Trw Limited

Northrop Grumman Systems Corporation

Eldad Perahia

Donald C Wilcoxson

Chamroeun Kchao

David A Wright

Stuart T Linsky

Gregory S Caso

Oliver W Saunders

Jean A Develet, Jr

David G Klemes

A satellite based cellular communications system () for servicing multiple user terminals () is provided. The satellite based cellular communications system () includes at least one processing communications satellite () which supports communications uplinks () and communications downlinks () between multiple user terminals (). A network operations center () having a central control processor () communicates with the processing communication satellite () on the communications uplinks () and the communications downlinks (). The central control processor () minimizes intra-system interference between the multiple user terminals () by allocating a connection parameter to each user terminal () based upon accessing a plurality of communication system parameters.

Interference management of a processing communications satellite

The present invention provides a comprehensive method for controlling, independently, transmit power and coding levels for data transmitted in uplinks and downlinks. One preferred embodiment of the present invention provides a method for adaptive coding of data in a downlink. A data error rate associated with downlink data (e.g., a character error rate provided by a Reed Solomon decoder) is determined. The method, based upon pre-established error rate thresholds, controls the level of coding (e.g., heavy or light) on data in the downlink to achieve a desired data error rate. Heavy coded data is typically associated with a code rate half that of light coded data, and changes between heavy and light coding may be selected using a destination address applied at an originating terminal and interpreted at the satellite.

Adaptive coding scheme for a processing communications satellite

The present invention provides a method for custom coding uplink signals and downlink beams in a satellite communications system. The method includes the step of applying, at a ground station ( ), an outer code ( ) to an uplink signal to produce an outer coded uplink signal. Next, the ground station ( ) applies a selected reduced complexity inner code ( ) to the outer coded uplink signal to produce a concatenated coded uplink signal. The ground station ( ) transmits the concatenated coded uplink signal to a satellite ( ). At the satellite ( ), the inner code of the concatenated coded uplink signal is decoded ( ) to produce an outer coded satellite data stream. Next, the satellite ( ) applies a selected inner code ( ) to a portion of the outer coded satellite data stream to produce a concatenated coded satellite data stream. The satellite ( ) then transmits the concatenated coded satellite data stream in a downlink beam to a destination ground station ( ).

Concatenated coding system for satellite communications

Communication satellite downlink transmitting and reception techniques includes circuitry which groups a predetermined number of data cells with a predetermined error correction code to generate frame bodies. The circuitry also groups the frame bodies with header symbols and trailer symbols to generate data frames. One or more modulators enable the placement of the modulated data frames into a plurality of frequency bands having a predetermined frequency range and a predetermined transmission rate. One or more antennas transmit the modulated data frames over one or more beams with different forms of polarization to other antennas. A demodulator is connected to demodulate the radio carrier signals and the beams into data frames from a plurality of frequency bands. Decoders are connected to decode the frame bodies with header symbols and with trailer symbols from the data frames and to decode four data cells as a group by using a predetermined error correction code.

Downlink transmission and reception techniques for a processing communication satellite

Uplink transmission and reception techniques for a processing satelliteation satellite

The present invention provides an open-loop method for determining uplink transmission power in a satellite communication system,that compensates for antenna pointing error attenuation and for rain attenuation. Satellite downlink signal,attenuation is measured. Antenna pointing information is then used in conjunction with antenna gain pattern information,to determine antenna pointing error attenuation. The measured downlink attenuation and antenna pointing error attenuation are then used to determine the amount of rain attenuation on the downlink,. The downlink attenuation information is then used to determine the amount of uplink,attenuation to be expected. Uplink transmission power levels are then adjusted accordingly to overcome the expected uplink,attenuation.

Performance enhancement of open-loop power control for satellite communication systems

A method for maximizing satellite downlink information rate is disclosed. A ground transmitter (,) applies an outer block code to a data channel, modulates it, and transmits an uplink data stream (,) to a satellite (,) which demodulates the uplink data stream to produce a demodulated uplink data stream consisting of 1 to N user channels (,). The method uses a first multiplexer (,) to produce 1 to M multiplexed data signals (,) which are fed into quality encoders (,). The quality encoders (,) encode the multiplexed data signals (,) according to a selected quality level to produce custom-coded data signals (,). The level of coding applied to the custom-coded data signals (,) may be controlled by information received by a channel measurement element (,). Next, the method passes the custom-coded data signals (,) into a second multiplexer (,) which produces one multiplexed data stream (,). The multiplexed data stream (,) is then fed into the satellite's modulator before transmission back to a ground receiver.

