Abstract: In a system having a received PN clock signal, a method is disclosed for providing a synchronized system clock signal having reduced jitter wherein the synchronized system clock signal is synchronized with the received PN clock signal. The method includes providing a stable high frequency reference signal and dividing the high frequency reference signal to provide a system clock signal having a plurality of system clock phases. The method also includes adjustably selecting a system clock phase of the plurality of system clock phases in accordance with the received PN signal in order to provide the synchronized system clock signal. The received PN clock signal is recovered by providing PN phase adjustments of the received PN clock signal. A tracking control signal is provided in accordance with the PN phase adjustments and the system clock phase is adjustably selected in accordance with the tracking control signal. The high frequency reference signal can be multiplied prior to the dividing.

Abstract: A method and apparatus for searching for neighboring base stations by waking from a power-saving sleep mode to receive an incoming signal. The incoming signal is received and at least a portion of the incoming signal is stored. The stored information signal is then processed with each of several different codes to determine a power level corresponding to each of the different codes.

Abstract: In a system having a received PN clock signal, a method is disclosed for providing a synchronized system clock signal having reduced jitter wherein the synchronized system clock signal is synchronized with the received PN clock signal. The method includes providing a stable high frequency reference signal and dividing the high frequency reference signal to provide a system clock signal having a plurality of system clock phases. The method also includes adjustably selecting a system clock phase of the plurality of system clock phases in accordance with the received PN signal in order to provide the synchronized system clock signal. The received PN clock signal is recovered by providing PN phase adjustments of the received PN clock signal. A tracking control signal is provided in accordance with the PN phase adjustments and the system clock phase is adjustably selected in accordance with the tracking control signal. The high frequency reference signal can be multiplied prior to the dividing.

Abstract: A method 10 is provided to mitigate DC offset in a sign bit correlator associated with a packet detection circuit. The input sign pattern is monitored; and if a long run of the same sign is seen, a sign bit is replaced with a bit generated using a desired pseudorandom noise (PN) sequence. This ensures that the correlator only reacts substantially to correlations that are not due to DC offset.

Abstract: A clock signal desired to be transmitted to various components of the electronic system is combined with a noise signal to generate a spread spectrum clock signal which, in turn, is distributed with an associated reference signal to selected components of the system using two-channel communication links. A receiving circuit within each of the selected components recovers the original clock signal from the spread spectrum clock signal and its associated reference signal. In one embodiment, the clock signal is combined with the noise signal in an exclusive-OR logic gate to generate a spread spectrum clock signal which is distributed to receiving components using a first channel. The noise signal is transmitted as the reference signal using the second channel. The two channel signals are combined in an exclusive-OR gate of one or more receiving circuits to recover the clock signal.

Abstract: A receiving device in a multi-code mobile communication system is disclosed. In the multi-code mobile communication system, user serial data is broken down into a plurality of parallel data channels and parity data is generated from the user parallel data. The parity data is transmitted on a redundancy channel. In the receiving device, each symbol is decided using multi-codes from a signal received on the data and redundancy channels. An energy calculator in the receiving device calculates the energy of each decided symbol. A parity checker determines whether errors have been generated by checking the parity of symbol data, and a sign inverter inverts the sign of a symbol with the smallest energy as calculated by the energy calculator if it is determined that errors have been generated and thus corrects the errors.

Abstract: A method for tracking a locally generated spread spectrum signal sequence includes the step of correcting the spread spectrum signal sequences with respect to the synchronization time in an early/late interval. The correlation responses are subtracted from one another and the clock of the locally generated spread spectrum signal sequence is controlled as a function of the subtraction. Correlations are performed through the use of at least two hierarchically staggered closed-loop controls having different early/late intervals. The early interval of the one closed-loop control having a small early/late interval must not become earlier than the early interval of the other closed-loop control system having a next-larger early/late interval. Furthermore, the late intervals of the one closed-loop control system having a small early/late interval must not become later than the late interval of the other closed-loop control system having a next-larger early/late interval.

Abstract: A device includes a request arbitration unit that (1) receives a number of requests for PN vectors from a number of processing units and (2) provides a control indicative of each request selected for processing. An address generator provides one or more addresses (which may be dependent on a particular PN sequence being requested and the offset of the PN sequence) for each selected request. One or more memory units store all “base” PN sequences (e.g., and X(i) sequence and a Y(i) sequence defined by W-CDMA) that may be used to generate all requestable PN vectors. The memory unit(s) provide one or more segments of one or more base PN sequences, based on the address(es). A buffering unit provides a set of one or more PN vectors derived from the one or more PN segments for each selected request.

