Abstract: In a CDMA receiver, an A/D converter over-samples an analog reception baseband signal with a sampling clock a frequency of which is 2n times higher than a chip clock, and converts it into a digital reception baseband signal. A correlator obtains a correlation value between the digital reception baseband signal and a pilot spreading code which is synchronous with a reception timing. A phase difference detecting unit obtains a phase difference between the digital reception baseband signal and the reception timing based on the correlation value. A timing controlling unit changes the reception timing in such a manner as to eliminate the phase difference obtained by the phase difference detecting unit.

Abstract: The present invention comprises a method and apparatus for synchronizing data frames from a wide bandwidth data stream which is divided up and transmitted across a plurality of parallel channels in a mobile telephone system. Prior to transmitting the data frames, a transmit synchronizer synchronizes data frames aligned in the same position in different parallel channels by inserting a common bit from a repeating PN synchronization sequence into the aligned data frames. Upon receiving the data frames at a destination, a receive synchronizer extracts the synchronization bit from each data frame. A series of sequential bits from each parallel channel is compared against the original PN synchronization sequence to identify the position of each data frame relative to the other data frames and reconstructs the original wide bandwidth data stream.

Abstract: The present invention comprises a method and apparatus for synchronizing data frames from a wide bandwidth data stream which is divided up and transmitted across a plurality of parallel channels in a mobile telephone system. Prior to transmitting the data frames, a transmit synchronizer synchronizes data frames aligned in the same position in different parallel channels by inserting a common bit from a repeating PN synchronization sequence into the aligned data frames. Upon receiving the data frames at a destination, a receive synchronizer extracts the synchronization bit from each data frame. A series of sequential bits from each parallel channel is compared against the original PN synchronization sequence to identify the position of each data frame relative to the other data frames and reconstructs the original wide bandwidth data stream.

Abstract: A method and apparatus for replacing lost PSTN data in a packet network and for generating variable power white noise are disclosed. In one embodiment, the method for replacing data includes the steps of receiving data packets, detecting lost data packets, and producing in response a lost data output indicating when replacement data needs to be provided. The method preferably generates the replacement data by re-using data stored in an extended playback buffer (with the re-used replacement data starting with the oldest output data byte stored in the extended playback buffer), and placing the re-used replacement data on an external network. Another aspect of the invention is a variable power white noise generator for providing replacement data. The variable power white noise generator may use, for example, a multi-bit register that stores a magnitude, and a pseudo-random sign bit generator to change the positive and negative sense of the magnitude.

Abstract: A method, system, and apparatus assigns each sector in a cell a unique preamble spreading code and a unique long-code which is concatenated with a signature-associated short code to spread the data in the data field. The period selected for the long-code can be relatively long in duration (e.g., up to hours or days in length). The widths of the transmission time slots are set equal to the length of the preambles. Subsequent to the preamble period, the matched filter is still enabled to receive the preambles of other random access requests. Therefore, the matched filter can be utilized continuously and more efficiently. Additionally, the length of the data field is not restricted. The method of concatenated spreading of the data field portion of the random access packet allows a user to generate a packet which is as long as desired. Moreover, there is very little danger that the resulting packet will collide with other random access request packets.

Abstract: In a cellular communications system having synchronized base stations and unsynchronized base stations, wherein the synchronized base stations are synchronized to system time and have a common pilot PN sequence used for all synchronized pilot channels, a marker sequence is selected. The selected marker sequence is comprised of an M-chip portion of the common pilot PN sequence. Next, a coded portion of an unsynchronized pilot PN sequence is generated wherein the coded portion identifies a selected unsynchronized base station. The marker sequence and the coded portion of the unsynchronized pilot PN sequence are combined to form the unsynchronized pilot PN sequence that is different from the common pilot PN sequence. Thereafter, an unsynchronized pilot channel baseband signal of an unsynchronized base station is spread with the unsynchronized pilot PN sequence to produce the unsynchronized pilot channel.

