Abstract: Aspects of the invention provide a system and method to allow inroute frame timing synchronization without the aid of hub signal loopback or satellite ephemeris data. Furthermore, it allows tracking and compensating of the satellite motion to allow multiple remotes to use TDMA on the inroute frequencies, while minimizing the aperture. Two main techniques proposed are CLT and polling based approaches, which are used in combination for an optimum solution. In CLT based approach, hub transmits remote specific timing correction feedback messages on the outroute on as needed basis. In polling based approach, the remotes derive their timing based on a per-beam average delay estimate broadcast by the hub and a measured local delay specific to each outroute stream from a remote. An aspect of the invention uses triangulation method to determine satellite position. Furthermore, an aspect of the invention uses hub burst arrival method instead of polling approach.

Abstract: Aspects of the invention provide a system and method to allow inroute frame timing synchronization without the aid of hub signal loopback or satellite ephemeris data. Furthermore, it allows tracking and compensating of the satellite motion to allow multiple remotes to use TDMA on the inroute frequencies, while minimizing the aperture. Two main techniques proposed are CLT and polling based approaches, which are used in combination for an optimum solution. In CLT based approach, hub transmits remote specific timing correction feedback messages on the outroute on as needed basis. In polling based approach, the remotes derive their timing based on a per-beam average delay estimate broadcast by the hub and a measured local delay specific to each outroute stream from a remote. An aspect of the invention uses triangulation method to determine satellite position. Furthermore, an aspect of the invention uses hub burst arrival method instead of polling approach.

Abstract: A receiver is used with third code blocks based on first code blocks, second code blocks, and a planning code block. The first code blocks are associated with a first sequence number and modulated with a first modulation scheme. The second code blocks are associated with a second sequence number and modulated with a second modulation scheme. The planning code block associates the third code blocks with the first code blocks and the second code blocks. The receiver includes a de-multiplexing portion, which includes a code block selector and a look up table, that outputs a de-multiplexed signal based on the third code blocks. The code block selector selects a code block from the third code blocks to output as the de-multiplexed signal based on entries in the look up table. The receiver also includes a recovery portion that outputs received code blocks based on the de-multiplexed signal.

Abstract: A system for a multiplexing scheme for wideband signals in a communications system is provided. A codeblock of a multiplexed datastream is decoded. The codeblock includes a flag indicating whether the codeblock contains a timeplan, signifying a multiplexing structure of the datastream. A determination is made whether the flag indicates the presence of the timplena, and, if so, the timeplan is acquired. In response to a determination that the codeblock does not contain the timeplan, a subsequent codeblock is determined, and decoded. Each codeblock includes a an indicator of a sequence position of the codeblock within a group of codeblocks of the datastream. The subsequent codeblock is determined based on one or more of a decode rate of the processor device and the sequence position indicator. A determination is made whether the flag of the first subsequent codeblock indicates the presence of the timeplan, and, if so, the timeplan is acquired.

Abstract: A transmitter is provided for use with a first input signal and a second input signal. The transmitter includes a first modulating portion, a second modulating portion and a multiplexing portion. The first modulating portion can output a first plurality of code blocks based on the first input signal, wherein each of the first plurality of code blocks has a first sequence number associated therewith and is modulated with a first modulation scheme. The second modulating portion can output a second plurality of code blocks based on the second input signal, wherein each of the second plurality of code blocks has a second sequence number associated therewith and is modulated with a second modulation scheme, and wherein the second modulation scheme is different than the first modulation scheme. The multiplexing portion can a third plurality of code blocks based on the first plurality of code blocks, the second plurality of code blocks and planning code block.

Abstract: A satellite communications system having a fallback mode of operation, during which uplink signals are transmitted at a reduced data rate, is provided with a novel fallback mode ingress/egress mechanism utilizing a combination of a feedback-based fade detection scheme and fade detection based on parameters independent of the uplink signal transmission. The fallback mode ingress/egress mechanism is responsive to a satellite beacon signal independent of the uplink signals and to feedback signals produced by the satellite in response to the uplink signals, for requesting a satellite terminal to switch into the fallback mode when either the feedback signals indicate an increase in a fade level or in response to a first value of a selected parameter of the satellite beacon signal. The fallback mode ingress/egress mechanism requests the satellite terminal to switch out of the fallback mode in response to a second value of the satellite beacon signal parameter.

