Abstract: Linear space-time multiuser detectors are described that combine array processing, rake detection, and multiuser detection and that satisfy a minimum mean-squared error criteria. Both embodiments can be implemented adaptively so as to account for unknown sources of interference. The adaptive implementation of the first embodiment of a linear space-time detector requires explicit estimates of the channel coefficients. On the other hand, the adaptive implementation of the second embodiment does not require these estimates since they can be adaptively obtained. Both of these detectors provide significant performance advantages over single-user space-time detectors and over multiuser detectors which do not account for CDMA interference from unknown sources.

Abstract: A CDMA synchronous acquisition circuit for receiving a CDMA signal and performing synchronous acquisition on the CDMA signal, comprises a receiving unit for receiving a signal and decoding the received signal to a reception base band signal which is spread-modulated in a CDMA mode, a correlation circuit for calculating a correlation value for the received base band signal every timing within one chip of a spread code by a correlator, and means for detecting the maximum value of the correlation value to estimate the spread code generation timing of a spread-modulated transmission base band signal within a precision of one chip of the spread code, wherein the correlator includes offset removing means for removing a DC offset component due to unbalance of the code balance of the spread code.

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: 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 shift register 22 is normally generating recurrence spreading codes and, when actual state data of the shift register 22 and the state data stored in the reset data register, initial data stored in the initial data register 24 beforehand is fed to the shift register 22. As a result, the shift register 22 is initialized and generates recurrence spreading codes. No counter need determine the timing of restoration of the shift register 22 to the initial state, and thus no spreading code phase deviation due to any count deviation occurs. Thus, preventing phase deviation of spreading codes utilized for spread and despread of communication data.

Abstract: A burst classifier is useful in a digital communication system transmitting a signal burst of a plurality of different burst types. The burst classifier includes a plurality of filters associated with the plurality of different burst types, respectively. Each filter generates correlation data based on the signal burst and a respective plurality of reference signals offset by a plurality of time offsets. The respective pluralities of reference signals are indicative of a corresponding burst type of the plurality of different burst types. A comparator then analyzes quantities based on the correlation data from each filter to determine the burst type of the signal burst.

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 method for determining a fading correction factor to be used for correcting a sample of a power delay profile of a received signal in a communication system, the fading correction factor associated with a fading channel characteristic through which the received signal propagates, includes estimating a number (N) of complex samples, obtaining fading channel autocorrelation sequence (R(n)) of the fading channel for a plurality (n) of complex samples, the number of the plurality (n) of complex samples corresponding to the number (N) of complex samples, and computing the fading correction factor based on the number (N) of complex samples, autocorrelation sequence (R(n)), and the number of the plurality (n) of complex samples.

Abstract: A compact and easily-assembled circuit for a complex despreading system, arranged such that the circuit does not contain pairs of adders at the output area. The configuration of the circuit enables the addition and subtraction of different signal components to occur before the multiplication stage and not at a pair of adders located at the output area The complex despreader system employs a complex matched filter at a receiver for despreading received signals with a QPSK system in the primary modulation and a BPSK system in the secondary modulation modulated at a transmitter. The input area of each matched filter of I and Q channels includes a pair of adders. One adder generates a first signal having a positive in-phase and a positive quadrature component. The other adder generates a second signal having a negative in-phase component and a positive quadrature component.

Abstract: This invention provides a spread spectrum signal demodulator in which a noise component included in respective demodulation symbols is reduced and an effect of interference removal is further improved. Symbol decorrelating means detect correlations between spread codes allocated to spread spectrum signals to be removed and a receiving signal. A symbol deciding means 121 synthesizes one or the plurality of one symbol correlation values b1 to bk in common phase, namely, diversity-synthesizes them so as to decide a symbol. As the symbol decision, hard decision or soft decision can be used. Correlation modification means input the one symbol correlation values b1 to bk output from the symbol decorrelating means and the symbol decided result output from the symbol deciding means 121 thereinto, and modify the symbol correlation values b1 to bk. The modified symbol correlation values d1 to dk are transmitted into interference replicating means so as to be spectrum-spread by corresponding spread codes.

Abstract: A synchronization circuit with correlated signal is capable of generating synchronizing signals to provide a stable correlated signal when correlation processing is conducted by digital sampling and/or even when multiplexing is conducted and a low spread factor is preset in the direct spread spectrum telecommunication system. A discriminator compares a correlated signal represented by the root of the sum of the squares of the input signals with a predetermined threshold. A processing unit generates a signal when an output which does not exceed the threshold in a unique delay interval preset in a multiplexing block so that one output signal is obtained in one period of spreading. An initial synchronization circuit establishes a synchronization relationship between signals from the processing unit. A synchronization counter causes either of a correct lock counter or error lock counter to operate via a determining unit to synchronizing pulses in a synchronization relationship with correlation.

