Abstract: The ultra wide band communication system of the present invention includes a transmitter (station) and a receiver (station). The transmitter and the receiver employ spreading code comprised of code groups, which respectively comprise varied, auto-correlated codes. Consecutive information bits are spread and de-spread with differing code and the code groups are correlated with each other (e.g., orthogonal) so as to reduce channel impulse response estimation noise. At the receiver, subsequent channel estimates can be added or averaged with an initial channel estimate so as to reduce the channel impulse response estimation noise and thereby provide a relatively more accurate channel response.

Abstract: The radio communication apparatus (10) comprises a buffer (14) which temporarily stores data to be sent, a transmission/receiving circuit (12) having a data transmission circuit (30) and a data receiving circuit (40). The data transmission circuit (30) includes an input processor (41) which generates, when transmitting the data, a preamble to output it to a QPSK modulator (42), thereafter reads from the buffer (14) a data row of 256 bits and outputs it to the QPSK modulator (42). Accordingly, the transmission circuit (30) is constituted such that the data sets each including the preamble and the data row are repeatedly transmitted. On the other hand, the receiving circuit (40) includes a DMF (86) which accomplishes acquisition using a portion in the received data corresponding to the preamble.

Abstract: A circuit is designed with a matched filter circuit including a plurality of fingers (700, 702, 704) coupled to receive a data symbol. Each finger corresponds to a respective path of the data symbol. Each finger produces a respective output signal. A plurality of decoder circuits (706, 708, 710) receives the respective output signal from a respective finger of the plurality of fingers. Each decoder circuit produces a respective output signal. A joint detector circuit (1310) is coupled to receive each respective output signal from the plurality of decoder circuits. The joint detector circuit produces an output signal corresponding to a predetermined code.

Abstract: Known sequences are detected and identified in a fast fading environment using a segmented correlator and FHT (Fast Hadamard Transform) architecture. The incoming sequence of samples or data is segmented into blocks. Each block is individually detected using a correlator/FHT segment. Each sequence identifying output of each correlator/FHT segment is summed with the corresponding output of other correlator/FHT segments. Each sum is compared with a threshold to determine whether a particular sequence has been detected and identified.

Abstract: A peak magnitude of a signal is estimated from a set of signal samples. From the set of signal samples, a largest signal sample and an adjacent next largest signal sample are selected that occurs, respectively, at a time, s1 and at a time, s2. A first ratio of a first derived signal sample and a second derived signal sample is generated, the first derived signal sample being derived from the largest signal sample, and the second derived signal sample being derived from the next largest signal sample. A second ratio is determined from the first ratio, the second ratio representing a peak magnitude of a communication system response divided by a second magnitude of the communication system response, wherein the second magnitude is the communication system response at the time s1. The peak magnitude of the signal is generated from the second ratio and the first derived signal sample.

Abstract: A code division multiple access communication system receiver includes block-based chip timing estimation. A chip timing estimate is generated from samples of a received signal by performing an averaging operation over a designated block of chips in each of first and second legs of an early-late synchronizer. The chip timing estimate is determined as a function of an error signal corresponding to the difference between outputs of the first and second legs, and is utilized to adjust a code generator clock or to otherwise control chip timing in the receiver. In an illustrative embodiment, a separate block-based chip timing estimator is implemented in each of the fingers of a Rake receiver.

Abstract: A system and method for transmitting a plurality of spread-spectrum signals over a communications channel having fading. The plurality of spread-spectrum signals are radiated by a plurality of antennas, with each antenna preferably spaced by one-quarter wavelength. A plurality of receiver antennas receive the plurality of spread-spectrum signals and a plurality of fading spread-spectrum signals. Each receiver antenna is coupled to a plurality of matched filters having a respective plurality of impulse responses matched to the chip-sequence signals of the plurality of spread-spectrum signals. A RAKE and space-diversity combiner combines, for each respective chip-sequence signal, a respective plurality of detected spread-spectrum signals and a respective multiplicity of detected-multipath-spread-spectrum signals, to generate a plurality of combined signals. The symbol amplitudes can be measured and erasure decoding employed to improve performance.

