Abstract: A class-S modulator (5) receives an input signal (10) having envelope information and pulse-width modulates the input signal (10) using a reference waveform (26) from a waveform generator (25). The envelope becomes a pulse-width modulated signal is level-shifted and amplified through a pre-driver (40). A driver (50) controls switches (60, 70) which drive an output (80) into a low-pass filter (90) wherein the envelope is restored to the amplified signal for driving a power amplifier in a wide-band transceiver.

Abstract: A satellite communication system provides users with global cellular coverage. To facilitate delivery of calls to users having subscriber units, a fixed channel is defined wherein subscriber units are notified of incoming calls. Subscriber units monitor this ring alert channel and examine subscriber unit IDs transmitted in a ring alert message contained therein. When a subscriber unit determines from the subscriber unit ID that a call is being directed to it, it calls into a network to receive a call. Subscriber units also monitor this fixed channel to receive a control channel directory identifying the location of a subscriber unit's broadcast (control) channels.

Abstract: A time-delay compensating class-S modulator (4) receives an input signal (10) having RF envelope information and generates a delay error signal (18) from a comparison to an attenuated output signal. The delay error signal (18) is pulse-width modulated using a reference waveform (26) from a waveform generator (25). The envelope becomes a pulse-width modulated signal and is level-shifted and amplified through a pre-driver (40). A driver (50) controls switches (60, 70) which drive an output (80) into a low-pass filter (90) wherein the envelope is restored to the amplified signal for driving a power amplifier in a wide-band transceiver.

Abstract: A digital rotating complex phasor generator (60) provides a constant magnitude continuous phase signal at either a positive or a negative frequency for translating the frequencies of a modulated signal from a near-zero intermediate frequency (IF) to baseband. The rotating complex phasor generator allows a digital receiver front-end to down-convert the received signal to an IF of substantially zero Hertz prior to analog to digital conversion, even in the presence of large Doppler frequency shifts and tuning uncertainties which may result in a residual IF carrier which has either a positive or a negative frequency.

Abstract: In a dynamic communication system (90) wherein communication parameters vary appreciably between transmissions, subscriber units (200) are susceptible to link blockages resulting in a loss of successive feedback instructing subscriber units (200) of adjustments to communication parameters to be employed in a subsequent transmission on a communication link (105). A method and system are employed to predict subsequent communication parameters and employ these predictions during link blockages in an attempt to reestablish communications and upon the removal of a link blockage, a subscriber unit (200) employs the predicted communication parameters in resuming communications without requiring complex reallocation of an additional communication link.

Abstract: A power amplifier (10) provides linear amplification of noise-like multi-carrier signals over a wide range of power levels. A power divider (40) divides an input signal for distribution in three amplifier networks (70, 72, 74) for selective amplification based upon input signal levels. Each amplifier network (70, 72, 74) is biased to respond when the efficiency of the previous stage diminishes. Successive staging of amplifier networks (70, 72, 74) broadens the efficiency bandwidth of power amplifier (10). A combiner (28) merges output signals from each successive amplifier networks to provide an improved efficiency output to a power amplifier (10) load.

Abstract: A plurality of subscriber units (16) operate in a communication system (10) having dynamic nodes such as satellites (12). A communication management center (14) controls interface parameters and protocol employed by subscriber units (16). A system and method is employed to dynamically alter interface protocol used by subscriber units (16). Communication management center (14) calculates a balance between a first portion of subscriber units (16) assigned to perform attach-detach registration and a second portion of subscriber units (16) assigned to abstain from performing attach-detach registration when associating and disassociation from communication system (10). As available communication bandwidth varies according to present of future communication patterns, subscriber units (16) may be dynamically reassigned perform or abstain from performing attach-detach registration.

