Abstract: In one implementation, a method for scheduling beams of an antenna on a satellite during a defined time period includes calculating a beam score for each beam based on the expected gain of the beam and determining that the number of beams having non-zero beam scores during the defined time period is less than a threshold value. In addition, the method also includes accessing a set of beam weights for each of multiple different candidate beam patterns, and, for each set of weights, multiplying individual beam weights by corresponding beam scores, and generating a candidate beam pattern score by calculating a sum of the products of the beam weights and corresponding beam scores. The method further includes comparing the candidate beam pattern scores, selecting a particular one of the candidate beam patterns, and scheduling the selected beam pattern for the defined time period.

Abstract: In one implementation, first and second messages are received that include encoded position information for a transmitter. It is determined that both were received within some time of a previous message and that the second message was received within some time of the first message. A first location of the transmitter is determined based on the encoded position in the first message and the previously determined location. A second location of the transmitter is determined based on the encoded position in the second message and the previously determined location. It also is determined that the first and second locations are within a threshold distance. An updated second location of the transmitter is determined based on the encoded position information in the second message and the first location. A determination is made that the second location and the updated second location are within a threshold distance.

Abstract: In one implementation, a receiver has a module to calculate the cross-correlation between a portion of a digital representation of a received signal and a reference signal. The receiver also has a module to generate an estimate of a portion of a message potentially included in the digital representation of the received signal and a screening module to determine the likelihood that the received signal includes a message. For a received signal that is determined likely to include a message, the receiver includes a carrier refinement module to shift the frequency of carrier pulses in the digital representation of the received signal toward a desired frequency and to align the phase of carrier pulses in the digital representation of the received signal with a desired phase and a coherent matched filter to recover the message from the digital representation of the received signal.

Abstract: In one implementation, a method includes receiving versions of a message from a first satellite-based receiver and a second satellite-based receiver that both received a radio frequency (“RF”) transmission of the message, the message comprising a self-reported position of a transmitter of the message. The method also includes determining a time difference between a first arrival time of the RF transmission of the message at the first satellite-based receiver and a second arrival time of the RF transmission of the message at the second satellite-based receiver. The method further includes determining a measure of the likelihood that the self-reported position of the transmitter is valid based on the time difference between the first and second arrival times. The method still further includes transmitting an indication of the measure of the likelihood that the self-reported position is valid.

Abstract: In one implementation, a method includes receiving a number of instances of a message that includes a self-reported position of a transmitter of the message from a corresponding number of satellite-based receivers that each received an RF transmission of an instance of the message. The method also includes determining the number of satellite-based receivers that received an instance of the message and selecting a validation technique based on the number of satellite-based receivers that received an instance of the message. If the number of satellite-based receivers that received an instance of the message is one, a propagation-based validation technique is selected. The method further includes determining a measure of the likelihood that the self-reported position of the transmitter is valid using the selected validation technique, and transmitting an indication of the measure of the likelihood that the self-reported position is valid.

Abstract: In one implementation, a method includes receiving simulated RF transmission data indicative of anticipated RF transmissions from a plurality of transmitters, wherein individual anticipated RF transmissions carry corresponding messages, and simulated position data indicative of an anticipated position of each of the plurality of transmitters. The method further includes modeling characteristics of a communications channel expected between a satellite-based receiver and at least some of the transmitters, wherein the satellite-based receiver is configured to define one or more beams for receiving anticipated RF transmissions. The method additionally includes determining a likelihood of the receiver successfully extracting one or more components of a message from one of the anticipated RF transmissions based on at least the simulated RF transmission data, the simulated position data, and the modeled characteristics of the communications channel.

Abstract: In one implementation, a pair of messages are received from one or more space-based receivers that each received the pair of messages. The pair of messages comprise encoded position information of a transmitter, and a plurality of candidate locations for the transmitter is determined therefrom. A location of the transmitter is determined by eliminating candidate locations until only one remains. In particular, each candidate location that is not within a coverage area of each of the space-based receivers is eliminated, and each candidate location that is not within a predetermined distance of at least one previous candidate location is eliminated. In addition, it is determined that the remaining candidate location is within the coverage area of each of the space-based receivers as well as within the predetermined distance of at least one previous candidate location. Upon determining the location of the transmitter, it is transmitted to a subscriber system.

Abstract: In one implementation, a receiver has a module to detect a carrier within a portion of a digital representation of a received signal. In addition, the receiver includes a module to calculate the cross-correlation between the portion of the digital representation of the received signal and a reference signal representing an expected pulse pattern. The receiver also has a module to generate an estimate of a portion of a message potentially included in the digital representation of the received signal. The receiver further includes a screening module to generate a feature vector representing the estimated message, project the feature vector into a feature space, and determine the likelihood that the digital representation of the received signal includes a message. If the digital representation of the received signal likely includes a message, the receiver includes a non-coherent matched filter to recover the message from the digital representation of the received signal.

Abstract: In one implementation, satellite coverage provisioning for a service area may be performed by updating power consumption states for satellites in a constellation of satellites and determining whether each satellite of the constellation is required to be in the minimal power consumption mode based on its updated power consumption state. For satellites that are not required to be in the minimal power consumption mode, a power consumption score may be calculated and these satellites may be sorted according to their respective power consumption scores. Based on the sorted order, it may be determined whether at least some of these satellites can be put into a reduced power consumption mode based on their respective power consumption scores and coverage of the service area. Then it may be determined if each of the satellites that are in the reduced power consumption mode can be put into the minimal power consumption mode.

Abstract: In one implementation, satellite coverage provisioning for a service area may be performed by updating power consumption states for satellites in a constellation of satellites and determining whether each satellite of the constellation is required to be in the minimal power consumption mode based on its updated power consumption state. For satellites that are not required to be in the minimal power consumption mode, a power consumption score may be calculated and these satellites may be sorted according to their respective power consumption scores. Based on the sorted order, it may be determined whether at least some of these satellites can be put into a reduced power consumption mode based on their respective power consumption scores and coverage of the service area. Then it may be determined if each of the satellites that are in the reduced power consumption mode can be put into the minimal power consumption mode.

Abstract: In one implementation, a method for scheduling beams of an antenna on a satellite during a defined time period includes calculating a beam score for each beam based on the expected gain of the beam and determining that the number of beams having non-zero beam scores during the defined time period is less than a threshold value. In addition, the method also includes accessing a set of beam weights for each of multiple different candidate beam patterns, and, for each set of weights, multiplying individual beam weights by corresponding beam scores, and generating a candidate beam pattern score by calculating a sum of the products of the beam weights and corresponding beam scores. The method further includes comparing the candidate beam pattern scores, selecting a particular one of the candidate beam patterns, and scheduling the selected beam pattern for the defined time period.

Abstract: In one implementation, a receiver has a module to calculate the cross-correlation between a portion of a digital representation of a received signal and a reference signal. The receiver also has a module to generate an estimate of a portion of a message potentially included in the digital representation of the received signal and a screening module to determine the likelihood that the received signal includes a message. For a received signal that is determined likely to include a message, the receiver includes a carrier refinement module to shift the frequency of carrier pulses in the digital representation of the received signal toward a desired frequency and to align the phase of carrier pulses in the digital representation of the received signal with a desired phase and a coherent matched filter to recover the message from the digital representation of the received signal.