Abstract: A method of processing a pulse response with an adaptive threshold and corresponding receiver. According to the method, an adaptive threshold is calculated that is a function of a maximum reached by the pulse response, noise, and a coefficient adjustable between 0 and 1. The processing only comes into operation for signals that exceed this threshold. Such a method may find application notably to digital radio-communications with spread spectrum.

Abstract: A circuit is designed with a matched filter circuit including a plurality of fingers (700, 702, 704) coupled to receive a data symbol. Each finger corresponds to a respective path of the data symbol. Each finger produces a respective output signal. A plurality of decoder circuits (706, 708, 710) receives the respective output signal from a respective finger of the plurality of fingers. Each decoder circuit produces a respective output signal. A joint detector circuit (1310) is coupled to receive each respective output signal from the plurality of decoder circuits. The joint detector circuit produces an output signal corresponding to a predetermined code.

Abstract: A direct sequence spread spectrum system in which a plurality of substantially redundant second blocks are derived from a first block of data. Each of the second blocks is spread using a distinct spreading sequence, and one or more signals representing each of the spread blocks is modulated and transmitted over a wireless interface. The transmitted one or more signals are received, and estimates of one or more of the second blocks derived therefrom. The first block is then estimated from one or more of the estimated second blocks.

Abstract: Methods and apparatuses for processing Satellite Positioning System (SPS) signals. In one exemplary method, a first set of frequency coefficients, which corresponds to a first Doppler frequency of an SPS signal, is determined, and said SPS signal is processed in a matched filter with the first set of frequency coefficients during a first window of time. A second set of frequency coefficients, which corresponds to a second Doppler frequency of the SPS signal, is determined, and the SPS signal is processed in the matched filter with the second set of frequency coefficients during a second window of time, where the first and second windows of time occur within a period of time which is not greater than one SPS frame period.

Abstract: Methods and apparatuses for processing Satellite Positioning System (SPS) signals. In one exemplary method, a first set of frequency coefficients, which corresponds to a first Doppler frequency of an SPS signal, is determined, and said SPS signal is processed in a matched filter with the first set of frequency coefficients during a first window of time. A second set of frequency coefficients, which corresponds to a second Doppler frequency of the SPS signal, is determined, and the SPS signal is processed in the matched filter with the second set of frequency coefficients during a second window of time, where the first and second windows of time occur within a period of time which is not greater than one SPS frame period.

Abstract: A matched filter has a circuit calculating an exclusive-OR of two input data, a circuit calculating an exclusive-OR of two codes corresponding to the two input data, respectively, and a correlation processor. The correlation processor, using the exclusive-OR of the two input data, one of the two input data, the exclusive-OR of the two codes, and the code corresponding to one of the two input data, calculates a correlation value of the two input data and the two codes.

Abstract: An improvement to a spread-spectrum receiver having a matched filter. A symbol sampler samples at the symbol time TS, a symbol sample from the matched filter. A noise sampler samples at a plurality of chip times kTC, but not at the symbol time TS, a plurality of noise samples from the matched filter. An estimator or low-pass filter estimates the plurality of noise samples from the symbol sampler, to generate a noise estimate. A combiner subtracts the noise estimate from the symbol sample, thereby generating a comparison signal. A magnitude device determines a magnitude of the comparison signal. A comparator compares the magnitude of the comparison signal to the threshold voltage, thereby generating the erasure signal. An erasure decoder erasure decodes the input data using the erasure signals from the erasure detector.

Abstract: The invention relates to a receiver and method for improving synchronisation. In the solution of the invention, a signal is received and filtered by a matched filter (500) or processed by a correlator (520). Two or more consecutive samples in the output of the matched filter or correlator are combined and re-sampled in such a manner that the re-sampling is done over as many samples as the combination, and one or more correlation peaks are found in the combined samples.

