Abstract: A multi-band receiver for use with satellite ranging systems is provided. The receiver has a simplified architecture in which input signals of various frequencies are multiplexed together to form a single composite analog signal. In accordance with one embodiment of the invention, this composite signal only requires a single RF circuit for down conversion to an intermediate frequency. The composite, downconverted signal is sampled, and the digitized samples are demultiplexed to form digital counterparts of the original signals from each frequency band. An embodiment for use with elements of a phased array antenna is also provided.

Abstract: An apparatus and method for generating an octal code for identifying cells in a mobile communication system. In the octal code generating apparatus, a binary code generator generates a binary code with a predetermined minimum Hamming distance. A column permutator permutes the order of columns of the binary code in a predetermined interleaving method. A 3-bit combiner generates a plurality of codewords using the column-permuted binary code as a generator matrix and groups the bits of each of the codewords by threes. An octal code generator converts the 3-bit grouped binary codewords to octal code sequences.

Abstract: An uplink signal transmitted by a terminal is received by a satellite wireless communications system. The uplink signal includes a known information element, e.g., a reverse access channel (R-ACH) preamble, spread according to a spreading code specific to a component of a satellite wireless communications system, e.g., a pseudonoise (PN) sequence associated with a satellite beam. A correlation of the received uplink signal with the spreading code over a range of time shifts is determined. The known information element is detected from the determined correlation. The satellite wireless communications system is synchronized with the terminal responsive to detection of the known information element. For example, a delay may be assigned to a receiver of the satellite wireless communications system responsive to detection of the known information element.

Abstract: A system and method for mitigating a multi-path-induced error in a global navigation satellite system (GNSS) is described. In one embodiment of the method, a composite signal is received. The composite signal includes a band-limited direct-path signal and at least one band-limited multi-path signal that are each modulated with periodic phase reversals. The composite signal is measured as a function of time during a time interval having at least one of the periodic phase reversals. A phase error ?? between the composite signal and the direct-path signal due to the multi-path signal is determined using the measured composite signal as a function of time and a pre-determined filter characteristic corresponding to a filter used to band limit the direct-path signal and the multi-path signal. The phase error ?? in a navigation computation is corrected.

Abstract: Methods and systems for detecting bit synchronization boundary in a received signal. A counter is set for defining a bit boundary of the received signal. Transitions in the received signal are detected and compared with the counter value as the transitions are expected to occur only at the bit boundary. The bit boundary is confirmed if a preset number of transitions aligned with the bit boundary.

Abstract: A method of transmitting communications codes is used in spread spectrum communications systems. The method includes transmitting a first pseudo-noise code, and transmitting a second pseudo-noise code, wherein the second pseudo-noise code is a time-reversed version of the first pseudo-noise code. A device includes a first shift register to store a first code and a second register to store a second code in a time-reversed version. A comparison circuit then compares the two codes and a result is output.

Abstract: According to one embodiment, a low phase noise clock generator includes a frequency multiplier using a crystal oscillator, which is configured to receive a reference clock and to generate a multiplied reference clock. The low phase noise clock generator further includes a prescaler module configured to divide down a frequency and significantly reduce phase noise of the multiplied reference clock to generate a low phase noise clock. In one embodiment, a tester can be configured to input the low phase noise clock into the crystal oscillator input of a device under test to accurately test a phase noise of the device under test.

Abstract: A method and system for performing initial cell search is disclosed. Step 1 processing is preformed to detect a peak primary synchronization code (PSC) location (i.e. chip offset or chip location). Step 2 processing is performed to obtain the toffset and code group. Step 3 processing is performed to identify the midamble of a base station with which the WTRU performing the initial cell search may synchronize with.

