Abstract: An orthogonal frequency division multiplex signal and a digital modulation signal or an analog modulation signal can be identified by blind processing. The modulation mode identifying apparatus comprises: a correlation signal generating circuit which generates a duplicate signal for correlation processing based on an unknown communication signal; an autocorrelation circuit which performs autocorrelation processing through carrying out sliding processing on the duplicate signal with respect to the unknown communication signal; a detection unit which detects information regarding a pilot symbol and a guide interval symbol of the communication signal based on a correlation value output obtained by the autocorrelation processing; and an identifying circuit which identifies a modulation mode of the unknown communication signal based on the information regarding the pilot symbol and the guide interval symbol of the communication signal.

Abstract: A receiver and method for the same are provided. In the receiver, a decoder may decode an equalized signal to generate symbol decisions and a soft information signal. An equalizer may select boundary levels for non-uniform quantization using a soft information signal delayed by a symbol interval. The equalized signal may be generated from a feedback-filtered signal using the symbol decisions.

Abstract: A plurality of decoding metrics for a current frame may be generated based on a correlation set for a current frame and a correlation set for at least one previous frame. Whether a signal is present on a control channel may then be determined based on the generated decoding metrics.

Abstract: A method for communication over a communication link, which includes a transmitter and a receiver, includes transmitting and receiving data, which is encoded using a specified forward error correction (FEC) code, modulated using a specified modulation scheme and transmitted at a given power level. One or more parameters of the communication link are monitored. A condition, which is based on values of one or more of the parameters monitored at a plurality of historical time instants, is evaluated. At least one feature of the transmitted data, selected from a group of features consisting of the FEC code, the modulation scheme and the power level, is modified based on the condition.

Abstract: A method for ICI self-cancellation and ICI reconstruction and cancellation is introduced. The method includes receiving input signals; receiving boundary information regarding a length q of an ISI-free region of the received signals; selecting a plurality of ISI-free signals from the received signals; combining the plurality of ISI-free signals to provide combined signals z(n); performing FFT operations on the combined signals to provide output signals Z(k); reconstructing ICI based on the output signals Z(k) and the length q of the ISI-free region of the input signals r(n) in order to provide an estimated ICI; subtracting the estimated ICI from the output signals Z(k) to provide a cancelled signal W(k); performing a channel estimation for the cancelled signal W(k); equalizing the cancelled signal W(k) to provide an equalized signal; and de-mapping the equalized signal to provide a de-mapped signal d(k).

Abstract: Techniques for efficiently performing partial FFT for subcarriers of interest are described. The N total subcarriers may be arranged into M sets. Each set may contain K subcarriers uniformly distributed across the N total subcarriers, where M·K=N. For the partial FFT, pre-processing is initially performed on time-domain samples to obtain intermediate samples. The pre-processing may include performing M-point FFTs on the time-domain samples and multiplying the FFT outputs with unit complex values. For each set of subcarriers of interest, a K-point FFT is performed on a set of intermediate samples to obtain a set of frequency-domain symbols for that set of subcarriers. Since K is typically much smaller than N, substantial savings in computation and power may be realized when only one or few sets of subcarriers are of interest.

Abstract: A programmable clock generator circuit receives control signals and a global clock and generates a pulsed data clock and a scan clock in response to gating signals. The clock generator has data clock and scan clock feed-forward paths and a single feedback path. Delay control signals program delay elements in the feedback path and logic gates reshape and generate a feedback clock signal. The global clock and the feedback clock signal are combined to generates a pulsed local clock signal. A scan clock feed-forward circuit receives the local clock and generates the scan clock. A data clock feed-forward circuit receives the local clock and generates the data clock with a logic controlled delay relative to the local clock signal. The feedback clock is generated with controlled delay thereby modifying the pulse width of the data and scan clocks independent of the controlled delay of the data clock feed-forward path.

Abstract: One embodiment of an equalizer circuit has an FIR filter 116 in the asynchronously oversampled domain with a filter coefficient adaptation module that adapts the filter coefficients to the transfer function of a data read channel. Applications include tape drives, drives for optical and magnetic discs as well as receivers. The filter adaptation is performed on the basis of an error signal delivered by a slicer 128 which operates on synchronous samples after timing recovery and sample reconstruction.

Abstract: Frequency compensated communications reception includes compensating for frequency offset in a received signal by constructing a reference signal for comparison with a training sequence in a received signal. The reference signal is formed from basis functions and the training sequence. It is obtained by minimising a cost function J constructed from an adaptively weighted combination of basis functions, the training sequence, the received signal and a constraint requiring non-zero signal power. Multi-element antenna signals are weighted with a beamforming weight vector w in J given by formula (I), where X is a matrix of received signal samples, C is a diagonal matrix containing elements of the training sequence, F is a matrix having columns defining basis functions, v is a vector of adaptive weights, index H indicates complex conjugate transpose and ? is a Lagrange multiplier constraining beamformer power.

