Abstract: In a normalization process, overflow occurring in limited size registers, holding the alpha or beta values in a map decoder, may be overcome by subtracting a constant value from all of the alpha or beta values when they reach a limit. Because subtracting a constant value may slow down the computation, detection of a constant value may occur on one decoding cycle and normalization on the succeeding decoding cycle. A multiplexor type circuit can be used to direct either zeros, in the normalization case, or a most significant bit(s), in computations without normalization, into the register holding the alpha or beta values. To minimize the impact on the computation by the normalization process, the multiplexor circuit can be set by the previous decoder cycle so that the computation does not have to wait for the multiplexor to be set to normalization or normal computation.

Abstract: Systems and methods for receiving layered modulation for digital signals are presented. An exemplary apparatus comprises a tuner for receiving a layered signal and producing a layered in-phase signal and a layered quadrature signal therefrom, an analog-to-digital converter for digitizing the layered in-phase signal and the layered quadrature signal and a processor for decoding the layered in-phase signal and the layered quadrature signal to produce one or more discrete layer signals.

Abstract: Techniques for reducing peak-to-average power in multicarrier transmitters employ peak cancellation with subcarriers that are impaired by existing channel conditions. The use of Carrier Interferometry (CI) coding further improves the effectiveness of peak reduction. CI coding can also be impressed onto pulse sequences in the time domain, which enhances spectral selection and facilitates peak-power control.

Abstract: A modulation and demodulation system is provided. The system uses n sub-carrier frequencies and an oversampling positive integer and includes a modulation circuit and a demodulation circuit. The modulation circuit includes a modulation ROM that stores columns of elements independently in a modulation ROM matrix. The demodulation circuit includes 2n numbers of a ROM1 that stores elements of a combined matrix. The combined matrix is generated by combining a number of inverse matrices where the inverse matrices are generated from the modulation ROM.

Abstract: Transmit power adaptation for DS/CDMA systems is disclosed for a CDMA system that utilizes a successive interference cancellation receiver on fading channels. The transmission power is adapted in response to channel variations to achieve an arbitrary power profile for received signal powers at the system base station. That is, the received signal powers are distributed with some factor xi's given as: SRi=SR(1)xi, (i=2, 3, . . . , K and x1=1) where K is the number of users and SR(i) is the received signal power of the user having the ith strength, and wherein user strengths are ranked in the order of estimated channel gains. The factor xi gives a measure of the disparity between the received power levels. The channel is estimated at both the transmitter and receiver. In one embodiment, the factors, xi, for distributing the signal powers are selected such that the average BER for each user is minimized.

Abstract: There is provided a flexible transmission device capable of automatically setting an optimal point for a signal decision making with high accuracy, so that highly reliable high-quality signal regeneration control is achieved. A clock timing extraction circuit dynamically sets a frequency-dividing ratio based on the transmission rate of an input signal to perform a phase synchronization control so that there is a fixed phase difference between the input signal and an oscillation output, whereby clock timing based on the transmission rate can be extracted. A regeneration control circuit sequentially sweeps a voltage threshold level and the phase of the extracted cock with respect to the input signal and determines whether the levels of adjacent monitor points match, whereby a decision point within the valid zone of the eye pattern can be automatically measured and used as the optimal point for regeneration control.

Abstract: A clock recovery circuit includes a demodulator which generates in-phase and quadrature signals from a data signal and a phase adjuster which adjusts a phase of the quadrature signal independently from a phase of the in-phase clock signal. The phase adjustment causes a non-orthogonal relationship to exist between the phases of the quadrature and in-phase signals. The independent phase adjustment may be dynamically performed or may be performed in fixed increments to achieve a predetermined level of performance. In one application, the adjusted quadrature phase signal serves as a clock signal for controlling sampling of the data signal.

Abstract: One embodiment of the present invention provides a system that optimizes synchronization between monitored signals in a computer system. During operation, the system receives a number of monitored signals. The system then forms a number of signal pairs by grouping each signal with every other signal. Next, the system optimizes synchronization between the signals by iteratively perturbing the timing of each signal in an attempt to increase the value of an objective function which reflects the overall synchronization between all the signals.

Abstract: A system incorporates time-hopped impulse radio (TH-IR) and transmitted-reference impulse radio (TR-IR) transceivers in the same wireless network. A transmitter modulates a sequence of bits in a wireless communications network by generating a reference waveform and a data waveform of a waveform pair for each current bit. The phase of the reference waveform depends on a previous modulated bit, and a difference in phase between the reference waveform and the data waveform pair depend on the current bit. A symbol period for the current bit is partitioned into multiple time intervals, and the reference waveform and the data waveform are encoded in a selected one of the time intervals that depends on the current bit.

Abstract: A method of computing an inversion (X) of a nearly Toeplitz n by n matrix (A). A perturbation matrix (E) is first determined such that the sum of the nearly Toeplitz matrix (A) and the perturbation matrix (E) is a Toeplitz matrix (T). The inversion is solved by solving the equation X=T?1(B+EX), where B is a vector or matrix of dimension n by m. An initial estimate X(0) is selected and estimates of the inversion X are iteratively computed through the recursion X(n?1)=T?1(B+EX(n)). The initial estimate X(0) may be equal to an inversion (T?1) of the Toeplitz matrix (T). The present invention may be utilized in a radio receiver to efficiently compute (1) a least-squares (LS) channel estimate, (2) minimum mean squared error (MMSE) prefilter coefficients for a decision feedback equalizer (DFE), or (3) an autoregressive (AR) noise-spectrum estimation from a finite number of observed noise samples.

