Abstract: In a digital information modulating apparatus, first information signal is separated every m bit or bits, and n bit or bits are added to the head of every m bit or bits to change every m bit or bits of the first information signal into every m+n bits of a second information signal, where "m" and "n" denote predetermined natural numbers. The second information is pre-coded into plural pre-coded information signals in accordance with combinations of the added n bit or bits. A determination is made as to whether or not predetermined sync information is present in the pre-coded information signals. A sync detection signal is generated which represents the result of the determination. One of the pre-coded information signals is selected as a modulation-resultant output signal in response to the sync detection signal.

Abstract: A technique for demodulating CPM spread spectrum signals and variations thereof. A receiver receives a CPM spread spectrum signal, splits it into two signals, demodulates the signals (either coherently or non-coherently) and simultaneously attempts to correlate for a plurality of chip sequences (e.g., I and Q or even and odd), ultimately combining the results into a unified correlation signal. A plurality of A/D converters quantize the demodulated signals into multi-bit digital signals prior to correlation, and multi-bit correlators operate on the multi-bit digital signals to produce correlation signals that are combined to form a unified correlation signal for detection.

Abstract: The optimum decoding of component codes in Block Coded Modulation (BCM) schemes requires the use of the Log-Likelihood Ratio (LLR) as the signal metric. The essence of the invention is a means of accurately approximating the computation of the LLR in a way which is simple to implement directly. The invention, the Log-Likelihood Ratio Planar Approximation (LLRPA), mathematically consists solely of planar equations with fixed point arithmetic that provides both an accurate estimate of the LLR and is easily realized in electronic hardware.

Abstract: A toll quality terrestrial wireless digital multiple access terrestrial communication system is disclosed having a base station in communication with telephone lines and with mobile subscriber stations. The system comprises a switching matrix at the base station and set-up means at the subscriber stations. Means are provided for a periodic exchange of information during the course of communication operation concerning the present status for the connection between the base station and a subscriber station, the link quality, power, and timing adjustment thereof and providing adjustment to the subscriber station based thereupon. Base station and subscriber station apparatus are also disclosed including means for periodically exchanging information during the course of communication operation concerning the present status for the connection between the base station and a subscriber station, the link quality, power, and timing adjustment thereof and providing adjustment to the subscriber station based thereupon.

Abstract: A frequency-hopping-communications system, assigned a system bandwidth B, with the system bandwidth B divided into N sets of frequencies, with each set of the N sets of frequencies not having the same frequencies as other sets of the N sets of frequencies, for communicating base-message data to a plurality of remote units. The frequency-hopping-communications system includes a plurality of base stations for communicating base-message data to the plurality of remote units. Each of the base stations has a coverage area divided into a plurality of N concentric regions with each concentric region assigned one of the N sets of frequencies.

Abstract: A communication device is arranged to send a communication signal in the form of code pulses down an electric fence line which is energized by electric pulses from a fence energizer. The code pulses are generated to be distinct and separate from the electric pulses generated to energize the fence. A controller is included to control the charge and discharge of an energy storage device to generate at least the code pulses to be transmitted along the electric fence line. A coupling device is also included to couple both the code pulses and the electric fence energizing signal to the fence.

Abstract: In response to a received carrier wave modulated in accordance with a digital signal, a digital radio receiver recovers in digital form a modulating signal that is at times subject to undesirable amounts of multipath distortion. This recovered modulating signal is applied as respective input signals to first and second finite-impulse-response (FIR) filters, each of an N-tap type, the taps of which are adaptively weighted. The first FIR filter responds to the modulating signal to supply an output signal in which multipath distortion is suppressed. The second FIR filter responds to the modulating signal to generate corrections for the tap weights of the first FIR filter, which corrections are generated more rapidly than can be done with a microprocessor of the type commonly known as a "digital signal processor" or "DSP". A digital comparator compares samples of the first FIR filter response to corresponding samples of an ideal response, thereby to generate updated tap weights for the second FIR filter.

Abstract: A technique for modulating and demodulating CPM spread spectrum signals and variations of CPM spread spectrum signals. A transmitter divides a signal data stream into a plurality of data streams (such as I and Q data streams), independently modulates the I and Q data streams using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and simultaneously attempts to correlate for a plurality of chip sequences (such as I and Q chip sequences), and interleaves the correlated I and Q data streams into a unified signal data stream. In one embodiment, a spread spectrum transmitter comprises a plurality of lookup tables for storing spread spectrum code chip sequences, at least one preamble code chip sequence, and at least one fill code chip sequence. An output from each of the tables is provided to a selection circuit (e.g.

Abstract: A rake receiver for use in direct-sequence code-division multiple-access communication systems employs a novel channel estimator capable of resolving multipath components spaced closer than a chip interval of the direct-sequence signature sequence. The estimator utilizes a constrained iterative deconvolution technique which employs projection onto convex sets (POCS). In a matched filter rake receiver embodiment, the delay T.sub.SC between two taps of a delay line is smaller than the duration T.sub.C of a chip of pseudo-random sequence. A rake receiver constructed in this manner is capable of detecting signals that have propagated through multipath channels and that have path components spaced closer than one chip of the signal sequence (i.e. closer than the inverse of the signal bandwidth).

Abstract: The invention is used to shape noise in time domain and frequency domain coding schemes. The method advantageously uses a noise weighting filter based on a filterbank with variable gains. A method is presented for computing the gains in the noise weighting filterbank with filter parameters derived from the masking properties of speech. Illustrative embodiments of the method in various coding schemes are illustrated.

