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

Abstract: Methods and systems are provided whereby correlations between a received signal sample set and a plurality of potential codeword data set are determined and a potential codeword with the highest correlation value is selected as the decoded codeword. The correlation of a potential codeword may be determined by computing a squared magnitude of correlation values between the potential codeword and the received sample set starting at various time points and then summing the squared magnitudes of the correlation values at those points. The number of time points used for correlation computation and summing depends on the time spread of the received symbol pulse. Furthermore, the correlations may be weighted before summing.

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

Abstract: According to an embodiment of the invention, a DS-CDMA receiver receives an input signal which comprises a plurality of received signals that are received over a corresponding plurality of antennae. These signals are demodulated and sampled to create digital signals. The digital signals are decorrelated and each of the decorrelated signals are multiplied by a weight to derive weighted estimates. The weighted estimates are summed to generate an estimate of an information symbol. The weights are based upon a cross correlation between the decorrelated signals and a desired signal. According to the invention, this cross correlation may be derived by filtering a pilot signal.

Abstract: An apparatus and method allow receivers to quickly acquire a pseudorandom noise signal. A receiver advantageously detects frequency shifts using a compact parallel process hardware implementation of a Discrete Fourier Transform (DFT). The method applies a sequential test algorithm to the detection of a correlation signal. The method allows the receiver to search a range of frequency-time space relatively quickly.

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

Abstract: 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: In a direct sequence spread spectrum receiver an “as received” signal is decoded by correlation. Phase shift key, complementary code key modulated signals are correlated by transforming samples of the signal in a series of butterfly transform processors producing a number of correlations equal to the number of possible transmitted codewords. The largest correlation is selected as the transmitted signal. To reduce the number of processors required to transform a multi-level phase shift key signal, a correlation method and apparatus are disclosed wherein the butterfly transforms are modified with additional twiddle factors selected from a set of twiddle factors. In the alternative, the inputs to the butterfly processors of a correlator can be weighted as a function the additional twiddle factors. A set of signal samples is correlated for each combination of the set of additional twiddle factors and the largest correlation selected as the signal.

Abstract: A method of establishing a search window size for a mobile station in a cellular system is disclosed. For the mobile station searching for a pilot signal of base transceiver station (BTS), the information of maximum index being outputted from the mobile station is gathered, wherein the maximum index is an index number at which the strongest signal is detected within a predetermined window size. For the gathered maximum indexes, confidence level is established and mean value is calculated and then confidence interval is calculated for the gathered maximum indexes using the established confidence level and calculated mean value. A maximum offset of the search window to be applied to the present radio morphology of the cellular system is calculated from the calculated confidence interval and a search window to be applied to the present radio morphology is estimated by increasing the maximum offset by two times.

Abstract: A code-multiplexing communication apparatus includes a splitting unit for splitting incoming serial transmitted data into N (N is integer equal to or greater than 2) number of signal trains; N number of spread unit for performing spreading for each of the N number of signal sequences with use of a spread code; an adding unit adding the N number of signal sequences with the spreading processed by the N number of spread unit, for outputting a code-multiplexed signal; and a modulating unit for modulating the code-multiplexed signal, comprising, filter unit having an inverse characteristic to a frequency characteristic of an autocorrelated distortion caused by the spreading, removing a transmission path distortion.

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 demodulation.

Abstract: The frame of data is partitioned into a plurality of portions of data symbols. A plurality of channel elements (300) is assigned to demodulate data symbols of correspondingly the plurality of portions of data symbols. The number of the plurality of portions of data symbols is higher in a case at high data rate than a case at low data rate.

