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 represenative 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: For determining the operating point of a non-linear amplifier 2 of a communication channel 1, for example of a transponder in a communication satellite, a first input signal I1 is transmitted through the communication channel 1 at a power level PI1 which drives the non-linear amplifier 2 in a non-linear operation mode. In addition, a second input signal i2 is transmitted through the communication channel 1 simultaneously with the first input signal I1. The second input signal i2 is transmitted at a level below the level of the first input signal I1. If the contribution of the second input signal i2 to the total input of the non-linear amplifier is small, the operating point of the non-linear amplifier is determined almost only by the first input signal. Therefore, the output power P02 corresponding to the second signal i2 is determined most strongly by the input power PI1 of the first signal I1.

Abstract: In a conventional data transmission and receipt apparatus using PN flags according to PN sequence, there has occurred a flag emulation due to a bit stream similar to a PN flag in a frame of the data stream, which disables transmission of the frame therebetween. To solve the problem, the data transmission and receipt apparatus of the present invention inserts a mark representing that there is laid a bit stream similar to the PN flag into the frame while the data receipt apparatus distinguishes such a bit stream from the PN flag. Thereby, the data receipt apparatus is capable of receiving the frame involving the bit stream similar to the PN flag without occurrence of a flag emulation.

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 shift register shifts or cycles a replica or delayed replica of the chip-sequence signal. The shift register has a plurality of taps, which correspond to the plurality of chips. A plurality of comparators compares the chip-sequence signal embedded in the spread-spectrum signal with the replica of the chip-sequence signal stored in the shift register. 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. The plurality of counters thereby generates a plurality of totals, respectively.

Abstract: A spread spectrum receiver having a smaller circuit scale is accomplished by a circuit construction wherein the number of taps is set to a number smaller than a spread factor, and a cyclic accumulation process for determining a correlation value of one symbol is executed by a circuit construction using an input sequence register block in common with an addition block of a spread spectrum receiver by MF according to the prior art.

Abstract: A method is disclosed for operating a mobile station (10). The method includes a first step of receiving a message from a base station (30), the message being descriptive of an assigned forward digital channel and including an information element that specifies an order of occurrence of time slot synchronizing word sequences within a frame. A next step receives a forward channel from the base station, the forward channel being transmitted to contain repeating frames each having N time slots, individual ones of the time slots including a synchronization word. A further step correlates the received forward channel in accordance with the received information element so as to obtain a plurality of frame synchronization indications within one frame, thereby decreasing the frame synchronization time.

Abstract: In a direct sequence spread spectrum communication system, a system and method for recovering the timing of a pseudo-random noise (PN) sequence used for despreading the received signals. In one embodiment, the communication system is a time-division duplexing (TDD) or a time-division multiple-access (TDMA) system. A receiver in the communication system uses a “sliding correlator” maximal-likelihood (ML) detection system to scan through a range of possible PN phases to determine the correct one. In one embodiment of a method for performing the synchronization, a receiver acquires the PN phase by repeating the ML detection for a time greater than or equal to the period of the TDD or TDMA frames, with a sufficiently high repetition rate to ensure that the correct PN phase is examined at least once during a received frame. The acquisition is thereby completed within a fixed amount of time.

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

Abstract: 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: A method and device in which only a single symbol is required for synchronization, and which permits the detection of appreciable deviations from the normal receiver oscillator frequency or of a deviation of the transmitter frequency from the given frequency pattern, and the correction of the oscillator frequency. The invention further includes an evaluation method for the signal which contains a multiplicity of modulated carriers. In a decoder, additional sequences are evaluated after demodulation and differential reconversion by means of a correlation.

Abstract: Variable rate data transmissions are accommodated having BRI transmitted in the same frame as the data itself. When Walsh code spreading is employed, the despreading process can be split into two separate despreading operations, with buffering between the two operations. Buffering is made of the intermediate symbols between the despreading stages, and can be made at the maximum user data rate instead of the much higher chip rate. In this way, the size of the buffer in the receiver can be significantly reduced.

