Abstract: The invention relates to a data transmission method, a transmitter and a receiver in a system which utilizes the CDMA method, in which several users communicate simultaneously on the same frequency band, and in which each user has its own spreading code, and in which the information channel capacity of at least one user differs from the capacity of the other users, the receiver comprising converter means for converting a received transmission into a digital form, and a number of means for synchronizing and for calculating the characteristic required for a decision from the transmission of each received user.

Abstract: A peak detecting circuit capable of accurately detecting a peak of a time discrete signal without increasing a circuit scale. The peak detecting circuit detects a peak of a waveform of a time discrete signal by calculating an approximate function which approximates the waveform of the time discrete signal. A peak of the approximate function is detected according to parameters of the approximate function so that the peak of the approximate function is estimated as the peak of the waveform of the time discrete signal.

Abstract: A parallel digital matched filter is constructed which performs numerous simultaneous correlations of a received spread spectrum signal against various replica offsets of its spreading sequence. This allows for the rapid acquisition of the received signal code phase, and subsequent handoff to tracking for a multi-channel receiver. A novel matched filter computational architecture is utilized, in which common digital arithmetic elements are used for both acquisition and tracking purposes. As each channel is sequentially acquired by the parallel matched filter, a subset of the arithmetic elements are then dedicated to the subsequent tracking of that channel. This process is repeated, with the remaining available arithmetic elements accelerating the acquisition of the next channel, and so on, until all resources are allocated as tracking channels. Additionally, multiple data inputs and delay lines are present in this architecture, and are available for processing at each arithmetic element.

Abstract: The present invention is an apparatus for reducing transmission errors by a base station when transmitting a communication signal. An RF communication signal is received at the base station and analyzed for errors. A correction signal is then generated based upon the analysis. Prior to transmission of the communication signal from the base station, the communication signal is corrected using the correction signal.

Abstract: A VSB receiver and a method for processing a receiving signal in the same are disclosed, which is not subject to frequency offset. The VSB receiver includes an intermediate frequency signal generator generating an intermediate frequency band signal from a received signal; a demodulator generating a complex base band signal consisting of an I channel signal and a Q channel signal using the intermediate frequency band signal and at least one local carrier wave signal; and a complex base band matched filter filtering at least one of the I channel signal and the Q channel signal. In the VSB receiver, since a complex signal responds to a required channel of the I channel and the Q channel, it is possible to prevent performance of the system from being deteriorated by frequency offset.

Abstract: A system and method are provided for achieving slot synchronization in a Wideband CDMA system in the presence of large initial frequency errors. A FSC matched filter having a reduced coherence window is provided for reducing degradation of a symbol due to carrier phase rotation resulting from oscillator error, thereby preventing severe loss of signal energy at the peaks of the FSC matched filter output. Additionally, a circular sliding integrator is provided to combine the accumulated disbursed signal energies due to the oscillator error and multipath interference, thereby allowing easier identification of the time index representing the time slot boundary. Further, a sorter is provided for determining a predetermined number of time index candidates representing the time slot boundary, thereby increasing the possibility that the true time index boundary is sent to the second stage of synchronization.

Abstract: In a matched filter, a plurality of data holding circuits adapted to sequentially hold a plurality of straight binary data and a plurality of correlators are provided. Each of the correlators receiving one bit of a known code and one bit of a selected code as a 2-bit code outputs the straight binary data as it is when the 2-bit code is “00”, outputs the straight binary data after logically inverting when the straight binary data when the 2-bit code is “11”, and outputs exclusive OR values between the straight binary data except for its most significant bit and the most significant bit while outputting “1” for the most significant bit when the 2-bit code is one of “01” and “10”. Also, an adder adds output signals of the correlators and outputs an addition result as a correlation value.

Abstract: A spread-spectrum-matched-filter apparatus including a code generator, an in-phase-symbol-matched filter, a quadrature-phase-symbol-matched filter, an in-phase-frame-matched filter, a quadrature-phase-frame-matched filter, and a controller. The code generator generates replicas of a chip-sequence signal, which are used to set the symbol-impulse responses of the in-phase-symbol-matched filter and the quadrature-phase-symbol-matched filter. The in-phase-frame-matched filter and the quadrature-phase-frame-matched filter detect a despread-header-symbol-sequence signal and generate a maximum output signal which may be used as a data-start signal or for synchronizing the timing of the controller as to when to trigger sampling of the A/D converter, the output of the symbol-matched filters, detection of the data-symbol-sequence signal and other time-dependent processes.

