Abstract: A high speed data transfer system includes a WAU (201) which is utilized to provide high speed access to satellite transferred data. The system is configured such that a plurality of data utilization (205) may access the high speed data via wireless links to the WAU (201). Advantageously, high speed data services may be provided to users without the users requiring individual satellite antennas.

Abstract: Apparatus are provided for a communication signal processing apparatus having a channel estimator configured to generate a first channel estimation at a first time point, a linear predictor coupled to the channel estimator, and an adaptive filter coupled with the linear predictor. The linear predictor is configured to predict a second channel estimation based on a second time point and a channel frequency. The second time point is concurrent or subsequent to the first time point. The second channel estimation includes a first coefficient. The linear predictor includes a first predictor having a sample time point. The first predictor is configured to generate the first coefficient of the second channel estimation based on the sample time point and the second time point. The sample time point is prior to the second time point. The adaptive filter is configured to recursively determine the second channel estimation.

Abstract: A symbol synchronizer (100) is provided for a software-defined communications system (10). The symbol synchronizer (100), when integrated into either a pre- or post-detection diversity signal combiner (108, 208), enables highly accurate signal synchronization with minimal added system complexity. The symbol synchronizer (100) includes a single complex sliding window-matched filter (102) for filtering an input digital signal with a match filtering function based on predetermined signal transfer function characteristics to average out receiver noise from the signal. A signal delay bank (84) includes a plurality of delay blocks each for delaying the digital signal filtered by the single matched filter for a predetermined number of samples. A complex correlator (88) correlates the digital signal filtered by the single complex sliding window matched filter (102) and delayed by the complex correlator (88) with a correlator reference signal, and selects an index of a path having a peak correlator value.

Abstract: An embodiment of a method for parameterizing an input signal includes non-linearly transforming the input signal, removing higher order terms by passing the input signal through a low pass filter to produce a linear combination of data symbols and DC components, solving for the DC components, separating a plurality of mixed baseband signals from the input signal, and coordinate transforming each of the separated signals from polar coordinates to Cartesian coordinates. An embodiment of a receiver includes a non-linear transform operator receiving a digitized input signal and adapted to produce a linear combination of data symbols, DC components, and carrier effects; a low-pass filter for removing higher order terms; a separator unit for separating the plurality of mixed baseband signals; and a coordinate transform for converting the separated signals from polar coordinates to Cartesian coordinates.

Abstract: Methods and apparatus are provided for distributed polyphase spread spectrum communication and non-contiguous spectrum underlay. The method includes polyphase channelizing a direct sequence spread spectrum (DSSS) signal, determining available spectrum in an observed frequency range having a noise floor based on detection of polyphase users below the noise floor, distributing the polyphase channelized signal among the available spectrum, and interference mitigation using a combination of standard signal detection and cyclostationary feature detection methods.

Abstract: A symbol synchronizer (100) is provided for a software-defined communications system (10). The symbol synchronizer (100), when integrated into either a pre- or post-detection diversity signal combiner (108, 208), enables highly accurate signal synchronization with minimal added system complexity. The symbol synchronizer (100) includes a single complex sliding window matched filter (102) for filtering an input digital signal with a match filtering function based on predetermined signal transfer function characteristics to average out receiver noise from the signal. A signal delay bank (84) includes a plurality of delay blocks each for delaying the digital signal filtered by the single matched filter for a predetermined number of samples. A complex correlator (88) correlates the digital signal filtered by the single complex sliding window matched filter (102) and delayed by the complex correlator (88) with a correlator reference signal, and selects an index of a path having a peak correlator value.

Abstract: A high speed data transfer system includes a WAU (201) which is utilized to provide high speed data access to satellite transferred data. The system is configured such that a plurality of data utilization devices (205) may access the high speed data via wireless links to the WAU (201). Advantageously, high speed data services may be provided to users without the users requiring individual satellite antennas.

Abstract: A high speed data transfer system includes a WAU (201) which is utilized to provide high speed data access to satellite transferred data. The system is configured such that a plurality of data utilization devices (205) may access the high speed data via wireless links to the WAU (201). Advantageously, high speed data services may be provided to users without the users requiring individual satellite antennas.

Abstract: A communications system (100) includes a multi-rate source coder (MRSC) (102), a variable size/rate buffer (VSRB) (112), a speech buffer (104), and a buffer control block (106). The variable size/rate buffer (112) includes a source coder bit buffer (SCBB) (114) and an adaptive transmit frame buffer (116). The source coder bit buffer (114) receives speech frames coded at different rates from the multi-rate source coder (102), and deposits an integer or non-integer number of frames in the adaptive transmit frame buffer (ATFB) (116). A receiver includes a seamless rate transition module (SRTM) (308) and an variable buffer (310). The seamless rate transition module (308) correlates speech data previously coded at different rates, and it then truncates or alternatively appends, concatenates, and warps the speech data to remove any annoying artifacts at the rate change boundary.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.

Abstract: A wireless access unit (12) for providing an interface between a satellite communications system (32) and a plurality of terrestrial user devices (14-26) in a centralized or distributed architecture includes a spectrum allocation unit (92) for dynamically allocating spectrum to the plurality of terrestrial user devices (14-26) based on a spectral environment about the wireless access unit (12). A spectrum scan unit (60) scans the spectral environment about the wireless access unit (12) and generates a spectrum signal indicative thereof. An environment understanding unit (61) provides signal information corresponding to signal emitters in proximity to the distributed or centralized network. A spectrum table (90) assembles data related to the spectral environment and the proximity emitters for use by the spectrum allocation unit (92) in dynamically allocating spectrum.

Abstract: A multiple access and data channel scheme is presented for reducing network communication collisions and susceptibility to jamming signals in a distributed network to increase network connectivity and communication throughput. An order wire channel (202) is used to gain access to a data channel (204). To gain access to the data channel (204), a source radio sends a transmit probe (TXP) over the order wire channel (202) to the target radio. The target radio senses its environment and responds with a receive probe (RXP) which comprises data channel transmission parameters including the data channel frequency, transmit power, spread code, and transit timing to be used for the data transmission. Source radio moves to the data channel using the data channel transmission parameters specified by the receive probe (RXP) to communicate with the target radio. If a collision occurs of the order wire channel (202), the source radio retransmits the transmit probe after a random time period.

Abstract: The present invention relates to a communications system (100) that is capable of adapting to an unknown or varying spectral environment in a channel (14) between two communications units (12, 16). The system (100) maintains a spectral profile of the channel (14) and uses the spectral profile to determine appropriate transmit parameters for the system (100). The system (100) can be programmed to provide an optimal transmit signal for achieving a predetermined performance goal (such as, for example, maximum data rate at a given bit error rate (BER)) in light of the spectral environment in the channel (14). In one embodiment, the spectral profile is maintained in a spectrum table memory (27) that is periodically (or continuously) updated.