Abstract: A constellation (12) of satellites (14) distributed around the earth supports satellite-based communication system (10) involved in global communication of subscriber units (24). Subscriber units (24) may potentially transmit from any location on earth. Some locations such as radio astronomy sites (28) may be interfered with by nearby transmissions from subscriber units (24) or transmissions from satellites (14). Subscriber units (24) located within a potentially interfering proximity to radio astronomy sites are prohibited from transmitting potentially interfering signals by reception of a non-interfering control signal transmitted by a radio astronomy special equipment located at radio astronomy sites. A radio astronomy special equipment (44) repeatedly transmits to a subscriber unit (24) a control signal synchronous with a control signal of a servicing satellite. The radio astronomy special equipment control signal (46), (48), and (54) is compatible with a subscriber unit's communication receiver.

Abstract: A communication system (10), having dynamic nodes such as satellites (12), require narrow-tolerance communication parameters such as timing and frequency. A voice subscriber unit (26) establishes a traffic channel (17) by negotiating communication parameters. A user of voice subscriber unit (26) generates inherent voice pauses in communications. A data subscriber unit (31) possess a datagram for delivery through communication system (10). Instead of negotiating a dedicated traffic channel for delivery of the datagram, data subscriber unit (31) monitors an active voice subscriber unit (26) and determines if the communication parameters used by voice subscriber unit (26) are compatible for data subscriber unit (31). Data subscriber unit (31), upon detecting a voice pause by voice subscriber unit (26), transmits the datagram to satellite (12) using the negotiated communication parameters of voice subscriber unit (26).

Abstract: A satellite-based, world-wide cellular messaging system (5) transmits paging messages to pagers (2) via multiple beams. A pager (2) monitors multiple beams, recording the schedules for each beam, and by combining the schedules for multiple beams, ultimately determines which frames in the message groups to monitor for messages. As propagation characteristics degrade, an adaptive method refines the criteria for including frames into a monitoring schedule.

Abstract: A communication system includes base communication units (105, 155) facilitating a communication link with portable communication units (110) in motion relative to base communication units. The relative motion between base communication units (105, 155) and portable communication units (110) introduces Doppler frequencies into communication links (115, 165). When portable communication units (110) travel in a predictable direction (119), frequency offsets for Doppler compensation are generally predictable. However, when portable communication units (110) move erratically in relationship to a base communication unit (105, 155), frequency offsets for Doppler compensation are not easily calculated. Incorporation of velocity vector data into the frequency offset calculation for Doppler compensation provides reliable tracking and Doppler frequency compensation for erratic motion of portable communication units (110).

Abstract: A communication system dispatches packet data (130) from a master transceiver (10) to a slave transceiver (20). A slave transceiver (20) records the successful arrival of the data packet (130) in an acknowledgment history (115). When propagation conditions between a slave transceiver (20) and a master transceiver (10) are non-ideal, an acknowledgment (140) may be lost and needless retransmission of data packet (130) commenced. However, a slave transceiver (20) generates an acknowledgment (140) from an acknowledgment history (115) containing confirmations for multiple data packets contained within an outstanding packet window (120). If a specific acknowledgment (140) does not arrive at a master transceiver (10), a subsequent acknowledgment (140) contains confirmation of a previously received data packet (130) thus avoiding the needless retransmission of a previously successfully received data packet (130).

Abstract: A satellite cellular communication system includes satellites in motion that project cells upon the surface of the Earth. These cells are in motion and pass over individual subscriber units (26) engaged in communications, thus requiring individual subscriber units (26) to perform handoffs as an active current cell (300) currently servicing them advances. Selection of a subsequent servicing cell requires evaluation of active neighboring cells. A pre-computation of candidate cells is performed in advance according to a cell activation schedule. Active neighboring cells of an active current cell (300) are evaluated and prioritized in advance of individual subscriber unit's need for them. A candidate handoff cell list is then delivered to a satellite (12). A candidate handoff cell list is broadcast to all individual subscriber units (26) located within active current cell (300) for use in handoff decisions.