Abstract: To simplify the structure of the demodulator and reduce the hardware scale in a code division multiple accessing communication apparatus. A plurality of base band received signals are multiplexed in a time division manner, so that one matched filter executes path searching or a time division multiplexing processing is executed for demodulation in a despreader. Or path searching and demodulation for a plurality of codes are executed with time division multiplexing of outputs from a plurality of code generators.

Abstract: An MMSE linear detector is implemented using a variable step-size Griffiths' algorithm. The received signal is sampled and stored. The stored samples are multiplied with components of a spreading sequence to provide products that are summed to provide a first output. The stored samples are also multiplied with components of a weight vector to provide products that are summed to provide a second output. A computing unit uses the Griffiths' algorithm to iteratively compute the weight vector. Another computing unit computes the step-size for each successive iteration of the Griffiths' algorithm based on the first and second outputs.

Abstract: A receiver for spread spectrum communication system receives a traffic channel and common control channel by a plurality of matched filters at least one of which is selectively available for the traffic or the common control channel. At the initial acquisition, a plurality of matched filters are used for receiving the common control channel. At the hand-over, a plurality of matched filters are used to receive traffic channels of the current base station and the base stations in the adjacent cells.

Abstract: An improvement to a spread-spectrum receiver at a bse station 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 filters the plurality of noise samples from the symbol sampler, to generate a noise estimate. A combiner circuit subtracts the noise estimate from the low-pass filter from the symbol sample from the symbol sampler, thereby generating a comparison signal. A magnitude device determines a magnitude of the comparison signal. A comparator has threshold voltage applied to a threshold input. The 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: Incoming signals in a receiver for Direct Sequence Code Division Multiple Access systems are despread using Offset-QPSK spreading as the transmitting spreading format combined with arbitrary data modulation formats, such as BPSK and QPSK. The receiver has a pseudonoise (PN) generator for generating a unique PN sequence signal. The PN sequence signal is divided into a real and an imaginary component. The complex input signal is divided into inphase and quadrature components. The inphase and the quadrature components of the input signal are downsampled to provide either two complex samples per chip period or one complex sample per chip period. In the latter case, the downsampling instants are delayed by a quarter of a chip period. Each downsampled complex signal is correlated with the corresponding segment of the complex PN sequence signal of the receiver.

Abstract: An improvement to a spread-spectrum base station 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, thereby 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 estimator processes the plurality of noise samples. The 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 thereby generates an erasure signal. An erasure decoder erasure decodes the input data using the erasure signals from the erasure detector.

Abstract: A high data rate, high processing gain, direct sequence spread spectrum system that transmits a BPSK or QPSK signal. The system FEC encodes and interleaves data which are collected and stored and forwarded N bits at a time by transmitting one of 2N pseudo random waveforms every time N bits are collected. The 2N pseudo random waveforms can be sent as an orthogonal, bi-orthogonal, or nearly orthogonal waveform. During acquisition, a plurality of product devices multiply a received spread-spectrum signal by a header chip-sequence signal. In each case, the header chip-sequence signal has a different delay, with each delay being at most one chip. Acquisition can also be achieved using a matched filter.

Abstract: In order to obtain the signals necessary for the formation of an interference signal corresponding to the multiple access noise, use is made both of the non-coherent part of the receiver, namely the differential demodulation device, and the coherent part thereof, namely the two matched filters performing the correlations. This gives a reliable, precise, clock symbol signal (Hs) and also the reconstituted data (D(I), D(Q)) and the amplitudes of the signals in the two channels (A(I), A(Q)). Formation then takes place of the correction signal by respreading the data (D(I), D(Q)) and the weighting the respread data by the amplitudes (A(I), A(Q)).

Abstract: A method of acquiring a transmitted pseudo noise (PN) code c(t) from a received signal r(t) that is data modulated. The method includes, for a BPSK modulated signal, multiplying the received signal r(t) by cos(&ohgr;0t) and sin(&ohgr;0t), respectively to produce in-phase and quadrature (I-Q) down converted signals. Then multiplying the I-Q down converted signals by the PN code c(t), having a second PN code phase, to produce f(t) and g(t) respectively. Thereafter, summing separate contiguous portions of f(t) and g(t) and multiplying the summed portions of f(t) and g(t) by a matrix. The matrix represents data patterns within an interval MTc that spans the separate contiguous portions of f(t) and g(t). Lastly, the results of the matrix multiplication are compared to a threshold value to determine if the first PN code phase is equal to the second PN code phase.