Abstract: A communication device includes a transmitter and receiver. The transmitter includes an M-ary encoder configured to generate an M−1 number of distinctive symbols each comprising k bits. M is equal to 2k and k is a positive integer. The transmitter also includes a code generator configured to produce spread spectrum codeword sequences based on the symbols generated by the M-ary encoder and based on a first and a second Gold code polynomials. The transmitter sends a radio signal based on the spread spectrum codeword sequences. The receiver is configured to receive the radio signal. The receiver includes a first shift register configured to receive an input signal generated based on the received radio signal and a second shift register configured to receive and circularly shift a locally generated codeword sequence that is identical to the codeword sequence used to encode the symbols.

Abstract: A receiver in a communications system is operated by receiving a radio communications signal transmitted by a station of the communications system and generating a correlation output representing a correlation of the received radio communications signal and a subsequence of a modulation sequence that is selected based on a correlation between the selected subsequence and the modulation sequence. The receiver is then synchronized based on the generated correlation output. The selected subsequence preferably has an optimal out-of-phase correlation with the modulation sequence. According to an aspect of the present invention, the selected subsequence has a minimum out of phase correlation with the modulation sequence in comparison to other subsequences of the modulation sequence. For example, the selected subsequence may have a “minimum maximum” out-of-phase correlation value, a “minimum aggregate” out-of-phase correlation metric, or a combination thereof.

Abstract: In a method for radio communication of exchanging a transmission signal, which has been modulated by a prescribed method based on information data, between plural communication terminals and controlling the plural communication terminals by a control terminal, the control terminal generates a first code sequence to synchronize with the plural communication terminals, and transmits it to the plural communication terminals. The communication terminal synchronizes with the control terminal based on a reference timing obtained by receiving the first code sequence, generates a second code sequence representing the demodulation timing for the transmission signal and transmits it to another communication terminal out of the plural communication terminals, and then transmits the transmission signal to the other communication terminal.

Abstract: Reference phase is a radio communication system using orthogonal M-ary modulation is determined, so that a coherent detection system for a CDMA radio communication system is readily achieved. The determination of reference phase is performed by the step of determining a reference phase in a radio communication system, which uses orthogonal M-ary codes comprising the steps of determining the correlation values of an in-phase component and quadrature component corresponding to respective Hadamard matrices resulting from fast Hadamard transform or inverse Hadamard transform of a signal, which possesses said in-phase component and quadrature component, and which is sent from the sending end by phase shift keying an orthogonal M-ary code computing the sum of the squares of the respective correlation values of said in-phase component and quadrature component and selecting either said fast Hadamard transform or inverse Hadamard transform output, which outputs a maximum value of said computed sum of the squares.

Abstract: The invention relates to a method for controlling a receiver and to a receiver realized with the rake principle and comprising a number of correlator branches (200-204) that can be synchronized with the received signal. In order to enable the rapid operation of the receiver, the correlator branches (200-204) of the receiver according to the invention comprise means (304) for searching for advantageous signal components and means (116, 310) for guiding a branch to receive an advantageous signal component it has found.

Abstract: A GPS communication system including a server and a client, each including a GPS receiver, for reducing the code phase search space of the GPS receiver of the client. The communication system includes a transmitter for transmitting timing information from the server to the client to help the client locate a first satellite, and a receiver for using timing differences between the satellites to synchronize and locate other satellites. The code phase search space is reduced by reducing the number of phase hypotheses that must be calculated to establish communication between the server and the client.

Abstract: A matched filter computes complex correlations between a sequence of complex input values and a complex code. The matched filter includes a set of N changeover switches having a first input connected to receive real parts of the input sample values and a second input connected to receive imaginary parts of the input sample values. The switches further include a control input for receiving a control signal in first and second states. When the control signal in the first state is applied, a first output of the changeover switch contains the real value part of the input sample values and a second input contains the imaginary part of the input sample values. When the control signal is in the second state the first input contains the imaginary value part of the input sample values and the second input contains the real value part of the input sample values.