Abstract: A spread spectrum receiver uses a comparison of the magnitude of the code correlation amplitudes at equal power at a one chip spacing to the magnitude at a central position there between to determine if multipath interference is present. The lead or lag error from constructive or destructive multipath interference may also be determined. Inaccuracies due to such interference may then be corrected or minimized by, for example, determining the residual code phase error and/or the prompt or accurate code phase delay.

Abstract: CDMA communication over multiple channels by phase shifting at baseband and then RF modulating without a phase shift. Total number of baseband filters is reduced by summing channel components prior to baseband filtering.

Abstract: A method and an apparatus for decoding trellis coded direct sequence spread spectrum communication signals are provided. A transmitted QPSK signal is received. Binary phase-shift keyed (BPSK) despreading is performed on the QPSK signal. The BPSK despreading comprises correlating the in-phase and the quadrature components of the received QPSK signal with independent PN sequences for the each of the in-phase and the quadrature components. The despread signal is then demultiplexed, and the pilot signal and the BPSK data signal are recovered. The recovered pilot signal is used to provide a channel phase estimate and a channel magnitude estimate. The recovered BPSK data signal is demodulated, despread, and decoded. The despreading and decoding comprises determining a number of cross-correlation terms of the received signal using a number of transmitted biorthogonal Walsh sequences. The cross-correlation terms are used as the branch metrics in a maximum likelihood decoding algorithm.

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 system and method for adaptive-power control of a spread-spectrum transmitter of a mobile station operating in a cellular-communications network using spread-spectrum modulation. A mobile station transmits a first spread-spectrum signal. A base 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. The base station also has a correlator for despreading the AGC-output signal, a power-measurement circuit responsive to processing the received signal with the despread AGC-output signal for generating a received-power level, a comparator coupled to the power-measurement circuit for generating a comparison signal by comparing the received-power level to a threshold level, a transmitter for transmitting a second spread-spectrum signal, and an antenna.

Abstract: A method of searching reverse traffic channels in a code division multiple access (CDMA) mobile radio communication system for allowing for acquisition of reverse traffic channels without increase or decrease of size of a search window for traffic channels, the method comprising the steps of: storing an offset by a propagation delay after acquiring a reverse access channel; determining whether or not a pseudonoise (PN) random delay is employed for the reverse access channel and, when the PN random delay is used, calculating the PN random delay using a hash function with a factor of an electronic serial number (ESN) transmitted from a mobile station; computing the stored offset and the PN random delay and setting a new offset to a result of the computing; setting a center of a search window for searching the reverse traffic channel to the new offset and establishing the search window; and searching a reverse traffic channel preamble with the established search window.

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: In a spread spectrum communications system, method and apparatus are provided for reducing transmission error and power consumption despite an increase in sampling. There are serially provided 4k (k denotes a spreading factor) shift registers (1) to (4) to deal with at most four samples to develop input spread signals, which are multiplied by spread-code replica signals from a replica generator. Sums &pgr;1 to &pgr;4 of respective k products are obtained. An output of a correlator is obtained by further adding the sums. At this time, the shift registers (1) to (4), adders and the replica generator are controlled in response to a control signal depending upon the number of samples.

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: An adaptive CDMA sequential detection method is provided. The method permits the use of the sequential detection process to determine an unknown spreading code in an environment where the signal to noise ratio of the received signal varies. A communication system, such as W-CDMA, provides a periodic reference signal that the receiver can demodulate without the spreading code. The reference signal is used to estimate and constantly update the signal to noise calculation. From this estimate a bias is updated for use in the sequential detection of the spreading code. A system to update the CDMA sequential detector bias value is also provided.

Abstract: A pseudo-noise generator (516) generates an on-time component, an early component and a late component of a pseudo-noise code signal in response to an error signal. The on-time component is routed to a deinterleave and demodulate device (210) which demodulates and decodes baseband signals from received spread spectrum signals. An adder (518) subtracts the early component from the late component to form a summation signal. A multiplier (520) multiplies the summation with the received signal to form a product signal. An integrator (522) integrates the product signal to form the error signal. The error signal is fed back into the pseudo-noise generator (516) to fine tune the on-time component, the early component and the late component of the pseudo-noise code signal. As a result, a spread spectrum signal is demodulated and decoded using only one correlator (504) instead of two.