Abstract: A matched filter for use in a radio telephone receiver that receives Code Division Multiple Access (CDMA) signals. The matched filter produces precombinations of input values to significantly reduce the number of multiplication and addition operations, compared to conventional matched filters, required to produce a correlation value. This reduced number of required operations, along with a reduced number of delay elements required to despread CDMA signals, significantly reduces the overall power consumption of the matched filter. The use of such a matched filter in a device like a cellular phone, for example, would thus lead to longer battery life.

Abstract: A receiver for a spread spectrum burst signal having a predetermined period includes a time invariant matched filter for comparing an input signal to at least one reference signal based upon a pseudo-noise (PN) code and providing a stream of data values and a threshold comparator for comparing each of the stream of data values to a threshold to determine an acquisition time for the spread spectrum burst signal. The receiver may further include a contrast filter connected between the time invariant matched filter and the threshold comparator for varying the threshold based upon an interference level to reduce instances of false acquisition detections. Additionally, the receiver may include a window sampler for selectively sampling the data values based upon the acquisition time and the predetermined period.

Abstract: A spread-spectrum demodulator architecture is presented which utilizes parallel processing to accomplish rapid signal acquisition with simultaneous tracking of multiple channels, while implementing an integrated multi-element adaptive beamformer, Rake combiner, and multi-user detector (MUD). A matched filter computational architecture is utilized, in which common digital arithmetic elements are used for both acquisition and tracking purposes. As each channel is sequentially acquired by the parallel matched filter, a subset of the arithmetic elements are then dedicated to the subsequent tracking of that channel. Additionally, multiple data inputs and delay lines are present, connecting the sampled baseband data streams of numerous RF bands and antenna elements with the arithmetic elements. The matched filter/despreader processing is virtually independent of channel origin or utilization; e.g., CDMA users, RF bands, beamformer elements, or Rake Fingers.

Abstract: A spread-spectrum system having a transmitted data rate determined by an error rate syndrome at a spread-spectrum receiver. A demultiplexer demultiplexes input data into a plurality of data channels. A plurality of FEC encoders FEC encodes the plurality of data channels, as a plurality of FEC encoded channels. A plurality of spread-spectrum processors spread-spectrum processes the plurality of FEC encoded channels as a plurality of spread-spectrum channels. The plurality of spread-spectrum channels preferably uses a plurality of orthogonal or quasi-orthogonal chip-sequence signals to define a particular spread-spectrum channel. A combiner combines the plurality of spread-spectrum channels as a code-division-multiplexed signal. At a receiver, a plurality of spread-spectrum despreaders despreads the code-division-multiplexed signal into a plurality of despread channels. A multiplicity of adders is electronically controlled by an adder-control signal.

Abstract: A system and method for encoding and transmitting data with a spread-spectrum packet-switched system. Data to be transmitted by a packet transmitter are encoded for privacy and to restrict intelligent receipt of the data to the intended recipient. The encoded data is demultiplexed into sub-data-sequence signals which are spread-spectrum processed and then combined as a multichannel spread-spectrum signal. The multichannel spread-spectrum signal is concatenated with a header to output a packet-spread-spectrum signal which is transmitted over radio waves to a packet receiver. The packet receiver obtains timing for the multichannel spread-spectrum signal from the header. The multichannel spread-spectrum signal is then despread and multiplexed as received-encoded data. The received-encoded data is decoded by the intended recipient and stored in a receiver memory for output.

Abstract: A system and method for encoding and transmitting data with a spread-spectrum packet-switched system. Data to be transmitted by a packet transmitter are encoded for privacy and to restrict intelligent receipt of the data to the intended recipient. The encoded data is demultiplexed into sub-data-sequence signals which are spread-spectrum processed and then combined as a multichannel spread-spectrum signal. The multichannel spread-spectrum signal is concatenated with a header to output a packet-spread-spectrum signal which is transmitted over radio waves to a packet receiver. The packet receiver obtains timing for the multichannel spread-spectrum signal from the header. The multichannel spread-spectrum signal is then despread and multiplexed as received-encoded data. The received-encoded data is decoded by the intended recipient and stored in a receiver memory for output.