Abstract: A system incorporates time-hopped impulse-radio (TH-IR), transmitted-reference impulse-radio (TR-IR) and noncoherent transceivers in the same wireless network. A transmitter modulates a sequence of bits in a wireless communications network by selecting one coding sequence from a set of orthogonal or quasi-orthogonal coding sequences based on a current subsequence of bits of the input sequence, generating a reference waveform and a data waveform of a waveform pair for each sequence.

Abstract: The present invention is related to a method and apparatus for providing service availability information to a user in a wireless communication system. After receiving a beacon signal from a base station, a WTRU measures a power level and an interference level of the beacon signal. A target SIR and a power offset for each service is pre-defined and stored in a memory of the WTRU. A processor calculates an estimated SIR for each service, and generates a service availability indicator by dividing the estimated SIR with a target SIR for each service. A user is informed of the availability of various services simply by looking at the display of the WTRU.

Abstract: In multicarrier transmission for multiplying transmit data individually by each code constituting orthogonal codes and transmitting each result of multiplication by a prescribed subcarrier, a plurality of different subcarriers are assigned exclusively to each user and each user performs multicarrier transmission of the transmit data by the subcarriers assigned. Further, a base station assigns a plurality of different subcarriers to each user exclusively, applies beam-forming processing on a per-user basis and performs multicarrier transmission of transmit data to each user by the subcarriers assigned.

Abstract: A demodulating semiconductor integrated circuit device used in a wireless communication system of an FM-modulation scheme, wherein a circuit for canceling a frequency offset is made of a digital circuit, so as to make a high-accuracy decision as to received data and prevent error frequency offset cancel due to a pseudo pattern contained in the received data. Consequently, a high-accuracy received data decision is carried out.

Abstract: Wireless communication systems are provided with an adaptive subcarrier loading function for a mobile receiver in a wireless communication system based on Orthogonal Frequency Division Multiplexing (OFDM) that can advantageously be applied to predict the channel transfer function of a multipath propagation channel being severely impaired by frequency-selective fading and an extremely time-variant behavior by detecting the position and/or movement of zero points of the transfer function, thereby reducing the probability of incorrect assignment of the modulation scheme for each subcarrier caused by mobile terminals moving at high velocity. The zero points of the estimated channel transfer function are determined by detecting the position of deep notches on the associated amplitude response of the measured channel transfer function caused by frequency-selective fading whose depths are larger than a predefined threshold.

Abstract: A technique to boost the output power of portable radio terminals without increasing the power dissipation is described. The input to the terminal transmit amplifier is modified by a peak-to-average reduction and an amplitude pre-distortion circuit, prior to being applied to the amplifier. The peak-to-average reduction and pre-distortion circuit modifies the baseband samples before applying any amplitude pre-distortion. The amplitude pre-distortion uses a lookup table updated at power up or power down of the terminal radio, during idle time, just before origination of a call, before termination of a call, or while the call is active. During the updating of the lookup table the radio could be in its normal transmit mode, or transmit into a dummy load.

Abstract: Disclosed is a method for compensating for a residual frequency offset in an orthogonal frequency division multiplexing system comprising the steps of: a) performing a fast fourier transform for an input signal to convert the input signal into a serial signal; b) detecting signal power of the serial signal to control the passthrough a signal greater than a predetermined critical value; c) selecting each section of a quadrant for each passed signal; d) estimating a phase error in each section of the quadrant for one orthogonal frequency division multiplexing symbol with respect to the selected section of the quadrant; and e) frequency-oscillating a signal based on the estimated phase error, generating the input signal by multiplying an oscillated signal by a band-passed signal, and then returning to step a).

Abstract: An apparatus for generating a preamble sequence in an orthogonal frequency division multiplexing (OFDM) communication system using A subcarriers in a frequency domain. A preamble sequence generator generates a length?M+N+k preamble sequence, where M+N+k is less than A, by combining a length?N Golay complementary sequence with a length?M Golay complementary sequence. An inverse fast Fourier transform (IFFT) processor assigns elements constituting the preamble sequence to the M+N+k subcarriers among the A subcarriers on a one-to-one mapping basis, assigns null data to remaining subcarriers excluding the M+N+k subcarriers from the A subcarriers, and then IFFT-transforms the assigned result into time-domain data.

Abstract: A decision-driven control loop wherein a first reconstructed signal is compared to an unreconstructed data symbol signal to initially drive the control loop. A second reconstructed signal that is based on a longer memory path than the first reconstructed signal is evaluated against the first reconstructed signal. The decision-driven control loop is ultimately controlled based on the results of the evaluation between the first and second reconstructed signals. The inventive decision-driven control loop, which may be implemented in software, may form part of a read channel in a storage device.

Abstract: A system for implementing Incremental Redundancy (IR) operations in a wireless receiver includes a baseband processor, an equalizer, a system processor, and an IR processing module. The baseband processor receives an analog signal corresponding to a data block and samples the analog signal to produce samples. The equalizer receives the samples from the baseband processor, equalizes the samples, and produces soft decision bits corresponding to the data block. The equalizer may be implemented as a distinct processing component or may be performed by the baseband processor or system processor. The system processor receives at least the soft decision bits and initiates IR operations. The IR processing module receives the soft decision bits of the data block and performs IR operations on the data block in an attempt to correctly decode a corresponding data block.