Abstract: An analog input signal that is sampled at a predetermined rate is multiplied by a corresponding binary code sequence, i.e. “+1” or “−1” by the multiplier. The output of this multiplier is applied in conjunction with a signal supplied by the negative feed back circuit to the analog integrator. The quantization circuit quantizes the output signal of the analog integrator into N levels and outputs a digital word. This digital word is delayed by a unit time interval by a digital delay circuit and then processed by the above mentioned negative feed back circuit. As a result of this signal magnitude reducing process, the required integrating capacitance can be minimized without risks of saturation effects. Additionally, the output is already in digital form as required by the subsequent system blocks.

Abstract: A method for estimating and compensating for a fading communications channel includes the steps of generating matched filter data from a received data burst, interpolating between reference symbols to generate a fading channel estimate from the matched filter data, applying a phase correction to the matched filter data from the fading channel estimate to recover free data from the matched filter data, and performing decision feedback on the free data to improve the fading channel estimate.

Abstract: A multi-channel direct sequence spread-spectrum communication system with the capability of automatic rate detection consists of a plurality of signal channels and a plurality of data channels. During signaling period, only the signaling channels corresponding to the desired symbol repetition and the data channels corresponding to the highest index among the indexes of all active data channels will be allowed to transmit. During data transmission period, only the active data channels will be allowed to transmit. Receiver will use the information provided in preamble signal and mid-amble signal to obtain the number of symbol repetition, the set of active data channels and etc, and to set up initial synchronization.

Abstract: A multi-channel spread spectrum communications system utilizes the combination of spreading codes to represent and transfer information. On the transmitter side, every block of data bits is divided into two sub-blocks of data bits. One sub-block is mapped to a number of spreading codes, while another sub-block is separated further into several smaller sub-blocks with each of them mapped into an M-ary phase. Each selected spreading code is modulated by the corresponding M-ary phase. On the receiver side, first determine the most likely transmitted spreading codes and their respective phases, then reverse map the set of estimated transmitted spreading codes into a block of bits and each of the phases into another block of data bits, and finally combine all these blocks to a single block of data bits.

Abstract: An improvement to a code-division-multiple-access (CDMA) system employing spread-spectrum modulation, with the CDMA system having a base station (BS) and a plurality of remote stations. The base station has a BS-spread-spectrum transmitter and a BS-spread-spectrum receiver. A remote station has an RS-spread-spectrum transmitter and an RS-spread-spectrum receiver. The BS transmitter transmits a broadcast common-synchronization channel, which includes a frame-timing signal. The broadcast common-synchronization channel has a common chip-sequence signal, which is common to the plurality of remote stations. In response to the RS-spread-spectrum receiver receiving the broadcast common-synchronization channel, and determining frame timing from the frame-timing signal, an RS-spread-spectrum transmitter transmits an access-burst signal. The access-burst signal includes a collision-detection portion.

Abstract: A matched filter having a set of registers to successively store a digital voltage. The matched filter includes a cumulative shift register, a number of exclusive-or circuits, and an analog adder. The cumulative shift register has a number of stages in which each stage has one bit corresponding to the shift register. The exclusive-or circuits each perform an exclusive-or function on each bit of the digital data and the one bit coefficient while the analog adder sums outputs from the exclusive-or circuits.

Abstract: A system for labelling and subsequently identifying a multi-frequency signal, includes means for inserting a code signal into a multi-frequency signal, signal distribution means, signal receiving means, code extraction means, and monitoring means to determine which parts of the frequency spectrum will at least partly mask the code signal at a given time using predetermined criteria. The means for inserting a code signal includes means for eliminating one or more frequency ranges being located in a part of the frequency spectrum that will at least partly mask the code signal, the location of the frequency ranges being eliminated from the said multi-frequency signal varies with the frequency content of said multi-frequency signal.

Abstract: A communication apparatus and method that includes generating a series of successive spread-spectrum signals formed through the concatenation of a direct sequence spread spectrum code with a Doppler Tolerant Polyphase Code (DTPC) is herein disclosed. By transmitting concatenated codes, it is possible to demodulate received sequences that are very long compared to the inverse of the Doppler frequency and/or the local oscillator drift. The method and apparatus may be applied to implement a wireless telecommunication system that efficiently transfers small quantities of data, such as status/telemetry, identification information and/or establishes device location at a low data rate over long distance in challenging radio environments and with low power consumption.

