Trw Limited

Northrop Grumman Systems Corporation

Donald C Wilcoxson

Eldad Perahia

David A Wright

Stuart T Linsky

Gregory S Caso

Chamroeun Kchao

Oliver W Saunders

Gefferie H Yee-Madera

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

A method and apparatus for mitigation of false co-channel uplink reception, also known as show-thru, in an uplink A due to an uplink B at a satellite receiver. The method includes storing multiple scrambling sequences associated with respective individual uplinks, including a scrambling sequence A, receiving uplink A signals at an uplink A receiver, applying scrambling sequence A to the uplink A signals to generate descrambled A data, and then decoding the descrambled A data. The decoding step includes the generation of a decoder failure signal in the event that decoding is unsuccessful, and the method discards the descrambled A data if the decoder failure signal is asserted. Therefore, any show-thru data derived from uplink B will be discarded in the uplink A receiver, and vice versa. The step of applying the scrambling sequence may be effected using an exclusive-or operation.

Mitigation of false co-channel uplink reception in a processing satellite communication system using scrambling sequences

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

Information is transmitted in an uplink to a satellite by applying an outer code to an information block to form an outer coded block. The outer coded block is then inner coded when a short block code is applied, thereby producing a concatenated coded block.

Concatenated error control method and system for a processing satellite uplink

A load shedding method and apparatus to enhance uplink margin between a terrestrial terminal (,) and a satellite (,) in a satellite based communications system (,) is provided. The terrestrial terminal (,) includes a multi-carrier network (,) that generates a plurality of uplink carrier channels. A RF transmit and receive system (,) transmits the plurality of uplink carrier channels to the satellite (,). A terminal control unit (,) determines an attenuation level on the plurality of uplink carrier channels transmitted to the satellite (,). The terminal control unit (,) also instructs the multi-carrier network (,) to increase or decrease the number of uplink carrier channels to be transmitted to the satellite.

Load shedding method to enhance uplink margin with combined FDMA/TDMA uplinks

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).

Growing community of inventors

Redondo Beach, CA, United States of America

Donald C Wilcoxson