Abstract: A terrestrial C/A code GPS receiver system digitally samples, filters and stores a segment of 11 half chips of the received composite as a binary number and multiplexes this number for parallel correlation with each of a series of multibit code replicas for the satellites to be tracked. Each of the time delay specific correlation products are accumulated in a cell of a memory matrix so that at least twenty two delays for each satellite may be evaluated each code period providing fast reacquisition, even within a city intersection, as well as correction of multipath tracking and multipath interference. All cells of the memory matrix may be used for a acquisition of a single satellite in about 4 ms. Two satellite tracking, in addition to altitude hold, uses cross track hold alternating with clock hold to update the cross track estimate. Single satellite tracking uses cross track and clock hold together. Navigation data is updated with detected changes in motion including turns.

Abstract: The present invention discloses methods, apparatuses, and systems for eliminating auto- and cross-correlation in weak signal CDMA systems, such as GPS systems. The invention uses parallel data paths that allow standard correlation of signals in parallel with verification of the lock signal to determine whether the system has locked onto the proper signal within the scanned signal window. The invention can be made with multiple CPUs, a single CPU with dual input modes, on multiple IC chips, or as a single IC chip solution for small, low cost reception, downconversion, correlation, and verification systems.

Abstract: A method of acquiring a communications signal is provided. The method includes the steps of storing a forward chirp sync segment (106) of an auto-correlating forward chirp sync (102) and storing a reverse chirp sync segment (108) of a symmetric auto-correlating reverse chirp sync (104). A header comprising of either a forward chirp sync FCS (102) or a reverse chirp sync RCS (104), a predetermined number of data blocks comprising a data frame (308), and the symmetric auto-correlating trailer is received. The header, the data blocks, and the symmetric trailer are susceptible to frequency error. The method correlates the FCS segment (106) with the auto-correlating FCS (102) to provide a FCS correlation signal (312) and correlates the RCS segment (104) with the auto-correlating RCS (108) to provide a RCS correlation signal (314). The method determines the frequency error, symbol timing, and frame timing based upon the FCS correlation signal (312) and the RCS correlation signal (314).

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 terrestrial C/A code GPS receiver system digitally samples, filters and stores a segment of 11 half chips of the received composite as a binary number and multiplexes this number for parallel correlation with each of a series of multibit code replicas for the satellites to be tracked. Each of the time delay specific correlation products are accumulated in a cell of a memory matrix so that at least twenty two delays for each satellite may be evaluated each code period providing fast reacquisition, even within a city intersection, as well as correction of multipath tracking and multipath interference. All cells of the memory matrix may be used for a acquisition of a single satellite in about 4 ms. Two satellite tracking, in addition to altitude hold, uses cross track hold alternating with clock hold to update the cross track estimate. Single satellite tracking uses cross track and clock hold together. Navigation data is updated with detected changes in motion including turns.

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: This invention relates to a method and apparatus for increasing the performance of searcher by using the array antenna when the signal to interference plus noise ratio is low. The two-dimensional searcher performs the spatial-filtering to reduce the noise and interference components and then correlates the spatial-filtered signal with a pseudo noise (PN) code to thereby detect the incoming signals and acquire the corresponding code timings. Furthermore, the two-dimensional searcher can be used to increase the performance of a finger beamformer in two ways. One is to use searcher beamforming weight as initial finger beamforming weight to increase the convergence speed in the adaptive beamforming algorithms. The other is to reduce an amount of computation in the angle of arrival estimation algorithms by calculating the azimuth power spectrum only for the specific angle range.

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: Delays in a spread spectrum signal transmitted in a communications medium according to a spreading sequence may be determined by receiving a composite signal including the spread spectrum signal from the communications medium. The composite signal is correlated with the spreading sequence according to a first correlation length, to produce first time-offset correlations of the composite signal with the spreading sequence. Selected ones of the first time-offset correlations of the composite signal then are further correlated with the spreading sequence according to a second correlation length that is longer than the first correlation length, to produce second time-offset correlations of the composite signal with the spreading sequence. At least one of the second time-offset correlations may be selected.

