摘要:
Methods and systems for calculating pre-distortion coefficients in a closed-loop communication system are presented. Transmission terminals that include high power amplifiers are difficult to operate at or near the saturation point without transmitting signals with nonlinear distortions. By pre-distorting the signal prior to amplification the transmitted nonlinear distortions may be decreased. A closed-looped pre-distortion system may include a receiver that calculates the pre-distortion coefficients and transmits these coefficients back to the transmitter. These coefficients may be stored in a pre-distortion coefficient lookup table and may be updated by the receiver terminal.
摘要:
A system to provide narrowcast communications uses adaptive data rate control to individual subscribers such that the effects of precipitation or other link conditions, which are not common to all subscribers, is mitigated. The invention takes advantage of the fact that the narrowcast data consist of packets which are individually addressed to specific subscribers, or groups of subscribers. The narrowcast data is communicated on a plurality of channels, each of potentially differing data rates. The subscribers are assigned a particular channel, based upon their link quality, to receive packets addressed to them. The lower data rate channel will be less affected by adverse link conditions and are hence assigned to subscribers most likely to incur adverse link conditions.
摘要:
A method of distributing first aid kits includes providing a tool to a user. The tool includes a first list and a second list. The first list includes a plurality of different environments, and the second list includes a plurality of different first aid kits. Each of the plurality of environments is correlated to individual ones of the plurality of first aid kits. The tool identifies one of the plurality of first aid kits that is appropriate for use in a corresponding one of the plurality of environments. The method also includes receiving a communication from the user that the one of the plurality of first aid kits is desired. Furthermore, the method includes transferring to the user the one of the plurality of first aid kits.
摘要:
A communication technique based on direct sequence spread spectrum signaling employs, for all users sharing an access channel, a single spreading code that has a duration sufficiently longer than the symbol length that the likelihood of confusion between users is minimized if not eliminated. The length of the spreading code is sufficiently long that contention events can occur only when two bursts occur at the receiver within one chip time of one another.
摘要:
A method, satellite and system utilizes non-geostationary satellite orbit (NGSO) frequency spectrum in geostationary satellite orbit (GSO) satellite communication in a non-interfering manner. A ground station transmits signals to a GSO satellite using a GSO frequency band and an extended frequency spectrum including the an NGSO frequency band whenever a noninterference situation exists, i.e., when an NGSO satellite is not in-line between the earth terminal and the GSO satellite or when the NGSO satellite is not utilizing the NGSO band of interest. A command module is provided to instruct the ground station to transmit signals to the GSO satellite using the GSO frequency band and the extended frequency spectrum.
摘要:
Nonlinearity characterization that transmits bursts of information where symbols vary by a value Delta. The bursts can be bursts of a constant power, followed by another burst of a different constant power. An alternative burst system uses interleaved power symbols, where some symbols in a single burst are at the first power and others are at the second power. The signal-to-noise ratio of the two groups of symbols is estimated, and the difference is used to determine whether or not to reduce the amount of saturation in the transmitter.
摘要:
Techniques for monitoring transmission performance of a satellite communications systems are provided, including techniques for measuring the primary contributors to the end-to-end SNR, including the uplink SNR, the downlink SNR, and the C/I for each link in the network. These individual measurements are used to estimate satellite effective isotropic radiated power (EIRP), satellite antenna gain-to-noise-temperature (G/T), and loss due to an Earth Terminal pointing error. The EIRP, satellite antenna G/T and loss due to Earth terminal pointing error may then be used to determine operating parameters for the satellite communications network that enable the network to operate more efficiently.
摘要:
Techniques are provided herein for monitoring the performance of a satellite communications system, including techniques for determining the pointing loss of a plurality of user terminals in the satellite communications system using the isotropic radiated power (EIRP) of the satellite.