Abstract: A method and apparatus are disclosed for modulating a communication signal in a code division multiple access (CDMA) environment using orthogonal N by N Hadamard spread spectrum codes Orthogonal spreading codes are used that have lengths that are not a power-of 2 to provide additional channel variability for various multimedia applications and increase the flexibility of the number of channels/bandwidth relationship. The Hadamard codes are multiples of 4 (4n) and demonstrate a good cross-correlation property, making them very useful in the flexible design of code division multiple access (CDMA) systems. A transmitter encodes each of to N data streams (N not being a power of 2), to be transmitted using a 4n codeword, Ni. The received signal is passed through a filter matched to the characteristics of the appropriate codeword, Ni, and PN spreading sequence.

Abstract: Methods and apparatus for time tracking using assistance from TDM pilots in a communication network. In an aspect, a method is provided for time tracking in a device operating on a communication network, wherein the device performs a time tracking algorithm. The method includes determining a delay spread, and modifying at least one parameter used by the time tracking algorithm based on the delay spread. In another aspect, an apparatus is provided for time tracking in a device operating on a communication network, wherein the device performs a time tracking algorithm. The apparatus includes computation logic for determining a delay spread, and control logic for modifying at least one parameter used by the time tracking algorithm based on the delay spread.

Abstract: A receiving system dynamically searches a communications band for transmissions of messages having the same nominal communications parameters, including the use of the same spreading code, but having potentially different specific frequencies and code-phases. The receiver samples the communications band at each code-phase of the spreading code over a span of down-converted transmission frequencies. When a message element is detected at a particular code-phase and frequency, it is forwarded to a demodulator that demodulates the message and sends it to its intended destination. This technique allows each transmitter to be independent of the receiver. In a preferred embodiment of this invention, a Fast M-Sequence Transform (a Walsh-Hadamard Transform) is used to determine the power level at multiple code-phases at a given frequency in parallel, thereby substantially reducing the time required to search for transmissions at each discrete code-phase.

Abstract: Method and apparatus for performing midamble cancellation to remove midamble interference from the convolution tail of data field 1 and the first W-1 chips of the midamble field which results from the delay spread of the multipath channel and for canceling the first W-1 chip midamble spread in the data field 2, which operations are performed substantially simultaneously. The received burst, typically a TDD burst, is stored, the midamble interference and the corresponding parts in the received burst is removed and the resulting burst is applied to a multi-user detector to obtain the symbol sequences.

Abstract: A simple and robust CTL is used for time tracking of multipath components of a spread spectrum signal transmitted over a wireless multipath fading channel. A digital code-tracking loop includes the implementations of despreading early and late data samples by use of a pseudonoise sequence, an error signal output generated by the despreading, and adjustment for a plurality of on-time, early and late samples, a data rate of a control signal provided as a fractional proportion of a data rate of error signals.

Abstract: A receiver in an OFDM system may include a joint maximum likelihood (ML) estimator that estimates both time offset and frequency offset. The estimator may use samples in an observation window to estimate the time offset and frequency offset.

Abstract: A system and method for GPS acquisition in relatively high interference is described. Acquisition is aided by an Advanced Tightly Coupled (ATC) tracking filters that compute a satellite range residuals and range rate residuals for satellites being acquired. Multiple channels are used in parallel to search for the desired satellites. Range residuals from the ATC filters are used to correct the computed receiver offset and thus allow acquisition in the presence of relatively high interference.

Abstract: A method and apparatus for use in connection with wireless communication to adjust the frequency of an oscillator to synchronize with a received signal by correlating a synchronization code channel with training sequences to estimate positive and negative offsets which are employed to estimate an error, which is then filtered. The filtered output preferably provides a voltage controlling a voltage controlled oscillator (VCO). The same technique may be employed to control a numeric controlled oscillator (NCO).

Abstract: An A-D conversion unit performs analog-to-digital conversions on baseband signals. A correlation processing unit carries out a correlation processing. A power computing unit computes the power of correlation values. An inter-signal condition determining unit compares a relationship between the peak of a main signal and the peak of sub-signals to a first condition, and excludes, from combining diversity, baseband signals corresponding to the sub-signals if the relationship does not satisfy the first condition. An intra-signal condition determining unit 30 compares the main signals and sub-signals to a second condition, respectively, and excludes signals from combining diversity if the signals do not satisfy the second condition. A timing adjusting unit adjusts the timing of sub-signals so that the timing thereof comes close to the timing of the main signal. A shift unit shifts the timing of sampled signals corresponding to the sub-signals.