Abstract: Rate detection of a data rate within a sequence of transmitted symbols employs correlation to calculate estimates of the auto-correlation values, or estimated coefficients, of the sequence. When the sequence of transmitted symbols includes repeated symbol values, the auto-correlation values indicate a degree of self-similarity within the sequence. A decision statistic may be formed from the auto-correlation values. The self-similarity of the auto-correlation values may be employed as a decision statistic with associated hypothesis test pair values. Various decision methods may be implemented to compare auto-correlation values to thresholds based on the hypothesis test pair values. Based on the comparison, the data rate of the sequence may be determined. Once the information is determined related to the data rate, the information may be employed by a Viterbi detector to adjust the decoding rate for decoding the symbols.

Abstract: An apparatus for generating a precision frequency includes a receiver that tracks a CDMA pilot signal and extracts frequency and phase information. This information is then used by a processor to control a precision oscillator. The precision oscillator generates a precise frequency based on the CDMA pilot signal. Time of day information is also extracted by the receiver and processor.

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 spread spectrum communication system including a transmission side for transmitting a frame-structured transmission signal containing at least one preamble (having information on a transmission destination) and data subsequent to the preamble(s) while spread-spectrum-modulating the transmission signal with a PN code, and a reception side having a correlator for performing correlation between the PN code of the transmission signal and a reference PN code and a PN code generator for generating the reference PN code. At the reception side, the PN code of the preamble of the transmission signal and the reference PN code are correlated with each other to obtain correlation peaks, and the periodicity of the correlation peaks is detected and a prescribed number of correlation peaks is counted, thereby identifying the transmission signal as being addressed to the receiver.

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: 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: 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: The CDMA synchronous capture circuit which calculates correlation values by using a part of received data for the detection of the peak position, and then decides an upper temporal peak position where the correlation values are great. The CDMA synchronous capture circuit of the present invention calculates the remaining correlation values, giving priority over the temporal peak position, by using the remaining received data, and finally decides a peak value from the correlation level by adding the above-mentioned two kinds of correlation values.

Abstract: A method for processing a direct sequence spread spectrum signal, and a receiver for performing the method. A correlation is preformed between a received signal and the direct sequence used to determine peaks of different amplitudes. The spectrum of the information corresponding to the highest amplitude peak is respread using the direct sequence. The respread signal is subtracted from the received signal to create a new signal. This process is reiterated on the new signal until all of the peaks have been exhausted.

Abstract: A code division multiplex communications system has a receiver for receiving a radio wave and transforming the radio wave to an electric signal. A voltage-current converter converts the electric signal to a current signal. A current delay mechanism then sequentially reads the electric signal during a clock pulse. Adders and subtractors manipulated output currents of the current delay mechanism in accordance with a spread code and a reproducing mechanism reproducing a transmission signal depending on the output of the adder and subtractor.

Abstract: A CDMA receiving apparatus which can accurately perform phase tracking for a reception signal even under an environment wherein the reception delay amount varies in a period shorter than the processing time of a synchronization detection and phase tracking section. The CDMA receiving apparatus includes a plurality of FINGER processing sections individually provided for a plurality of paths and including de-spreading sections for receiving a signal spread with a spread code and arriving through the paths and de-spreading the reception signal with a de-spread code and channel estimation sections for estimating the paths based on results of the processing of the de-spreading sections, and a synchronization detection and phase tracking section for outputting a reception delay amount of the reception signal in a predetermined period to the de-spreading sections.

Abstract: An ultra-wideband (UWB) communications system combines the techniques of a transmitted reference (TR) and a multiple access scheme called delay hopping (DH). Combining these two techniques using UWB signaling results in a penalty in signal-to-noise ratio (SNR) over conventional pulse position modulation (PPM) techniques but avoids the synchronization difficulties associated with conventional approaches. The signaling pulse waveforms are designed to insure that their power spectral densities, after any frequency translation to the center of an operating band, are essentially spectrally disjoint with frequencies that must be protected. This TR technique is combined with the DH multiple access technique to create a UWB communications scheme that has a greater multiple access capacity than does the UWB TR technique by itself.