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 synchronization acquisition apparatus and a method thereof are disclosed. The apparatus includes a local code generator coupled to a plurality of delayers, a plurality of multipliers commonly coupled between the delayers and a plurality of integrators, and a plurality of switches coupled between the multipliers of an integrator. The plurality of integrators are coupled to a detector that detects the maximum integrator output. A plurality of comparators form a feedback loop for obtaining a reliable signal level under any environment and implementing a quick synchronization acquisition without checking all PN code offsets.

Abstract: The present invention is a system and method for increasing user capacity on a slotted random access channel in a spread spectrum communications system by using a multi-part access probe. First and second parts of the access probe are modulated using a short PN code sequence, and the entire access probe is modulated using a long PN code sequence. Information to be transmitted by the access probe is modulated on the second part of the access probe, and the access probe is transmitted so that the first part of the probe falls within the boundaries of an access channel slot. In one embodiment, time slots in access channels used for access signal reception are made the length of the first part. In a further embodiment, time slots in a plurality of adjacent access channels used for access signal reception may be longer than said first part but are offset in time from each other by the length or period of the first part.

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 parallel acquisition system configured using a reference matched filter, thereby obtaining a superior acquisition performance and a high throughput as compared to conventional serial acquisition systems and conventional parallel acquisition systems including no reference matched filter. The parallel acquisition system includes a reference matched filter connected in parallel to a plurality of detection matched filters connected together in parallel. The reference matched filter serves to estimate a dispersion of interference components of reception signals respectively input at the detection matched filters. The parallel acquisition system can be applied to the receiver of a spread spectrum system for a packet radio data communication in a multiple access environment.

Abstract: There is provided an apparatus for detecting a synchronizing signal, including a first circuit for extracting bit clocks from serial data received, a shift register for shifting the serial data bit by bit on the basis of the bit clocks, and latching the thus shifted serial data, a second circuit for counting the bit clocks, and generating word clocks in accordance with the number of count of the bit clocks for outputting parallel data, a third circuit for detecting a synchronization pattern from the serial data stored in the shift register, and generating a first synchronization-detecting signal, a fourth circuit for detecting a synchronization pattern from the parallel data, and generating a second synchronization-detecting signal, and a fifth circuit for determining whether frame synchronization is made, by the first and second synchronization-detecting signals, and generating a frame synchronization indication signal indicative of whether frame synchronization is made or not.

Abstract: The data communications systems disclosed herein accommodates terminals having different throughput capabilities by flexibly allocating cyclicly rotated phases of a common pseudo-noise (P/N) code. Throughput capabilities of the terminals are expressible in multiples of a preselected minimum throughput rate so that a single respective code phase is assigned to any terminal operating at the minimum throughput rate while a plurality of sequential consecutive phases are assigned to each terminal having a capability greater than the minimum throughput rate. One or more unassigned phases are provided between phases assigned to different terminals. Any terminal operating at the minimum throughput rate utilizes all time slot intervals in a predetermined frame interval while terminals of greater capability are assigned time slots in accordance with the amount of data traffic to be carried by that terminal and the number of code phases assigned thereto.

Abstract: In a communication system (100) where a remote unit is given a time offset for a base station (102) and hands off to the base station (102) if the remote unit (113) can acquire the base station within a time window surrounding the time offset, a remote unit (113) utilizes the time offset of each base station (supplied by a serving base station (101) via a downlink communication signal (116) and searches for neighboring base stations within the time window surrounding its PN offset. The time window surrounding an individual base station's PN offset is allowed to vary depending upon whether the communication system (100) is time synchronized. In particular, a base station (101) supplies the remote unit (113) with an indication that the communication system (100) is operating in a synchronized or an unsynchronized mode, and the remote unit (113) varies the time window (search window) accordingly.

Abstract: The present invention has an object to provide a data padding apparatus capable of appropriate padding processing to input data and input insignificance information which are not synchronized. Receiving input data and input significance information which are not synchronized as inputs, the data padding apparatus performs synchronization by data storage means and significance information storage means included in a storage and padding means, generates original data and synchronized significance information with synchronism between them and outputs them to a padding information holding means where padding information consisting of padding data and padding address information is generated based on the data and information input.

