Abstract: A UW multiplexing circuit multiplexes a fixed pattern over the leading edge of each frame of transmit data. A spreading code generating circuit generates spreading codes TP1 at a timing synchronized with the frame. A spreading circuit spread-modulates data from the UW multiplexing circuit with the spreading codes TP1. A correlation detecting circuit has spread-modulated fixed patterns as multiplication coefficients, and detects correlations between spread-modulated fixed patterns in received data. A despreading code generating circuit supplies, if a fixed pattern is detected, the leading code of despreading codes RP1. A despreading circuit despread-modulates the receive data with the despreading codes RP1. As a result, the spread spectrum communication apparatus according to the invention is capable of setting the code length and the bandwidth expansion factor independent of each other, and thereby enhancing the performance to detect correlated values.

Abstract: A phase-lock loop circuit in a demodulator includes a timing recovery block and a carrier recovery block. The demodulator for demodulates a digital signal including symbols. The phase-lock loop includes an integrator processing a block of N samples to produce an average of the N symbols, and means for supplying the average of the N symbols to the timing recovery block and the carrier recovery block every NT period, where T is a sample time interval.

Abstract: A receiver for recovering data from received spread spectrum radio signals includes an equalizer, which mitigates at least some inter-symbol interference present in a sampled base band signal and which conditions the remaining inter-symbol interference such that the radio signals received via at least one propagation path are present in the conditioned remaining signals. The receiver also includes a symbol estimator coupled to the equalizer and configured to estimate the data by de-spreading the spread spectrum radio signals which correspond to the at least one propagation path with a corresponding spreading code. A communications system including the receiver for recovering data and a method of recovering data from spread spectrum signals are also provided.

Abstract: A spread spectrum modulated signal generator is disclosed that reduces the storage requirement for storing values representing filter responses of input signal samples in a digital filter by taking advantage of time-reversal symmetry of the responses. Moreover, the disclosed signal generator supports up-ramping and down-ramping for smooth transmission of spread spectrum modulated signals.

Abstract: An improved constellation pruning and partial Gray coding method for generating constellations that are transmitted by a transmitter. The approximate symbol error rate (SER) for each possible subconstellation is first determined. Then, each of the subconstellations are scaled in terms of power so that each subconstellation has the same symbol error rate. Then, the subconstellation that requires the least amount of power to generate is selected as the pruned constellation for use by the transmitter. After the pruned constellation is determined, it is then coded a single time, and this coded pruned constellation is used by the transmitter.

Abstract: A method and system for the transmission, reception, and processing of 4-level and 8-level signaling symbols is provided. An inventive modulator is provided for modulating 4-level signaling symbols using an 8-level modulator. Further, this inventive modulator is able to produce 4-level modulation when modulating 4-level signaling symbols using an 8-level modulator, where the 4-level modulation represents the 4-level symbol sequence modulated. Further, a constrained/unconstrained demodulator is provided which is able to demodulate both 4-level signaling symbols and 8-level signaling symbols. The inventive demodulator accomplishes this by limiting the number of new symbol hypotheses and path histories to 4 when working with 4-level signaling symbols, and setting the number of new symbol hypotheses and path histories to 8 when working with 8-level signaling symbols.

Abstract: In order to transmit variable length encoded data in low signal to noise ratio environments, a first data pattern is added to a beginning portion of encoded data to signify a beginning of the encoded data. Further, a second data pattern is added to end portion of the encoded data to signify and end of the encoded data. Additionally, since the encoded data may naturally include the second data pattern and thereby mistakenly indicate an end of the encoded data, the encoded data is first checked for such a pattern. If the pattern is found within the encoded data, a new pattern is substituted therefore. In order to counter errors, patterns similar to the first data pattern are also substituted with new patterns. As such, a variable length encoded data can be transmitted in a low signal to noise ratio environment, and can thereafter be easily decoded.

Abstract: A system and method are disclosed for equalizing a read signal from a data storage media is disclosed. An analog output signal is equalized by reading the data storage media using an analog equalization filter. The analog output of the analog equalization filter is converted to a raw digital output signal. The raw digital output signal is processed to detect and correct an error in the raw digital output signal. The error is detected and an adjustment is made to the boost of the analog equalization filter according to the error detected.

Abstract: The performance of a multiphase and/or multiple amplitude receiver, such as a 64/256 quadrature amplitude modulation (QAM) receiver, is improved in the presence of single and multiple echoes. A moving window adaptive decision feedback equalizer (DFE) is provided according to the adaptive equation Cn(k+1)=Cn(k)−&Dgr;·W(k)·En(k)·Xn(k), where &Dgr; (delta) is the step size, Cn(k) is the tap value of tap n for the k symbol, En(k) is the error output at the symbol k, Xn(k) is the received signal for pre-cursor taps (FFE) and past decision output for post-cursor taps (DFE), and W(k) is the sliding window function at symbol k. In the adaptation process, some coefficients are fixed while other taps are being adapted. In particular, the adaptation is focused on a group of taps which correspond to received echoes.

Abstract: An antenna switching diversity radio communication system includes a base station and a radio terminal. Transmission and reception are separated in both time and frequency in both the base station and the radio terminal. Reception quality uplink is measured on a set of several antennas belonging to the base station. The base station stores and later retrieves this quality measurement for selecting one of the antennas for uplink reception. The radio terminal measures and reports downlink reception quality to the base station, which stores this information to later select one of the antennas for downlink transmission.