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

Abstract: A system for maintaining orthogonality among a plurality of spread-spectrum signals arriving at a base station from a plurality of remote units. Each spread-spectrum signal of the plurality of spread-spectrum signals from each remote unit of the plurality of remote units is transmitted as a packet having a header followed by data. A base station sends a plurality of adjustment signals over a communications channel to the plurality of remote units, respectively. At each remote unit, a circuit selects, from the plurality of adjustment signals, a received-adjustment signal designated for each remote unit. A chip-sequence generator, located at each remote unit, generates a chip-sequence signal assigned to a respective remote unit and, responsive to the adjustment signal, adjusts timing of a chip-sequence signal generated by the chip-sequence generator.

Abstract: A method and circuit for adaptively determining a pilot signal reacquisition time. A searcher subsystem measures a phase of the pilot signal. A control processor measures a magnitude of a shift in the pilot signal phase, compares the measured magnitude to a shift threshold, and decreases the reacquisition time if the measured magnitude is not greater than the shift threshold. The control processor also may compare the reacquisition time to a minimum reacquisition time, and decrease the reacquisition time only if the reacquisition time is greater than the minimum reacquisition time. Additionally, the control processor may increase the reacquisition time to a maximum reacquisition time if the measured magnitude is greater than said shift threshold.

Abstract: A network interface in a workstation computer includes a pattern matching circuit to enable the workstation computer to wake up to perform prescribed operations requested by a remote workstation. The pattern recognition circuit includes a pattern memory configured for storing a pattern entry for at least a portion of a predetermined pattern. The pattern entry includes a pattern data field and a second field specifying a number of bytes in the input data stream to be ignored prior to comparison with the pattern data field. The pattern matching circuit also includes a comparator for comparing the pattern data field with a selected group of bytes from the data stream. Pattern match logic determines whether the received data packet includes the predetermined pattern based on the comparison result.

Abstract: When a mobile communication unit (e.g. a cellular telephone) is powered up, the unit must lock on to a local base station, or "acquire" a base station signal, to enable the user to send and receive calls. To lock on a local base station, the mobile unit must determine the delay at which the base station is sending the pseudo random (PN) code. This process is called the "acquisition." The current art of acquiring a base station involves collecting a set of samples at a particular code phase, or delay, testing the collected sample, and repeating these steps using another code phase until the correct code phase is found. The present invention discloses a method and apparatus for collecting a set of samples at a particular code phase, and simultaneously testing the collected sample and collecting the next set of samples for another code phase.

Abstract: A method of communication between a base station with at least a mobile unit communication apparatus, a base station and a mobile unit communication apparatus employing the method are disclosed. The base station has a plurality of antennas for the antenna diversity. Transmission data is spectrum-spread with a pn code for a target mobile unit communication apparatus and a pilot signal is also spectrum-spread with a pn code every antenna, which are frequency-multiplexed. A mobile unit de-spectrum-spreads the pilot signal with one of pn codes selected, which corresponds the transmitting antenna. The pilot signal and data may be time-division-multiplexed in a time slot. Data of the used antenna is transmitted by the base station by a position of null data in the time slot, or differentially coded which is detected by a null data detection circuit or by the delayed detection. Data of the antenna used may be transmitted by a mobile unit communication apparatus.

Abstract: When a mobile communication unit (e.g. a cellular telephone) is powered up, the unit must lock on to a local base station, or "acquire" a base station signal, to enable the user to send and receive calls. To lock on a local base station, the mobile unit must determine the delay at which the base station is sending the pseudo random (PN) code. This process is called the "acquisition." The current art of acquiring a base station involves searching the possible code phases, or delays, one by one until the first signal is found. However, multiple base stations may be available to the mobile user, and the first found pilot signal may not be the strongest and may not be from the nearest base station. The present invention discloses a method and apparatus for searching all possible PN code phases and selecting the strongest phase instead of selecting the first phase.

Abstract: A method of chip interleaving in direct sequence spread spectrum communications. A binary code sequence is chosen to have a length N=2.sup.k -1 and to be self-orthogonal. A data string of M=QN.+-.1 bits, where Q is a positive integer, 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.

Abstract: A wireless telecommunications system (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 transmitted from the transmitter (200) to the receiver (202) during setup and operation of the wireless telecommunications system (1). The downlink signal (212) includes an overhead channel (224) having a code synchronization signal (234). The code synchronization signal (234) is capable of adjusting a phase of a transmitter (204) in the subscriber terminal (20). A receiver (206) in the central terminal (10) monitors an uplink signal (214) transmitted by the transmitter (204) in the subscriber terminal and provides changes to the code synchronization signal (234) such that the transmitter (204) is synchronized to the receiver (206).

