Abstract: A satellite communications system (10) provides for digital beamforming acquisition. The communications system (10) has an antenna configuration (20) for maintaining communications links with satellite networking equipment, and a signal processing system (30) for processing signals resulting from the communications links. A beamforming subsystem (40) dynamically forms traffic beams and overhead beams, wherein the overhead beams scan overhead areas of the satellite footprint. Overhead areas are defined by areas of the satellite footprint without active traffic channels. The beamforming subsystem (40) includes a channel database configuration (50) containing traffic channel input data and overhead channel input data. A beamforming processor (60) converts the input data contained in the channel database configuration (50) into traffic beams schedules and overhead beam schedules. An antenna management system (70) dynamically forms traffic beams and overhead beams based on the beam schedules.

Abstract: A satellite communications system (10) provides for snap to grid variable beam size digital beamforming. The communications system (10) has an antenna configuration (20) for maintaining communications links with satellite networking equipment, and a signal processing system (30) for processing signals resulting from the communications links. The beamforming subsystem (40) forms beams based on the processed signals wherein the beams match predetermined grid information. The beamforming subsystem (40) includes a grid database (50) containing predetermined grid information. A beamforming processor (60) converts the predetermined grid information contained in the grid database (50) antenna coefficients. An antenna management system forms beams based on the antenna coefficients.

Abstract: A conflict resolution center (130 FIG. 1) is used to manage and resolve resource allocation conflicts in communications system (100) including a number of semi-autonomous communications nodes (SACNs). SACN (110) operates semi-autonomously because SACNs cannot independently allocate and de-allocate resources but rather operate within the confines of at least one local neighborhood. SACNs (110) allocate and de-allocate resources locally based on local neighborhood information. A conflict occurs when at least two SACNs try to allocate the same resource. Conflict resolution center (130) resolves conflicts using a number of different procedures. When a conflict can be resolved, conflict resolution center (130) provides resource reallocation data to at least one SACN (110). When a conflict cannot be resolved, conflict resolution center (130) notifies a system administrator.

Abstract: A method and apparatus for acquiring satellite signals and subscriber unit signals utilizes broadcast beams (205) and acquisition beams (215) projected from a satellite (20). The broadcast beams (205) and acquisition beams (215) form broadcast acquisition beam pairs that are swept within the footprint (50) of the satellite (20) on the surface of the earth. Broadcast bursts are transmitted by the satellite (20) in the broadcast beams (205), and acquisition bursts broadcast by subscriber units (30) are received by the satellite (20) in acquisition beams (215).

Abstract: A multicast message is transmitted from an originating subscriber unit (110, FIG. 1) through a network of satellite communications nodes (120, 130, and 140) to a plurality of receiving subscriber units (150, 160, and 170). Each message is distributed through the network of satellite communications nodes (120, 130, and 140) and replicated at the node nearest to the receiving subscriber unit. Receiving subscriber units (150, 160, and 170) are mapped into geographic cells which allows a single multicast transmission to be transmitted from the satellite communications node to those subscriber units within the same geographic cell. Multicast groups and membership rules are established by the originating subscriber unit (110) through a service provider (180). A multicast session manager (185) manages the multicast session.

Abstract: In a code division multiplexed system, a subscriber unit (260, FIG. 1), which includes a pseudonoise code generator (70), is synchronized with the pseudonoise code generator (220) of a communications node (200). Synchronization between the pseudonoise code generators (70, 220) is achieved through measuring the time delay of a signal transmitted from the communications node (200) to the subscriber unit (260) and advancing the code generator of the subscriber unit in accordance with the time delay. This permits transmissions from the subscriber unit (260) to be received synchronously at the satellite. The synchronization is maintained through the periodic transmission from the communications node (200) to the subscriber unit (260) of a message which commands the subscriber unit (260) to adjust the timing of its pseudonoise code generator. The resulting synchronous code division multiplexed system offers increased capacity over conventional systems.

Abstract: A communications network is capable of using time division multiple access (TDMA) techniques, code division multiple access (CDMA) techniques, or a combination of both. A subscriber unit (30) makes a request for a traffic channel over a CDMA pilot channel or a TDMA broadcast channel. A satellite (20) or a base station (40) receives the request and determines whether to assign a TDMA or CDMA traffic channel. The downlink and uplink can have the same access scheme (e.g., TDMA) or different access schemes (e.g., TDMA on the uplink and CDMA on the downlink).

Abstract: A satellite (110 FIG. 1) is used to make channel allocations for SUs (120) in communications system (100). Satellite (110) operate within the confines of at least one subset of satellites. Satellites (110) allocate channels using a maximum cost list that is based on a cost function methodology. A list of potentially interfering antennas is determined using a cost function analysis. A list of active channels on each one the potentially interfering antennas is also established. Another list that includes a set of potentially interfering channels for each active channel is established. Cost functions are computed for each pair of active channels and its potentially interfering channels. These cost functions establish interference potentials for the available channels in the maximum cost list (400). Channels are allocated using the maximum cost list and interference potential thresholds. Cost functions are based on spatial isolation, spectral isolation, and temporal isolation.

Abstract: In cellular communication systems, hand-offs are performed to maintain links as subscriber units (110) and cells (420, 450) move relative to each other. The hand-off process is improved by using a pre-stored time-based cell map (400) and precise geo-location data. This information is used to set a hand-off timer for deterministically initiating the hand-off process in the current cell (500). The timer diminishes the amount of power monitoring which is required in the hand-off initiation process. This capability is especially important in satellite communication systems with fast moving cells and sharp boundaries.

Abstract: A control facility (130) within a wireless communication system receives, from a communication unit (120) (CU), a power measurement (306) of a signal (150) projected by a transceiver node (102). The power measurement (306) can be associated with location information (304) for the CU (120) and a time stamp (302). The control facility (130) uses this information to determine whether the CU (120) is being provided with a signal (150) having an acceptable link margin. If not, the control facility mitigates (408, 508, 512, 514, 518, 520) the effects of the unacceptable link margin, if possible. When power measurements (306) are received from multiple CUs (120), the control facility (130) can use the measurements (306) to create (402, 502) a link margin map which correlates CU location (304) with power measurements (306). The map is used to analyze the link margins within the system.

Abstract: A decimating digital PN receiver (10) processes a target return signal. The target return signal is decimated (34) processed at a slower speed. The decimated target return signal is then digitally correlated (28). The correlated signal is digitally filtered (30) and a fast Fourier transform (32) is applied to produce the output (33).