Abstract: An automatic equalizer which converges by a received signal and a data mode convergence method. A variance extracting unit extracts the variance of an output signal of a transversal automatic equalizing section and changes a predecision input signal to a proper level according to the extracted variance. A decision unit makes a decision for the predecision input signal which has been changed by the variance extracting unit and allocates the predecision input signal to a signal point. An amplitude error extracting unit extracts an amplitude error from a predecision input signal and a postdecision output signal of the decision unit and corrects the tap coefficients of the transversal automatic equalizing section according to the extracted amplitude error.

Abstract: A transmission system using multicarrier modulation applies FECC (forward error correcting code) coding and codeword interleaving differently to input signals from a plurality of different data channels to produce encoded data signals having different reliabilities and different coding delays. Bits of encoded data signals having relatively less delay are allocated to carriers that are subject to relatively more attenuation and/or channel noise, and hence that are allocated fewer bits for transmission in each symbol period, to reduce the effects of impulse noise. The data channels can comprise video, data, and control channels transmitted on an ADSL (asymmetric digital subscriber line) two-wire telephone line.

Abstract: A method and circuitry are provided for detecting and measuring a phase difference between the output signals from a primary stratum clock and a standby stratum clock in a telecommunications system, computing a period of time needed for a numerically-controlled oscillator to shift the frequency of the standby clock enough to cancel the phase difference, transforming the required period of time into a signal representing a corresponding number of frequency shift steps, and controlling the numerically-controlled oscillator with the step signal to shift the frequency of the standby clock accordingly and thereby cancel the phase difference. Both the frequency and phase alignments of the two clocks are thus maintained. Therefore, when either the system or user switches operations from the primary stratum clock module to the standby stratum clock module, phase-related transients are not generated, which results in a significant increase in the overall performance and reliability of the system.

Abstract: A spread spectrum code pulse position modulated communication system is disclosed. The frequency spectrum of a transmitted signal is spread by encoding bits with a predefined spectrum-spreading codeword which is in accordance with regulatory requirements or other standardization decisions. When the predefined spread spectrum codeword is passed through a filter matched to the characteristics of the codeword, a peak is detected in the main lobe. A positive main lobe can indicate a binary value of "0" and a negative main lobe, associated with the inverse of the predefined codeword, can represent a binary value of "1". Additional information is conveyed by modulating the position of the center of the codeword within the symbol duration. In one embodiment, the position of the center of the codeword is varied among eight positions. Thus, eight signal states are available, and three additional bits may thereby be conveyed.

Abstract: Apparatus for use in equipment providing digital radio link between a fixed radio unit and a mobile radio unit. The apparatus includes demodulators arranged to receive inphase and quadrature phase input signals. A channel estimator is provided for deriving a decision directed channel estimate from one or more signals which is used by the demodulator for demodulating one or more of the signals transmitted over the same radio channel. The apparatus is for use in the demodulation of dual binary phase shift keying signals and various embodiments are possible. In addition, the apparatus may be used in conjunction with precombining Rake architecture.

Abstract: The invention provides a frequency subband encoding apparatus wherein the amount of comparison operation processing of a bit allocator is minimized. A subband filter divides a PCM signal into and outputs a plurality of frequency subbands. A SMR calculator calculates, for each of the frequency subbands, an SMR which is a ratio between a signal level and a mask level. A bit allocator calculates a reference NMR which is a value obtained by subtracting, from an SMR of the entire frequency band, a S/N ratio calculated from a reference bit number to be allocated to one of the frequency subbands which exhibits a maximum SMR, and adjusts the reference NMR to perform bit allocation to the frequency subbands.