Abstract: A semiconductor integrated circuit for processing a plurality of received broadcast signals, such as GPS signals, is operable in two modes: acquisition and tracking. In an acquisition mode, sample reducer combines samples of a received signal for correlation with a locally generated version of a GPS code. In a tracking mode, the sampled signal is provided direct to the correlators without sample reduction. The same correlators are thereby used to increase acquisition speed.

Abstract: A clock generator circuit, comprising: a multi-phase clock signal generator for generating a plurality of clock signals having a same frequency but difference phases according to a reference clock signal; a modulation device for generating a phase modulation signal through Delta-Sigma modulation; and a phase modulator, which is electrically coupled to the modulation device, for selecting one of the clock signals to be a modulated clock signal according to the phase modulation signal.

Abstract: A User Equipment (UE) has a circuit that performs the acquisition for the low chip rate option of the Universal Mobile Telecommunication System (UMTS) Time Division Duplex (TDD) standard as formulated by the Third Generation Partnership Project (3GPP). The present invention implements the detection of the basic SYNC code; the determination of the midamble used and the detection of the superframe timing based on SYNC code modulation sequence. This enables reading of a full Broadcast Channel (BCH) message.

Abstract: A semiconductor integrated circuit for processing a plurality of received broadcast signals, such as GPS signals, is operable in two modes: acquisition and tracking. In an acquisition mode, a memory arrangement comprising two circulating shift registers circulates samples of a received signal for correlation with a locally generated version of a GPS code. In a tracking mode, the sampled signal is provided direct to the correlators. The same correlators are thereby used to increase acquisition speed.

Abstract: A method is provided for synchronizing a receiver with a transmitter, wherein a first synchronization signal with a multiplicity of second synchronization signals is transmitted from the transmitter to the receiver, a set of second synchronization signals is subdivided into used code sets and at least one unused code set in such a way that the maximum in the peak values of the cross-correlation functions of the second synchronization signals, which are determined by a used code set, with a first synchronization signal is minimal.

Abstract: A method of generating a pseudo-noise sequence without masking a linear feedback shift register (LFSR) generator is provided. An offset pseudo-noise sequence is generated at a desired offset from a reference psuedo-noise sequence by determining a corresponding initial state vector of the LFSR based on an arbitrary mask.

Abstract: An apparatus including a spreading code generator for generating a spreading code; a scrambling code generator for generating a scrambling code; and a modulator for scrambling the spreading code using the scrambling code to produce a modified spreading code.

Abstract: The ultra wide band communication system of the present invention includes a transmitter (station) and a receiver (station). The transmitter and the receiver employ spreading code comprised of code groups, which respectively comprise varied, auto-correlated codes. Consecutive information bits are spread and de-spread with differing code and the code groups are correlated with each other (e.g., orthogonal) so as to reduce channel impulse response estimation noise. At the receiver, subsequent channel estimates can be added or averaged with an initial channel estimate so as to reduce the channel impulse response estimation noise and thereby provide a relatively more accurate channel response.

Abstract: Provided is a method of compensating for energy loss and eliminating inter-symbol interference (ISI) and inter-chip interference (ISI) in wireless signals, and a rake receiver for wireless LANs adopting the same. The rake receiver compensates for energy loss of a CCK signal transmitted in a multi-path wireless channel environment and eliminates ISI and ICI from the received CCK signal because a DFE structure per chip used for calculating ICI components, is connected in parallel with a DFE structure per symbol, thus eliminating ISI and ICI components.

Abstract: A method of adjusting the relative timing of a spreading sequence and a sampled input signal for a spread spectrum receiver correlator, the spreading sequence having an associated spreading sequence chip clock, the input signal being sampled at sample clock intervals, the method comprising: delaying the sampled input signal by an integral number of sample clock intervals to provide a fine relative timing adjustment; and delaying the spreading sequence by an integral number of spreading sequence chip clock periods to provide a coarse relative timing adjustment.