Abstract: Received quality detecting section 108 detects a received quality, bit determining section 111 determines whether a TPC bit is 0 or 1, amplitude reading section 112 reads a ratio of an amplitude of a signal other than the TPC bit and an amplitude of the TPC bit, accumulating section 113 determines an increase or decrease of transmit power and an amount of the increase and decrease of the transmit power using a symbol of the TPC bit for the increase or decrease, and an amplitude ratio for the amount of the increase and decrease to instruct to transmission amplifier 104, and multiplying section 114 multiplies the amplitude of the signal other than the TPC bit by a correction value corresponding to the received quality to determine the amplitude of the TPC bit.

Abstract: According to the present invention, the effects of the transmission medium on transmitted information symbols are estimated separately from other effects, e.g., those associated with receive and transmit filters, using knowledge of the pulse shaping. The medium response estimate is then used to detect information symbols. Previously, receivers had used estimates of the composite channel to detect symbols. This, however, assumed uncorrelated noise, which is not always the case.

Abstract: A configurable cellular terminal engine (CTE) in accordance with an exemplary embodiment of this invention is configurable by an external agent (e.g., microcontroller, DSP, or state machine) to suit the particular requirements of different spread spectrum systems. In an exemplary embodiment, the CTE comprises on a chipset a modem unit and a channel codec unit. The modem unit has a front end unit for coupling to an antenna; a matched filter searchers unit coupled at least to the front end unit; a searchers unit coupled to at least the front end unit; a finger processing unit coupled to the front end unit; a parameter estimation processor unit coupled to at least the finger processing unit and the searchers unit; and a transmitter unit. The channel codec unit has a channel decoder unit coupled at least to the finger processing unit; and a channel encoder coupled at least to the transmitter unit.

Abstract: Techniques for coherent demodulation in the presence of phase discontinuities is described. In the exemplary embodiment, times when phase discontinuities occur are known apriori by a receiver in which demodulation is being performed. In an alternate embodiment, the discontinuity location is signaled to the receiver in advance by the transmitter which generates the signals being demodulated. A pilot signal is prepared for optimal coherent demodulation by the use of two filters: one capable of withstanding the effects of phase discontinuity; a second providing superior filtering performance than the first so long as phase discontinuities are not present. Both filters are simultaneously operated. However, the superior performing filter is selected for use in demodulation whenever possible.

Abstract: In a matched filter, a spread data path unit holds inputted spread data, a multiplier unit multiplies an output of the spread data path unit by a spreading replica code, and an adder unit adds results of the multiplication and outputs an added result. The spread data path unit comprises a first selector being able to selectively output the spread data, a plurality of sub spread data path units each having a plurality of latch circuits temporarily holding the spread data from the first selector, and a second selector being able to selectively output outputs from the sub spread data path units, whereby a circuit scale of the spread data path unit is decreased.

Abstract: A system and method for canceling interference present in a code-division multiple access (CDMA) channel signal received at a CDMA receiver that is caused by multipath components of a transmitted pilot channel signal or by soft handoff conditions is computationally efficient because it operates at symbol rates. The channel signal from which such multipath interference is canceled can be either a traffic (data) channel or the pilot channel itself. Interference signals are produced in groups corresponding to the fingers of the CDMA rake receiver. The interference signals corresponding to each finger are used to cancel interference in the other fingers.

Abstract: A system and method for transmitting a plurality of spread-spectrum signals over a communications channel having fading. The plurality of spread-spectrum signals are radiated by a plurality of antennas, with each antenna preferably spaced by one-quarter wavelength. A plurality of receiver antennas receive the plurality of spread-spectrum signals and a plurality of fading spread-spectrum signals. Each receiver antenna is coupled to a plurality of matched filters having a respective plurality of impulse responses matched to the chip-sequence signals of the plurality of spread-spectrum signals. A RAKE and space-diversity combiner combines, for each respective chip-sequence signal, a respective plurality of detected spread-spectrum signals and a respective multiplicity of detected-multipath-spread-spectrum signals, to generate a plurality of combined signals. The symbol amplitudes can be measured and erasure decoding employed to improve performance.