Abstract: A spread spectrum receiver uses a comparison of the magnitude of the code correlation amplitudes at equal power at a one chip spacing to the magnitude at a central position there between to determine if multipath interference is present. The lead or lag error from constructive or destructive multipath interference may also be determined. Inaccuracies due to such interference may then be corrected or minimized by, for example, determining the residual code phase error and/or the prompt or accurate code phase delay.

Abstract: A CDMA chip synchronization circuit is provided for a mobile communications system employing a wide band CDMA method, for example, a direct spread code division multiple access (DS-CDMA) method. The circuit is designed to perform detection of multipath receiving timing, particularly synchronous tracking, under a low Eb/No environment where multipaths are received in an overlapping manner. Herein, a radio receiver converts radio frequency signals to digital base band signals, and a search section detects a receiving timing with respect to multipath components contained in the digital base band signals. The detected receiving timing is used as a center position for receiving on a time axis. The radio receiver is connected with multipath receivers, each of which contains a number of correlators which produce correlation values between the multipath components and dc-spreading codes which are delayed by different delay times respectively.

Abstract: A parallel M-sequence generator is disclosed which outputs an identical bit stream of a serial M-sequence generator of equal chip length. In a parallel N-bit implementation, the first N bits of the sequence are read at the output, the remaining bits are shifted, and the new N bits are generated, all in one clock cycle. The effect of obtaining N bits at the output is to multiply the present contents of the shift register by a companion matrix of the Nth order. Linear combining elements (e.g. XOR gates) are selectively positioned to combine the contents of various delay elements of the parallel structure and feedback the results to other delay elements in order to produce the identical output of the serial structure.

Abstract: The present invention provides a system and method for radio communications wherein the transmitted signals include an intermediate frequency in addition to a carrier frequency to aid in demodulation of data modulated on the signals and regulate the local oscillator frequency at the receiver. The invention greatly reduces the number of components required to implement a radio, and in particular, a direct sequence spread spectrum radio, reduces the frequency stability requirement at the transmitting and receiving ends of the communication, automatically tracks changes in the transmission signal after transmission, and permits the use of a single frequency reference to provide all required frequencies to operate both the receiver and the transmitter in each radio.

Abstract: A pull-in circuit of the present invention which can shorten the time of the pull-in operation. The pull-in circuit comprises: a pseudo-random pattern operating circuit for operating an operated pseudo-random pattern on the basis of consecutive bits of the parallel receiving data; a comparison circuit for comparing the operated pseudo-random pattern with a receiving pattern of the receiving data corresponding to the operated pseudo-random pattern; a one-shot circuit for passing a first pulse outputted from the comparison circuit when the operated pseudo-random pattern is coincident with the receiving pattern; a parallel pseudo-random pattern generation circuit for generating the reference parallel pseudo-random pattern when the first pulse passes through the one-shot circuit; a delay circuit for delaying the receiving data; and a bit error detection circuit for detecting a bit error, which compares the receiving data outputted from the delay circuit with the reference parallel pseudo-random pattern.

Abstract: In a spread spectrum receiver, when a preliminarily set integration period for integrating a correlated power of a received signal is significantly offset with respect to a fading period, accurate follow-up of a path becomes difficult to lower synchronization acquisition ability. To avoid this, in a fading period computing unit, an offset of the transmission power is obtained from a transmission power control information extracted by a decoder, correlated power calculation is performed for deriving the fading period on the basis of the result of the correlated power calculation. According to this fading period, the integrated period is determined to accurately perform synchronization acquisition by performing integration of the correlated power depending upon the fading period.

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: 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 direct sequence spread spectrum receiver samples an incoming signal and stores the sample in memory. Prior to sampling and storage, the incoming signal is translated to an IF signal. Also prior to storage, the IF signal is corrected for a frequency offset signal. The frequency offset may be caused by many sources, Doppler shift or local oscillator error, for example. Once the signal is corrected for the frequency offset, the signal sample is stored in memory. The signal sample is read from memory as necessary to process the signal. Such a receiver is useful in global positioning satellite (GPS) signal processing where the incoming signal contains several satellite transmissions encoded with CDMA encoding.

Abstract: A system and method for a synchronizing acquisition of a transmitted signal with a local code in a code modulated communication system. The local code is comprised of a replica of the transmitted code. Samples of the transmitted code are correlated with the local code and resulting periodic output samples having indexes are compared with a threshold. Selected indexes of the samples exceeding the threshold are stored and verified for synchronization. Stored correlation indexes which exceed the threshold are combined, and a responder achieves synchronization between transmitted signal and the local code.