Abstract: A spread spectrum receiver architecture comprising: a spread spectrum signal sampler; a sample delay stage, coupled to the spread spectrum sampler, to provide a set of spread spectrum samples having a plurality of different delays on a delayed sample bus; a plurality of scramble code generators to provide a plurality of scramble codes on a scramble code bus; and a plurality of correlators, each comprising a correlator module coupled to the delayed sample bus and comprising at least one spreading code generator coupled to the scramble code bus, and each said correlator having at least one correlation output.

Abstract: There is provided a code acquisition device and method using a two-step search process in a DS-CDMA UWB modem. The device includes: an I/Q channel symbol generating unit for, generating a plurality (i) of nth I/Q channel symbols in a first search process and generating a plurality of nth I/Q channel symbols in a second search process; a spread code selecting unit for receiving the plurality of nth I/Q channel symbols in the first search process; an NNC2NS tap I/Q channel symbol matched filter unit for, in the second search process, receiving the plurality (i) of nth I/Q channel symbols; a switching unit for changing to a closed state of the second search process; and a super frame and symbol boundary time deciding unit for deciding a super frame time and a symbol boundary time.

Abstract: A method for initial synchronization in a mobile telecommunications network to connect a mobile terminal (10) to a base station (12). The mobile terminal has a search frequency list comprising a limited number of search frequencies. The method comprises the step of searching for an available frequency in the order of the search frequency list. The search frequency list further comprises count values, indicating how frequently the corresponding frequency has been used, wherein the order of at least some of the search frequencies depends on the count values.

Abstract: Common components are used to detect messages from a variety of transmitters, and the characteristics of each detected message are used to dynamically configure the demodulation process for each message. Channelization is selectively performed before, after, or before-and-after de-spreading, depending upon the particular environment and/or the particular characteristics of the received messages. Frequency synchronization to each transmitter is achieved by initializing a tracking loop within the demodulator associated with the transmitter, and code-phase synchronization to each transmitter is achieved by selectively inserting or deleting bits, based on the frequency and code-phase characteristics of the detected message.

Abstract: Techniques to iteratively detect and decode data transmitted in a wireless (e.g., MIMO-OFDM) communication system. The iterative detection and decoding is performed by iteratively passing soft (multi-bit) “a priori” information between a detector and a decoder. The detector receives modulation symbols, performs a detection function that is complementary to the symbol mapping performed at the transmitter, and provides soft-decision symbols for transmitted coded bits. “Extrinsic information” in the soft-decision symbols is then decoded by the decoder to provide its extrinsic information, which comprises the a priori information used by the detector in the detection process. The detection and decoding may be iterated a number of times. The soft-decision symbols and the a priori information may be represented using log-likelihood ratios (LLRs).

Abstract: A simple and robust CTL is used for time tracking of multipath components of a spread spectrum signal transmitted over a wireless multipath fading channel. A digital code-tracking loop includes the implementations of despreading early and late data samples by use of a pseudonoise sequence, an error signal output generated by the despreading, and adjustment for a plurality of on-time, early and late samples, a data rate of a control signal provided as a fractional proportion of a data rate of error signals.

Abstract: A simplified timing correction method is provided for data despreading of serial offset quadrature pulse-shaped spread signals. The simplified timing correction algorithm is applied to a rake receiver for improved performance in a multi-path channel. Serial formatting of the spreading modulation waveform is selected to reduce the SYNC/serial probe correlation complexity. The method includes the steps of: (a) decimating serial inphase (I) and quadrature (Q) signals to form decimated I and Q even samples and decimated I and Q odd samples; (b) obtaining an autocorrelation profile of a spreading sequence used by the receiver; (c) detecting a synchronization starting point using the I and Q even samples; and (d) deciding to either move, or not move, the synchronization starting point, based on the autocorrelation profile obtained in step (b). Step (d) decides to move the synchronization starting point, and uses the I and Q odd samples for subsequent despreading of the I and Q signals.