Abstract: In a packet switched network, a method and system order packets arriving out-of-sequence from a lower service. An ordering service temporarily buffers packets (101-115) while delayed packets arrive and forwards in-sequence packets to an upper service. Delay introduced by buffering does not accumulate as a propagation toleration timer (304) is activated for a predetermined time period (120) while awaiting the arrival of delayed packets or until the delayed packet arrives. Out-of-sequence packets are grouped between a lower-bound and an upper-bound of sequence identifiers to avoid accumulated delay due to repetitive lost packets.

Abstract: A subscriber unit (30) operates in a synchronous communication system having dynamic nodes such as satellites (12). Satellites (12) employ a strict transmit and receive time window and all transmissions directed to satellites (12) must fall within the receive window to be recognized. In a dynamic communication system where low earth orbit satellites (12) continuously orbit, propagation timing between a satellite (12) and a subscriber unit (30) vary rapidly over a wide range. Subscriber unit (30) must approximate a transmit timing advance for use in inaugurating a transmission to satellite (12). Subscriber unit (30) utilizes a valid geolocation position when available but when a position is unavailable or stale, relies on configuration characteristics of the constellation for generating an initial approximation of propagation delay.

Abstract: A communication and position locating system (2) suitable for air traffic control is described. Multiple satellites (40) are provided in two geosynchronous constellations. One constellation (e.g., 4 satellites) has a first closed ground track (14). The other (e.g., 2 satellites (161, 182)) has a different ground track (18) or is geostationary, located outside of the first ground track (14). Geolocation information is transmitted by the satellites (40) to aircraft (28) and ground stations (26) so that aircraft (28) can determine their current position. A pseudo range correction map is provided to the aircraft (28) by the base stations (26) to permit differential geolocation measurements. The satellites (40) include communication transceivers (80) so that aircraft (28) can communicate voice and data to other aircraft (28) and to the ground stations (26, 30, 32) and automatically report their position to air traffic control centers (30), e.g., via the satellites (40).

Abstract: A calibration system utilizing existing location techniques for a global radio telecommunication system 10 autonomously calibrates the communication system's location system by routing precision location data through system 10. Calibration reduces system errors by allowing time slots to remain narrow. The precision data is carried by existing commands throughout the system to measure location errors inserted by satellites 12. A gateway 16 compiles and evaluates received calibration data and determines when to update all gateways 16 with new satellite variance data tables 435. The calibration system provides early warning of degradation of system components and long-term analysis of system performance.

Abstract: In a packetized communication system, packets are dispatched to a receiving node (10) for reassembly and presentation to a user. Packets propagating over dynamic paths have propagation variations between subsequent packets. Interactive packetized voice communication systems mandate that end-to-end delays be minimized. This results in voice gaps between an on-time synthesized voice data (602"') and a subsequent delayed synthesized voice data (603"'). Voice gaps are temporarily patched with voice prediction samples and end-to-end timing is adjusted to minimized prediction samples. When packets are lost in the network, prediction packets are substituted and annunciated to a user until valid packets are received.

Abstract: A satellite cellular communications network performs cell-to-cell handoffs between cells of different satellites (30, 32). Inter-satellite handoffs require resynchronization to the prospective propagation timing and Doppler frequency parameters of the prospective satellite. Calculation of these parameters prior to transitioning to the prospective satellite minimizes interruptions to communications. Subscriber units (24) perform handoff parameter calculations while on narrow band communications channels without occupying broadband shared acquisition resources.

Abstract: In a method and system for performing location determination using multi-beam satellites each beam of a multi-beam satellite transmits identification information which is received by a user terminal. This identification information either identifies the unique beam by enumeration or by geometrics. A user terminal processes multiple received signals from orbiting satellites. The user terminal maps the projected beam patterns of multiple received samples to determine an approximate self-location. The user terminal passively monitors its location and compares its current location with its previously reported location. When the user terminal has sufficiently roamed from its previously registered location, the user terminal performs an auto-registration to the system allowing for efficient routing of information.