Abstract: A message transmission system includes at least one primary station arranged for making transmissions on a down-link and a plurality of secondary stations arranged for making transmissions on an up-link, each of the secondary stations having its own address which is transmitted as part of the down-link message. Each of the secondary stations is configured for generating responses to messages as pseudo-random data sequences, the pseudo-random data sequence being generated by a secondary station at any one time being dependent on at least the address assigned to the secondary station and/or information contained in the message.

Abstract: In a direct sequence spread spectrum digital communication receiver, a system and method for recovering and verifying the timing or phase of a pseudo-random noise (PN) sequence used for despreading received signals. In one embodiment, the method includes steps of: (a) determining an initial value of a received PN phase, (b) setting the receiver's PN phase equal to the initial value of the received PN phase, (c) a first testing to verify that the receiver identifies a SYNC field within a testing time of predetermined duration, (d) a second testing, to verify that temporarily shifting the receiver's PN phase results in a degraded correlation between the receiver's PN sequence and the received signal, and (e) repeating steps (a)-(d) if either of the testings indicate that the receiver's PN sequence is not correct.

Abstract: In a digital communication system for voice signals, a system and method for recovering the timing of a pseudo-random noise (PN) sequence used for direct-sequence spreading and despreading of the communicated signals. In one embodiment, a received signal is a time-division duplexing (TDD) or time-division multiple access (TDMA) signal, and a receiver performs a complete "sliding correlator" examination of the received signal in a fixed time by using the timing of the TDMA or TDD frames. This examination allows a rapid initial acquisition of the PN synchronization. In another embodiment of the receiver, the initially acquired PN phase is verified by reading a SYNC field from the received signal and by checking that shifting the receiver's local PN phase results in a degraded correlation between the local PN sequence and the received signal.

Abstract: A method for synchronism acquisition between a spread code sequence at a transmission side and a despread code sequence at a reception side in spread spectrum (SS) communication such as a direct sequence (DS). The method includes steps of (a) calculating correlation values for the despread code at different chip phases with successively displacing the chip phases of the despread code at intervals of 1/N chip over a full search range for the synchronism acquisition, N being an integer equal to or larger than 2, (b) selecting, as candidates, a plurality of chip phases which correspond to comparatively high values from among the correlation values, (c) adding, for each of the candidates, correlation values of chip phases adjacent the candidate to the correlation value of the candidate, and (d) determining one of the candidates which exhibits a highest result of addition as a chip phase having acquired synchronism.

Abstract: A digital cordless telephone system can prevent control signals transmitted from a plurality of base stations from interfering with each other. In a digital cordless telephone system wherein a communication signal is transmitted among it and terminal stations by transmitting digital data through a predetermined channel and a communication among it and the terminal stations is controlled by a control channel different from the predetermined channel, data in a slot arrangement is used as a control signal, the control signal of the slot arrangement is intermittently transmitted at a constant interval, and a transmission at every constant interval is randomly extinguished.

Abstract: A correlator used for spread spectrum communications which reduces consumed power. A signal extraction circuit (6) is provided for directly extracting phase information from an input signal which expresses two values of code data by each phase of a plurality of cycles. A signal transferring circuit (1) is connected to the signal extraction circuit (6) for transferring the phase information to a multiplying circuit (2) comprised of a plurality of multipliers. Signals in each cell of the signal transferring circuit (1) are multiplied by fixed coefficients within the multiplying circuit (2) and supplied to an adding circuit (3) for determination of a correlation peak value.

Abstract: Disclosed is a method for transmitting information in a CDMA communication system, the method including steps of (a) multiplexing data and control information into a data stream; (b) encoding the data stream to form a stream of encoded I/Q symbol pairs; (c) inserting synchronization information into the stream of encoded I/Q symbol pairs; and (d) spreading the encoded I/Q symbol pairs and the inserted synchronization information using a same pseudonoise (pn) spreading code prior to transmission as a frame. The preferred frame structure includes an unencoded synchronization field followed by a plurality of multi-byte data fields. Individual ones of the plurality of data fields are separated by a control message field. Individual ones of the control message fields contain a single byte of a multi-byte control message frame.

