Abstract: 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.

Abstract: A downlink orderwire integrator (63) and separator (81) for use in a processing satellite (12) and a user terminal (14) in a satellite based communications system (10) is provided having a formatter (64), a cell switch (72) and a cell sieve (80). The formatter (64) generates orderwire cells (54) with each orderwire cell (54) having a header (60) and a body (62). The cell switch (72) receives the orderwire cells (54) from the formatter (64) and traffic cells (56) from at least one uplink (16) and arranges the orderwire cells (54) and the traffic cells (52) in at least one frame (48) to transmit on at least one downlink (18). The frame (48) includes a fixed custom frame portion (42) and a fixed traffic portion (50) that contains both the traffic cells (52) and the orderwire cells (54).

Abstract: The present invention provides an uplink frame structure in a satellite communications system, and a method for providing control access to a plurality of user terminals transmitting the inventively structured uplink frames. The uplink frame structure comprises a superframe which includes a predetermined number of individual frames. Each individual frame comprises a traffic burst field and a control burst field, where the control burst fields may be located at the same position within each frame. Each control burst field further comprises several individual control time slots. The individual control time slots may include, for example, timing probes and orderwire information.

Abstract: 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.

Abstract: A decoder of a data signal subjected to phase shifting keying (PSK) modulation uses an inner decoder for short block codes within a phase locked loop which is adapted to process the data signal with multiple initial phase/frequency error estimates and to output sets of codewords and phase/frequency error estimates respectively corresponding to the initial phase/frequency estimates. A selection circuit (720) selects and forwards the output corresponding to one of the multiple phase/frequency estimates. An outer Reed-Solomon block decoder (319) corrects errors in the codewords from the set of associated codewords selected by the selection circuit.

Abstract: A demodulator for demodulating a QPSK modulated signal waveform in a data communication system, has a phase tracking loop tracking the phase of said QPSK modulated signal waveform and having an inner block decoder configured to decode a set of vector pairs of the modulated signal waveform at a decode rate to generate associated codewords and phase estimates. A group of data symbols consisting of the first data symbols of the QPSK modulated signal waveform are stored until a future waveform is received and then run backwards through the phase tracking loop concurrently with the data from the future waveform. An outer block decoder receives the associated codewords generated by said inner block decoder and utilizes and corrects only codewords associated with symbols after and including the group of data symbols consisting of the first data symbols of the QPSK modulated signal waveform.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: A demodulator demodulates a modulated signal waveform in a data communication system. A phase tracking loop tracks the phase of said modulated signal waveform and having an inner block decoder configured to decode a set of vector pairs of the modulated signal waveform at a decode rate to generate associated codewords and phase estimates. A group of data symbols consisting of the first data symbols of the modulated signal waveform are run backwards through the phase tracking loop. An outer block decoder receives the associated codewords generated by said inner block decoder and utilizes and corrects only codewords associated with symbols after and including the group of data symbols consisting of the first data symbols of the modulated signal waveform.

Abstract: A decoder of a data signal subjected to phase shifting keying (PSK) modulation uses a plurality of phase locked loops (801-1 to 801-n) having an inner decoder for short block codes, at least one of which is adapted to apply excess processing power to process a selected burst of the data signal, such as processing the burst with multiple initial phase/frequency error estimates. A selection circuit identifies the burst and supplies to said one of said plurality of phase-locked loops (801-1 to 801-n) for re-processing the bust with excess processing power. An outer Reed-Solomon block decoder (319) may be used to correct errors in the codewords from the phase locked loops and may be used in the selection of the burst by the selection circuit.

Abstract: A decoder of a data signal subjected to phase shifting keying (PSK) modulation uses an inner decoder for short block codes within a phase locked loop which is adapted to process the data signal with multiple initial phase/frequency error estimates and to output sets of codewords and phase/frequency error estimates respectively corresponding to the initial phase/frequency estimates. A selection circuit (720) selects and forwards the output corresponding to one of the multiple phase/frequency estimates. An outer Reed-Solomon block decoder corrects errors in the codewords from the set of associated codewords selected by the selection circuit. The Reed-Solomon block decoder corrects a combination of random errors and erasure errors where the erasure errors are chosen based on reliability metrics generated by the inner code or else the first positions of the data bursts are chosen for erasures as these are most likely to be in error relative to other positions.