Abstract: The received radio signal comprises contributions from channels multiplexed by spread codes. A receiver with adapted filter (41, 42, , 4U) is assigned to each multiplexed channel to estimate the channel pulse response and determine first flexible estimations of a block of bits transmitted on the channel. In output of the receivers with adapted filters, the first flexible estimations are re-processed so as to take into account the inter-symbol interference and the interference caused by the other channels. The contributions of said interfering channels are evaluated on the basis of decisions taken on the values of the symbols and autocorrelation and intercorrelation values of convoluted spread codes with the estimated pulse responses of the channels.

Abstract: A spread-spectrum system with a base station and a plurality of user equipment. The base station has a plurality of spread-spectrum transmitters. Each spread-spectrum transmitter spread-spectrum processes data with a particular code-division-multiple-access (CDMA) code from a plurality of CDMA codes to generate a particular spread-spectrum signal The particular CDMA code has a zero correlation window. The spectrum transmitter transmits the particular spread-spectrum signal over the communications channel using radio waves. The plurality of user equipment has a plurality of spread-spectrum receivers. Each spread-spectrum receiver spread-spectrum processes, from the communications channel, the particular spread-spectrum signal with the particular CDMA code from the plurality of CDMA codes, to obtain the data.

Abstract: A mobile station is provided for receiving a spread spectrum, code division transmission from at least one transmitter, such as a base station. The mobile station contains a receiver for outputting data samples, and further contains a multi-tap ring matched filter. The ring matched filter is constructed to have first circuitry for storing an individual one of a received data sample into an individual one of a plurality storage registers such that a active data sample that has been stored for the longest period of time is overwritten with a most recently received data sample. The ring matched filter is further constructed to have second circuitry for serially shifting coefficient bits of at least one multi-bit spreading code relative to the storage registers for sequentially and simultaneously correlating the at least one multi-bit spreading code with a plurality of corresponding stored data samples, while significantly reducing power consumption by limiting state changes of flip-flops.

Abstract: A method and system are disclosed for facilitating the timing (e.g., the known relative timing differences) of base stations (BSs) in asynchronous CDMA mobile communications systems. A plurality of mobile stations (MSs) measure the relative time differences between various pairs of BSs, and these measurements are stored by the BSs. A source BS sends to an MS, in a neighbor list message, estimates of the relative time difference between the source BS and each of the BSs on the neighboring cell list. Each BS on the list can maintain a relative time difference estimate table, which can be updated continuously from the reports received from MSs. Subsequently, the BSs can send entries from this table to the MS in the neighbor list message. Using this novel technique, the BSs have known relative timing differences. Consequently, when the MS initiates a cell-search for a candidate BS, the MS already has an estimate of the timing of that BS as compared to its source BS.

Abstract: Despreading codes are switched at effective timings to perform despreading calculations by providing a rate difference between the first clock signal to input a spread signal to be subjected to the correlation detection to a data holding section and the second clock signal to switch a despreading code used to detect the correlation of the spread signal held in the data holding section.

Abstract: An improvement to a spread-spectrum receiver having a matched filter. A symbol sampler samples at the symbol time TS, a plurality of symbol samples from the matched filter. A relative-signal-level decoder decodes the plurality of received-symbol samples, generating a plurality of decoded-symbol samples. A noise sampler samples at a plurality of chip times kTC, but not at the symbol time TS, a plurality of noise samples from the matched filter, before, after, or a combination of before and after, a symbol sample. An erasure detector detects for each decoded-symbol sample from the plurality of decoded-symbol samples and from the plurality of noise samples, an erasure condition for the corresponding decoded-symbol sample, and generates an erasure signal. An erasure decoder erasure decodes the input data using the erasure signals from the erasure detector.