Abstract: A digital cordless telephone system can prevent control signals transmitted from a plurality of base stations from interfering with each other In a digital cordless telephone system wherein a communication signal is transmitted among it and terminal stations by transmitting digital data through a predetermined channel and a communication among it and the terminal stations is controlled by a control channel different from the predetermined channel, data in a slot arrangement is used as a control signal, the control signal of the slot arrangement is intermittently transmitted at a constant interval, and a transmission at every constant interval is randomly extinguished.

Abstract: In a mobile communication system using spread spectrum, performing respective multiplications of an I and Q channel signals by a spreading code replica, integration over one spreading code period, and square-law detection of the integrated signals to remove data modulation components and residual carrier frequency components. The square-law detected signals are added to obtain signal power over one spreading code period while updating the clock phase of a digital control clock generator. The information of power is stored in a memory in an acquisition mode controller, and the clock phase of the digital control clock generator 30 is fixed at the spreading code replica phase at which a maximum correlation detection power over one spreading code period is obtained. Subsequently, a confirmation mode is started for confirming the spreading code acquisition phase.

Abstract: For a CDMA communication system using an interference canceller, a communication system which enables the interference canceller to easily confirm pulling-in of its own signal is disclosed. Input transmission signals are stored through a serial-parallel converter 101 in storage circuits 301 and 302, each of which holds one frame of transmission signals for I and Q axes. An area for holding one cycle of spreading codes for the I and Q axes output from a spreading code generator 105 is formed in the rearmost part of each of the transmission data strings of the storage circuits 301 and 302. One frame of transmission signals prepared by a pilot inserting device 102 and frame synchronizing signals are transferred to a transmitted circuit 103 in sequence. These signals are then transmitted as data for the I and Q axes by symbol rate clocks.

Abstract: A wireless telecommunications system (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 transmitted 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. Matching of the slave code sequence to the master code sequence facilitates establishment of the downlink communication path.

Abstract: A method and system aggregate data on multiple physically separate lower-speed E1/J1 channels of a communications network to generate higher bandwidth. A high speed data stream is first divided into lower bandwidth channels and transmitted through the network. The data arrives with varying delays depending on the physical characteristics of the network. Low bandwidth channels are aggregated together into a high bandwidth channel by determining the different geographical delay parameters among the lower speed channels, adjusting the transmission delays by alignment circuitry, and then combining the lower speed signals into one high bandwidth channel for the user. The transmission delay adjustment consists in adding a pseudo-random noise pattern to each of the lower bandwidth channels, measuring the time difference among all the channels, and then adjusting the time differences in the received data stream so that the combination of the signals produces a coherent higher bandwidth data stream.

Abstract: A star configured multiple access radio communication system wherein a hub station communicates, in time division multiplex mode, with a plurality of remote subscriber stations by a forward link signal path and the remote subscriber stations communicate with the hub on a return link signal path and wherein all received return link signals are time synchronous, and all signals possess the same time division multiplex structure in which a portion of the signal is dedicated to time synchronization. Each remote subscriber station has a synchronization burst sequence generator, each generated burst sequence is constructed such that the time tracking and synchronization process of each return link is relatively unaffected by all other remote stations. At the hub station there is a delay discrimi-nator for each remote subscriber, each delay discriminator includes a first and a second channel. The first channel has a one symbol delay device, a matched filter, and a squaring circuit.

Abstract: A discrete multitone modulation transmission system is described in which frame synchronization is monitored using a transmitted synchronizing frame. The existence or loss of frame synchronization is determined by comparing the values of the synchronizing frame with corresponding stored values.

Abstract: In a time division multiple access spacecraft communication system, each ground station determines when to send its information packets to arrive at the spacecraft at the beginning of a time slot. The calculation is based upon knowledge of the locations of the spacecraft and the transmitting ground station. A master ground station determines the location of the spacecraft by the use of the propagation delays between the various ground stations (including itself) and the spacecraft, together with knowledge of the locations of the ground stations. The spacecraft location is then transmitted back to the various ground stations. The determination of propagation delay by each ground station is performed by repeatedly transmitting a ranging signal containing a multiple-bit unique word to the spacecraft, and counting spreading code chips until the next unique word is received from the spacecraft.

