Abstract: A communication system that can satisfactorily communicate with a mobile station by a transmitter and receiver of a simple arrangement wherein a plurality of carriers having different frequencies are transmitted simultaneously and data is transmitted on the basis of a phase difference between the carriers. Also, the carriers are multiplied with a predetermined time waveform and transmitted, so that a reception side receives data by use of a time waveform narrower than the above time waveform.
Abstract: A simple block coding arrangement is created with symbols transmitted over a plurality of transmit channels, in connection with coding that comprises only of simple arithmetic operations, such as negation and conjugation. The diversity created by the transmitter utilizes space diversity and either time or frequency diversity. Space diversity is effected by redundantly transmitting over a plurality of antennas, time diversity is effected by redundantly transmitting at different times, and frequency diversity is effected by redundantly transmitting at different frequencies. Illustratively, using two transmit antennas and a single receive antenna, one of the disclosed embodiments provides the same diversity gain as the maximal-ratio receiver combining (MRRC) scheme with one transmit antenna and two receive antennas.
Abstract: A digital communication method and system wherein in response to input 3-bit data, a phase and amplitude of a carrier signal are controlled so that a symbol at a given time is located at one of allowed signal points depending on the content of the symbol. The allowed signal points include six signal points where a phase shift equal to .+-..pi./4, .+-.2.pi./4, or .+-.3.pi./4 occurs relative to the signal point at which the immediately previous symbol was located and where the amplitude is equal to a first level, and also include two signal points where a phase shift equal to .+-.2.pi./4 occurs relative to the signal point at which the immediately previous symbol was located and where the amplitude is equal to a second level lower than the first level. The digital communication method and system allows for a transmitter which does require a high-performance power amplifier, and a simplified receiver circuit.
Abstract: A spread spectrum transmitter and receiver are provided wherein data can be accurately decoded by removing the effect of mutual interference of the quadrature component and in-phase component even when there is carrier frequency error. In a method of spread spectrum communication using a QPSK modulation system, there are provided: a demodulating circuit that receives and demodulates a signal transmitted with a prescribed time difference Td applied between the IQ components; correlators that find the mutual correlation of the IQ components and spreading code; a sampling circuit that samples their output signals; a phase calculator that calculates the phase from the ratio of the IQ components of these output signals; a differential decoding circuit that performs differential decoding on this output signal; an automatic frequency control circuit that corrects the frequency error of this output signal; a decoding circuit; and a clock recovery circuit.
Abstract: In a radio communication system with a radio control apparatus in radio communication with radio communication apparatus, a frequency hopping method is used in which the frequencies of a hopping pattern are determined by the radio control apparatus. When the frequencies of the hopping pattern are redetermined, the radio communication apparatus is intstructed to end intermittent reception and is notified of the reconfigured hopping pattern. In response to the instruction, the radio communication apparatus ends intermittent reception and shifts to a state of receiving the notification of the hopping pattern from the radio control apparatus. The frequency for performing intermittent reception is based on the relationship between the period of the notified hopping pattern and the time interval of intermittent reception.
Abstract: A fractionally-spaced adaptively-equalized self-recovering digital receiver includes a fractionally-spaced adaptive filter for equalizing channel distortion which includes means for adaptively adjusting the coefficients of the fractionally-spaced filter with a self-recovering (blind) algorithm or a decision directed algorithm; means for changing the timing at which the data is sampled; means for estimating the sampling frequency offset in order to derive the optimal timing; means for synchronizing the signal resampling at the symbol rate using the statistics of the received data samples; means for evaluating the profile of the equalizer coefficients; and means for tracking carrier frequency offset.
Abstract: An asymmetric filter combination (F1, F2) for the transmission of a binary data stream (st) between a transmitter (T) and a receiver (R) is disclosed which includes a first filter (F1) at the transmitter end having an FIR structure and a second filter (F2) at the receiver end having an IIR structure, with the combination of the first and second filters (F1, F2) yielding a common transfer function which satisfies both the Nyquist criterion and the noise-matching criterion.
