Abstract: Systems and methods are described for processing a digital signal. In one embodiment, the method comprises receiving time-aligned input samples of an input signal; computing at least one moment using the time-aligned input samples; determining at least one of signal energy per symbol and noise power spectral density based on the at least one moment; and adjusting an input signal level based on the at least one of the signal energy per symbol and the noise power spectral density.

Abstract: A method and apparatus for rapidly characterizing a communications channel is used to mitigate the effects of the communications channel as present in a received signal. A satellite (20) transmits a data signal (40) and a pilot signal (50). The data signal (40) and the pilot signal (50) are substantially orthogonally polarized. A user terminal (30) receives the orthogonally polarized data signal (40) and pilot signal (50). The user terminal includes a channel information recovery circuit (250) and a channel effects mitigation circuit (240). The channel information recovery circuit (250) characterizes the communications channel by analyzing the pilot signal (50), and then provides the channel information (260) to the channel effects mitigation circuit (240) which then mitigates the effects of the channel.

Abstract: Methods (600, 700), an access controller (350), and a communication system (300) for optimizing utilization of a wireless communication link in a limited bandwidth communication system or network are provided. Statistical multiplexing is achieved by partitioning a wireless communication link (240) into multiple communication channels (250) and assigning communication sources (220) to communicate information over an air interface for a predetermined time interval, where the number of communication sources (220) assigned to the communication channels (250) during a particular time interval exceeds the number of available communication channels (250). The methods (600, 700), access controller (350), and communication system (300) disclosed also allow a system operator to provide varying levels of quality of service (QoS) guarantees in a communication system or network using statistical multiplexing by designating varying levels of QoS among the communication channels (250).

Abstract: A communication network (20) includes a multiplicity of switching nodes (18), many of which are located in orbiting satellites (16). Communication links (30) interconnect the switching nodes (18). A control center (32) performs a request for connection process (40) which routes a new call request over a current internodal topology of links (35) if possible. If the new call request cannot be routed over the current internodal topology of links (35), the process (40) determines how to augment the network with the creation of new links (45) so that the new call can be routed. As calls terminate, unused links are taken out of service.

Abstract: A method and apparatus predicts a ground-to-satellite terminal's (16) percentage of successful communication linkage time to at least one satellite of a communication system in response to a terminal blockage profile (410), as created from the location of an antenna of the terminal, and a satellite blockage profile (412). The prediction may also be based upon a weather model data base (358) corresponding to the area where the terminal is located.

Abstract: A method and apparatus for responding to a blockage environment (50) in a communication system includes creating (158, 163) a terminal blockage profile and/or a satellite blockage profile with respect to terminal antenna (19) and responding (200) to the terminal blockage profile and/or the satellite blockage profile to prevent fading and/or blocking of communication pathways (15, 18) between one or more satellites (12) and the terminal (16).

Abstract: An intelligent digital beam former (10) in conjunction with a satellite based array antenna (20) provides a plurality of dynamically controllable antenna beams (52) for communication with subscriber units on earth's surface. The location of a subscriber unit (90) requesting communication services is determined and an individual antenna beams is formed and assigned to the subscriber unit. The antenna beam tracks the subscriber units as the satellite and/or the subscriber unit moves. The digital beam forming coefficients are dynamically adjusted and controlled to help maximize the signal quality of communications with the subscriber units.

Abstract: Crosspolarized signals of unrelated baud rates transmitted through a communication channel (10) become depolarized due to channel distortions such as rain and antenna imperfections. The resulting interference is canceled in a Modified Adaptive Crosspole Interference Canceler (MAXPIC) receiver (50, 70) by adjustment the timing in the crosspolarization path to compensate for the differential delay. Near equivalent bit error rate (BER) performance is achieved for systems utilizing crosspolarized signals with independent baud rates. In one embodiment, the receiver uses a fractionally spaced finite impulse response (FIR) filter (78) that operates at an integer multiple of the direct channel signal baud rate. In another embodiment, a variable delay (54) is used to time-align the received crosspolarized channel signal with the crosspolarization interference contained in the received direct signal.

Abstract: A satellite communication network (10) coordinates multiple steerable satellite beams (28) with user requests for connections requiring varying bandwidth in real-time. A control station (22) gathers user requests for connections (64) and transmits those requests (70) to a satellite (20) over an uplink (70). Requests for bandwidth (72) are processed in the satellite (20) where time slot assignments (74) and steerable beam schedules (84) are determined in response to user requests (74). Steerable beam schedule (84) and time slot assignments (74) are transmitted to subscriber units (24) and control station (22) over a broadcast downlink (86). Subscriber units (24) complete a data transfer interval of a call (62) while a steerable beam schedule (84) is executed in real-time.

Abstract: An intelligent digital beam former (10) in conjunction with a satellite based array antenna (20) provides a plurality of dynamically controllable antenna beams (52) for communication with subscriber units (90) in response to demand for communication services. Geographic portions within the satellite's footprint that have a higher-demand for communication services are dynamically provided additional antenna beams while geographic portions having a lower demand for communication services are provided less antenna beams. When used on a non-geostationary satellite, the digital beam forming coefficients are dynamically adjusted to steer the antenna beams to maintain their ground location. The antenna beams are also shaped to help optimized geographic coverage.

Abstract: An intelligent digital beam former (10) in conjunction with a satellite based array antenna (20) provides a plurality of dynamically controllable antenna beams (52) for communication with subscriber units (90) on earth's surface. Interference is mitigated placing a null in the transmit and receive antenna patterns at the location of the interfering signal by adjusting digital beam forming coefficients. As the interfering signal moves relative to the satellite, the interfering signal is tracked to maintain interference mitigation. The digital beam forming coefficients are also dynamically adjusted to help maximize signal quality of communications with subscriber units.