Abstract: A circuit is designed with a plurality of logic circuits (370-374) for producing an offset state matrix. The circuit includes a first logic circuit (380-383) coupled to receive N elements of a respective row of a transition matrix and N elements of column of an input state matrix. The first logic circuit produces a multi-bit logical combination of corresponding bits of the respective row and the column. A second logic circuit (390) is coupled to receive the multi-bit logical combination and produces a respective element of the offset state matrix.

Abstract: A signal generator and signal receiver, as well as method of signal generation and transmission, in which selected unstable periodic orbits of a lossy chaotic system are identified and extracted, and portions of the orbits concatenated together to form a resultant signal. The selected orbits are known to the signal detector a priori. The signal detector detects the transmitted signal by correlation of the received signal with the known extracted orbits, also allowing the detector identify information which the generator imposed onto the signal.

Abstract: Methods and systems for time synchronizing a receiver to a spread spectrum signal are described. Exemplary embodiments of the present invention provide for at least a two step process in which, at a first step, a number of candidate synchronization frequencies or timings are identified, followed by confirming one of the candidates as a correct synchronization state at a second or final step. According to the present invention, the confirmation step may be performed at the same time as the step of identifying further candidates by processing the same received signal samples in different ways.

Abstract: A method and apparatus for computing a convolution between an input GPS signal and a C/A code reference by generating the convolution result in real time without storing unprocessed signal samples. The apparatus comprises a vector multiplier running at high speed to achieve the same result as a vector multiplier sized to process an entire epoch.

Abstract: The invention determines the geographic location of a subscriber unit within a CDMA communication system. At least one base station transmits a spread spectrum signal with a chip code sequence unique to that base station. A subscriber unit receives the base station signal and transmits a spread spectrum signal with a unique chip code sequence time synchronized with the chip code sequence of the received base station signal. The base station receives the subscriber unit signal and compares the chip code sequence of the received subscriber unit signal with the chip code sequence signal transmitted by the base station to determine the location of the subscriber unit.

Abstract: A multi-sectored, multiple access communication system provides for low-skew sector transceiver clocks by novelly utilizing a multi-tap digital Phase-Locked Loop (PLL) in the delay match circuitry of each transceiver to efficiently and inexpensively generate clock signals for each transceiver that are temporally aligned within acceptable limits of the other transceivers. The inventive system and method obviate the need for matching the lengths of all of the cables connecting the base station (“master sector equipment”) to the transceivers (“slave sector equipment”), and also reduces the power requirement as a byproduct.

Abstract: A method for mitigating the effect of interference between a first base station and a second base station, the first base station and second base stations both sharing a same primary synchronization code. The method includes generating a primary synchronization channel having the primary synchronization code. In a W-CDMA system, all base stations share this primary synchronization code, causing code timing collisions. The present invention includes rotating the primary synchronization channel in phase according to a phase rotation sequence before transmitting the primary synchronization channel. By rotating the primary synchronization channel in phase according to the phase rotation sequence, the interference can be reduced. The phase rotation sequence may be pseudorandom in phase. The phase rotation sequence may include changing phase once per slot, or alternately once per frame. The phase rotation sequence may also be based at least in part on a secondary synchronization code.

Abstract: A data communications system, particularly suited for shared or wireless communications channels, capable of accommodating terminals having different throughput capabilites by flexibly allocating cyclically rotated phases of a common code is disclosed. One or more shifts of a cyclic orthogonal code are assigned to a terminal. These codes are preferably cyclically padded to increase their tolerance to arbitrary time shifts, and the resulting codes are used to spread the signals for transmission.

Abstract: A method and apparatus for improving bit error performance within a hard decision radio interface processing environment is provided, whereby a sampling unit collects a number of samples per channel symbol of an input signal to generate a number of sampling streams, and a correlator computes a correlation value of each of the number of sampling streams with a predetermined bit sequence. The correlation values are fed into a threshold comparator which utilizes a variable threshold value to generate threshold comparator values or trigger output values. By examining a set of trigger output values, a phase decision unit determines the optimum sampling timing or sampling phase.

Abstract: A method and system for synchronizing the PN phase of a pseudo-noise (PN) coded signal with a phase of a master PN decade-code is provided. The method includes the steps of associating the master PN decade-code initialization t0 with a first time zone reference date and time and determining an elapsed time t1. The next steps equate the elapsed time t1 to a corresponding phase of the master PN code and synchronize the phase of the PN coded signal with the corresponding phase of the master PN decade-code.