Satellite communication adaptive control coding

A satellite-based telecommunication system is provided which communicates with earth-based users located within a predetermined communications area. The communications areas have an associated interference pattern. A satellite antenna is controlled to form an antenna gain pattern distributed across the communications area. The antenna gain pattern represents the gain at any given point within the communications area. The interference pattern corresponds to the amount of interference associated with each point within the communications area. A method and apparatus are provided for controlling the gain defined by a transmitter and/or receiver of a satellite. The transmitter/receiver produces a desired antenna gain pattern. The preferred embodiment includes determining an interference pattern associated with a communications area of interest. Once the interference pattern is identified, a desired antenna gain pattern is then identified. It is preferable that the antenna gain pattern conform to the interference pattern for the communications area.

Cellular satellite communication system and method for controlling antenna gain pattern therein

The present invention provides a method for determining antenna pointing error of a satellite antenna (702-716) that produces at least one spot beam having a corresponding gain pattern. The method obtains from a first unique location (510) on the ground a first measurement of a spot beam strength for a first cell (502). Similar measurements are obtained at second and third unique locations (512, 514). Attitude component errors, for example the roll or pitch attitude component errors may then be determined. The method may further determine a yaw attitude component error based on fourth, fifth, and sixth measurements of spot beam strength made from unique locations (616-620) in a second cell (604) also generated by the antenna. Additional measurements may be collected in each beam at unique locations (510-514, 516-520, 610-614, 616-620) and averaged to reduce the temporary or zero means effects of rain, scintillation, or other atmospheric conditions on the spot beam strength. Furthermore, the method may transmit any of the measurements to a central processor (422) which determines the attitude component errors based on the measurements.

Method for enhancing the performance of a satellite communications

The present invention provides a method for custom coding uplink signals and downlink beams in a satellite communications system. The method includes the step of applying, at a ground station (100), an outer code (102) to an uplink signal to produce an outer coded uplink signal. Next, the ground station (100) applies a selected reduced complexity inner code (104) to the outer coded uplink signal to produce a concatenated coded uplink signal. The ground station (100) transmits the concatenated coded uplink signal to a satellite (110). At the satellite (110), the inner code of the concatenated coded uplink signal is decoded (116) to produce an outer coded satellite data stream. Next, the satellite (110) applies a selected inner code (120) to a portion of the outer coded satellite data stream to produce a concatenated coded satellite data stream. The satellite (110) then transmits the concatenated coded satellite data stream in a downlink beam to a destination ground station (126).

A method for reducing interference and increasing spectral efficiency in a frequency reuse pattern (600) is disclosed. The method includes the steps of generating n original communications beams (302-308) assigned to substantially non-overlapping frequency bands, with the original communications beams extending over a first set of predetermined bandwidths. The method also generates n shifted communications beams (402-408) shifted by an orthogonal frequency separation from the n original communications beams (302-308), with the n shifted communications beams (402-408) extending over a second set of predetermined bandwidths. The method projects the n original communications beams (302-308) and the n shifted communications beams (402-408) in a frequency reuse pattern (600) over a region of interest by alternating the n original communications beams (302-308) with the n shifted communications beams (402-408).

Method for reducing interference and increasing spectral efficiency

A method for enhancing the performance of a communications system is disclosed. The system generally includes an originating ground station (300) which produces error-control coded uplink signals and transmits the coded uplink signals to a satellite (310). The system also includes a destination ground station (326) which receives a downlink beam from the satellite (310). The method includes the steps of receiving uplink signals transmitted by an originating ground station (300) at a destination ground station (326) and determining a downlink channel signal quality indication (504) at the destination ground station (326). The method also includes the steps of measuring an error rate associated with at least a portion of a downlink beam at said destination ground station (326) and determining an operating point (506) relative to a desired performance curve (502) based on the signal quality indication (504) and the error rate. At least one signal processing parameter of said originating ground station (300) is adjusted based on the operating point (506) when said operating point (506) lies in a predetermined region relative to the performance curve (502).

Method for enhancing the performance of a regenerative satellite

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).

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Hermosa Beach, CA, United States of America

Eldad Perahia