Abstract: A transmission rate control system is adapted for an information processing system which exchanges data between a host unit and at least one terminal equipment via a first transmission line. The transmission rate control system includes a first part provided in the host unit for generating a clock switching signal which instructs a switching of a first clock signal which determines an operation of the terminal equipment, a second part provided in the terminal equipment for generating the first clock signal which determines the operation of the terminal equipment, a third part provided in the terminal equipment for switching a period of the first clock signal generated from the second part in response to the clock switching signal received from the main unit, so that a transmission rate of the terminal equipment is switched, and a second transmission line provided exclusively for transmitting the clock switching signal from the host unit to the terminal equipment.

Abstract: A method for demodulating pulse messages, which have been converted into modulated signals, preferably for wireless digitized speech transmission, which is distinguished by minimal technical outlay and which can be carried out using circuits which can be designed in integrated circuit technology. The signal which is to be demodulated is subjected to quadrature modulation. Of the two quadrature components which have been thereby obtained one is subjected to a differentiation or an integration and the signal obtained in this manner and the signal of the other quadrature component are supplied, after analog-to-digital conversion, to in each case one comparator (9, 10). The digital output signals of the two comparators (9, 10) are assembled by means of a coincidence gate (11) to form the pulse message.

Abstract: A method and corresponding apparatus for error correction of MSK-coded data receives a signal (101) partitionable into adjacent frames (111,113) each subdividable into three tridents (103, 105, 107). A first sample quality metric (225) applicable to a p (123) of the signal (101) associated with a last trident (107) of the tridents of a first frame (111) of the adjacent frames (111, 113) is synthesized, and a second sample quality metric (227) applicable to a portion (125) of the signal (101) associated with a first trident (103') of the tridents of a second frame (113) following the first frame (111) is synthesized. Each of the first and second sample quality metrics (225, 227) have a magnitude dependent on a time that the associated portion (123) of the signal (101) has a magnitude exceeding an average magnitude (127) of the signal (101).

Abstract: A communication system for transmitting variable rate data is disclosed wherein redundancy is added to the variable rate data to provide repetition symbols. The repetition symbol data is transmitted with symbol energy scaled in accordance to the rate of the variable rate data when the variable rate data is greater than or equal to a nominal data rate. When the variable rate data is less than the nominal data rate, the symbol data is transmitted at nominal symbol energy and redundancy is removed by transmission gating of a proportion of the transmission symbol data determined in accordance with the rate of the variable rate data. Furthermore, a receiver for receiving the variable rate data is disclosed which uses the redundancy in the transmitted data symbol stream to make a corrected estimate of the transmitted symbol data.

Abstract: A timing phase detector and timing recovery using a quadrature amplitude modulation is disclosed including a 4-point fast Fourier transforming portion for Fourier-transforming a digital output signal from an analog-to-digital converter; a sum/dump portion for adding and outputting the output of the 4-point fast Fourier transforming portion; and a cordic portion for calculating the phase of a complex number so as to indicate the output of the sum/dump portion on the X-Y coordinates.

Abstract: A system and method for adaptive power control of a spread spectrum transmitter of a mobile unit operating in a cellular-communications network having a plurality of mobile units in communication with a base station. In response to a received signal from the mobile unit, the received signal having a first spread-spectrum signal and an interfering signal, an automatic gain control (AGC) circuit within the base station generates an AGC-output signal which is despread by base despreader and then processed as a received-power level. The received power level is then compared to a threshold level to generate a power command signal. The power command signal is transmitted to the mobile station as a second spread-spectrum signal. The mobile station despreader despreads the second spread-spectrum signal as a power adjust signal and, responsive to the power adjust signal, increases or decreases the power level of the first spread spectrum signal.

Abstract: Spread spectrum chirps (i.e., wideband frequency packets) are propagated on a local area network in a hostile communications environment, such as a powerline or a crowded radio frequency band. Chirps are self-synchronizing, data bit (or subdata bit) in length and detectable by all network nodes, to allow the contention resolution and collision detection needed to support carrier-sense based network protocols. A matched filter of the same time length and encoding sequence as the transmitted chirp provides the self-synchronized chirp reception at each receiver.

