Abstract: A transmitter/receiver apparatus and method provide adaptive data rate fading compensation that utilize dual-polarization transmissions at a constant modulation-symbol rate over a forward-scatter radio link and that employ adaptive receiver techniques that operate efficiently at the noisy uncoded signal-to-noise ratio threshold of present-day forward-error correction codes over the range of multipath widths in such forward-scatter environments. The dual-polarization transmissions support both dual transmission and dual diversity configurations. The adaptive receiver techniques include adaptive channel matched filtering and adaptive equalizing at the modulation-symbol rate.

Abstract: A transmitter/receiver apparatus and method provide adaptive data rate fading compensation that utilize dual-polarization transmissions at a constant modulation-symbol rate over a forward-scatter radio link and that employ adaptive receiver techniques that operate efficiently at the noisy uncoded signal-to-noise ratio threshold of present-day forward-error correction codes over the range of multipath widths in such forward-scatter environments. The dual-polarization transmissions support both dual transmission and dual diversity configurations. The adaptive receiver techniques include adaptive channel matched filtering and adaptive equalizing at the modulation-symbol rate.

Abstract: A method and apparatus are provided for demodulating a received signal containing modulated desired-signal digital data and relayed-interference that results from a nonlinear-distorted interference signal. Estimation of the nonlinear-distorted interference from a pre-distortion interference signal and subsequent cancellation within the received signal of the distorted interference produces a residual-interference signal that is subsequently demodulated to produce estimates of the desired-signal data. The estimation is adapted for changing nonlinear distortion effects.

Abstract: A method and apparatus are provided for demodulating a received signal containing modulated desired-signal digital data and relayed-interference that results from a nonlinear-distorted interference signal. Estimation of the nonlinear-distorted interference from a pre-distortion interference signal and subsequent cancellation within the received signal of the distorted interference produces a residual-interference signal that is subsequently demodulated to produce estimates of the desired-signal data. The estimation is adapted for changing nonlinear distortion effects.

Abstract: The present disclosure provides methods and apparatuses for nonlinear channel identification and estimation of the distorted signals in digital data transmission systems that include signals traversing a dispersive nonlinear channel that produces noisy distorted signals. The identification and estimation are accomplished with an amplitude-based signal expansion and are adapted for changing nonlinear distortion effects using a Least-Means Square direct solution that includes a precomputed matrix.

Abstract: The present disclosure provides methods and apparatuses for demodulating discrete-time desired signals in a period-Td bandpass desired signal in the presence of interference that results from a period-T bandpass interference signal that has been nonlinear distorted. Estimation of the nonlinear-distorted interference and subsequent cancellation from a received signal, that includes the interference and desired signal, produces residual-interference signals. The demodulation of the residual-interference signals uses an equalization technique when Td is not equal to T. The estimation, cancellation, and demodulation are adapted for changing nonlinear distortion effects.

Abstract: The present disclosure provides methods and apparatuses for nonlinear channel identification and estimation of the distorted signals in digital data transmission systems that include signals traversing a dispersive nonlinear channel that produces noisy distorted signals. The identification and estimation are accomplished with an amplitude-based signal expansion and are adapted for changing nonlinear distortion effects using a Least-Means Square direct solution that includes a precomputed matrix.

Abstract: The present disclosure provides methods and apparatuses for demodulating discrete-time desired signals in a period-Td bandpass desired signal in the presence of interference that results from a period-T bandpass interference signal that has been nonlinear distorted. Estimation of the nonlinear-distorted interference and subsequent cancellation from a received signal, that includes the interference and desired signal, produces residual-interference signals. The demodulation of the residual-interference signals uses an equalization technique when Td is not equal to T. The estimation, cancellation, and demodulation are adapted for changing nonlinear distortion effects.

Abstract: A method and apparatus at a local terminal are described for demodulating a remote-terminal signal located at a subband offset frequency in a frequency subband of relayed interference from a transponder satellite link. The demodulation of the remote-terminal signal is accomplished by transferring the digital data that produced the local-terminal transmit signal to the local-terminal receiver. The digital data is time-delayed and converted to a narrowband offset-constellation signal that cancels the relayed interference in an adaptive equalizer. Providing cancellation in the subband of the relayed interference produces larger interference cancellation factors than those obtained in conventional broadband cancellation systems. A phase-noise error signal is also generated and used to increase cancellation levels limited by phase noise generated in the satellite link frequency converters.

Abstract: Techniques for deriving and using noise estimate for data reception in a wireless communication system are described. A noise estimate may be derived for each packet received in a data transmission. The noise estimate may be derived by determining a phase offset between a first and second sample sequence, applying the phase offset to the first sample sequence to obtain a third sample sequence, and deriving the noise estimate based on the second and third sample sequences. Data detection may then be performed for each packet using the noise estimate for that packet. At least one weight may be derived for each packet using the noise estimate for the packet. Data detection is then performed for each packet with the at least one weight for the packet.

Abstract: Techniques for deriving and using noise estimate for data reception in a wireless communication system are described. A noise estimate may be derived for each packet received in a data transmission. Data detection may then be performed for each packet using the noise estimate for that packet. For noise estimation, a first sample sequence and a second sample sequence may be obtained from each receiver used for data reception. A phase offset between the first and second sample sequences may be determined and applied to the first sample sequence for each receiver to obtain a third sample sequence for that receiver. A noise estimate may then be derived based on the power of the differences between the second and third sample sequences for the at least one receiver.