Abstract: The present invention provides a method of decoding a spread spectrum composite signal, the composite signal comprising plural user signals that have been spread with plural respective codes, wherein each coded signal is despread, averaged to produce a signal value, analyzed to produce a tentative decision, respread, summed with other respread signals to produce combined interference signals, the method comprising scaling the combined interference signals with a weighting factor to produce a scaled combined interference signal, scaling the composite signal with the weighting factor to produce a scaled composite signal, scaling the signal value by the complement of the weighting factor to produce a leakage signal, combining the scaled composite signal, the scaled combined interference signal and the leakage signal to produce an estimate of a respective user signal.

Abstract: A digital despreader and downconversion technique useful for spread spectrum communications receivers digitally tracks a timing phase of a PN sequence without the need for steering an external hardware clock. An additional benefit of the technique is the use of a receive filter matched to the bandlimited transmit chip sequence prior to despreading which reduces the amount of noise present after despreading. A narrowband filter also permits the use of a single A/D converter in the receiver, IF sampling at a relatively low sample rate compared to other techniques. A method for reducing a total number of computations required thereby facilitating implementation in a single custom digital integrated circuit is also described.

Abstract: A communication system wherein known data sequences characterize both wanted transmitted signals and interfering co-channel transmitted signals, comprising a receiver for receiving a wanted transmitted signal in the presence of unwanted co-channel interfering signals. The receiver comprises a signal sequence identifier means which includes a memory for known data sequences and a correlator which serves to correlate received signals with the stored known data sequences, whereby the relative location in time of received signal sequences is identified.

Abstract: Apparatus for governing information transfer among a plurality of data utilization elements, without rate oscillation, which apparatus is operative according to a rate based transport protocol having apparatus for determining the rate of information transfer between data utilization elements.

Abstract: Apparatus and method for data compression in which a coded message representing a digital bit stream is transmitted over a low bandwidth transmission link and received by apparatus which includes a calculator operable to create a sequence of output values comprising the calculated result of a generator equation. The output values comprising a digital bit stream may be converted to analogue form by a digital to analogue converter. By clocking the output of the waveform generating apparatus asynchronously, with respect to its inputs, a high level of data compression occurs.

Abstract: An apparatus for adaptive-power control of a spread-spectrum transmitter of a mobile station operating in a cellular-communications network using spread-spectrum modulation. A base station transmits a first spread-spectrum signal. A mobile station has an automatic-gain-control circuit for generating an AGC-output signal, from a received signal. The received signal includes the first spread-spectrum signal and an interfering signal.

Abstract: A technique for modulating and demodulating continuous phase modulation (CPM) spread spectrum signals and variations thereof. A transmitter encodes M data bits using a selected spread spectrum code, divides the spread spectrum code into a plurality of chip codes (such as even chips and odd chips), independently modulates the even and odd chips with orthogonal carrier signals using CPM or a related technique, and superposes the plurality of resultants for transmission. A receiver receives the superposed spread spectrum signal and divides it into a real signal and an imaginary signal. The real signal is connected to a first correlator which divides its input into a real I signal and a real Q signal, serially correlates the real I signal with the odd chips of a chip code and the real Q signal with the even chips of the chip code, and combines the correlation signals into a real correlation signal.

Abstract: A spread-spectrum-matched-filter apparatus including a code generator, an in-phase-programmable-matched filter, a quadrature-phase-programmable-matched filter, an in-phase-frame-matched filter, a quadrature-phase-frame-matched filter, and a controller. The code generator generates replicas of a pilot-chip-sequence signal and a data-chip-sequence signal, which are used to set the programmable-impulse responses of the in-phase-programmable-matched filter and the quadrature-phase-programmable-matched filter. The programmable-impulse responses are alternately changed between that of the pilot-chip-sequence signal and the data-chip-sequence signal so that the in-phase-programmable-matched filter and the quadrature-phase-programmable-matched filter alternately detect the pilot-spread-spectrum channel and the data-spread-spectrum channel embedded in a received spread-spectrum signal, respectively.

Abstract: Apparatus and method for despreading a received continuous phase modulated spread spectrum signal includes a power divider for dividing a received spread spectrum signal into a real signal and an imaginary signal. A real CPM correlator demodulates the real signal into I and Q components and separately correlates the real I component and the real Q component without generating a correlation sequence, thereby performing self-synchronizing correlation. Likewise, an imaginary CPM correlator demodulates the imaginary signal into I and Q components and separately correlates the imaginary I component and the imaginary Q component without generating a correlation sequence, thereby performing self-synchronizing correlation. The real I and imaginary I correlation signals are combined into a final I correlation signal, and the real Q and imaginary Q correlation signals are combined into a final Q correlation signal.

Abstract: A data transfer apparatus includes a transmitting apparatus having a pulse generation circuit for generating a plurality of data and a clock having a predetermined timing relation to the plurality of data, a receiving apparatus having latch circuits supplied with the clock and data for latching the plurality of data at a timing of the clock, respectively, transmission lines for connecting the transmitting apparatus and the receiving apparatus, a variable delay circuit for delaying the clock or data to be supplied to the latch circuits, and a variable delay control circuit for controlling an amount of delay of the variable delay circuit by means of output signals of the latch circuits to thereby minimize the cycle time of the data and clock in the data transfer between apparatuses.