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

Abstract: A pseudo noise code acquisition apparatus in a direct sequence spread spectrum receiver capable of minimizing a retard involved in the updating of a pseudo noise code sequence, thereby achieving a reduction in pseudo noise code acquisition time. The apparatus is configured to conduct a pseudo noise code update prior to a threshold comparison after a spread spectrum signal is subjected to despreading and correlation for a desired number of chips. By this configuration, when it is determined, based on the result of the threshold comparison, that acquisition of a desired pseudo noise code has failed, it is possible to receive data associated with a new pseudo noise sequence without any delay.

Abstract: A system and method for detecting an impulse radio signal obtains a template pulse train and a received impulse radio signal. The system compares the template pulse train and the received impulse radio signal to obtain a comparison result. The system performs a threshold check on the comparison result. If the comparison result passes the threshold check, the system locks on the received impulse radio signal. The system may also perform a quick check, a sychronization check, and/or a command check of the impulse radio signal.

Abstract: A DAB (Digital Audio Broadcasting) receiver includes a delay circuit for delaying a received DAB signal by a prescribed period, a correlation circuit for taking correlation between a delayed output of the delay circuit and the DAB signal, a moving average circuit for moving-averaging a correlation output of the correlation circuit over a width that is equal to a guard period, a peak detection circuit for detecting a position in time of a peak of a moving average output of the moving average circuit, a calculation circuit for calculating an error in a reception frequency based on a phase deviation in the DAB signal at the position in time that is indicated by a peak detection output of the peak detection circuit, an FFT (Fast Fourier Transform) circuit for subjecting the DAB signal to FFT processing, and a detection circuit for determining a reception center frequency based on an FFT output of the FFT circuit.

Abstract: In a receiver receiving a signal, the signal including data which is at least modulated by a cyclic sequence, a method for operating the receiver, the method including the steps of receiving a portion of the signal, the portion being modulated by a predetermined section of the cyclic sequence, receiving an additional portion of the signal, the additional portion being modulated by the predetermined section of the cyclic sequence, jointly processing the portion and the additional portion and producing a set of receiver parameters, the receiver parameters minimizing a predetermined cost function for the predetermined section of the cyclic sequence.

Abstract: The invention relates to a system for transmitting packets from interactive terminals to a head station. The terminals intended for consumers are provided with local oscillators which are not very accurate and use carriers having frequency errors which are relatively large with respect to the theoretical reference value (Fp). The invention provides an improvement of the reception of signals having such a frequency shift at the receiver end. To this end, the invention provides a method of estimating the frequency error &Dgr;{circumflex over (f)}, which consists of rapidly obtaining the maximum value of a discrete error function denoted Z(&Dgr;{circumflex over (f)}) for a given accuracy (Acc) by computing the function Z(&Dgr;{circumflex over (f)}) for a minimal number of points.

Abstract: A method for improving the performance of a random access communications system in a variable radio environment is disclosed, whereby at least one valid set of burst signatures is used for transmission by one or more mobile stations. Each set includes at least one signature with a different signature-length than the signatures in other sets. The different signature-lengths can be optimized for the operational environments involved (e.g., longer signatures for slower-moving mobile stations, and shorter signatures for high-speed mobile stations). Alternatively, at least one differentially-encoded signature is used for random access transmissions, in order to reduce the radio channel's sensitivity to large doppler spreads and frequency errors.

Abstract: An improvement for obtaining synchronization to a chip-sequence signal. The chip-sequence signal has a plurality of chips, and is embedded in a spread-spectrum signal. A set of M shift registers stores a replica or delayed replica of the chip-sequence signal. Each shift register has a plurality of taps, which correspond to the plurality of chips. A plurality of comparators compares, with a delay of 1/M chip duration per shift register, the chip-sequence signal embedded in the spread-spectrum signal with the replica of the chip-sequence signal stored in the set of M shift registers. From the comparison, the plurality of comparators generates, for each tap of the shift register, a plurality of compared values at each comparator of the plurality of comparators. A plurality of counters up and down counts, from each comparator, a respective plurality of compared values. The respective plurality of compared values appears at an output of a respective comparator of the plurality of comparators.