Abstract: Techniques for deriving and using noise estimate for data reception in a wireless communication system are described. A noise estimate may be derived for each packet received in a data transmission. Data detection may then be performed for each packet using the noise estimate for that packet. For noise estimation, a first sample sequence and a second sample sequence may be obtained from each receiver used for data reception. A phase offset between the first and second sample sequences may be determined and applied to the first sample sequence for each receiver to obtain a third sample sequence for that receiver. A noise estimate may then be derived based on the power of the differences between the second and third sample sequences for the at least one receiver.

Abstract: A method of phase correction at a wireless device includes: estimating a phase slope for an OFDM symbol in a data portion of a packet based on an elapsed time from the start of the packet; measuring a residual phase slope from tracking pilots for the OFDM symbol in the data portion of the packet; and adjusting a phase correction based upon the phase slope and the residual phase slope. Apparatus in a wireless device performs the method and machine-readable media carry instructions for carrying out the method.

Abstract: A method and apparatus at a local terminal are described for demodulating a remote-terminal signal located at a subband offset frequency in a frequency subband of relayed interference from a transponder satellite link. The demodulation of the remote-terminal signal is accomplished by transferring the digital data that produced the local-terminal transmit signal to the local-terminal receiver. The digital data is time-delayed and converted to a narrowband offset-constellation signal that cancels the relayed interference in an adaptive equalizer. Providing cancellation in the subband of the relayed interference produces larger interference cancellation factors than those obtained in conventional broadband cancellation systems. A phase-noise error signal is also generated and used to increase cancellation levels limited by phase noise generated in the satellite link frequency converters.

Abstract: In a duplex radio link digital data information is transmitted to a remote terminal at a constant symbol rate in accordance with a selected data rate mode that is a function of direct sequence spreading gain, error correction code rate, and signal constellation type. The data rate is adapted by selecting a data rate mode that is a function of a data packet arrival rate and a link quality measure fed back from the remote terminal. The data packet arrival rate is controlled as a function of the link quality measure and the current data packet arrival rate. In systems with multiple transmit diversity channels, independent data is sent over each of the transmit diversity channels. In an idealized feedback communication example, a single antenna troposcatter system in a Ku-band application is shown to have 15.5 times the data rate capability of a conventional two-antenna system at S-band.

Abstract: In high data rate communication applications where digital data information is error-corrected coded and interleaved and transmitted with spectral limitations over fading dispersive channels, a method and receiver is described that incorporates channel estimation and decision-feedback equalization. Channel estimation is accomplished within a receiver time block with locally generated reference symbol sequences. The parameters of the decision-feedback equalizer (DFE) are computed directly from the channel estimates. The DFE is an optimum finite length realization that includes effects from spectrum control filtering, a space-time block coder (STBC) on multiple transmit antennas, multiple receiver diversity signals, and the fading dispersive channel. The DFE includes a matched filter, forward filter, backward filter, and detector. A symbol combiner within the matched filter produces a P+1 dimensional signal that provides ideal cancellation of P intersymbol interferers in the forward filter.

Abstract: A radio communication method and system for transmitting multiple-user digital data information in a Code Division Multiple Access (CDMA) format over multipath and mutual-interfering channels to a receiving terminal with diversity antennas and equalization signal processing. At the receiving terminal, diversity antenna signals are grouped into time blocks and replicas are generated of the user-unique CDMA sequence signals for a set of K mutually interfering users. Within each time block the multiuser channel is estimated, equalization parameters are calculated, and decision-feedback equalization is used to produce multiuser estimates associated with a subset ? of the K users. These estimates are deinterleaved and error-correction decoded to recover transmitted digital data information for the subset of ? users.

Abstract: A method of phase correction at a wireless device includes: estimating a phase slope for an OFDM symbol in a data portion of a packet based on an elapsed time from the start of the packet; measuring a residual phase slope from tracking pilots for the OFDM symbol in the data portion of the packet; and adjusting a phase correction based upon the phase slope and the residual phase slope. Apparatus in a wireless device performs the method and machine-readable media carry instructions for carrying out the method.

Abstract: A matrix {circumflex over (V)} of eigenvectors is derived using an iterative procedure. For the procedure, an eigenmode matrix Vi is first initialized, e.g., to an identity matrix. The eigenmode matrix Vi is then updated based on a channel response matrix ? for a MIMO channel to obtain an updated eigenmode matrix Vi+1. The eigenmode matrix may be updated for a fixed or variable number of iterations. The columns of the updated eigenmode matrix may be orthogonalized periodically to improve performance and ensure stability of the iterative procedure. In one embodiment, after completion of all iterations, the updated eigenmode matrix for the last iteration is provided as the matrix {circumflex over (V)}.

Abstract: Techniques for deriving and using noise estimate for data reception in a wireless communication system are described. A noise estimate may be derived for each packet received in a data transmission. Data detection may then be performed for each packet using the noise estimate for that packet. For noise estimation, a first sample sequence and a second sample sequence may be obtained from each receiver used for data reception. A phase offset between the first and second sample sequences may be determined and applied to the first sample sequence for each receiver to obtain a third sample sequence for that receiver. A noise estimate may then be derived based on the power of the differences between the second and third sample sequences for the at least one receiver.