Abstract: The present invention provides an efficient means of estimating symbols transmitted in a multi-user environment in overloaded or super-saturated conditions by employing a deferred decorrelating decision feedback detector. In one embodiment, the present invention comprises a parameter estimation unit, filter bank, overloaded whitener and decision tree-based hypothesis testing. Parameter estimation defines the matched filter bank, whitening filters, and the terms of the hypothesis testing module. The whitening filter partially decouples co-channel interference and partially whitens the noise. The decision tree approach defers decisions until more evidence is accumulated and is a generalization that encompasses the jointly optimal maximum likelihood detector as well as the simpler decision feedback detectors.

Abstract: A complementary code keying (CCK) demodulator used in a RAKE receiver receiving CCK symbols in a multipath environment computes multipath interferences (MPIs) required for canceling intra-codeword chip interference (ICI). The algorithmic structure jointly computes the ICI of a plurality of possible codewords. The algorithmic structure is similar to the optimal architecture required for CCK correlation computations. The similarity between these two structures allows for the use of the same hardware at different times to compute MPIs and to compute the CCK correlation of a plurality of possible codewords.

Abstract: A digital matched filter receives an input signal in natural order, correlates the input signal against a code and generates a filtered output signal in a permuted order with respect to the input signal. The code is a factorization of a first and second patterns. The filter includes a first filter to correlate against the first code and a second filter to correlate against the second pattern. A memory is included to store intermediate values produced from the first filter correlation operation. Certain ones of the intermediate values are selectively retrieved from memory in accordance with a unique addressing scheme for each second filter correlation operation. More specifically, the addressing scheme allows retrieved intermediate values to be reused in successive second filter correlations. The permuted order outputs of the filter are of no concern in many applications, like cell searching, where buffering is available.

Abstract: A synchronization code detecting apparatus is designed for synchronization code detection in cell search in a code division multiple access (CDMA) system. The synchronization code detecting apparatus mainly includes a compensation unit for providing frequency offset compensation to the incoming signal and for determining a plurality of sampling points of the incoming signal. A plurality of sub-detecting units is coupled to the compensation unit for detecting a synchronization code of the incoming signal transmitting from the compensation unit. A selection unit is coupled to the output of each sub-detecting unit for selecting a plurality of slot boundaries as a plurality of candidates to be forwarded to a second processing stage. Consequently, the synchronization code detecting apparatus effectively reduces the effect of clock offset in the system without increasing the hardware complexity and power consumption.

Abstract: A signal received by a base station is fed to a set of filters matched to spreading codes allocated to pilot channels originating from radio terminals. The outputs from the matched filters are processed so as to estimate parameters comprising, for each channel, eigenvectors representing propagation paths associated with respective amplitudes of reception along these paths. The processing of the output signals from the matched filters comprises an estimation of parameters for a first channel received with a fairly high power by the base station, a correction of the output from the matched filter of a second channel having less energy, taking account of at least one of the eigenvectors of the first channel, and an estimation of parameters for this second channel on the basis of the modified output from said matched filter.

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 receiver for detecting, tracking and combining multipath components spanned over several symbol periods employs signal register arrays, a reference signal generator, matched filters, a signal combiner, and a decision circuit. The signal register arrays cascade for capturing different sections of a received signal with each section corresponding to a symbol period. The reference signal generator produces blocks of a local reference signal with each block as the local reference signal of a corresponding matched filter, holds these blocks for a symbol period, and then generates next blocks with each block being the successive block of its previous block. Each matched filter finds the correlations between corresponding section of received signal and corresponding section of local reference signal. The signal combiner delays the outputs of different matched filters by different amount of time and then combines the delayed outputs together for the decision circuit to make decisions.

Abstract: The invention provides improved CDMA, WCDMA (UTMS) or other spread spectrum communication systems of the type that processes one or more spread-spectrum waveforms, each representative of a waveform received from a respective user (or other transmitting device). The improvement is characterized by a first logic element that generates a residual composite spread-spectrum waveform as a function of an arithmetic difference between a composite spread-spectrum waveform for all users (or other transmitters) and an estimated spread-spectrum waveform for each user. It is further characterized by one or more second logic elements that generate, for at least a selected user (or other transmitter), a refined spread-spectrum waveform as a function of a sum of the residual composite spread-spectrum waveform and the estimated spreads-spectrum waveform for that user.