Abstract: A method for estimating an interference phase shift when receiving a multicarrier signal formed of a time series of symbols modulating a plurality of carrier frequencies, at least some of the carrier frequencies of at least some of the symbols bearing reference elements, whereof the value at transmission level is known by the receiver carrying out the reception. The phase variation &dgr;n between at least two symbols bearing reference elements is estimated by analysing the reference elements. Each of the reference elements in the estimation is weighted by information representing the noise affecting the carrier frequency bearing the reference element.

Abstract: Short pseudo-random (PR) probing sequences that comply with ITU V.90 digital impairment learning (DIL) descriptors provide DIL probing sequences that yield high performance in severe inter-symbol interference (ISI) channels. The short PR sequences do not require the insertion of extra zero symbols to get rid of ISI. Further, a novel receiving structure corrects for propagation of digital impairment common in conventional equalizers for an ISI free receipt of the probing sequences within the strictly time constrained probing sequence. Based on the reliably received signals, general digital impairment mapping tables, digital pads, regular and strange RBS patterns, and different types of PCM codecs (A-law/&mgr;-law) are identified.

Abstract: A multi-carrier transmission system using orthogonal carriers with high order QAM constellations for the transmission of multiple bits per carrier and symbol. Such systems place high demands on the synchronization of the receiver with the transmitter. The maximum permitted deviation from exact synchronization is usually a small fraction of a sampling interval. A reserve carrier, the pilot carrier, which is given a fixed phase, is usually used as the reference to achieve this high accuracy. The receiver sampling clock oscillator is phase locked to the pilot carrier. It is therefore necessary to estimate the phase of the pilot carrier. Using a bandpass filter to recover the pilot carrier, regardless of the frame structure of the DMT signal, does not eliminate the influence of neighboring carriers on the pilot carrier.

Abstract: An orthogonal frequency division multiplexed wideband communication system provides improved time and frequency synchronization by inserting an unevenly spaced pilot sequence within the constellation data. A receive correlates the received data using the unevenly spaced pilot sequence. The pilot sequence is generated with a maximum length pseudo random noise code and inserted into frequency bins having prime numbers.

Abstract: A signal receiving device, and a radio transmission device and radio transmission method utilized a code sequence extracting circuit for receiving transmission data that is information data to be transmitted having a code sequence of a fixed bit length, formed based on prescribed identification data, and for extracting the code sequence from said transmission data received, a comparison circuits for comparing the code sequence previously allocated to the receiving side with the code sequence of the transmission data extracted by the code sequence extracting circuit, and a control unit for conducting control based on the information data of the transmission data when the comparison result of said comparison circuit shows identity.

Abstract: A method, system and device for code-phase tracking and/or carrier tracking the broadcast signal streaming a spread spectrum signal using an adaptive and time variant digital filter based on an AutoRegressive (AR) model of a Maximum Entropy Method (MEM) algorithm for signal filtering. Alternatively, the Maximum Likelihood Method, the Minimum Variance Method or any statistical method can be used in the adaptive filter for noise filtering. The method and device use a code generator to produce a replica of a PRN code and at least two correlators to separately perform signal correlation between the PRN replica and the received spread spectrum signal in order to extract the code signal for code-phase tracking, and the carrier signal for signal tracking. One or more A/D converters are used to convert the received spread spectrum signal into a digital signal so that signal filtering can be performed digitally. A demodulating step is used to extract the message from the received signal.

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: A method is disclosed for receiving a transmitted signal in a communication system employing CDMA techniques wherein the transmitted signal includes a plurality of short codes, each of which is transmitted repetitively over a fixed period of time and where the received signal has CW interference in addition to the transmitted signal. The method includes using a Sequential Ratio Probability Test (SPRT) for detecting the presence of the short code in a plurality of time phases of the received signal by calculating a likelihood ratio for each phase. A likelihood ratio is a comparison of the signal's Probability Distribution Function (PDF) with a background noise PDF. The background noise PDF is calculated by combining in the RAKE the current short code with the input signal.

Abstract: A loop error detector for use in a Pseudo Noise (PN) code timing tracking loop is disclosed. A first multiplexer receives an early I-channel signal and an early Q-channel signal, and alternately selects the received early I and Q-channel signals at a ½-chip period. A first accumulator accumulates the early I and Q-channel signals multiplexed by the first multiplexer for a specific chip period. A second multiplexer receives a late I-channel signal and a late Q-channel signal, and alternately selects the received late I and Q-channel signals at a 1/2-chip period. A second accumulator accumulates the late I and Q-channel signals multiplexed by the second multiplexer for the specific chip period. An operator calculates a sum and a difference of the early and late I-channel signals accumulated by the first and second accumulators, calculates a sum and a difference of the early and late Q-channel signals, and multiplies the sums by the differences.