Abstract: In a channel estimating circuit, a Sync Word is demodulated by using a channel estimation value not with a symbol or a slot including the Sync Word to be demodulated, but with its preceding and succeeding symbols or slots. Furthermore, in a channel estimation process, if a Synch Word to be demodulated is included in any of groups into which a plurality of symbols are divided, the Sync Word is demodulated by using a channel estimation value obtained with the channel estimation process using not this group but another group.

Abstract: A method of acquisition a signal having a low signal to noise ratio (SNR). The method comprises the steps of: (A) detecting a non-zero power in the signal having the low SNR during a power detect process; (B) receiving the signal having the low SNR by using a signal receiver having an antenna; (C) accumulating a plurality of digital samples of the signal within a predetermined period of time; and (D) employing an algorithm to correct defects in reception of the signal having the low SNR by minimizing a set of parameters selected from the group consisting of: {a carrier frequency offset; a code phase offset; and a data bit misalignment}.

Abstract: A channel tracking module, configured for generating updated equalization coefficients for a frequency equalizer, is configured for determining a digital-based error value between equalized signals output by the frequency equalizer relative to predicted signals, for each subcarrier frequency of an OFDM symbol. The channel tracking module determines an accumulated error based on accumulating the digital-based error values for all the subcarrier frequencies of the OFDM symbol, for a prescribed successive number of OFDM symbols. The channel tracking module also determines a step size based on the accumulated error and relative to a prescribed step function configured for optimizing equalizer adjustments within stability limits. The channel tracking updates the equalization coefficients for each subscarrier frequency based on the accumulated error and the step size.

Abstract: A method is provided for adjusting timing alignment in which a receiver generates a plurality of imbalanced correction codes (1310), and square waves both having the same frequency. The receiver mixes the imbalanced correction codes with the square waves to create a mixed signal (1320), and integrates the mixed signal over a correction code period to generate a signal power value (1330). The receiver adjusts a phase of the square wave in a first direction when the signal power value satisfies a first criterion (1340, 1350), and in a second direction when the signal power value satisfies a second criterion (1340, 1360). Each imbalanced correction code is symmetrical. And a total integrated value of one of the imbalanced correction codes over the correction code period is either above a first threshold, or below a second threshold, the first threshold being greater than or equal to the second threshold.

Abstract: A method for supporting a determination of the correlation between at least one received code modulated signal and at least one available replica code is shown. In order to reduce the total memory size required for such correlations, the method comprises storing signal samples of the at least one received code modulated signal with a first rate in a memory. The stored signal samples are then read with a second rate from the memory for determining a correlation between the read signal samples and samples of the at least one available replica code, wherein the second rate is higher than said first rate. The disclosure relates equally to a corresponding electronic device, to a chip for such an electronic device, to a system comprising such an electronic device and to a corresponding software product.

Abstract: A digital broadcast receiving apparatus for receiving a broadcast signal generated by combining sub signals modulated using a random sequence generated based on an initial value set in accordance with a frequency of a broadcast channel by a signal transmission control use signal and a main signal generated based on information source data and reproducing the information source data contained in the received broadcast signal.

Abstract: A timing-reference circuit is employed by a multi-time-based system in which a timing reference is required for system processing. The timing-reference circuit may be used in a wireless receiver in which one or more transmitted signals are received as multipath signals, each corresponding to a different time reference. The timing-reference circuit is configured for selecting at least one received signal in a set of multipath signals as a timing reference, tracking the timing reference with a virtual timing reference, and synchronizing receiver processing to the virtual timing reference, even when the actual timing reference from which the virtual reference was derived vanishes. The timing-reference circuit provides for re-acquisition of a new timing reference when the virtual reference no longer qualifies as a timing reference.