Abstract: A method for synchronization of a receiver to a direct sequence spread spectrum (DS-SS) signal in a telecommunications system. A verification process is performed in the receiver upon initial detection of a first DS-SS signal prior to attempting synchronization to a second signal. In the verification, a window search is performed in a window centered on the PN phase of the initially detected first signal. A number K of search passes are made, each on M PN offsets. At least one parameter for each of the K window search passes is saved. The at least one parameter from each pass is then processed according to a predetermined algorithm. Based on the results of the algorithm, a decision is made as to whether or not to attempt synchronization to the second signal or to restart the search.

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 receiving apparatus is disclosed which comprises: a receiving circuit for receiving a radio wave signal including a pilot signal and data signal respectively spectrum-spread and converting the received radio wave signal in a base band signal; a Doppler frequency prediction portion for predicting a Doppler frequency due to a fading; a correlation detector including pilot signal PN code generation circuit for detecting a correlation between the pilot signal in the base band signal and a pilot signal PN code from the pilot signal PN code generation circuit every data length of the pilot signal; a correlation length changing portion for outputting a portion of the detected correlation with a length of the portion of the detected correlation varied in accordance with the Doppler frequency from the Doppler frequency prediction portion; and a demodulator for demodulating the base band signal to detect and output the data signal with a distortion of the data signal due to the fading compensated in accordance with t

Abstract: A correlation system for use in wireless direct sequence spread spectrum systems includes a RF down converter which receives an encoded RF signal and generates therefrom analog in-phase (I) and quadrature (Q) signal components. These components are digitized and the digitized signals are then passed to each of the high precision correlator circuit and a low precision correlator circuit. The low precision correlator circuit consist of a bank of a plurality of low precision correlators which receive the I and Q signal components as inputs and correlates the same with progressively phase shifted or delay pseudo noise (PN) codes. A low precision correlation circuit locks on to the appropriate PN code phase shift or delay and applies the same as a reference PN code to the high precision correlation circuit for data acquisition and demodulization.

Abstract: A communication system facilitates multi-rate data transmission by using a set (N) (210) of spreading codes from which a subset (n) (214) of the spreading codes is dynamically selected based on a first set of bits from source digital information to be transmitted. The subset (214) of spreading codes are simultaneously transmitted and used for coding a second set of bits from the source digital information. A receiver has correlators (306-309) to correlate each of the set of spreading codes with a received spread spectrum signal (302) to produce correlated signals. A code subset estimation circuit (312) is coupled to each correlator (306-309) and determines the magnitude of each of the correlated signals. The code subset estimation circuit (312) selects a subset of spreading codes from the set of spreading codes based on the magnitude of all correlated signals and determines the polarity of the subset of codes to decode the encoded received data.

Abstract: A delay diversity processor for use in receiving direct sequence spread spectrum data utilizes multipath signals to enhance bit synchronization performance by integrating the magnitude of each multipath signal to allow for erratic fluctuations in the multipath signal. As a result, the receiver is less prone to sudden signal strength variation that might trigger erroneous bit resynchronization. The delay diversity processor comprises a first circuit which determines a magnitude value for each of a plurality of correlated signal samples of individual data bits of plural data streams of the received spread spectrum data. A second circuit integrates each of the magnitude values over a period of time corresponding to receipt of a plurality of the individual data bits. The integrated magnitude values provide a measure of confidence of a particular one of the correlated signal samples with respect to remaining ones of the correlated signal samples.

Abstract: A maximal correlation symbol estimation (MCSE) method for estimating the symbols that are modulating an information signal component of a received signal, which can be applied to received signals that additionally contain an interference signal component, is disclosed. The method is achieved by correlating the received signal with all possible reference signals, each reference signal being one of a closed set of all possible information signals recognized by the given digital modulation scheme, and selecting as an estimate of the information signal the reference signal whose correlation with the received signal most closely resembles a weighted average of correlations between previously estimated information signals and their corresponding received signals. Demodulators that implement this method are adapted to perform many functions, including the estimation of symbols modulating frequency modulated (FM) received signals prior to the signals being FM demodulated.

Abstract: A receiver for detecting spread spectrum binary data particularly on a power line in the presence of channel distortion. In one embodiment a standard pattern ideally suited for minimal distortion in the channel is used in conjunction with an alternate pattern which is developed to better detect carrier and data in the presence of certain channel distortion. The receiver switches between the standard and alternate pattern to provide improved detection. In another embodiment an adaptive pattern is used which is developed from the receive signal. For instance, the signal over several bit times is averaged to provide a pattern which is correlated with a receive signal.

