Abstract: A satellite-based, world-wide cellular messaging system transmits paging messages to pagers via multiple beams. A message unit monitors multiple beams, recording the visit information for each beam, and ultimately determines the optimum beam to monitor for messages. The message unit, which conserves battery resources by entering into a sleep mode, synchronizes quickly to its message block when it awakes.

Abstract: Handoff methods perform cell-to-cell handoff between cells of the same satellite and between cells of different satellites. Handoff is initiated by an individual subscriber unit (ISU) based on local conditions. Once handoff is needed, the ISU chooses a candidate cell to transfer its communication based on a dynamic handoff candidate list provided by the satellite. After selecting a candidate cell, the ISU requests handoff, the satellite or satellites perform the handoff and communication begins over a new channel in the candidate cell.

Abstract: In a satellite communication system, communication channels are dynamically assigned in real-time based on actual demand using a regionalized channel assignment and reuse scheme. The tradeoff between system capacity and channel interference:is optimized through the use of interlocking local regions. Satellite communication stations within a radio line-of-sight of each other make up each local region. The communication stations of a local region change as the communication stations move through orbital positions. Channel reuse rules are adapted to system load and demand for services. Each communication station establishes its local region and notifies the other communication stations within its local region whenever it assigns a communication channel to a subscriber unit. Channel assignments within each local region are maintained locally by the defining communication station.

Abstract: A constellation of satellites distributed around the earth serves as a communication network that supports global communication of subscriber units. Subscriber units may potentially transmit from any location on earth. Some locations such as radio astronomy sites may be interfered with by nearby transmissions from subscriber units. Subscriber units located within a potentially interfering proximity to radio astronomy sites are prohibited from transmitting potentially interfering signals by reception of a non-interfering beacon at radio astronomy sites. The beacon repeatedly transmits a synchronous control signal with a subscriber unit's servicing satellite's control signal. The beacon's control signal is compatible with a subscriber unit's communication receiver. Control signal information contained in a beacon control signal inhibits the subscriber unit from transmitting.

Abstract: A location system relies upon a non-coherent, FDM/TDM communication scheme to measure location parameters. A locator unit moves relative to the locatable unit. A series of messages are communicated between the locator unit and the locatable unit. Through feedback provided from the locator unit to the locatable unit, the locatable unit adjusts its reference frequency and time base so that signals it transmits arrive at the locator unit on a desired frequency and at a desired time slot. The locatable unit estimates Doppler and propagation duration and transmits the estimates to the locator unit. The locator unit measures offsets between desired frequencies and time slots and actual frequencies and time slots. The offsets are combined with the locatable unit's estimates of Doppler and propagation duration to form an integrated Doppler parameter and an integrated propagation duration parameter. The integrated Doppler and propagation duration are used to determine location.

Abstract: A radio telecommunication system includes a number of satellites in low earth orbits. Any number of subscriber units communicates with the satellites. A single subscriber unit communicates with a single satellite using electromagnetic signals so that a measurement processor can obtain Doppler component, propagation duration, and real time measurements of the signals. A location processor converts these measurements into a geographic location with respect to the earth. A service processor determines which qualifications to apply to communication services offered by the system. These qualifications are based on the subscriber unit's location. A call processor carries out the qualifications when requests to setup calls involving the subscriber unit are received by the system and during calls involving the subscriber unit.

Abstract: Ongoing communications over radio links between communication stations and subscriber units may be unexpectedly broken. Where the communication stations include low-Earth orbit satellites, communication links are difficult to re-establish because of the timing differential and Doppler-frequency shift associated with the satellite's movement. The communication link is re-established by initially changing the modulation technique in an attempt to re-synchronize the communication station and the subscriber unit. If this fails, the subscriber unit performs an acquisition attempt on another antenna beam of the communication station. If this is not successful, the subscriber may perform an acquisition attempt on antenna beams of another communication station.

Abstract: A radio telecommunications system includes a number of satellites in low earth orbits. Subscriber units communicate with the satellites. A single subscriber unit communicates with a single satellite using electromagnetic signals so that a measurement processor can obtain Doppler component, propagation duration, and real time measurements of the signals. A location processor converts these measurements into a geographic location with respect to the earth through an iterative process. The location processor determines the accuracy required for each location determination, and performs only the number of iterations needed to meet the accuracy requirements. A service processor determines which qualifications to apply to communication services offered by the system. These qualifications are based on the subscriber unit's location.

Abstract: A radio telecommunications/location system includes a number of locator satellites in low earth orbits. The satellites include multibeam antennas. Locatable subscriber units communicate with the satellites. A single subscriber unit communicates with a single satellite using electromagnetic signals so that measurement processors can obtain Doppler component, and propagation duration measurements of the signals. A location processor converts these measurements into a two-position location solution. The two-position solution includes an actual position and an image position. The actual position may be detected in some situations by identifying a cell within which communications take place.

Abstract: A radar transceiver and communications transmitter mounted on a target for communicating video signals from the radar to a remote receiver which has associated therewith an FFT detector for detecting scoring encounters, and a computer or microprocessor which first analyzes the video signals to provide signals indicative of the Doppler frequency shift at a plurality of different times through the use of autoregressive spectral estimation and then computes a model projectile flight pattern, including miss distance and closing velocity, which flight pattern fits the computed Doppler frequency shifts at the plurality of different times.

Abstract: In a radar enhancing transponder, apparatus for determining the percent of modulation on a received signal and apparatus for determining the percent of modulation on a signal transmitted by the transponder, with means for comparing the percentages to develope an error signal which is used to control the modulation in the transponder so that the percent of modulation on the return signal remains the same as that on the received signal.

Abstract: A frequency locked loop having a surface acoustic wave time delay device disposed on the same substrate, or a substrate on the same material, as a surface acoustic wave device being compensated. As temperature causes changes in the surface acoustic wave device, changes in the time delay of the surface acoustic wave time delay device will also occur. These changes in the time delay are used by the frequency locked loop to adjust the frequency of an incoming signal of the frequency locked loop and to provide an adjusted input signal frequency to the surface acoustic wave device. This adjusted input compensates for the change in the output caused by the temperature change.

Abstract: An amplitude adjusted pulse width discriminator and method therefor wherein a received video pulse is sampled and held when it crosses a threshold. An indication of a valid pulse being present is given if the level of the signal at the input is within a preset range around the level of the held sample pulse at the end of a preset pulse width discrimination interval.