Abstract: Improved performance, particularly gain in SNR, in high-bandwidth OFDM receivers, software and systems is achieved by compensating channel estimates not only for carrier frequency offset and phase noise, but also for interference caused by sample phase jitter. At high bandwidths, e.g. using 256 QAM symbol constellation, significant SNR improvement is gained by determining and applying a corresponding compensation to each data sub-carrier channel, the compensation preferably including a term that increases linearly with the sub-carrier index.

Abstract: A radio signal receiving method grasps features of a propagation path at the start of communication and generates a template waveform corresponding to the features. A receiver examines a reception waveform of a propagation path condition judgment portion contained in a header portion of a packet, individually generates the template waveform in each communication session and performs correlation detection on the basis of the template waveform generated individually.

Abstract: A system and method are provided for determining whether a chipping code from a group of codes is used in a signal. In one embodiment of the invention, a signal is received and each code from the group is correlated with the received signal. The ratio of the highest correlation value to the second highest correlation value is calculated. If the ratio exceeds a threshold, the chipping code may be determined as the chipping code used in the signal. In another embodiment, the ratio of the highest correlation value and the total received power of the signal is calculated. If the ratio exceeds a threshold, the chipping code may be determined as the chipping code used in the signal.

Abstract: A communication device can reliably find a frequency and establish frequency synchronization, despite relying on a variable reference frequency, and may do so, e.g., by searching only during one or more periods of frequency stability. Once gained, such synchronization may be held continuously. An acquisition unit receives from a control unit information about a frequency change of a reference signal. The acquisition unit may nonetheless continue to search for, e.g., a satellite at the frequency that had been in use before the frequency change of the reference signal. An acquisition unit in such a device may search over extended periods, e.g., by using two or more frequency-stable periods. The acquisition unit may, e.g., transmit information about a change in the reference frequency to a tracking unit to maintain synchronization with the satellite.

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

Abstract: A spreading code determining section (107) determines which spreading code is multiplexed in a received signal that has been received by an antenna (101) and has gone through a radio receiver (102), a correlation processing section (103), a delay profile generator (104), a midamble shift determining section (105), and a path selector (106). When determining that it is during DTX, from the output of the spreading code determining section (107), a DTX determining section (110) reports this to the radio receiver (102), the path selector (106), a JD operation section (108), and a despreading/RAKE-combination section (109) to make them stop processing. Thus, despreading, RAKE combination, and JD demodulation of the received signal are suspended during DTX, so that power consumption can be suppressed.

Abstract: A method of GPS bit synchronization is disclosed. The method includes the steps of a) receiving plural serial C/A Codes, wherein a data bit is formed by m C/A Codes; b) sequentially providing a bin number ranged from 0 to m?1 to the plural C/A Codes; c) setting a sampling value k; d) sequentially determining adjacent two C/A Codes, C/A Code nk and C/A Code (n+1)k, wherein n={0, 1, 2, 3, . . . }, and calculating a sign change aggregate value of each bin number ranged from 0 to m?1; e) repeating step d) till there are k bin numbers having the sign change aggregate value equal to or greater than a first threshold, and summing the k bin numbers for obtaining a lookup value; and f) acquiring a bit boundary of the data bit according to the lookup value in the plural serial C/A Codes.

Abstract: A method for determining boundaries of information elements for a PRN code modulated signal is provided. The method of the present invention uses an estimated symbol phase of the received signal and correlation values of different durations to determine the information element boundary. By the method of the present invention, the determination of the information element boundary can be more effective especially in the common dump receiver architecture, where the correlation window cannot match the received waveform exactly.

Abstract: An apparatus for making a plurality of terminals have a random access to the reverse common channel system in CDMA, comprises code synchronization detection information broadcast means provided in the base station for broadcasting the state information of a channel card in real time for the terminals to recognize the code synchronization detection when the code synchronization of a certain data is acquired through performing the code synchronization of the preambles transmitted from the terminals through the reverse common channel, and data transmission determination, means provided in the terminals for making the terminals to have attempted data transmission in the same time slot with the data of the code synchronization detection continuously transmit data and the other terminals stop data transmission.