Abstract: A method for determining an optimum number (Nopt) of complex samples for coherent averaging of a complex signal S(n) in a code division multiple access communication system includes estimating an initial number (Nint) of complex samples, obtaining fading channel autocorrelation sequence (R(n)) for a plurality (n) of complex samples, the plurality (n) number of complex samples corresponding to the initial number (Nint) of complex samples, computing a constant (K) based on the autocorrelation sequence (R(n)) and the plurality (n) of complex samples, substituting the initial number (Nint) of complex samples for the optimum number (Nopt) of complex samples if the constant (K) is equal or substantially equal to zero.

Abstract: A modulation/demodulation system and method comprising transmitting structure having first and second PN generators which produce distinct, synchronized, first and second PN sequences. A tapped delay line generates a plurality of symbols from the second PN sequence, each symbol corresponding to an offset of the second PN sequence by one or more chips from the epoch of the first PN sequence. A plurality of output taps are associated with the tapped delay line, with each tap corresponding to one of the symbols. A symbol selection device associated with the output taps selects from amongst the symbols based upon one or more message signal bits. The selected symbols and first PN sequence are applied to separate channels of a modulator to modulate a carrier signal. At a destination, first and second local PN generators generate first and second PN sequences which correspond to the first and second PN sequences in the transmitting structure.

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: The invention relates to a method and an arrangement for implementing a bank of correlators, corresponding to a set of Orthogonal Gold codes, in a receiver used in a Direct Sequence Code Division Multiple Access system (DS-CDMA). The bank of correlators generates N correlation values (CV.sub.0, . . . , CV.sub.N-1) from N received symbols (s.sub.0, s.sub.1, . . . , s.sub.N-1) in a sequence. The received symbol sequence (s.sub.0, s.sub.1, . . . , s.sub.N-1), where each symbol has been spread by an Orthogonal Gold code respectively, is buffered (401). The buffered symbol sequence is multiplied (402) element-by-element with an arbitrary sequence (a.sub.0, a.sub.1, . . . , a.sub.N-1), in order to obtain a set of products (s.sub.0 *a.sub.0, s.sub.1 *a.sub.1, . . . , s.sub.N-1 *a.sub.N-1). Said arbitrary sequence is the same sequence used when generating the Orthogonal Gold Codes. The set of products (s.sub.0 *a.sub.0, s.sub.1 *a.sub.1, . . . , s.sub.N-1 *a.sub.

Abstract: A cell search circuit which does not invite an increase in search time, even if coherent integration is performed, and which minimizes an increase in the scale of the circuitry. The circuit comprises a spread signal generator having a phase shifting function, a multiplier for multiplying an output of the spread signal generator by an input signal, a ring buffer accumulating results of correlation, performed a number of times, in order to perform coherent integration over a plurality of signals, and an accumulator constructed by a single-signal portion of the ring buffer and an adder. Integration is performed over a length of time the same as unit-signal duration prior to spreading, coherent integration is performed by summing results of time integration of each signal, which results have been accumulated in the ring buffer, and the shifting operation of the spread signal generator is controlled based upon results of coherent integration.

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: A code acquisition circuit for acquiring code synchronization between an n-chip spreading code of a received spread spectrum radio signal and an n-chip local reference code generated by a code generator within a receiver, includes a variable delay means which operates to introduce a delay shift into the said received radio signal. A correlator operates to correlate n-chips of the local reference code with n-samples of the received signal communicated thereto, and generates a correlation signal representative of a result of the correlation. A code acquisition controller operates in combination with the correlation signal to maintain the delay shift for at least one correlation and thereafter to change the delay shift, wherein the delay shift is a fraction of one chip period.

Abstract: Enabling reception quality to be improved and the capacity in terms of the number of simultaneous users in a cell to be increased, and speeding up the establishment of spreading code synchronization and the convergence of weighted coefficients, by feedback controlling weighted coefficients such that desired signal power to interference power ratio (SIR) becomes maximum. A coherent adaptive diversity configuration is employed to which absolute coherent detection is applicable. Adaptively feeding weighted coefficients back to diversity branches makes it possible to reduce the influence of the interference power from other users, and thus to increase the capacity in terms of the number of simultaneous users in the cell. Furthermore, the direction that provides the maximum received SIR is determined while rotating antennas in a state of having directivity with a predetermined angle range.