Abstract: An input data signal (102) in a digital signal processing system gets adaptively quantized by performing a LMS error algorithm on a signal of transformed coefficients (113), determining paths of minimum error (202), and forming a three-dimensional matrix (206) representing these paths. Centroids are computed (208) based on the paths of minimum error (206), and these computed centroids are used as part of a next iteration to represent new quantization states and levels.
Abstract: In a case where transmission and reception timing of a base station has not been synchronized to that of another base station in the vicinity, or in a case where it is necessary to establish such synchronization, a synchronous controller outputs a reception-mode changeover signal to change the prevailing mode from an ordinary reception mode to a synchronous control reception mode. As a result, attenuating means attenuates a strong input signal from the other base station and enters the attenuated signal into a demodulator via a front end. The demodulator proceeds to demodulate the received data. The synchronous controller detects synchronization information (a synchronizing word) from the received data to synchronize the transmission and reception timings of the two base stations and then returns the reception mode to the ordinary reception mode.
Abstract: An audio encoding transmission system is provided for a transmitting station which performs data transmission with respect to a receiving station through a network. The transmitting station contains a scalable encoder which performs an encoding process on audio signals input thereto in response to bit rate information representing a bit rate which is variable in response to a condition of the network. Results of the encoding process are partitioned into outline data, having a low bit rate, and detail data. Herein, the outline data correspond to low-frequency components of the audio signals while the detail data correspond to high-frequency components of the audio signals, for example. A bit stream is constructed using the outline data and detail data as well as additional information such as a header and a boundary identifier which are created on the basis of the audio signals and bit rate information. Thus, the transmitting station transmits the bit stream to the receiving station via the network.
Abstract: A system and method using a Costas loop to effect accelerated convergence with minimal system complexity. The system comprises an in-phase-limiter and a quadrature-phase limiter, operatively coupled to an EXCLUSIVE-OR gate, for exclusively-ORing an in-phase-sign signal and a quadrature-phase-sign signal to output a first error signal, responsive to the signals having same signs, or a second error signal, responsive to the signals having different signs. An AGC circuit, operatively coupled to an output of the EXCLUSIVE-OR gate, increases and decreases a voltage level of an AGC signal responsive to two consecutive first or second error signals and consecutive dissimilar error signals, respectively. A voltage-controlled oscillator, operatively coupled to an output of the AGC circuit and responsive to the increased or decreased voltage level, changes the frequency of a voltage-controlled-oscillator output signal.
Abstract: A method and apparatus for encoding and decoding QAM trellis modulated data. In the transmitter, a subset of bits of an input bit set are convolutionally encoded based upon a punctured convolutional code of a lower data rate to provide a set of coded symbols. The coded symbols and the uncoded bits of the input bit set are provided to a QAM modulator to provide a QAM modulation signal indicative of the values of coded symbols and the uncoded bits. In the receiver a QAM demodulator converts the received QAM signal to QAM signal space coordinates. A decoder employing the Viterbi algorithm is used to reconstruct a corrected estimate of the values of the coded data bits from the received signal coordinates. The corrected estimate of the values of the coded data bits are then used in conjunction with the received signal coordinates to provide corrected estimates of the values of the uncoded input bits.
Abstract: The invention relates to a communication system (300) having a receiver (304) that is capable of performing targeted interference suppression. An interference classifier (314) within the receiver (304) analyzes a signal received from a channel (306) and identifies and classifies interference components within the signal. An interference suppressor (316) then suppresses the interference components in the signal based on interference type. In one embodiment, the interference suppressor (316) includes a plurality of interference suppression modules that are each optimal for suppressing certain interference types. The interference suppressor (316) selects one of the interference suppression modules based on the type of interference present in the received signal. In another embodiment, a hybrid interference mitigation system (10) is provided by combining targeted interference suppression, frequency hopping adaptation, and processing gain adaptation.