Abstract: The invention provides methods and apparatus for multiple user detection (MUD) processing that have application, for example, in improving the capacity CDMA and other wireless base stations. One aspect of the invention provides a multiprocessor, multiuser detection system for detecting user transmitted symbols in CDMA short-code spectrum waveforms. A first processing element generates a matrix (hereinafter, “gamma matrix”) that represents a correlation between a short-code associated with one user and those associated with one or more other users. A set of second processing elements generates, e.g., from the gamma matrix, a matrix (hereinafter, “R-matrix”) that represents cross-correlations among user waveforms based on their amplitudes and time lags. A third procesing element produces estimates of the user transmitted symbols as a function of the R-matrix.

Abstract: A receiver device for a packet communication system receives a packet signal appended at its head with a known number (N) of repetition signals. A correlation value of a received signal is outputted from a normalizing correlator and compared with a threshold value in a comparator. The output of the comparator is inputted to a synchronization signal generating circuit, which includes M (?N?1) delay elements connected in series and an AND circuit for taking the logical product of the outputs of the delay elements. When the output of the comparator is high-level and the outputs of the M delay elements 431 are also all high-level, a synchronization signal at symbol timing is outputted from the AND circuit.

Abstract: The invention provides improved CDMA, WCDMA (UTMS) or other spread spectrum communication systems of the type that processes one or more spread-spectrum waveforms, each representative of a waveform received from a respective user (or other transmitting device). The improvement is characterized by a first logic element that generates a residual composite spread-spectrum waveform as a function of an arithmetic difference between a composite spread-spectrum waveform for all users (or other transmitters) and an estimated spread-spectrum waveform for each user. It is further characterized by one or more second logic elements that generate, for at least a selected user (or other transmitter), a refined spread-spectrum waveform as a function of a sum of the residual composite spread-spectrum waveform and the estimated spread-spectrum waveform for that user.

Abstract: The present invention includes a cellular pilot signal detector or searcher for use in a cellular mobile communications unit. The signal detector uses a matched filter to detect a pilot signal transmitted from a cellular base station. The matched filter includes a plurality of taps and a plurality of delays located between adjacent taps. The signal components of a received digital signal are held on the taps of the matched filter by the delays. The matched filter compares the signal components of the received signal to an expected or searched for digital pattern. The matched filter puts out a relatively large signal if the received digital signal matches the expected digital pattern. The matched filter can also be used in parallel with a correlator.

Abstract: Methods and apparatus for use in generating data sequences for direct sequence spread spectrum (DSSS) communications are described. One exemplary method includes the steps of serially generating a pseudo random noise (PN) sequence by, for each count value i of a plurality of count values, retrieving from memory a bit of the PN sequence corresponding to the (i)th position in the PN sequence. The exemplary method includes the further steps of serially generating a Gold code sequence by, for each count value i of the plurality of count values, retrieving from memory a bit of the PN sequence corresponding to the (i+n)th position in the PN sequence, retrieving from memory a bit of the PN sequence corresponding to the (q*i)th position in the PN sequence, and adding the bit corresponding to the (i+n)th position with the bit corresponding to the (q*i)th position.

Abstract: A method of transmitting and receiving a spread spectrum signal, wherein a product of a lower bit rate signal and a second PN-code equals the bit rate of a higher bit rate signal, and wherein a first PN-code sequence is used to spread the product or the higher bit rate signal to a predetermined output chip rate signal which is transmitted. At a receiver, the spread spectrum signal is received and demodulated and in a first operation the demodulated signal is correlated with the first PN-code sequence and in a second operation the output from the first mentioned correlating step is correlated with the second PN-code sequence. The demodulated signal is treated as either a higher bit rate signal or a lower bit rate signal based on the first and second correlations operations.