Abstract: A CDMA communication system comprises: N antennas, arranged for space diversity receiving, for receiving a CDMA direct conversion radio wave signal including data to respectively generate N reception CDMA signals; a searching circuit for searching a phase of PN code in one of the N reception CDMA signals; N phase tracking circuits having N correlation detectors for tracking phases of the PN codes in the N reception CDMA signals in accordance with the searched phase to generate phase information of the PN codes, respectively; N de-spreading circuits for de-spreading the N received CDMA direct conversion signals in accordance with the phase information, respectively; and a diversity combining circuit for combining outputs of the N de-spreading circuits to provide the space diversity receiving to output the combined signal.

Abstract: In a first embodiment of the invention, two sets of seven PN-sequences of length 128 are provided having favorable correlation properties for use as a preamble or midamble synchronization code. At the receiver a processor may be used to detect the code. In another aspect of the invention, a communication system using a synchronization code selected from sets of provided codes is claimed where the synchronization code may help to minimize possible misidentification of noise or interference by assisting in the detection of the start of a designated burst. The synchronization codes and their means for detection may be employed in various communication systems.

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

Abstract: 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: In the synchronous tracking apparatus of a spread spectrum receiver, data obtained by multiplying a receive signal by a pseudo-noise code for receiving is time-shared by differing time-sharing circuits, first and second correlation properties are created which are asymmetrical on both sides with respect to a correlation value axis in which the phase difference between a pseudo-noise code for transmitting contained in the receive signal and a pseudo-noise code for receiving is 0, a delay discriminating property is created by combining these correlation properties, a pseudo-noise code for receiving is controlled based on this delay discriminating property and the pseudo-noise code for transmitting tracks the pseudo-noise code for receiving.

Abstract: GPS satellite signals are received, and a C/A code is synchronized by utilizing the non-coherent DLL so as to remove the unique code of the GPS satellite. There are generated 1/2-bit lagging, 1/2-bit leading and normal satellite codes. Then a correlation between the former and a down-converted intermediate frequency signals is carried out. Mixers mix the correlated three different phase signals with signals of a local oscillator. The output signals of the mixers are filtered by a band filter, and envelopes are detected from the filtered signals by an envelope detecting section. The detected envelopes are subtracted from each other. The output signals of the subtractor are filtered by a loop filter, and the filtered signals are controlled by a voltage control oscillator. The oscillated signals are inputted as clock signals into a satellite code generating section.

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 RAKE receiver which is employed in a direct sequence spread spectrum communication system, and which can effectively receive multipath signals. A path searcher measures the amplitude of each path, selects N paths with larger amplitudes in descending order of magnitude, where N is the number of despreaders, and assigns the despreaders to the selected paths to despread the signals of the paths. This assignment of the despreaders to the paths is carried out such that a path with a large amplitude and a path with a small amplitude are assigned to adjacent despreaders and are input to the same pre-detection combiner. The outputs of the despreaders are combined by the pre-detection combiners, and detected by detectors whose outputs are RAKE combined by a post-detection combiner.

Abstract: An apparatus for receiving a data stream consisting of a simultaneous plurality of time domain spread spectrum messages in the same frequency channel, wherein each message is independent and spread spectrally with a unique code. The data stream contains a subset of all known codes in use. The apparatus finds a specific code and a constant phase shift between the incoming code and a reference code by serially moving the data stream through a shift register, subjecting all the shift register outputs to a single expected reference code and accumulating the result for each output. The code and phase shift is indicated by the largest magnitude of the accumulation, above a set threshold, corresponding to the shift register output for the correct phase shift between the incoming code and the reference. Upon completion of an integration cycle the time shift delay increases by the length of the shift register. The process continues for all the possible relative time shifts and for all the reference codes.

Abstract: A method, executed in a microprocessor, for providing a shift-and-add mask, M=m.sub.1, m.sub.2, . . . , m.sub.N-1, m.sub.N, for a pseudo-noise sequence generator ("PNSG"). The PNSG generates a first pseudo-noise ("PN") code, and has N stages, each stage being at one of two states. The PNSG also has an associated shifter for generating a shifted PN code which is the same code as the first PN code, but delayed by K chips. The shifted PN code is generated as the inner product of the shift-and-add mask with the states of the stages of the PNSG. According to the inventive method, a value of K is provided, and it is determined whether K is 0. If K is 0, M is provided such that m.sub.N =1 and, for all n.noteq.N, m.sub.n =0. However, if K is not 0, it is determined whether K is greater than N. If K is greater than N, the remainder, R, of the division D.sup.K-1 /f(D), is determined, whereD.sup.K-1 =(m.sub.1 c.sub.1 +m.sub.2 c.sub.2 + . . . +m.sub.N c.sub.N)+(m.sub.2 c.sub.1 +m.sub.3 c.sub.2 + . . . +m.sub.N c.sub.