January 30, 1998
Date of Patent:
September 12, 2000
Chad Scott Bergstrom, Jeffrey Scott Chuprun, John Eric Kleider
Abstract: A system and method for calculating survivor metrics in a Viterbi equalizer of a receiver, such as a receiver operative to receive a PSK-modulated signal, for example, a .pi./4, differential, phase-shift-keying, modulated signal. The state transition metric, defined as a function of two successive states, is converted into a function defined by pairwise differences between allowable symbols of a PSK-modulated signal. When operative to receive the .pi./4 DQPSK-modulated signal, the number of calculations required to calculate state transition metrics is reduced significantly.
February 13, 1996
Date of Patent:
August 29, 2000
Bruce Dale Mueller, David Edward Borth, Kevin Lynn Baum
Abstract: A wireless communication system including a base unit and a plurality of remote units, in which two remote units can communicate separately from and simultaneously with communication between the base unit and another remote unit. The wireless communication system can maintain synchronization between the base unit and remote units and process such control signals as call signals without interrupting communication currently in progress. To achieve this, a communication hop frequency data array D is provided for communication use. A control hop frequency data array G is also provided for control use. Both data arrays D and G are stored in a hopping table 36. Data elements In the control hop frequency data array G and in the communication hop frequency data array D are retrieved from the hopping table 36 so that data in the data array G will be distributed regularly throughout the communication hop frequency data array D.
Abstract: A plurality of stations (S), for instance measuring probes, preferably comprising respective microprocessors (KL), are connected successively to a common two-wire line (SL). Supply voltages and synchronization signals are distributed through this line (SL) from a central unit (CU), and at the same time a full duplex communication between single stations (S) and the central unit (CU) is enabled.
Abstract: A system for receiving information encoded in a train of pulse position modulated signals and then decoding the pulse train to produce amplitude modulated signals representing the original information includes a circuit for detecting the beginnings of successive PPM signals, a one-shot multivibrator responsive to the beginnings of the PPM signals for producing pulse width signals whose duration varies in accordance with the received intelligence, and an R-C low pass output circuit coupled to the output of the multivibrator to produce amplitude modulated output voltage waves. The R-C circuit has a time constant substantially greater than the unmodulated period between PPM pulses, and produces a rising voltage that spans the time duration of an associated high voltage level square pulse and whose decaying voltage level varies in amplitude in accordance with the maximum voltage attained at the output of the R-C integrator by the trailing edge of the associated high voltage level pulse.
December 12, 1996
Date of Patent:
August 22, 2000
Harry Clark Morgan, William Harsha Boyd
Abstract: A receiver for detecting spread spectrum binary data particularly on a power line in the presence of channel distortion. In one embodiment a standard pattern ideally suited for minimal distortion in the channel is used in conjunction with an alternate pattern which is developed to better detect carrier and data in the presence of certain channel distortion. The receiver switches between the standard and alternate pattern to provide improved detection. In another embodiment an adaptive pattern is used which is developed from the receive signal. For instance, the signal over several bit times is averaged to provide a pattern which is correlated with a receive signal.
Abstract: A clipping protection scheme for a discrete multi-tone (DMT) digital subscriber loop modem telecommunications system determines the occurrence of clipping by checking the overflow bits in the IFFT status register. The transmitter then sends a predefined data stream to notify the receiver of the event, and then breaks the data into two frames for consecutive transmission to the receiver.
Abstract: A system and method for demodulating digital information from a modulated signal that can be represented in a signal space diagram as an odd constellation of sample points. The system comprises filtering means for receiving the modulated signal that includes means for rotating the received sample points 45.degree. clockwise on the signal space diagram such that decision or neighborhood regions can be drawn having borders that are either parallel or perpendicular to the axes of the signal space diagram. As a result, a slicer can easily extract the symbol information from the rotated sample points with a minimum of computational complexity. Moreover, and perhaps most importantly, the rotation is accomplished through a one time modification of the tap coefficients used by the filtering means thus eliminating any additional processor real time required to perform the rotation.