Abstract: A pseudo-noise generating apparatus capable of starting a pseudo-noise sequence from an arbitrary phase using compact processing circuitry. Tap selection patterns corresponding to a plurality of phase shift amounts are stored in advance in a ROM. By giving a phase shift amount to the ROM and setting the corresponding tap selection pattern in AND gates, the pseudo-noise sequence generated by the pseudo-noise generator is shifted in phase, and is loaded into a shift register. After setting a new phase amount in the ROM, the contents of the shift register are transferred into a shift register in the pseudo-noise generator. By repeating this operation, the desired phase shift is accomplished as a sum of a plurality of phase shift amounts.

Abstract: Herein disclosed is a matched filter for synchronizing a phase of an input wave signal with that of a desired wave signal, thereby making it possible to decrease the power consumption. The matched filter comprises a plurality of correlation units each having a multiplier and an integrator. The multiplier of each correlation units is designed to multiply an input signal by a predetermined coefficient at predetermined intervals in a predetermined operation cycle of the matched filter. The coefficient sequentially varies at the intervals. The integrator of each correlation units is designed to integrate the product obtained by the multiplier over the operation cycle into a correlation value. The matched filter further comprises control and multiplexer. The control means is designed to output a plurality of control signals at the intervals to direct the correlation units, respectively, to start operating.

Abstract: An improvement to a spread-spectrum code-division-multiple-access system, using a channel sounding signal from a base station (BS) to provide initial transmitter power levels for remote stations (RS). The base station has a BS-spread-spectrum transmitter for transmitting BS-spread-spectrum signals at a first frequency and a BS-spread-spectrum receiver for receiving RS-spread-spectrum signals at a second frequency. The RS-spread-spectrum signals are transmitted by the remote stations at the second frequency. The BS-spread-spectrum signals at the first frequency are outside the correlation bandwidth of the RS-spread-spectrum signals at the second frequency. The base station has a BS transmitter for transmitting a BS-channel-sounding signal at the same carrier frequency being used by the remote stations to transmit a spread-spectrum signal to the base station. The bandwidth of the BS-channel-sounding signal is much of the bandwidth of the BS-spread-spectrum signal.

Abstract: A system and method for encoding and transmitting data with a spread-spectrum packet-switched system. Data to be transmitted by a packet transmitter are encoded for privacy and to restrict intelligent receipt of the data to the intended recipient. The encoded data is demultiplexed into sub-data-sequence signals which are spread-spectrum processed and then combined as a multichannel spread-spectrum signal. The multichannel spread-spectrum signal is concatenated with a header to output a packet-spread-spectrum signal which is transmitted over radio waves to a packet receiver. The packet receiver obtains timing for the multichannel spread-spectrum signal from the header. The multichannel spread-spectrum signal is then despread and multiplexed as received-encoded data. The received-encoded data is decoded by the intended recipient and stored in a receiver memory for output.

Abstract: To improve the throughput of a direct spread-spectrum communication system transmitting and receiving signals multiplexed according to a data format having a simplex portion and a multiplexed portion, a transmission error ratio of ACK and NAK signals is decreased and the transmission method is changed according to the transmission path conditions and is achieved by controlling the number of multiplexed data in data packets or aerial diversity based on the results of a number of counts of NAK signals or the calculation of an ACK to NAK signal count ratio.

Abstract: A spread spectrum signal is detected at an unknown spreading signal phase by sampling the signal at a selected sampling rate and performing a despreading function on the sampled signal using multiple reference signals, each of which represents one of multiple search phases of the spreading signal. Accumulation outputs then are produced by combining each despreading output with a phase-shifted version of the corresponding accumulation output.

Abstract: A mobile communications system is provided for significantly reducing the time required to process a random access mobile-originated call. During call setup, a mobile station transmits a random access packet that includes a preamble and a plurality of fields. The information provided in these fields is used by the base station to facilitate a more efficient call setup and more quickly allocate channel resources. A system is also provided for detecting, identifying and receiving multiple random access requests. Each mobile station transmits one of a plurality of different preamble symbol patterns in a random access request packet. The base station receiver includes a plurality of accumulators, each of which is tuned to a different preamble symbol pattern. Consequently, the base station receiver can distinguish between simultaneous random access requests.

Abstract: A spread spectrum receiver having a smaller circuit scale is accomplished by a circuit construction wherein the number of taps is set to a number smaller than a spread factor, and a cyclic accumulation process for determining a correlation value of one symbol is executed by a circuit construction using an input sequence register block in common with an addition block of a spread spectrum receiver by MF according to the prior art.