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: An input data obtained by differential-decoding a signal transmitted from a transmitting equipment is input to a DMF. The DMF obtains a correlation value, and outputs the correlation value and data value to a maximum value detection unit. The maximum value detection unit extracts the maximum value from the correlation values output at the sampling timing, and outputs the position of the maximum correlation value (synchronous point signal) and the data value corresponding to the maximum correlation value. The synchronous point comparison unit monitors a synchronous point signal, detects whether or not a synchronous point deviates, and resets a counter based on the deviation of the synchronous point. A counter reset determination unit also monitors the synchronous point signal, and resets the counter so that the apparent position of the synchronous point can be around the center of the window when the counter value indicating the synchronous point is not in a predetermined range.

Abstract: An impulse radio communications system using one or more subcarriers to communicate information from an impulse radio transmitter to an impulse radio receiver. The impulse radio communication system is an ultrawide-band time domain system. The use of subcarriers provides impulse radio transmissions added channelization, smoothing ad fidelity. Subcarriers of different frequencies or waveforms can be used to add channelization of impulse radio signals. Thus, an impulse radio link can communicate many independent channels simultaneously by employing different subcarriers for each channel. The impulse radio uses modulated subcarrier(s) for time positioning a periodic timing signal or a coded timing signal. Alternatively, the coded timing signal can be summed or mixed with the modulated subcarrier(s) and the resultant signal is used to time modulate the periodic timing signal. Direct digital modulation of data is another form of subcarrier modulation for impulse radio signals.

Abstract: The front end in GPS receivers has the functions of amplifying, down-converting, filtering and sampling the received signals. In the preferred embodiment, only two operations, A/D conversion and a sum, bring the signal from RF to filtered quadrature baseband samples. After amplification and filtering at RF, the L1 and L2 signals are each sampled at RF at a high selected subharmonic rate. The subharmonic sample rates are approximately 900 MHz for L1 and 982 MHz for L2. With the selected subharmonic sampling, the A/D conversion effectively down-converts the signal from RF to quadrature components at baseband. The resulting sample streams for L1 and L2 are each reduced to a lower rate with a digital filter, which becomes a straight sum in the simplest embodiment. The frequency subsystem can be very simple, only requiring the generation of a single reference frequency (e.g. 20.46 MHz minus a small offset) and the simple multiplication of this reference up to the subharmonic sample rates for L1 and L2.

Abstract: A system for recognizing degraded pseudo-random noise (PN) synchronization in a spread-spectrum receiver. The system uses a signal that indicates the correlation of the locally generated PN sequence with the received PN sequence. The correlation signal can be a symbol-length integration of the output from a square-law detector, or an appropriate similar signal. If the correlation signal is not degraded by demodulating with a deliberately shifted copy of the PN sequence, there is an indication that the unshifted PN sequence was itself not correctly synchronized. A sufficiently degraded correlation signal indicates that the receiver's PN synchronization is correct. To prevent the loss of transmitted data during the testing, each transmitted frame contains a Measurement field (that contains no payload data) for assessing the synchronization in this manner. The PN sequence is shifted only during this specific portion of the received frame.

Abstract: The apparatus and method for minimization the residual multipath pseudorange error signal present in the received composite spread spectrum signal are disclosed. In the preferred embodiment, the apparatus comprises at least two tracking channels. Each tracking channel includes a generator of a time-varying non-uniform weighting function. Each tracking channel processes an incoming composite signal and outputs a satellite signal and a multipath pseudorange error signal. The tracking channel output signals are scaled by the computer and combined to yield the output signal comprising a satellite signal and a minimized multipath pseudorange error signal in the area of small delays.

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.