Abstract: The invention provides improved CDMA, WCDMA (UTMS) or other spread spectrum communication systems of the type that processes one or more spread-spectrum waveforms, each representative of a waveform received from a respective user (or other transmitting device). The improvement is characterized by a first logic element that generates a residual composite spread-spectrum waveform as a function of an arithmetic difference between a composite spread-spectrum waveform for all users (or other transmitters) and an estimated spread-spectrum waveform for each user. It is further characterized by one or more second logic elements that generate, for at least a selected user (or other transmitter), a refined spread-spectrum waveform as a function of a sum of the residual composite spread-spectrum waveform and the estimated spread-spectrum waveform for that user.

Abstract: An exemplary signal processing system determines vector mismatch between a plurality of signal paths. Advantageously, the system can determine mismatch across a range of frequencies. A signal generator of the system can provide a periodic calibration signal having a plurality of frequency components. The system frequency can translate the calibration signal to provide a first set of observed samples. The first sample set can be compared to a second set of samples, which can be modeled by a function of parameters including an estimated vector mismatch and a plurality of basis functions. A value of vector mismatch can then be determined (at least to an estimate) that minimizes the difference between the first sample set and the second sample set. Methods and other systems with different advantageous configurations are also described.

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 and apparatus provide efficient synchronization recovery at the receiver end for a digital transmission system. At the receiving end, a digital signal is received including a transmitted data portion and a guard period. A signal envelope for the received digital signal is determined, and the signal envelope is filtered to find the center of the guard period, which provides a time reference for the received digital signal. Embodiments of the present invention described herein may be used for optimal operation of a digital transmission system by efficiently recovering synchronization from a received digital signal during noisy conditions without being dependent on signal shape or requiring complicated threshold calculations.

Abstract: Methods and apparatus are presented for improving the feedback of channel information to a serving base station, which allows a reduction in the reverse link load while allowing the base station to improve the forward link data throughput. Over a channel quality indicator channel, three subchannels are generated; the re-synch subchannel, the differential feedback subchannel, and the transition indicator subchannel. The information carried on each subchannel can be used separately or together by a base station to selectively update internal registers storing channel conditions. The channel conditions are used to determine transmission formats, power levels, and data rates of forward link transmissions.

Abstract: A reduced complexity correlator that enables the re-use of the most complex portions of a correlator, namely the multiplier and adder. The correlator of the present invention is especially well-suited for use in CDMA and W-CDMA spread spectrum communication systems that require the use of numerous correlators in their operation. Multiple input samples, multiple codes and integration results are stored in shift registers and circularly shifted and clocked out at appropriate clock rates such that the multiplication and accumulation steps of the correlation process are synchronized.

Abstract: A circuit for processing binary sequences is designed with a plurality of stages (530–534) coupled to provide plural signal paths (526,528). Each stage includes respective signal paths (550,562) for a first Ra1(k) and a second Rb1(k) data sequence. Each stage further includes a respective delay circuit (502) having a different delay from said respective delay circuit of each other stage (504,506) of the plurality of stages. A stage having a greatest delay (502) precedes other stages (504,506) in the plurality of stages of at least one of the plural signal paths.

Abstract: A baseband signal multiplexing circuit controls an amplitude level of a baseband signal to be transmitted on the basis of the number of transmission codes. A gain set value is calculated with which an amplitude value of the baseband signal outputted from a level adjustment circuit is adjusted to an amplitude value matching a dynamic range of a D/A converter based on transmission code number information transmitted from a signal processor. The level adjusting circuit is notified of the gain set value with a control signal.

Abstract: A digital filter or a receiver including a digital filter having at least two multiple stage shift registers. A plurality of multipliers corresponding in number to the number of stages in the at least two multiple stage shift registers receive as a first input an output from a corresponding stage of the at least two multiple stage shift registers. A tap weight shifter is coupled to a tap weight source to receive tap weights. The tap weight shifter is coupled to provide a second input to each multiplier. Each multiplier produces an output that is the product of inputs thereto. An adder sums the multiplier outputs to provide a sum output. The tap weight shifter then circularly shifts the tap weights and another multiply-add operation occurs. Several shift/multiply/add cycles may occur before data is again shifted into the at least two multiple stage shift registers, and another multiply-add operation occurs.