Abstract: A wireless data communication system includes a code encoder for transforming pulse code modulated data into a simple code having an alphabet with at least one spare symbol into which a delimiter symbol is introduced, which code is transmitted to a receiver including a matched filter arrangement and a code maximum decision arrangement for decoding the transmitted code signal and for detecting the delimiter symbol.

Abstract: A digital down converter with a programmable mixing down frequency and a programmable extraction bandwidth uses a ROM based sin/cos generator plus a programmable high decimation filter followed by a gain compensating scaling multiplier and a fixed FIR filter. Output format options are also programmable, and programming commands are serially loaded into registers. Various components may be isolated for efficient testing and also subsystem operation.

Abstract: During filtering of an image having different regions, the operation of a filter unit is adapted in response to the detection of a boundary between these regions. To this end, one or more intermediate signal values stored in the filter unit for recursive use and derived from signal values from a first region are replaced before any signal value from the second region is filtered. The intermediate signal values are replaced by one or more signal values from the second region, or by filtered signal values derived from the signal values from the second region.

Abstract: A cordless headset, requiring very low power using Time Variant Modulation (TVM) for reception of a magnetic signal and TVM of RF or infrared as the transmitter. The headset area or zone of operations is defined by the magnetic field that the headset operates within and uses a handshake protocol that takes advantage of the TVM fixed clock period. The headset communicates with a base station that includes a TVM transmitter and loop for transmitting a TVM signal to the cordless headset, and a RF or infrared receiver capable of receiving TVM signals from the headset. The base station also contains the headset protocol logic for controlling the headset transmission. The headset and base station receiver can both be fixed, mobile or portable and vary with respect to orientation and distance from each other. The receiver circuits in both base station and headset automatically adjust to the variance in signal strength.

Abstract: A new signal quantization scheme is proposed which reduces fluctuation of the output signal by a signal quantizer (10) providing a quantized output signal and multiplying (18) said input signal X by a factor (1-w.sub.1)and finding a difference signal .DELTA..sub.in (11) between both the input signal and the previous input signal and multiplying (16) that by a weighting factor w.sub.2 from a control (13). The previous quantizer output signal Q.sub.prev is summed (17) with the weighted difference signal .DELTA..sub.in w.sub.2 and the sum is weighted by a weighting factor w.sub.1 at a multiplier (19) to yield w.sub.1 (Q.sub.prev +w.sub.2 .DELTA..sub.in). This signal is then summed at an adder (21) and applied to the quantizer (10) so that the quantizer is forced to match the fluctuation in the input signal as well as the signal itself.

Abstract: In order to restore a clock signal which has been used for coding signals transmitted on a transmission channel, the transition instants of these signals are precisely detected by analyzing a series of samples taken from the signals during at least one fraction of the clock period. A device first determines the deviations between the respective amplitudes of the various samples that have been taken. Comparison of the deviation configuration obtained with standard configurations that have been determined previously makes it possible to estimate the position of the time window where the sampling was achieved in relation to the analyzed period fraction and therefore to decide whether this window is correctly centered. If it is not, a local clock is phase shifted so as to have the time window resynchronized.

Abstract: The effective (or logical) size of the encoder buffer in a video transmission system is varied with the transmission bit-rate. Also, a minimum fill level is maintained in the encoder buffer whenever the transmission rate is too high to assure otherwise that the decoder buffer will not overflow or underflow. The encoding rate is varied so as to maintain a fill level in the encoder buffer within limits. In the preferred embodiment, the logical encoder buffer has a size which is maintained at R.DELTA.T(1-m.sub.1)-M, where R is the average transmission bit-rate, which may vary, .DELTA.T is the fixed delay between the encoding and decoding processes for a transmitted video signal, R(1-m.sub.m) is the minimum instantaneous transmission rate that the communication system achieves at average rate R, and M is the maximum total buffer storage in the communication system. When the decoder buffer has a size less than R.DELTA.T(1+m.sub.2), where R(1+m.sub.