Abstract: An uplink power control system for terminals in a satellite communication system provides closed loop power control using feedback signals generated at a satellite. The satellite performs inter-beam routing of uplink signals from satellite terminals, and processing of uplink signals to generate terminal transmission-specific feedback information that is transmitted in downlink signals to the terminals. The satellite also generates a beacon signal. An uplink power control algorithm at each terminal uses the beacon signal and feedback data to adjust transmit power.

Abstract: A method and system for acquiring a time division multiplexed synchronization signal in a satellite communication system is provided. The signal is provided as a series of frames with beacon signals time division multiplexed into at least one time slot of each frame. The beacon signal in each frame comprises a unique word sequence, which is the same in each frame, and a portion of a PN sequence. The entire PN sequence is distributed into a plurality of frames forming a superframe. Initially, the power level of the incoming signal is determined by locating the maximum power received in half time slot intervals. Next a series of frames are correlated against the expected unique word, each at one of a plurality of possible frequencies. The frequency generating the maximum correlation with the unique word is selected.

Abstract: A method and system for tracking a time division multiplexed synchronization signal in a satellite communication system is provided. The signal is provided as a series of frames with beacon signals time division multiplexed into at least one time slot of each frame. The beacon signal in each frame comprises a unique word sequence, which is the same in each frame, and a portion of a PN sequence. The entire PN sequence is distributed into a plurality of frames forming a superframe. Frequency variations of the incoming signal are tracked at the satellite terminal by correlating the PN sequence of the incoming signal against early and late locally generated versions of the PN sequence in a discriminate circuit. The output of the discriminate is provided to a delay locked loop circuit of at least third order. The output of the loop is used to adjust the frequency of the VCO, which clocks the A/D converter operating on the incoming signal.

Abstract: An apparatus for providing automatic gain control for use in a satellite terminal of a satellite communication system capable of transmitting a plurality of different modes of data. The apparatus includes a demodulator circuit having an analog to digital converter; a first variable attenuator having an attenuation value set on the basis of a measured power level of a predetermined data signal; and a second variable attenuator having an attenuation value set on the basis of the mode of data being received by the satellite terminal, where each of the data modes have a corresponding predetermined attenuation value associated therewith which is utilized as the attenuation value of the second variable attenuator when the satellite terminal receives the data mode.

Abstract: A satellite communications system having a fallback mode of operation, during which uplink signals are transmitted at a reduced data rate, is provided with a novel fallback mode ingress/egress mechanism utilizing a combination of a feedback-based fade detection scheme and fade detection based on parameters independent of the uplink signal transmission. The fallback mode ingress/egress mechanism is responsive to a satellite beacon signal independent of the uplink signals and to feedback signals produced by the satellite in response to the uplink signals, for requesting a satellite terminal to switch into the fallback mode when either the feedback signals indicate an increase in a fade level or in response to a first value of a selected parameter of the satellite beacon signal. The fallback mode ingress/egress mechanism requests the satellite terminal to switch out of the fallback mode in response to a second value of the satellite beacon signal parameter.

Abstract: A communications system has a high altitude communication device generates a plurality of user link beams having a first communication characteristic and a feeder link having a first communication characteristic. A gateway terminal receives the user link beam for receiving a first received signal and a second received signal thereafter. The receiver circuit has a recursive filter for generating differential amplitude of symbol timing estimate from said first received signal.

Abstract: A system and method for establishing an integrated forward error correction (FEC) scheme to perform multi-rate encoding on different priority data bits of a channel access message transmitted on a random access channel between devices of a communications network, such as between an access terminal and a base station of a satellite-based communications network. The channel access message includes a first data group representing first information and a second data group representing second information, which is transmitted between an access terminal and a base station in a satellite-based communications network. The system and method encodes the second data group at an encoding rate to provide a second encoded data group, and encodes the first data group at the same encoding rate to provide a first encoded data group. The encoding of the first and second data groups is performed by a single encoder, such as a rate ¼ convolutional encoder.