Abstract: A chip synchronization composite code match filter and a frame synchronization composite code match filter are disclosed and respectively serve as the first and second stages of a mobile terminal which also has a third stage for providing a scrambling code identification function. These three stages complete the acquisition function for the mobile terminal. The mobile terminal is particularly suited for operational interaction in the Third Generation Partnership Project (3GPP) Standard. Both the chip synchronization and frame synchronization composite code match filters utilize the hierarchial structure of the Golay code in a manner so as to reduce the components needed to accomplish the chip and frame synchronization functions for the mobile terminal operating within the 3GPP standards.

Abstract: A multiple access, spread-spectrum communication tracking system includes apparatus which tracks a centroid of a transmitted code-division multiplexed (CDM) code sequence that is contaminated with multipath distortion. The apparatus includes an analog to digital converter which digitally samples the spread-spectrum channel signal to produce a sequence of sample values. The sample values are divided into a set of even-numbered sample values which correspond to early multipath signal components and the set of odd sample number values which correspond to the multipath signal components. The centroid tracking receiver generates a plurality of local code sequences, each of which is a code phase-shifted version of the transmitted code sequence. The centroid tracking receiver correlates each of the locally generated code sequences with the odd and even numbered sample values, respectively, to produce a group of early despread multipath signals and a group of late despread multipath signals.

Abstract: The present invention is a channel-aided, decision-directed delay-locked loop (CADD-DLL) implemented, in one embodiment of the present invention, for pilot-symbol-aided (PSA) code-division multiple-access (CDMA) communication. In one embodiment of the present invention initial pseudo-noise (PN) code acquisition is accomplished with the aid of a conventional non-coherent PN code acquisition system, and, upon acquiring the initial PN code epoch, PN code tracking is performed using a channel-aided, decision-directed PN code tracking mechanism. The tracking loop in accordance with the present invention includes delay and advance PN correlators. The correlators are followed by data and phase correction as well as amplitude matching devices, the outputs of which are subtracted to form an error signal for code tracking purposes.

Abstract: For synchronisation purposes, a transmitter (TX) multiplexes a pilot carrier with carriers whereon data elements (DATA) are modulated, and transmits the pilot carrier together with the modulated carriers to a receiver (RX). The immunity of the pilot carrier from interference, such as radio amateur signals, is improved by modulating the pilot carrier with a non-constant signal, for instance a random signal, an alternating signal or even scrambled data elements (DATA), before transmission thereof. Since demodulation of the pilot carrier in the receiver (RX) and averaging successive demodulated pilot carriers reduces the effect of the interference induced on the non-constantly modulated pilot carrier, the degradation of the synchronisation between transmitter (TX) and receiver (RX) is reduced significantly.

Abstract: A method and concomitant apparatus for adapting a logic threshold level in response to a background noise level in an information signal. Information signal excursions beyond the logic threshold are indicative of the presence of an information packet in the information signal. In this manner, a relatively low dynamic range information packet processor may reliably receive information packets.

Abstract: A receiver of signals modulated by pseudorandom noise that uses a hierarchy of delay lock loops (DLLs) to maintain code lock. Each DLL in the hierarchy produces a control signal representative of a timing mismatch between the incoming signal and an internally generated pseudorandom noise code, preferably by correlating the incoming signal with early and late instances of the code and subtracting the late correlation from the early correlation. The early correlation is advanced relative to the late correlation by successively shorter spacings in successively lower DLLs in the hierarchy. In each DLL, the control signal is transformed to a code phase signal for adjusting the timing of the code generator. In the lower DLLs, this code phase signal is compared to the delay signal of the immediately higher DLL and adjusted accordingly.

Abstract: A method of, and frame synchronizing device for, synchronizing systems having a digital interface. The systems are synchronized by extracting frame time information from a signal transferred from an external source through a digital interface, generating a frame reset signal, delayed by predetermined time based on the extracted frame time information, and resetting the entire systems based on the generated frame reset signal. Also, the color burst signal is free-oscillated during the digital interface mode in order to accommodate to the frame reset signal, which has a variable period.