Abstract: An over-sampling circuit is provided at a front stage of a digital matched filter, and a received signal is over-sampled with it. Synchronous acquisition of the received spread spectrum signal is implemented by adding the data obtained by the over-sampling, inputting it into the digital matched filter, and then performing a correlation thereon.

Abstract: In a cellular spread-spectrum communications network, a system and method for handing off a remote unit from a first base station to a second base station without loss of data. The remote unit receives a first spread-spectrum signal having a first signal quality from the first base station and transmits data to the first base station at a first data rate and a first power level. Responsive to monitoring the first signal quality and comparing 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.

Abstract: The invention relates to a method of processing multipath-propagated components of a signal in a communications system. In the method, a signal transmitted on the radio channel of the communications system is received in a RAKE receiver and an impulse response of the radio channel is formed. In the method, one or more taps having the highest signal energy in the impulse response are located and matched to a short matched filter. A weighting value for the impulse response is calculated on the basis of the one or more taps in the matched filter and a deviation between the weighting value and the center point of the matched filter is compared with a threshold value set for the deviation. The matched filter is moved toward the deviation when the deviation exceeds the threshold value set for the deviation.

Abstract: A spread-spectrum receiver for receiving data from a spread-spectrum packet-swioched system. A multichannel spread-spectrum signal includes encoded data, which is demultiplexed into sub-data-sequence signals. Each sub-data-sequence signal is multiplied by a respective chip-sequence signal to generate a plurality of spread-spectrum channels. The plurality of spread-spectrum channels are combined as a multichannel spread-spectrum signal. The multichannel spread-spectrum signal is concatenated with a header to output a packec-spread-spectrum signal which is transmitted over radio waves to a packet receiver. A processor at the packet receiver obtains ciming for the multichannel spread-spectrum signal from the header. The multichannel spread-spectrum signal is chen despread by a plurality of data-matched filters and multiplexed by a multiplexer as received-encoded data. The received-encoded data is decoded by a decoder and stored in a receiver memory for output.

Abstract: A high integrity process is provided to apply pilot phase rates to call processing decisions. An estimate or measurement of the rate of change of a pilot's PN phase offset is used to assist in making CDMA call processing decisions. The phase rate is a measure of the rate of change of a pilot's PN phase offset relative to a mobile time reference and is directly related to the multipath environment and movement of the mobile. Both an integrity algorithm to compute an integrity indicator and a technique to apply the integrity indicator to predict future pilot strengths are included.

Abstract: A demodulation apparatus for a base station of a CDMA mobile communication system is provided, having an analog-to-digital converter device to convert an intermediate frequency signal into a digital signal and provide a quadrature component and an in-phase component of the digital signal, a plurality of filters to filter the components of the digital signal in the low pass band respectively, and a CDMA modem to demodulate the outputs of the plurality of filters. Since direct control by the digital signal of the base-band I channel and Q channel at the intermediate frequency can be performed and the analog-to-digital converter simultaneously performs the QPSK demodulation and the analog-to-digital conversion, the circuit design can be simplified and the characteristics reducing the noise can be obtained.

Abstract: Disclosed is a W-CDMA wireless base station adapted to meet various specifications over a wide range to dynamically change the allocated numbers of RACH's and DPCH's depending on a cell radius and the number of Signatures. The W-CDMA wireless base station that performs an optimal channel allocation based on parameters received from an external network, comprises: a preamble detection and path search section adapted to perform an RACH preamble detection in a reception base band signal or perform a path search of the reception base band signal; demodulation section adapted to demodulate the reception base band signal by including therein a plurality of fingers and combining outputs of the fingers; a control section adapted to control said preamble detection and path search section to switch itself either to a preamble detection section or to a path search section so as to change the allocated numbers of RACH's and DPCH's based on the parameters.