Abstract: 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.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: Uplink transmission and reception techniques for a processing satellite including one or more earth terminals 400 connected to receive ATM data cells. One or more encoders 418 are connected to coordinate four data cells with an error correction code to generate data bursts and to coordinate the data bursts with synchronizing bursts to generate data frames. One or more modulators 420 are connected to modulate the data frames by frequency division multiple access modulation to enable placement of the modulated data frames into a plurality of channels. One or more antennas 406 transmit the modulated data frames to a satellite 100 over 48 beams with various forms of polarization. In satellite 100, a receiving multibeam antenna and feed 106 responds to one or more beams of radiocarrier signals having one or more forms of polarization. One or more demodulators 138 demodulate the radio carrier signals into data frames from various channels including a plurality of channel types.

Abstract: In a cellular satellite system such as Astrolink, where same frequency, same polarization (same “color”) signals are used in multiple ground cells, there exists the possibility of interference and false reception of uplink Synchronization Bursts (SB) in systems employing TDMA access of the frequency in question. In such systems, a SB transmitted from one terminal may be received in more than one satellite beam. The reception of the signal from a terminal in an undesired beam (330) is erroneous and may adversely impact the time synchronization (360) of the desired terminal. For example, a system may employ Maximal Length (ML) Pseudo-Noise (PN) sequences (410) for its SBs wherein every beam may use the same sequence. To minimize false reception, the ML PN sequences (410) of each SB may be cyclicly shifted a different amount for each beam to generate sequences (410, 420) having low corsscorrelation with each other.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: An uplink demodulator system (44) for use in a processing satellite (12) in a satellite based communications system (10) is provided with a first multiplexer (62), a second multiplexer (82), a multichannel preamble processor (66), and a multichannel phase tracker (68). The first multiplexer (62) is operable to receive channelized data from a plurality of channelization modes at a plurality of inputs and operable to route the channelized data to a first output. The multichannel preamble processor (66) is operable to determine a phase estimate for each channel of the channelized data. The multichannel phase tracker (68) is operable to receive the phase estimates from the multichannel preamble processor (66) and operable to track a phase for each channel of said channelized data to phase align each channel of said channelized data to corresponding uplink signals.

Abstract: A communications satellite method and are provided for controlling a configuration of spot beams produced by a communications satellite. A plurality of spot beams are generated by a communications satellite while maintained at a first orbital position with respect to a first portion of the earth. The plurality of spot beams are configured in a first cell pattern to substantially encompass a first portion of the Earth. The satellite is moved to a second orbital position with respect to a second portion of the earth. Once moved, the satellite is reconfigured such that a second plurality of spot beams form a second pattern 85 to substantially cover the new portion of the earth of interest. A network of switches allows the satellite 10 to be reconfigured for operation from multiple orbital positions. The switching network directs individual feeds to different signal paths having different bandwidth and power capabilities.

Abstract: Coordination of processing satellite uplink transmission and downlink transmission is achieved by an uplink encoder (418) and uplink modulator (420) which incorporate an adjustable IF amplifier (417) at a ground terminal (400). Information about data traffic transmission errors detected in a satellite (100) is formed into ATM traffic report cells by a cell former (157). The traffic report cells are sent on the downlink to the ground terminal. The traffic report cells are used to adjust the power level of the IF amplifier for the particular channel and slot for which errors were detected.

Abstract: 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.

Abstract: A local telecommunications network is provided for satellite based telecommunications. The network 10 includes multiple handsets 18-22, 50 and 54 which communicate directly with ground stations 14 and 16. The ground stations communicate with an overhead satellite 12 through a satellite telecommunications uplink. The ground stations include a router for determining whether outgoing calls are directed to a destination handset located within or outside a predefined local geographic cell 30 and 32 for the corresponding ground station 14 and 16. If the destination handset is located outside the local cell of the originating handset, the ground station passes the call to the overhead satellite 12 to establish a satellite telecommunications link. However, if the destination handset 50 is located within the same local cell 32 as the originating handset 22, then the router 16 establishes a direct link between the handsets 22 and 50 without establishing a satellite telecommunications link 26.