Abstract: In order to time track an incoming signal, a receiver demodulates a first instance of a signal to produce a first set of energy values corresponding to a set of possible data values of the signal. The receiver also demodulates a second instance of the signal to produce a second set of energy values corresponding to the set of possible data values. The receiver combines the first and the second sets of energy values to determine a combined set of energy values. The receiver determines a first estimate of a most likely transmitted data value based upon the combined set of energy values. The receiver decovers an early set of despread samples of the first instance using a symbol corresponding to the first estimate to produce a first early energy value. The receiver decovers a late set of despread samples of the first instance using the symbol corresponding to the first estimate to produce a first late energy value.

Abstract: A device and method for a multiuser detection in a DS-CDMA system largely reduces an amount of data computation while reducing noise due to MAI. The method for a multiuser detection in a DS-CDMA system includes the steps of receiving a band-spread signal by a plurality of spreading codes respectively transmitted by each of multiusers, obtaining a plurality of sampled outputs from each of multiuser's messages by despreading the received signal with a matched filter, obtaining an MAI signal included in the plurality of sampled outputs by applying a minus (−) value of a cross-correlation value between the multiuser's spreading codes to the plurality of sampled outputs, removing the MAI signal from the sampled outputs by subtracting the MAI signal from the sampled outputs, and generating a binary data by comparing the sampled outputs from which the MAI signal is to be removed with a threshold value to recover the multiuser's messages.

Abstract: A system and method for handing off a remote unit from a first base station to a second base station, in a cellular spread-spectrum communications network, without loss of data. The remote unit transmits data to the first base station at a first data rate, and receives a first spread-spectrum signal having a first signal quality from the first base station. The remote unit monitors the first signal quality and compares the first signal quality to a plurality of signal qualities of a respective plurality of received-spread-spectrum signals. The remote unit initiates handoff when any of a number of predetermined criteria are met. Upon initiating handoff to the second base station, the remote unit stores the data that would otherwise have been transmitted. Once handoff is complete, the remote unit transmits the stored data to the second base station at a second data rate, with the second data rate greater than the first data rate.

Abstract: The present invention has an object to provide a spread spectrum communication system for heightening the speed of communication. The present invention transfers the first PN code sequence itself as the first component, adds and transfers zero or more instances of the second PN code sequence given a phase difference as the second component, and defines an information for transmitting by the number of the second PN codes corresponding to a cycle of said first PN code sequence.

Abstract: A code division multiplex communications system comprising: receiving circuit for receiving a radio wave and transforming the radio wave to an electric signal; delaying circuit for sequentially reading the electric signal at a timing of a clock pulse; switching circuit for shutting off a drive current of the delaying circuit at an OFF timing of the clock pulse; adding and subtracting circuit for adding and subtracting outputs of the delaying circuit in accordance with a spread code; and reproducing circuit for reproducing a transmission signal on the basis of an output of the adding and subtracting circuit. RCS95-120 is similar with respect to a point that an analog LSI matched filter is constructed by a slide capacitor system.

Abstract: In one aspect, the present invention provides a low power consumption matched filter. The signal received at an input terminal is input to a shift register having stages equal to the spread code length number after conversion into digital signals in an A/D converter. The outputs of the shift register stages are input to XOR circuits set corresponding to each stage, so that XOR operations are performed between the outputs and corresponding spread code bits d1 to dN. The outputs of the XOR circuits are analogously added in an analog adder and output from an output terminal. In another aspect, a filter circuit uses an analog operation circuit to prevent lowered operational accuracy caused by residual charge. Input analog signals successively undergo sampling and holding in sample-and-hold circuits, are multiplied by coefficients stored in a shift register by multiplication circuits, and added in an addition circuit.

Abstract: A spread spectrum communications system is provided for reducing the number of required matched filters to simplify the configuration associated with the reception. In a spread spectrum transmitter, a plurality of spread channel signals are synthesized by shifting their respective phases by a time sufficiently shorter than one symbol period. In a spread spectrum receiver, a plurality of spread code sequences are set one by one at a tap of a single matched filter in one symbol period in a time division manner to recover transmitted data.

Abstract: A system and method for encoding and transmitting data with a spread-spectrum time-division-multiple-access (SS-TDMA) system. Data to be transmitted by a SS-TDMA transmitter are sent within a particular specified group of time slots. Random packets also can be sent by transmission during an open time slot. The TDMA data are demultiplexed into sub-data-sequence signals, each of which are spread-spectrum processed and then combined as a multichannel, BPSK, QPSK or QAM spread-spectrum signal. The multichannel spread-spectrum signal is concatenated with a header to output a packet-spread-spectrum signal which is transmitted over radio waves to a packet receiver. The packet receiver obtains timing for the multichannel spread-spectrum signal from the header. The multichannel spread-spectrum signal is then despread and multiplexed as received-TDMA data. The received-TDMA data are selected from a particular time slot by the intended recipient and stored in a receiver memory for output.