Abstract: A digital CDMA wireless communication system. The system includes one or more of said transmitters with a base station baseband processor, a finite impulse response (FIR) filter, a pre-distortion phase equalizer and a digital-to-analog (DAC) converter. Receivers have an analog-to-digital (ADC) converter, a FIR filter, a phase equalizer and a receiver baseband processor. The receiver FIR filter is matched to the transmitter FIR filter and the receiver phase equalizer is matched to the pre-distortion phase equalizer.

Abstract: The present invention relates to a correlation detection method using a matched filter. The correlation detection method of the present invention carries out a type of despreading calculation of fixing reception data and scanning spreading codes.

Abstract: A CDMA baseband receiver includes a first correlating unit, a long code phase candidate outputting section and a long code determining section. The first correlating unit calculates first correlation values from a spread modulation signal and a short code which is common to base stations. The long code phase candidate outputting section outputs selected long code phase candidates corresponding to ones selected from the first correlation values, based on the spread modulation signal, and determined long codes. The selected long code phase candidates are other than long code phase candidates for known ones of the base stations. The long code determining section generates the determined long codes for unknown ones of the base stations from the spread modulation signal, the short code, and long codes generated based on the selected long code phase candidates. Each long code is peculiar to one base station.

Abstract: A spread spectrum detector employs a Doppler phase correction system that improves correlation of pseudo-noise (PN) codes to a received spread spectrum signal by combining phase shifts, in the time domain, to correlation values that compensate for the Doppler shift error that is inherent in the signal and that is imposed upon the signal by movement between the signal source and receiver. In architecture, the Doppler phase correction system includes a receiver to receive a spread spectrum modulated signal having the Doppler shift error, a multiplier to produce a plurality of complex first correlation values based upon the signal and a code. A phase shifter generates a plurality of complex second correlation values respectively from the first correlation values. The second correlation values being phase shifted by respective different amounts from corresponding first correlation values, so that the second correlation values exhibit less of the Doppler shift error than the first correlation values.

Abstract: A spread spectrum detector employs a Doppler phase correction system that improves correlation of pseudo-noise (PN) codes to a received spread spectrum signal by combining phase shifts to correlation values, using a fast fourier transform (FFT), that compensate for the Doppler shift error that is inherent in the signal and that is imposed upon the signal by movement between the signal source and receiver. In architecture, the Doppler phase correction system includes a receiver to receive a spread spectrum modulated signal having the Doppler shift error. A multiplier produces a plurality of complex first correlation values based upon the signal and a code. A phase shifter generates a plurality of complex second correlation values respectively from the first correlation values using an FFT.

Abstract: A method of estimating a communication path formed of a plurality of channels, the method necessitating an estimate of the impulse response C1, C2, . . . , Cn of the channels, including the following steps of (1) acquiring a space statistic of the transmission path, and (2) establishing a corrected impulse response (C1, C2, . . . , Cn) at least by weighting the impulse responce estimates (C1, C2, . . . , Cn) by the space statistic and an estimate of the additive noise (N01, N02, . . . , N0n) of the channels.

Abstract: A wireless network is disclosed including at least one base station and a plurality of assigned terminals for exchanging user data and control data. The base station is arranged for transmitting the start time of at least one signaling sequence of at least terminal. For evaluating the signaling sequences transmitted by the terminals, the base station includes a device for correlating a received signaling sequence and for detecting the pulse evolving from a received and correlated signaling sequence. A terminal generates a signaling sequence by folding two code sequences.

Abstract: A spread-spectrum system having a transmitted data rate determined by an error rate syndrome at a spread-spectrum receiver. Data are demultiplexed into a plurality of data channels, and spread-spectrum processed as a plurality of spread-spectrum channels. A combiner combines the plurality of spread-spectrum channels as a code-division-multiplexed signal. At a receiver, the code-division-multiplexed signal is despread into a plurality of despread channels. A multiplicity of adders, which is electronically controlled by an adder-control signal, adds several of the despread channels to generate a multiplicity of added channels. A syndrome signal is generated from an error rate of the multiplicity of added channels. From the syndrome signal, a desired-data rate is determined for the spread-spectrum transmitter.