Abstract: The present invention describes a communications system that utilizes frequency division multiple access (FDMA), code division multiple access (CDMA), and time division multiple access (TDMA) techniques for providing efficient use of frequency spectrum while supporting a large number of transmitters/users (2-6). Many users of the communications system share a common frequency band, but each transmit their respective message bursts (50) at different and specific times via a TDMA technique. To facilitate synchronization of the TDMA technique, each transmitter of the system is synchronized to a common timing reference (1) thereby abating the need to maintain synchronization between the transmitters (2-6) and receivers (8-12) of the system.

Abstract: In a new receiver design, the specific transmitter unit is unchanged from a prior patent application but may also be substantially as described in the prior art. The transmitter is initially activated by the input of the pseudo-random generator code. This code may be any alpha-numeric series, but must be identical to that input to the receiver. When the code is input through the keypad, the transmitter uses internal algorithms to generate a unique shift-register feedback combination. This creates a pseudo-random (PN) code which repeats after a programmable number of bits, depending upon desired maximal signal correlation time. That is the longer the code the longer the correlation time. This PN code sequence is clocked at the desired clock (CHIP) rate inside the transmitter unit. The PN code sequence which is thus generated is then added in phase to the data which is a substantially lower rate than the CHIP rate.

Abstract: The object of the invention is a demultiplexing device.This device is characterized in that it comprises means for storing data of a multiplexed data stream (4), programmable means for storing data filters (8), comparison means (19) between the data of the multiplexed data stream and the data filters, and means (12) for transferring data of the multiplexed data stream to storage means (5) in relation to the comparisons made.The invention has a particular application in the field of digital television reception.

Abstract: A method and apparatus is provided to facilitate coherent communication in a random access channel. In encoding, reference symbols are inserted into a stream of access channel message data symbols and appended to a synchronization message to form a reference coded access channel transmission. Subsequently, the access channel transmission is prepared for transmission over a communication channel by being spread with a spreading code. In decoding, a known synchronization sequence is correlated with a received communication signal to generate a correlation peak when a synchronization message is present. The received communication signal is despread with a spreading code to derive a stream of reference samples and data samples. A channel response is determined from the correlation peak and revised based on estimates derived from the stream of reference samples. Finally, an estimated data symbol is detected from the stream of data samples by utilizing the revised channel response.

Abstract: A search method for acquisition of time synchronization between a spreading sequence of a receiver and a spreading sequence of a transmitter, the receiver receiving a spread signal and demodulating the signal using the spreading sequence of the receiver includes a test step consisting in measuring the energy of the demodulated signal by integrating the demodulated signal during a time interval Tobs.sub.i and comparing that energy with a threshold value to determine if the threshold value is exceeded, for a given hypothesis as to the time shift between the spreading sequences, and modifying the time shift hypothesis if the threshold value is not exceeded and incrementing the value of a counter. Steps a and b are repeated until the value of the counter reaches a predetermined value. When the predetermined value is reached, the time interval Tobs.sub.i is replaced with a time interval Tobs.sub.i+1, with Tobs.sub.i+1 =m.Tobs.sub.i and m>1, and the process resumes at step a replacing Tobs.sub.i with Tobs.sub.

Abstract: An orthogonal frequency division multiplexing signal transmitted from the transmitting end to the receiving end intermittently includes a particular symbol S0 having a predetermined particular pattern in addition to a symbol Sm including data to be transmitted. At the receiving end, the variation in the receiving level and/or the variation in the frequency band of a received signal are detected and corrected on the basis of the received particular symbol S0. Since the particular symbol S0 has a particular pattern, the variation in the level and/or the variation in the frequency are strongly correlated with the variation in the receiving level and/or the variation in the frequency band of the received signal. Consequently, the variation in the receiving level and/or the variation in the frequency band of the received signal can be accurately detected from the particular symbol S0 and consequently high-precision correction can be made.