Abstract: Spread spectrum receiver with correlating coprocessor having common datapath for received signal correlations and code cross-correlations for efficient interference cancellation methods.

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: The input data to a CDMA transmitter is used to introduce a slight frequency offset to the clock that is used to generate the CDMA code. At the receiver, the frequency-offset CDMA signal proportionately affects the magnitude of output signals from one or more CDMA correlators. A composite signal that is based on the magnitudes of the output signals is compared to a set of predefined threshold levels to provide the demodulated output data.

Abstract: A communication system transmits and receives a plurality of spread-spectrum signals having differences in at least one diversity parameter. The signals are highly correlated when their diversity parameters are similar, and the signals are uncorrelated when at least one diversity parameter is different. Any combination of a transmitter, a receiver, and a communication channel may diversity-encode the signals to effect differences in their diversity parameters. A receiver diversity-decoder compensates for differences in a diversity-parameter of at least one received signal to make the signal highly correlated with at least one other received signal. A correlator combines at least two of the received signals to recover an embedded information signal. The communication system enables the use of true-noise signals for spreading information signals, provides simplified receiver designs, and enables antenna arrays to spatially process spread-spectrum signals.

Abstract: An embodiment of the present invention described in the specification and the drawings is an apparatus and method for code correlation in spread spectrum communication systems. The apparatus receives a data sequence, and offsets the data sequence with a fixed sub-chip delay. The data sequence and the offset data sequence are each despread with a locally generated code sequence. The despread results are summed and accumulated. The accumulated results may then be used to achieve a lower “miss” probability during code correlation.

Abstract: A wideband CDMA handset (20) has a receiver (50) which simplifies initial sequence acquisition. The receiver (50) includes an efficient searcher receiver (54) which searches for long code mask sequences (LMS) using two correlators (80, 100). The searcher receiver (54) determines the complex conjugate of the output of the first correlator (80), and uses it to remove the phase ambiguity of the output of the second correlator (100). Thus the second correlator (100) is able to perform multiple correlations at the same time. The searcher receiver (54) coherently combines the output of the second correlator (100) to improve the reliability of the search decision.

Abstract: A single, common correlation filter (CF) core is provided in a wireless system using CDMA. A plurality of channels with different data rates are provided in the wireless system. The channels provided in the wireless system include the access channel, the maintenance channel, and the traffic channel in which information (e.g., pilot or data symbols or both) is transmitted at the tier 1, tier 2 and tier 3 rates. The data rate for transmitting the information is programmable by digital signal processor (DSP). A user-unique code, such as a PN code, is applied to the information being transmitted in the channels of the wireless system. The information is QPSK modulated and transmitted in any one of the channels at any data rate. The transmitted information is correlated at the smallest data rate (i.e., the tier 1 rate) in the correlation filter (CF) of the wireless system by time multiplexing delayed versions of the PN code to the correlation filter core.

Abstract: A method for extending a cell radius or access range of a base station without incurring ASIC correlator re-design. This is accomplished using a modified timing protocol that will cause signals transmitted by mobile-telephones positioned beyond the limitations of the ASIC correlator bit limitation to be received within a search window so the signals may be detected and demodulated. In one embodiment, the modified timing protocol incorporates a timing advance technique in which the base station transmits its signals at an advanced time before frame boundaries such that signals transmitted by out-of-range mobile-telephones can be received within a search window beginning at a frame boundary and spanning a time interval corresponding to the ASIC correlator bit limitation. In another embodiment, the modified timing protocol incorporates a shifted search window that begins at an advanced time after a frame boundary and spans a time interval corresponding to the ASIC correlator bit limitation.