CPE (104) then transmits data in the OFDM uplink signal (110) synchronously with the uplink clock. Each CPE (102, 104) may be synchronized in this manner. In addition, the satellite (106) may also periodically re-compare the reception timing of the OFDM uplink signals (108, 110) with the satellite timing reference to generate new timing corrections, if necessary, for the CPEs (102, 104).

Bulk filtering and demodulation of independent FDMA sources

A method is disclosed for efficiently transmitting large numbers of data channels through a satellite (24). The method uses a block encoder (28) that encodes the data channels with a block code to produce an encoded uplink data stream. A modulator (30) modulates the encoded uplink data stream. A transmit antenna (32) then sends the resultant modulated uplink data stream (34) to the satellite (24). The satellite uses a satellite demodulator (48) and a switch (50) to produce an internal data stream consisting of selected data channels in the uplink data stream (34). The internal data stream is fed into a convolutional encoder (52). The output of the convolutional encoder (52) is connected to a satellite modulator (54). The satellite transmit antenna (56) then sends the resultant modulated downlink data stream (58) to a receiver.

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Rancho Palos Verdes, CA, United States of America

Jean A Develet, Jr