Abstract: In a PRACH channel, colliding signals are resolved by use of a number of training-like symbols in the colliding data payloads. The signals are estimated by spatio temporal filters running a training-based or semi-blind algorithm, and a selection criterion is applied to the estimated signals, such as distance from the finite alphabet or the mean square error.

Abstract: A method of determining an end of a transmitted frame at a receiver on a frame-based communications network. An end of frame format for the transmitted frame is provided having an end of frame plurality of symbols. A received transmitted frame is filtered using filter coefficients matched to the end of frame plurality of symbols to provide a correlation sequence low-pass filtered signal. A squared magnitude of the correlation sequence is computed. The squared magnitude of the correlation sequence is low-pass filtered to provide a low-pass filtered correlation signal. The low-pass filtered correlation signal is delayed to provide a delayed low-pass filtered correlation signal. The delayed low-pass filtered correlation signal is multiplied by a fixed predetermined threshold to provide a multiplied correlation signal. The multiplied correlation signal is compared with the low-pass filtered correlation signal to provide a match/no match comparison indicative of the possible end of a transmitted frame.

Abstract: An apparatus is provided for detecting a correlation of samples with a spread code comprising: an L-chip accumulator which inputs the samples to generate and output an intermediate correlation signal; M memories, each of which stores L×M samples of the intermediate correlation signal; an adder which has input terminals as many as M and inputs from each of the input terminals the intermediate correlation signal which is outputted from the L-chip accumulator or the intermediate correlation signal which is outputted from a corresponding memory among the memories; and a controller which supplies the intermediate correlation signal outputted from the L-chip accumulator to the memories as many as M and to the M input terminals of the adder in rotation with a unit of L×N samples, and reads, and supplies to each of the input terminals of the adder, the intermediate correlation signal which has been stored in each of the memories M?1 times; wherein an output of the adder is outputted as an correlation signal outputted

Abstract: An electromagnetic matched filter based multiple access communications system having a source of modulated pulses from a digital data stream; an initial filter which shapes the incoming modulated pulse into a desired pulse for transmission across the communication medium; a second filter, identical to the initial filter, which is matched to the pulse which exit the communication medium, a detector which converts the modulated pulse stream into the original digital data stream, and signals which are designed with specific mathematical properties which make the system efficient and minimizes crosstalk between channels. The signals decay rapidly from the central lobe at a higher than 1/x rate and the zero points of the autocorrelation function having high order multiplicities. The type of system allows multiplexing of multiple data streams with much greater flexibility, robustness, and density.

Abstract: A receiving system or a received radio-wave estimation method is provided that can maintain received field strengths at a nearly uniform level under multipath conditions. The antenna switch can select outputs of four antennas at high speed. The high-frequency amplifier amplifies the output of the antenna switch and the demodulator demodulates amplified signals. The matched filter bank, surrounded with chain lines, receives a demodulated signal, for example, the I-phase component. In the matched filter bank, the phase shifter shifts respective signals output from four delay elements. The adder synthesizes the phase-shifted signals and then supplies the maximum matched output to the maximum level selector.

Abstract: The present invention relates to systems and methods that facilitate compensating for intersymbol interference (e.g. due to non-nyquist filtering) in Code Division Multiple Access (CDMA) systems (e.g., IS 95 and IS2000 systems). The subject invention employs equalization filters (e.g., T-spaced equalizers) at fingers of a RAKE receiver. By effecting such equalization filtering at a downstream point in a receiving system, e.g., at the fingers of the RAKE receiver, the filters can be run so as to operate at lower rates as compared to conventional systems where filtering is effected upstream where time is not necessarily known thus requiring equalization filters to operate at significantly faster rates (e.g., 2× or 4× expected chip rate). Accordingly, as compared to conventional systems where the matching filters often are of substantial complexity (e.g., >80 taps) the present invention provides for less complex equalization filters thereby reducing overall system complexity and cost.