Abstract: The modulator has an input (30) which receives data to be modulated. A plurality of memory regions acting as look-up tables (38-44) are arranged to contain information relating to the modulation method to be carried out by the modulator. At least one of the memory regions provides time independent modulation values and at least one of the memory regions provides time dependent modulation values. Values provided by the memory region is dependent on the data received via the input. Processing means provide a modulating signal based on the values provided by the memory regions.

Abstract: A transmitter for a multiple frequency radio communication system provides a capability for filtering spread spectrum signals of a multiple frequency system by using one lowpass filter, and variably controlling the sampling speed when converting the lowpass filtered digital signal into an analog signal.

Abstract: A method is disclosed relating to an arrangement for minimizing the autocorrelation error in the demodulation of a spread-spectrum signal subject to multipath propagation. The received signal is received from a transmitter via a plurality of propagation paths. A demodulator produces a local spread sequence, which is correlated with the received spread sequence in a first control loop on a first phase-angle pair which has a first early-late spacing 2 &Dgr;1, and which is correlated with the received spread sequence in a second control loop on a second phase-angle pair which has a second early-late spacing 2 &Dgr;2. The first and the second control loop emit a first point phase value T1 and a second point phase value T2, respectively, when in the steady state, which phase values express the phase angles of the received spread sequence with respect to the local spread sequence on the first phase angle pair or on the second phase angle pair, respectively.

Abstract: A method and apparatus for producing a variable rate precoded signal are presented in which a variable rate encoder receives a rate control signal and a data signal and generates a constellation size signal and data symbols. The data symbols and constellation size signal can be used by a precoder to produce a variable rate precoded signal. The precoder can be a Tomlinson/Harashima-Miyakawa precoder which uses the constellation size signal as part of the quantization process. The system can also be used to generate a variable rate modulation encoded signal. The invention provides the ability to create a variable rate signal which can be precoded and to which error correcting codes can be readily applied.

Abstract: The invention relates to a method and equipment for network independent clocking in a telecommunication system, particularly in data transmission where the maximum data rate on a traffic channel is equal to the user data rate. In the invention a transmitter compares the network independent clock and the network clock to detect a slip and, upon detecting a slip, performs compensation of the network independent clock by changing the number of the redundant bits in user data. The user data is transmitted through a traffic channel to a receiver. The receiver, upon detecting the network independent clock compensation in the received user data, restores the original redundancy and temporarily adjusts the network independent clock so as to compensate for the change caused by the restoration of the redundancy in the outbound user data stream.

Abstract: A multiple carrier communication system includes a primary impulse shortening filter that receives an output signal of an analog to digital converter and accepts coefficients. A secondary impulse shortening filter receives the output signal of the analog to digital converter, outputs an output signal, and passes coefficients to the primary impulse shortening filter. A reference signal generator outputs a reference signal. A comparator compares the: output signal and the reference signal and outputs a resulting error signal. An adaptive processor computes coefficients for the secondary impulse shortening filter based on the error signal.

Abstract: An ultratight coupling method generates navigation error state information from an integration Kalman filter for updating the navigation solution based upon inertial measurement data and computes pseudorange and pseudorange rate data from the navigation solution and from ephemeris data, to generate the prompt, early and late replica signals that drive the signal correlators having quadrature outputs samples by a federation of Kalman prefilters providing errors residuals to the integration Kalman filter in a closed coupled tracking loop. The coupled tracking loops offer improved tracking of the received signal based upon updated navigation solution.

Abstract: Method and apparatus for determining the correct set of samples to retain in applying a decimation process. The present method provides an automatic approach to determine the timing phase of the desired samples to decimate the oversampled input signal (data sequence), thereby producing the underlying data signal.

Abstract: A baseband spread modulation signal is input to a matched filter (131). The matched filter (131) despreads the spread modulation signal using the output of a spreading code replica generator (132). The matched filter (131) outputs the despread signals at L timings. The output signals are multiplied by multipliers (201) by corresponding weighting factors output from a weighting factor controller. The multiplied outputs are demodulated by demodulators (202), and RAKE combined by an adder (118). A data decision section (203) generates from the RAKE combined signal a data decision signal. An error signal generating section (204), receiving the RAKE combined output and the data decision signal, obtains an error signal.

Abstract: The invention proposes a digital filter adapted to transform an input digital signal into two output digital signals. The input digital signal includes input samples (xi). The first output digital signal includes output samples (y2i+1) of odd ranking, each equal to the input sample (x2i) of the same ranking decreased by the approximate value of a sum of input samples of even ranking respectively multiplied by first filtering coefficients (pk). The second output digital signal includes output samples (y2i) of even ranking, each equal to the input sample (x2i) of the same ranking decreased by the approximate value of a sum of output samples of odd ranking respectively multiplied by second filtering coefficients (uk). The second filtering coefficients (uk) are chosen from all the following sets of coefficients: (5/16, 5/16), (−1/16, 5/16, 5/16, −1/16) and (1/256, −15/256, 78/256, 78/256, −15/256, 1/256).