Abstract: A synchronizing method and circuit accurately and stably operates a direct spread spectrum multiple access communication system. A signal transmitted by modulating the spreading code with data at the transmission side is sampled by a signal of n times (n: 1 or larger integer) the clock speed of the spread spectrum signal at the reception side, and the correlation is detected by a digital matched filter. Consequently, the detection output in every sample in the symbol period is compared with the envelope detection output determined in every sampling period, and the sample positions for a specific number of determined samples are stored in the descending order of the output. The number of times of storage of large sample positions in the stored detection output is counted in every symbol period, and the position of the largest number of storage times is detected as the peak position. From this peak position, capturing or holding the symbol period and setting of the reception window position results.

Abstract: A method of synchronizing to a pseudo random sequence, which can be generated by a linear feedback shift register having k stages and p intermediate taps, where k and p are positive integers and k>p, and a synchronization arrangement for carrying out the method are described. A received symbol sequence is supplied to a k-stage shift register with p intermediate taps in positions corresponding to the p taps of the linear feedback shift register. A respective correlation signal is recursively added at an input for the received symbol sequence and at each intermediate tap. Each correlation signal is produced by correlating at least two signals from said input, intermediate taps, and output other than the signal to which the respective correlation signal is added. The invention is particularly applicable to pilot synchronization in CDMA terminals.

Abstract: A method is disclosed for synchronizing, in the presence of sign ambiguity, to a pseudo random maximal length sequence having a characteristic polynomial of order k with a coefficients vector A given by:A=?1 a.sub.1 a.sub.2 . . . a.sub.k-1 1!where each of the coefficients a.sub.1 to a.sub.k-1 is 1 for an intermediate tap location and otherwise is 0. A received symbol sequence is supplied to and shifted through a K=k+1 stage shift register with P intermediate taps in positions determined by a coefficients vector A.sub.in given by:A.sub.in =?1 a.sub.1 (a.sub.1 .sym.a.sub.2) (a.sub.2 .sym.a.sub.3) . . . (a.sub.k-2 .sym.a.sub.k-1) a.sub.k-1 1!where a.sub.1 and a.sub.k-1 are the inverse of a.sub.1 and a.sub.k-1 respectively and .sym. denotes a modulo-2 sum, whereby the shift register has P intermediate taps where P is a positive integer less than K. A respective correlation signal is recursively added at an input for the received symbol sequence and at each intermediate tap.

Abstract: A digital audio broadcasting (DAB) system includes a radio-frequency (RF) transmitter and a corresponding RF receiver. The RF transmitter formats a DAB signal into a sequence of frames, each frame having a header comprising a predefined grouping of psuedo-random number sequences comprising 100 symbols. Of these 100 symbols, 86 symbols of the header are used for frame synchronization and channel sounding (for characterization of a communications channel), while the remaining 14 symbols are used for interleaver and data synchronization in an interleaved fashion.

Abstract: In a digital audio broadcasting (DAB) system having a radio-frequency (RF) transmitter and a corresponding RF receiver, a system and method for providing improved frame synchronization is provided. In accordance with the preferred embodiment, the RF transmitter formats a DAB signal into a sequence of frames, each frame having a header with a predefined grouping of psuedo-random number sequences comprising 100 symbols. Of these 100 symbols, 86 symbols of the header preferable are used for frame synchronization and characterization of a communications channel, while the remaining 14 symbols are used for interleaver and data synchronization in an interleaved fashion. The formatted DAB signal, including the frame sequences, is transmitted to the receiver preferably using quadrature phase-shift keying modulation. At the receiver, a correlator, utilizing a synchronization detection algorithm, is generally designed to match a predetermined symbol pattern within the received signal.

Abstract: A wireless telecommunications system (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 transmitted 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. Matching of the slave code sequence to the master code sequence facilitates establishment of the downlink communication path.

Abstract: A process may be implemented which obtains a signal indicating a synchronization error between a pseudo-random signal sequence from a transmitter and a reference pseudo-random signal sequence from a receiver in a measuring device on the receiving end. In order to be able to detect a synchronization error as quickly and reliably as possible, successive sections (a, b, c) of a reference pseudo-random signal sequence (g'(n)) are each cross-correlated separately with the received pseudo-random signal sequence (g(n)), yielding partial cross-correlation functions (KKF.sub.a (n), KKF.sub.b (n) and KKF.sub.c (n)). The partial cross-correlation functions are added up to obtain a sum cross-correlation function (KKF.sub.s (n)). The sum cross-correlation function (KKF.sub.s (n)) is analyzed to detect the proper chronological occurrence of at least three maximums (m.sub.a, m.sub.b and m.sub.c). If the maximums (m.sub.a, m.sub.b and m.sub.