Abstract: A programmable matched filter bank comprises a sliding integrator and compensation calculation circuits. The integrator receives a chip stream of samples derived from a received spread-spectrum signal and integrates a number of the most recent samples, to form a common integration value. Each of the compensation calculation circuits receives the same most recent samples and receives a respective one of the possible reference spreading code sequences. In operation, each compensation calculation circuit derives a compensation value, and an associated circuit modifies the common integration value by the respective compensation value. The result is a value of correlation between the predetermined number of most recent samples, for each respective reference code sequence. The inventive approach reduces the number of bit adders and inverters in the implementation of a matched-filter, a programmable matched filter and a programmable matched filter bank for spread spectrum receivers.

Abstract: A multipath signal searcher (204) used in CDMA wireless communication systems is provided. Search paths (214) of the multipath signal searcher are grouped together and assigned by an offset assignment/timing block (210) to search a time offset within a search window. The search paths may be operated In serial or parallel operation mode. In either mode, the search paths are individually assigned to search over one of a group of time offsets that are distributed across the search window evenly. In parallel mode, the search paths are not only grouped to search only a given set of time offsets within the search window, but different groups of search paths are offset to commence searching at different times then other groups of search paths to more quickly update a finger manager and more quickly retrieve the mobile communication signal.

Abstract: In a mobile communication system, the tracking of synchronization is conducted in a stable state even in a multipath environment. A delay profile detector calculates a delay profile a(n) using a despread signal for each processing unit n. A delay profile averaging unit averages a(n) to produce Ave(|a(n)|2). A data symbol detector conducts rake combining of the despread signal using a(n) and Ave(|a(n)|2). According to a(n) and Ave(|a(n)|2, a weighting function unit calculates a representative value representing delay waves. A loop filter generates a control signal in response to the representative value. A clock controller controls a spread code generator according to the control signal.

Abstract: An apparatus, system, and corresponding method for acquiring a spread spectrum signal, where the acquiring includes matching the phase of a replica of a code component to the phase of the received code component and also determining the carrier frequency including any Doppler or other shifting, the apparatus including: a multi-section matched filter for providing successive section outputs each including elements corresponding to a different replica code phase; and a compensated acquisition module, responsive to each section output of each of the sections, for providing a sequence of frequency indicators, each corresponding to a different frequency offset, with each section output having elements each of which corresponds to a particular value of replica code phase, wherein each frequency indicator is based on a combining, phase element-wise, of the section outputs using compensating factors that depend on the corresponding frequency offset.

Abstract: A method and apparatus are disclosed for frequency offset estimation in a hybrid in-band on-channel (HIBOC) digital audio broadcasting (DAB) system. The frequency offset estimation algorithm first determines the coarse frequency offset, in terms of integer number of OFDM bin separations between an actual and measured location of a correlated peak, followed by estimation and tracking of the partial (residual) offset in a continuous fashion. A frame is correlated at a first frequency, and then the frequency is shifted by a predefined amount, such as half of the inter-bin frequency amount, &Dgr;f, before correlating again. The measurement with the highest peak of the plurality of frequency values is utilized to obtain the course frequency offset estimate. The partial frequency offset estimation algorithm utilizes phase information contained in reference frequency points in the frequency domain.

Abstract: A spread-spectrum communication system utilizes spreading code sequences, which can be expressed as a matrix. The matrix of code sequences has or can be transformed to have a certain orthogonal relationship. In accord with the invention, a matched filter bank in a spread-spectrum receiver processes input signals that purport to contain the code matrix using two halves of an input stream matrix and only two of four possible quadrants of the code matrix as the reference inputs. Such processing produces two quadrants of a correlation signal matrix. It is then possible to determine the other two quadrants of the full correlation signal matrix from the known relationship with the two quadrants derived from the matching operations. The processing of only two of the quadrants of the signal matrix substantially reduces the number of computations and the amount of processor hardware needed to implement a matched filter bank to recognize the codes embedded in a received spread-spectrum signal.