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 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 data clock signal for data in an incoming signal is generated by means of a clock recovery module. The incoming signal consists of a data burst having a periodic preamble followed by a data sequence. The clock recovery module comprises a first clock generator, a sampling device, a correlator, a control unit and a time registration device. The clock generator generates a clock signal having a first clock frequency which is a factor N higher than the frequency of the preamble. The sampling device samples the incoming signal at the first clock frequency. The correlator correlates the sampled signal with a predefined correlation word, the correlation between the incoming signal and the correlation word being represented as a correlation signal in the form of a series of discrete correlation signal values. The control unit detects local extreme values for the correlation signal.

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: A time division multiple access (TDMA) burst receiver and a method for recognizing and providing a time-of-arrival of a TDMA burst transmission having a selected preamble. The TDMA burst receiver includes a blanker for blanking the TDMA burst transmission when the signal level exceeds a pre-selected noise threshold, a signal threshold detector for providing a first tentative time-of-arrival when a correlation of the TDMA burst transmission and the selected preamble exceeds a first threshold and a second tentative time-of-arrival only when the correlation exceeds a second threshold within a selected time period following the first tentative time-of-arrival, and a state machine for providing an operational time-of-arrival corresponding to the first tentative time-of-arrival when the second tentative time-of-arrival is not received and the second tentative time-of-arrival when the second time-of-arrival is received.

Abstract: A synchronization method and apparatus for synchronizing a receiver, such as a radiotelephone operable in a cellular communication system with a transmitter. Synchronization sequences are transmitted as parts of a control signal to the receiver. The synchronization sequences are formed of either a dotting sequence or a set of m-sequences. Such synchronization sequences are of high margins and also permit synchronization of the user terminal responsive to a reduced number of calculations.

Abstract: A method for handoff of an analog connection within a cellular communication system which relies upon mobile station synchronization to a system time is disclosed herein. In order to reduce the acquisition time for a mobile station commencing operation in a digital mode, an estimate of master system time is transferred to the mobile station in analog mode before entering digital mode. The alignment operates within the protocols of existing analog systems, and hence requires only minimal changes in the mobile station. Time alignment may be initiated upon the base station sending to the mobile station a command to continually transmit a periodic signaling tone. The base station compares the phase of the signaling tone from the mobile station to a master system clock and determines an error signal. The base station notifies the mobile station to delay or advance in time the transmitted signaling tones based on the error signal.

Abstract: A spread spectrum communication system, which can detect the synchronization of the spread code surely even when the carrier-to-noise ratio is low, and can detect the boundary of the data. Wherein two types of spread code S20, S21 are transmitted from a transmitter 21 as an initial synchronizing signal based on a predetermined transmission pattern, and two types of spread code are respectively detected at a receiver 22. The predetermined transmission pattern is detected based on the detected two spread codes. Therefore, the spread code is detected several times at the receiver, and the synchronization of the spread code can be detected surely even when the carrier-to-noise ratio is low. Further, the boundary of the data can be detected by the predetermined transmission pattern.

Abstract: Methods for synchronizing to a reference signal the timing of a received composite, code phase SATPS signal, which consists of a preferred, interference-free signal distorted by at least one interfering signal, to determine an undistorted timing point of the preferred signal. An idealized correlation function A.sub.I (t), formed from the product of a digital reference signal with a time-shifted reference signal, and a measured correlation signal A.sub.M (t), formed from the product of a received signal and a time-shifted reference signal, are computed. Peak amplitudes A.sub.M (.sub.pM) and A.sub.I (.sub.pI) are found for the respective measurable and idealized punctual code phase shifts .sub.pM and .sub.pI. The correlation measurements formed on the early side (or on the late side) of the peak for the correlation function A(t) are combined to form an estimate of the time delay associated with a multipath signal.

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: A receiver comprising a digital code tracking loop which receives an input of real and imaginary components of a received signal and in which these components are processed in different branches which each comprise a multiplier (12a-12d) and a filter (13a-13d) connected in series. To improve the characteristics of the code tracking loop in the receiver, each branch of the code tracking loop further comprises circuitry (33a-33d) for absolute-valuing the signal, the circuitry (33a-33d) being connected in series after the filters (13a-13d).