Abstract: A matched filter bank including a plurality of matched filters and a sampling and holding units commonly used by the total matched filters. Therefore, the circuit size is diminished. An inverting amplifier for the matched filter with a variable gain includes an input capacitance, an inverting amplifier connected to an output of the input capacitance, and a plurality of feedback capacitances connected between an input and output of the inverting amplifier. A plurality of switches are connected to input side of the feedback capacitances for alternatively connecting the feedback capcitanec to the input of the inverting amplifier or a reference voltage. The feedback capacitances connected to the reference voltage are invalid with respect to a composite capacitance of the feedback capacitance and have no influence to the amplifier.

Abstract: An analog input signal that is sampled at a predetermined rate is multiplied by a corresponding binary code sequence, i.e. “+1” or “−1” by the multiplier. The output of this multiplier is applied in conjunction with a signal supplied by the negative feedback circuit to the analog integrator. The quantization circuit quantizes the output signal of the analog integrator into N levels and outputs a digital word. This digital word is delayed by a unit time interval by a digital delay circuit and then processed by the above mentioned negative feedback circuit. As a result of this signal magnitude reducing process, the required integrating capacitance can be minimized without risks of saturation effects. Additionally, the output is already in digital form as required by the subsequent system blocks.

Abstract: A novel and improved method and apparatus for searching is described. This searcher combines the ability to search multiple offsets of single pilots, such as those found in the IS-95 system, with the ability to search multiple pilots, such as those found in a GPS location determination system. Both types of searching can be done in a single architecture combining the parallel computation features of a matched filter with the flexibility of allowing a variable number of coherent accumulations and a variable number of non-coherent accumulations to be performed at high speed for a wide range of search hypotheses in a resource efficient manner. This invention allows for parallel use of the matched filter structure in a time-sliced manner to search multiple windows. In addition, the searcher allows for optional independent Walsh decovering for each search window. The time-sharing approach allows for optional frequency searching of any offset.

Abstract: A high frequency communications system comprises eight multiplexed (112) spread spectrum channels with data in each channel transmitted using, for example, 32 semi-orthogonal codes to enable 5 bits of data to be sent for every coded symbol transmitted. The multiplexed data is connected to a phase shift key (PSK) modulator (117) to modulate an hf carrier. At the receiver, inband interference is removed by frequency excision (92, 128) or weighting, making use of the facts that the interference is generally narrow-band and the spectrum of the frequency components of the received signal should be symmetrical about the carrier frequency. The detected signal is Fourier transformed by an FFT processor (91) and then connected to an interference exciser (92, 128) where signal samples symmetrical about the carrier frequency are compared and any sample which exceeds the respective symmetrical sample by more than a predetermined threshold is excised or given a low weighting.

Abstract: A system and method for transmitting a plurality of spread-spectrum signals over a communications channel having fading. The plurality of spread-spectrum signals are radiated by a plurality of antennas, with each antenna preferably spaced by one-quarter wavelength. A plurality of receiver antennas receive the plurality of spread-spectrum signals and a plurality of fading spread-spectrum signals. Each receiver antenna is coupled to a plurality of matched filters having a respective plurality of impulse responses matched to the chip-sequence signals of the plurality of spread-spectrum signals. A RAKE and space-diversity combiner combines, for each respective chip-sequence signal, a respective plurality of detected spread-spectrum signals and a respective multiplicity of detected-multipath-spread-spectrum signals, to generate a plurality of combined signals. The symbol amplitudes can be measured and erasure decoding employed to improve performance.

Abstract: An apparatus and method allow receivers to quickly acquire a pseudorandom noise signal. A receiver advantageously detects frequency shifts using a compact parallel process hardware implementation of a Discrete Fourier Transform (DFT). The simultaneous detection of multiple frequencies allows the receiver to search the frequency range of the transmitted signal in larger increments of frequency, thereby increasing the speed of acquisition. One receiver does not use coherent integration before computation of the transform and advantageously maintains a flat frequency response. The flat frequency response of the DFT circuit enables searching of multiple frequency offsets without CPU intensive processing to compensate for frequency response variations. A receiver can include a Doppler correction circuit, which permits correlation data with frequency shift in the code to be non-coherently integrated among relatively fewer addresses or tap positions in memory.