Abstract: A known training sequence of binary, pseudo random signals, PN, is received over the channel and correlated with a modified pseudo random sequence PN−1 in which the zeros of the known sequence PN have been mapped to −1. A transform of the correlator output will be observed to contain strong tones that indicate the degree of frequency offset. To facilitate synchronization in the presence of an unknown amount of frequency offset, the received signals may be rectified and the correlation step performed with the absolute value of the incoming signal to obtain new output samples. When the frequency offset is small its measurement is facilitated by modulating the incoming signals with a known, comparatively large frequency offset, before the correlation step to make sure that the overall frequency offset occurs around a frequency that is an integral multiple of the symbol rate divided by the number of symbols in the pseudo random sequence.

Abstract: In a multiplex transmission method, a plurality of digital signals having different frame lengths and bit-synchronized at the same signal rate are transmitted after the signals are multiplexed in a predetermined order. The received multiplexed signal is demultiplexed. A predetermined sync pattern is detected from each digital signal obtained by demultiplexing. The output position of each digital signal is determined on the basis of the sync pattern detection result. A multiplex transmission system is also disclosed.

Abstract: A current mode of operation is provided to a Walsh spreader (203), and based on the current mode of operation, the Walsh spreader (203) either varies a Walsh code at a symbol rate, or holds the Walsh code constant. During multi-carrier transmission a first symbol within a data stream (210) is spread with a first Walsh code, while symbols immediately preceding and following the first symbol are spread by a another, differing Walsh code. The sequence of Walsh codes exiting the spreader (201) is further scrambled by a pair of Pseudo-Noise (PN) codes (224) that are held constant for three Walsh code periods during multi-carrier transmission, and are not held constant during direct-spread transmission.

Abstract: A wireless telecommunications systems (1) includes a central terminal (10) for transmitting and receiving radio frequency signals to and from a subscriber terminal (20). A downlink communication path is established from a transmitter (200) of the central terminal (10) to a receiver (202) of the subscriber terminal (20). A downlink signal (212) is transmitter from the transmitter (200) to the receiver (202) during setup and operation of the wireless telecommunications system (1). The receiver (202) of the subscriber terminal (20) compares a code and phase of a master code sequence in the downlink signal (212) to a code and phase of a slave code sequence of the receiver (202). The receiver (202) adjusts the phase of the slave code sequence until a match is obtained with the master code sequence. The downlink signal (212) includes an overhead channel (224) having a power control signal (236), a code synchronization signal (234), and a frame alignment signal (232).

Abstract: A communication system and method for transmitting relatively short data messages in the communication system. A dedicated frequency is sequentially switched into each of a plurality of satellite beams or traffic channels to transmit data messages at an increased power level to provide an increased signal margin. The increased power level of the dedicated frequency can be combined with coding and bit and message repetition to further increase the signal margin.

Abstract: Synchronized receiver circuitry and methods are provided for a spread-spectrum communications system which includes a transmitter for generating a data-modulated carrier signal encoded with a predetermined discrete-stepped, cyclical pseudo-random noise code sequence, and a receiver for despreading and demodulating the encoded spread-spectrum modulated carrier signal. The receiver has a pseudo-random noise code generator, a mixer connected to the pseudo-random noise code generator for mixing the encoded spread-spectrum modulated carrier signal with the code sequence provided by the pseudo/random noise code generator to despread the carrier signal, and an indicator in the receiver for generating a received signal strength indicator analog signal. The synchronized receiver includes a clock which provides a frequency output corresponding to the frequency of the clock driving the pseudo-random noise code generator in the transmitter.

Abstract: A non-coherent method for (PN) code synchronization and eliminates the need for prior clock synchronization between a transmitter and receiver. The method further eliminates any need for prior knowledge of a transmitted data sequence to provide synchronization. In the method, based on a coarse estimation of the carrier frequency, a received CDMA intermediate frequency (IF) signal is baseband converted to in-phase (I) and quadrature-phase (Q) components. The baseband I and Q components are then used to calculate an estimated delay {circumflex over (&tgr;)} at a PN synchronization roll-over point. The estimated delay {circumflex over (&tgr;)} is used in an intermediate data sequence in the synchronization roll-over calculation process to more accurately estimate carrier frequency error and phase offset for the IF carrier signal used in the baseband conversion process.

Abstract: A method of chip interleaving in direct sequence spread spectrum communications. A binary code sequence is chosen to have a length N=2k−1 and to be self-orthogonal. A data string of M=QN+1 bits, QN−1 bits, or QN+S bits, where Q is a positive integer and S is an integer between 1 and N that lacks a common factor with N, is multiplied sequentially with the binary code sequence until N chip frames of M chips each are produced. These chip frames are transmitted to a receiver, and recovered in an equally straightforward manner. The integers Q and N are chosen according to transmission conditions.