Abstract: A receiving apparatus for a base station in a code division multiple access (CDMA) system performs a signal receiving method, and includes a pseudo-noise code generator that generates a pseudo-noise code corresponding to each receiving stage of a plurality of channels. A demodulator sequentially demodulates a received signal into baseband data according to the receiving stage in synchronization with the pseudo-noise code. A re-modulator re-modulates the baseband data to a signal of a channel corresponding to each mobile station in synchronization with a delayed pseudo-noise code.

Abstract: A bit insertion apparatus and method used to error encode data stored on data storage media monitors the number of bit insertions made on a given randomized block of data to determine if the number of bit insertions falls within the tolerable limits for storing the data. If the number of bit insertions is not tolerable, the pseudo-random code used to randomize the data stream is reconfigured. In a preferred embodiment, the bit insertion technique monitors the phase and amplitude content of the data stream and inserts appropriate bit patterns to ensure that phase and amplitude lock are maintained on the data stream for reading and decoding purposes.

Abstract: A system for receiving, correlating and interpreting secured wireless transmissions, periodic or otherwise, including multiplexed receivers, robust correlator design, a state machine device for controlling the receivers and correlation function, and the ability to determine signal spatial diversity via switched antenna signal processing. The correlator is constructed to include a synchronization scheme adaptive to any variety of input signals from the coupled receiver tuned frequencies.

Abstract: A wireless telecommunications system (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 transmitted from the transmitter (200) to the receiver (202) during setup and operation of the wireless telecommunications system (1). The downlink signal (212) includes an overhead channel (224) having a code synchronization signal (234). The code synchronization signal (234) is capable of adjusting a phase of a transmitter (204) in the subscriber terminal (20). A receiver (206) in the central terminal (10) monitors an uplink signal (214) transmitted by the transmitter (204) in the subscriber terminal and provides changes to the code synchronization signal (234) such that the transmitter (204) is synchronized to the receiver (206).

Abstract: An apparatus and method for synchronizing a spread spectrum receiver comprises a preamble matched filter and a plurality of symbol code correlators for receiving and correlating to a received spread spectrum signal. The preamble matched filter is preferably non-coherent in nature and outputs a correlation signal including a correlation pulse of variable width. The pulse is converted to a square wave having a duration of a discrete number of chip periods. The correlation pulse is used as a timing reference for the symbol code correlators, which are also non-coherent in nature. A center seeking circuit provides an offset to the timing reference according to the width of the correlation pulse. In a preferred TDMA system, a timing window is used for a subsequent time frame for defining a period of time in which the correlation signal output from the preamble matched filter can yield a valid correlation pulse.

Abstract: In one aspect of the present invention, a coding part of a transmitter side codes N series of input data into N+1 series of transmission data so that each of N+1 series of transmission data have frames and have the same transmission rates as those of the input data. For example, a bit transfer unit comprised in the coding part moves i-th bits of series i to the additional series N+1 where i=1 to N and a complement bit insertion unit inserts complements of an (N+1)-th bit of series 1 and (j-1)-th bits of series j into a first bit position of series 1 and j-th bit positions of series j, respectively, wherein J=2 to N. A frame signal insertion unit units alternate frame signal into the series N+1. BSI is secured by this simple construction.

Abstract: A multi-level correlation technique and apparatus for detecting symbol and data frame synchronization in high noise and multi-path environments, wherein received signals are correlated with known pseudorandom noise (PN) or other known codes at the base level and the base level correlation results are in turn correlated with PN or other known codes at the next higher level, such that the top level of correlation includes all lower levels of encoding in the complete synchronization pattern. In a two level implementation, the base level codes define symbols while the top level code defines the synchronization pattern in terms of the base level symbols. Correlation hardware is minimized while processing gain is maximized for enhancing low signal to noise levels over a long synchronization pattern. Additionally, precise ranging is facilitated because the top level correlation result covers the entire synchronization pattern.