Abstract: A receiver for and method of processing received signals comprising a linear combination of a plurality of signature signals having undergone some distortion. The receiver is comprised of a bank of correlators for receiving the signals, and a correlation shaper operating on a vector output from the bank of correlators. The bank of correlators may comprise a matched filter receiver or a decorrelator receiver. Optionally, a bank of detectors may operate on the vector output of the correlation shaper.

Abstract: A method for synchronizing a CDMA receiver to a transmitter when an adaptive antenna is utilized to receive transmitted data, wherein a receiving antenna system is adapted between a 360° reception angle pattern (i.e., an omni-directional pattern) and a fixed reception angle (i.e., a directional pattern) by permitting the receiver to identify a pilot signal having the largest magnitude. The receiver minimizes interference from other pilot signals by steering antenna pattern nulls toward other transmitters. As a result, the time required for the receiver to acquire a valid pilot signal is significantly reduced.

Abstract: A short PN code generating device in a mobile communication network having a N× CDMA communication system performing spreading at an N× chip rate using a short PN code of chip length N×2k and a 1× CDMA communication system performing spreading at a 1× chip rate using a short PN code of chip length 2k. The device generates a short PN code such that the N× CDMA communication system can distinguish at least the same number of base stations as the 1× CDMA communication system can distinguish. The device includes a sequence generator for generating an m-sequence having a chip length longer than the chip length N×2k to output an I-component short PN code; and a short PN code generator for switching the generated m-sequence at predetermined chip periods to alternately output the m-sequence as an I-component short PN code and a Q-component short PN code.

Abstract: A spread spectrum signal is processed after it is sampled at a selected sampling rate and tuned to a center frequency lower than the sampling rate and greater than zero. The signal is multiplied against a reference signal to produce a corresponding product output, and an accumulation output is formed by combining the product output with a phase-shifted version of the accumulation output.

Abstract: An audio data transmission and recording system and a recording medium according to the system. Gaps in the audio data are used to control the addition of spectrum-diffused data to the audio data. The gaps are also used to control demodulation of the spectrum-diffused data.

Abstract: Techniques are described for maintaining the orthogonality of user waveforms in multi-user wireless communication systems, such as systems using the code division multiple access (CDMA) modulation scheme in the presence of frequency-selective fading channels. Unlike conventional systems in which spreading is performed on individual information-bearing symbols, the “chip-interleaved block-spreading” (CIBS) techniques described herein spread blocks of symbols. A transmitter includes a block-spreading unit to form a set of chips for each symbol of a block of information-bearing symbols and to produce a stream of chips in which the chips from different sets are interleaved. A pulse shaping unit within the transmitter generates a transmission signal from the stream of interleaved chips and transmits the signal through a communication channel.

Abstract: A method and apparatus for enhancing the receiving and information identification functions of multiple access communications systems by employing one or more optical processors configured as a bank of 1-D correlators. The present invention is particularly useful in a DS/SS CDMA communications system, resulting in a multiuser CDMA system that approaches carrier to noise performance (C/N) as opposed to being limited by multiple access interference (MAI). The correlators are arranged in parallel to detect and/or demodulate the received signal, in conjunction with one or more complex algorithms to perform near-optimum multiuser detection, perform multipath combining and/or perform carrier Doppler compensation.

Abstract: An improved spread spectrum communication system includes a transmitter and a receiver utilizing a pilot channel for the transmission of pure rather than modulated PN codes for code acquisition or tracking purposes with a lower bit error rate. The pilot signal is used to obtain initial system synchronization and phase tracking of the transmitted spread spectrum signal. At the transmitter side, Walsh an orthogonal code generator, a Walsh modulator, a first PN code generator, a first band spreader, a second band spreader, finite impulse response filters, digital-to-analog converter, low-pass filters, an intermediate frequency mixer, a carrier mixer, a band-pass filter are used to transmit a spread spectrum signal.