Abstract: Information symbols are transmitted simultaneously on independent streams using the same spreading code but from different transmit antennas at the transmitter. These simultaneous data stream could be intended for the same user (and thereby the data rate for any particular user can be increased) or for different users (thereby increasing the system capacity). Each stream of data can belong to a different signal constellation and use a different channel code. At the receiver, a number of receive antennas equal to at least the number of multiple data streams is used to separate the different data streams. We consider two different cases. The first one when no transmit diversity is used (this case can also include the case when transmit diversity with simple antenna weighting is used) and the second when transmit diversity with space-time block coding is used.

Abstract: A method and apparatus for measuring the phase noise of an low noise block (LNB) and other devices while the device under test is on line is disclosed. Using a signal processing procedure over a short duration of a received signal, the technique demodulates the signal to expose the phase history of the underlying carrier for measurement. In an exemplary apparatus timing and carrier recovery on A/D samples are performed conventionally, a linear phase is estimated from minimum mean square fitting to the recovered carrier phase history, the single tone carrier is removed from the recovered phase to yield a residual phase. A fast Fourier transform (FFT) can be performed on the residual phase to produce a phase noise spectral measurement at an input of the demodulator.

Abstract: Systems and methods related to amplifier systems which use a predistortion subsystem to compensate for expected distortions in the system output signal. A predistortion subsystem receives an input signal and applies a predistortion modification to the input signal. The predistortion modification may be a phase modification, a magnitude modification, or a combination of both. The predistorted signal is then received by an amplifier subsystem. The amplifier subsystem decomposes the predistorted signal into separate components, each having a constant envelope phase modulation, and separately amplifies each component. The phase modulated and amplified components are then recombined to arrive at an amplitude and phase modulated and amplified output signal. The predistortion modification is applied to the input to compensate for distortions introduced in the signal by the amplifier subsystem.

Abstract: In a normalization process, overflow occurring in limited size registers, holding the alpha or beta values in a map decoder, may be overcome by subtracting a constant value from all of the alpha or beta values when they reach a limit. Because subtracting a constant value may slow down the computation, detection of a constant value may occur on one decoding cycle and normalization on the succeeding decoding cycle. A multiplexor type circuit can be used to direct either zeros, in the normalization case, or a most significant bit(s), in computations without normalization, into the register holding the alpha or beta values. To minimize the impact on the computation by the normalization process, the multiplexor circuit can be set by the previous decoder cycle so that the computation does not have to wait for the multiplexor to be set to normalization or normal computation.

Abstract: Methods and apparatus are provided for spread spectrum signal processing in a wireless communication system. The apparatus includes a control processor to generate commands for processing spread spectrum signal components and a reconfigurable coprocessor to process the spread spectrum signal components based on the commands and to provide reports to the control processor based on results of processing the signal components.

Abstract: Some embodiments store a training sequence in a communications system. The stored training sequence exhibits certain desirable characteristics when used by a peak to average power constrained modulation format. In one embodiment, a set of original ordered sequences is selected to have at least one desired property. A set of extended sequences is created from the original sequences by beginning with an element of an original sequence and cyclically appending elements of the original sequence in order to obtain a desired extended sequence length. Each extended sequence is modified using a corresponding modifying sequence, such that a training sequence can be generated from any one of the modified extended sequences. Each modifying sequence is selected so that the generated training sequence when modulated by a selected modulation format has the at least one desired property of the corresponding original ordered sequence.

Abstract: Systems and methods for receiving layered modulation for digital signals are presented. An exemplary apparatus comprises a tuner for receiving a layered signal and producing a layered in-phase signal and a layered quadrature signal therefrom, an analog-to-digital converter for digitizing the layered in-phase signal and the layered quadrature signal and a processor for decoding the layered in-phase signal and the layered quadrature signal to produce one or more discrete layer signals.

Abstract: Broadband, ultra wideband and ultra narrowband (UWN) reconfigurable, interoperable communication and broadcasting system architectures, combinations and hybrids of ultra wideband (UWB), ultra narrowband (UNB) and efficient broadband wireless, baseband, intermediate frequency (IF) and radio frequency (RF) implementations for Bit Rate Agile (BRA) reconfigurable and interoperable systems, Adaptive Modulation and Coding (AMC). Processing the data signals, of clock signals, and/or carrier cycles waveforms leads to shaped radio-frequency (RF) cycles, waveforms and wavelets. With Multiple Input Multiple Output (MIMO) diversity and protection system configuration the performance and capacity of these systems may be further enhanced.

Abstract: Techniques for reducing peak-to-average power in multicarrier transmitters employ peak cancellation with subcarriers that are impaired by existing channel conditions. The use of Carrier Interferometry (CI) coding further improves the effectiveness of peak reduction. CI coding can also be impressed onto pulse sequences in the time domain, which enhances spectral selection and facilitates peak-power control.

Abstract: Transmit power adaptation for DS/CDMA systems is disclosed for a CDMA system that utilizes a successive interference cancellation receiver on fading channels. The transmission power is adapted in response to channel variations to achieve an arbitrary power profile for received signal powers at the system base station. That is, the received signal powers are distributed with some factor xi's given as: SRi=SR(1)xi, (i=2, 3, . . . , K and x1=1) where K is the number of users and SR(i) is the received signal power of the user having the ith strength, and wherein user strengths are ranked in the order of estimated channel gains. The factor xi gives a measure of the disparity between the received power levels. The channel is estimated at both the transmitter and receiver. In one embodiment, the factors, xi, for distributing the signal powers are selected such that the average BER for each user is minimized.