Abstract: An uplink power control system for terminals in a satellite communication system provides closed loop power control using feedback signals generated at a satellite. The satellite performs inter-beam routing of uplink signals from satellite terminals, and processing of uplink signals to generate terminal transmission-specific feedback information that is transmitted in downlink signals to the terminals. The satellite also generates a beacon signal. An uplink power control algorithm at each terminal uses the beacon signal and feedback data to adjust transmit power.

Abstract: A system and method for establishing an integrated forward error correction (FEC) scheme to perform multi-rate encoding on different priority data bits of a channel access message transmitted on a random access channel between devices of a communications network, such as between an access terminal and a base station of a satellite-based communications network. The channel access message includes a first data group representing first information and a second data group representing second information, which is transmitted between an access terminal and a base station in a satellite-based communications network. The system and method encodes the second data group at an encoding rate to provide a second encoded data group, and encodes the first data group at the same encoding rate to provide a first encoded data group. The encoding of the first and second data groups is performed by a single encoder, such as a rate ¼ convolutional encoder.

Abstract: A method and system for acquiring a time division multiplexed synchronization signal in a satellite communication system is provided. The signal is provided as a series of frames with beacon signals time division multiplexed into at least one time slot of each frame. The beacon signal in each frame comprises a unique word sequence, which is the same in each frame, and a portion of a PN sequence. The entire PN sequence is distributed into a plurality of frames forming a superframe. Initially, the power level of the incoming signal is determined by locating the maximum power received in half time slot intervals. Next a series of frames are correlated against the expected unique word, each at one of a plurality of possible frequencies. The frequency generating the maximum correlation with the unique word is selected.

Abstract: An apparatus for providing automatic gain control for use in a satellite terminal of a satellite communication system capable of transmitting a plurality of different modes of data. The apparatus includes a demodulator circuit having an analog to digital converter; a first variable attenuator having an attenuation value set on the basis of a measured power level of a predetermined data signal; and a second variable attenuator having an attenuation value set on the basis of the mode of data being received by the satellite terminal, where each of the data modes have a corresponding predetermined attenuation value associated therewith which is utilized as the attenuation value of the second variable attenuator when the satellite terminal receives the data mode.

Abstract: A demodulator for use in a satellite communication system, which is operative for receiving a modulated signal having a data rate R (i.e., the demodulator receives R input samples per second). The demodulator includes a demultiplexer circuit having N shift registers, which functions to receive the R data samples per second as an input signal. The demultiplexer circuit operates to input the R input samples sequentially into the N shift registers such that each of the shift registers receives input samples at a data rate of R/N samples per second. The demodulator further includes signal recovery circuitry for processing the input samples contained in each of the N shift registers so as to regenerate the data contained in the incoming modulated signal transmitted by the satellite.

Abstract: The present invention is a method for generating short, non-systematic, non-linear (6,4) codes that may be implemented in a 4-ARY quadrature-quadrature phase shift keying (QQPSK or Q2PSK) system over GF(16). The codewords are non-systematic in that they do not directly contain the information that is to be transmitted and six symbols are sent to represent four symbols. The present invention uses a code construction method that generates two small, hand-optimized codeword sets and combines those two codeword sets to create two larger codeword sets. The two larger codeword sets are then combined to create a codeword set that is stored in a look-up table for use at a transmission station.

Abstract: A message format and associated method for estimating the frequency and timing offset of a reference burst of a random access channel in a time-division multiple access communications system. A signal structure in which the continuous wave segment is split into two parts separated by some portion of the content of the random access channel burst is used to provide more precise frequency estimation. Iteration of separate frequency and timing estimation procedures is used to refine both estimates, as the individual estimation processes are more accurate when there is less error in the other parameter. Multiple hypothesis testing is used, in which more than one initial frequency estimate is carried through the iteration process, with thresholding to identify the best frequency offset. Reliable rejection of false ambiguities is achieved because the degradation in timing estimation, due to large frequency offsets, can be detected with thresholding.