Abstract: In a first embodiment of the invention, a concatenated preamble code is formed by a kronecker product between two subcodes of the same or different lengths. The subcodes have favorable correlation properties and may be Barker codes, minimum peak sidelobe codes, Gold codes, Kasami codes, Boztas codes, or other codes. At the receiver a two-stage processor is used to detect the concatenated preamble code. The two-stage processor comprises a series of two filters, one of which is preferably a mismatched filter. In another aspect of the invention, a repeated codeword preamble is formed from a series of the same repeated short subcode. The short subcode may be an augmented or truncated odd-length code. At the receiver a single matched filter is preferably used to generate a series of spikes separated by the period of the subcode. An alert/confirm detector non-coherently adds together individual correlation spikes and reject false alarms.

Abstract: In a first embodiment of the invention, a concatenated preamble code is formed by a kronecker product between two subcodes of the same or different lengths. The subcodes have favorable correlation properties and may be Barker codes, minimum peak sidelobe codes, Gold codes, Kasami codes, Boztas codes, or other codes. At the receiver a two-stage processor is used to detect the concatenated preamble code. The two-stage processor comprises a series of two filters, one of which is preferably a mismatched filter. In another aspect of the invention, a repeated codeword preamble is formed from a series of the same repeated short subcode. The short subcode may be an augmented or truncated odd-length code. At the receiver a single matched filter is preferably used to generate a series of spikes separated by the period of the subcode. An alert/confirm detector non-coherently adds together individual correlation spikes and reject false alarms.

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 high frequency signal received by an antenna is converted into a base-band signal through frequency conversion and quadrature detection in a radio circuit. Through search processing of the base-band signal in a timing control circuit, timings for a plurality of paths are detected, whereby first and second replica code timing indicating signals, a timing pulse, and first and second delay time indicating signals are generated. In first and second replica code generators, first and second replica codes are generated at timings indicated by the first and second replica code timing indicating signals, respectively. In first and second correlators, a correlation value of the base-band signal and the first replica code and a correlation value of the base-band signal and the second replica code are determined, respectively. In first and second synchronous detectors, output signals of the first and second correlators undergo synchronous detections, respectively, whereby first and second symbols are outputted.

Abstract: According to a spread spectrum communication synchronization acquisition demodulating apparatus which can acquire synchronization timing and immediately track variation of the synchronization timing irrespective of lots of noise, in a synchronizing circuit 100, a reception signal form an antenna is converted to a base band signal in a local oscillator 1 and an LPF 2, and sampled in S/H 3. In a correlator 4, the spreading code of the reception signal is multiplied by the symbol thereof to obtain a correlation value. In a symbol integrator 5, the correlation value is demodulated on the basis of the theoretical value of the symbol corresponding to the correlation value or the judgment value after demodulation, and integrated over plural symbols to obtain a power value.

Abstract: A digital matched filter for a CDMA radio comprises a digital delay line having a plurality of successive delay stages adapted to receive a digital signal and propagate the digital signal therethrough at a fixed rate. A correlator is coupled to the digital delay line to correlate the digital signal to a predefined spreading code to provide a correlation signal representing a degree of correlation of the digital signal to the spreading code. A window logic unit is coupled to the correlator to enable operation of the correlator only during successive discrete time periods of the correlation signal corresponding to a high degree of correlation of the digital signal to the spreading code.

Abstract: In a time diversity radio communications system, quadrature-modulated spread spectrum signals of different mutual time delay are combined into a code division multiplex signal and up-converted to a radio-frequency signal and transmitted. At a receive site, the signal is received by an antenna and down-converted to recover the code division multiplex signal. Quadrature-modulated component signals contained in the recovered code division multiplex signal are converted to baseband signals which are then time-aligned with each other. The time-aligned baseband signals are multiplied respectively by complex weighting factors and are combined together to produce an input signal for an adaptive equalizer. This input signal is also applied to an AGC amplifier where it is amplified and applied to correlation detectors where correlations between the amplified signal and the baseband signals are detected and the complex weighting factors are derived respectively from the correlations.