Abstract: A modulation and demodulation system is provided. The system uses n sub-carrier frequencies and an oversampling positive integer and includes a modulation circuit and a demodulation circuit. The modulation circuit includes a modulation ROM that stores columns of elements independently in a modulation ROM matrix. The demodulation circuit includes 2n numbers of a ROM1 that stores elements of a combined matrix. The combined matrix is generated by combining a number of inverse matrices where the inverse matrices are generated from the modulation ROM.

Abstract: There is provided a flexible transmission device capable of automatically setting an optimal point for a signal decision making with high accuracy, so that highly reliable high-quality signal regeneration control is achieved. A clock timing extraction circuit dynamically sets a frequency-dividing ratio based on the transmission rate of an input signal to perform a phase synchronization control so that there is a fixed phase difference between the input signal and an oscillation output, whereby clock timing based on the transmission rate can be extracted. A regeneration control circuit sequentially sweeps a voltage threshold level and the phase of the extracted cock with respect to the input signal and determines whether the levels of adjacent monitor points match, whereby a decision point within the valid zone of the eye pattern can be automatically measured and used as the optimal point for regeneration control.

Abstract: A programmable logic device includes a plurality of programmable multi-gigabit transceivers, programmable logic fabric, and a control module. Each of the plurality of programmable multi-gigabit transceivers is individually programmed to a desired transceiving mode of operation in accordance with a plurality of transceiver settings. The programmable logic fabric is operably coupled to the plurality of programmable multi-gigabit transceivers and is configured to process at least a portion of the data being transceived via the multi-gigabit transceivers. The control module is operably coupled to produce the plurality of transceiver settings based on a desired mode of operation for the programmable logic device.

Abstract: A clock recovery circuit includes a demodulator which generates in-phase and quadrature signals from a data signal and a phase adjuster which adjusts a phase of the quadrature signal independently from a phase of the in-phase clock signal. The phase adjustment causes a non-orthogonal relationship to exist between the phases of the quadrature and in-phase signals. The independent phase adjustment may be dynamically performed or may be performed in fixed increments to achieve a predetermined level of performance. In one application, the adjusted quadrature phase signal serves as a clock signal for controlling sampling of the data signal.

Abstract: A receiver, system and method for providing symbol timing recovery that allows for inexpensive and low-complexity synchronization for communication systems. A receiver receives a signal including digital data in the form of packets that is transmitted from a transmitter. The receiver uses information contained in each of the packets to align a phase of the receiver clock with a phase of the transmitter clock. The receiver further controls a sampling device such that the in-phase (I) and quadrature (Q) components are sampled at an optimum sample rate and at an optimum instance of time without requiring a numerically controlled oscillator or voltage controlled oscillator.

Abstract: An interwoven spreading code is formed by a stretched spreading code series at a first frequency and a mirror of the stretched spreading code series at a second frequency. The interwoven spreading code can be used to spread a baseband signal. Data can be recovered through correlation of a received signal with the interwoven spreading code. The spreading code used in forming the interwoven spreading code can be a Barker code.

Abstract: One embodiment of the present invention provides a system that optimizes synchronization between monitored signals in a computer system. During operation, the system receives a number of monitored signals. The system then forms a number of signal pairs by grouping each signal with every other signal. Next, the system optimizes synchronization between the signals by iteratively perturbing the timing of each signal in an attempt to increase the value of an objective function which reflects the overall synchronization between all the signals.

Abstract: A digital wireless communications device enabling call distance to be increased while avoiding mute processing as far as possible, even if code error occurs in an ADPCM code. The digital wireless communications device may be configured to include: an error detector for detecting code error in an ADPCM code received via a wireless circuit; an ADPCM decoder for generating a PCM signal by decoding the ADPCM code; and a substitution unit for determining that a click noise is generated if the high-speed scale factor and the low-speed scale factor determined by the ADPCM decoder within a predetermined time period after the error detector has judged that there is a code error in the ADPCM code, and the received ADPCM code itself, respectively exceed prescribed threshold values, and for substituting the ADPCM code with a predetermined prescribed code.

Abstract: A system incorporates time-hopped impulse radio (TH-IR) and transmitted-reference impulse radio (TR-IR) transceivers in the same wireless network. A transmitter modulates a sequence of bits in a wireless communications network by generating a reference waveform and a data waveform of a waveform pair for each current bit. The phase of the reference waveform depends on a previous modulated bit, and a difference in phase between the reference waveform and the data waveform pair depend on the current bit. A symbol period for the current bit is partitioned into multiple time intervals, and the reference waveform and the data waveform are encoded in a selected one of the time intervals that depends on the current bit.

Abstract: A system and method for encoding and receiving data is provided. The data is encoded as a pulse amplitude modulated signal such that the amplitude signals do not transition from the highest signal level to the lowest signal level and do not transition from the lowest signal level to the highest signal level. The encoding and decoding is performed in some embodiments via a lookup table, and in further embodiments is designed to minimize the step between sequential pulse amplitude modulated symbols.