Abstract: A novel sigma delta amplitude modulator having a noise transfer function adapted to shift quantization noise outside at least one frequency band of interest. In one embodiment, the sigma delta amplitude modulator includes a programmable order low pass stage. In a second embodiment, the sigma delta amplitude modulator incorporates comb filtering wherein each comb filter comprises a plurality of fingers to permit greater programmability in the frequency location of notches. A polar transmitter incorporating the sigma delta amplitude modulator is presented that shapes the spectral emissions of the digitally-controlled power amplifier such that they are significantly and sufficiently attenuated in one or more desired frequency bands.

Abstract: A chaos spreading code c(n) is inputted to a spreading unit 32. Data D1 and c(n) are multiplied in the spreading unit 32. A chaos spreading code d(n) is inputted to a spreading unit 42. Data D2 and d(n) are multiplied in the spreading unit 42. The chaos spreading codes c(n) and d(n) orthogonally cross each other. Outputs of the spreading units 32 and 42 are added by an adder 35 and transmitted through a transmitting unit 36 to a transmission path 38. By making an initial value which is set in a chaos sequence generator having a construction of a digital circuit different, the chaos spreading codes which orthogonally cross can be formed. Since the chaos spreading codes c(n) and d(n) orthogonally cross, an orthogonal modulating unit having a construction of an analog circuit for amplitude-modulating carriers which orthogonally cross can be made unnecessary and the construction can be simplified.

Abstract: An RF receiver apparatus (31) is provided physically separately from a cooperating baseband processor apparatus (32). The RF receiver includes a mixer circuit (33) and an analog IF-to-digital baseband converter (34) formed on an integrated circuit. Sampling frequencies of the analog IF-to-digital baseband converter are controlled by the RF receiver apparatus.

Abstract: A space-time block encoder changes the patterns of space-time block code signals according to transmission data. The space-time block encoder makes the space-time block code signals by making first and second transmission symbols from transmission data and changing the order to output these first and second transmission symbols and signals representing the complex conjugates of the first and second transmission symbols according to transmission data.

Abstract: The present invention provides apparatus and methods for carrier frequency offset and phase compensation, which can compensate the phase rotation of an OFDM symbol resulted from carrier frequency offset between the receiver and transmitter of an OFDM System. The apparatus and method for carrier frequency offset compensation generates an estimated carrier frequency offset according to a phase error between estimated frequency responses of two consecutive received OFDM symbols within the pilot subchannel, and calculates an accumulated phase rotation, according to the estimated carrier frequency offset, for compensating the received OFDM symbol.

Abstract: In one embodiment, the present invention includes a method for receiving data corresponding to a portion of an incoming radio frequency (RF) spectrum, determining a set of estimates including one or more pairs of a channel frequency estimate and a symbol rate estimate from the data via a linear spectrum analysis, and determining a refined set of estimates from the set of estimates via at least one non-linear spectrum analysis.

Abstract: A method of selecting linked metric measurements from at least one of open loop and closed loop measurements is disclosed. The method includes sending by a first node a first radio communication and receiving by a second node the first radio communication over a communication link. The method also includes estimating by a second node dynamics of the communication channel using at least one of the variance and mean deviation of linked metric measurements. The link metric measurements are at least one of symbol error rate (SER), packet error rate (PER), frame error rate (FER), bit error rate (BER), signal to noise ration (SNR), and received signal strength (RSS). The method also includes the use of the above link metric measurements by the second node as Open Loop metrics and the sending back of these metrics to the first node for use a Closed Loop metrics by the first node. The method also includes categorizing the dynamics of the communications channel into one of at least two groups based on the estimate.

Abstract: A timestamp-based all digital phase locked loop is utilized for clock synchronization for Circuit Emulation Service (“CES”) over packet networks. The all digital phase locked loop at a CES receiver includes a phase detector, a loop filter, a digital oscillator and a timestamp counter. The all digital phase locked loop enables the CES receiver to synchronize a local clock at the receiver with a clock at a CES transmitter, where indications of transmitter clock signals are communicated to the receiver as timestamps. The phase detector is operable to compute an error signal indicative of differences between the timestamps and a local clock signal. The loop filter is operable to reduce jitter and noise in the error signal, and thereby produce a control signal. The digital oscillator is operable to oscillate at a frequency based at least in-part on the control signal, and thereby produce a digital oscillator output signal.

Abstract: An nonlinear digital signal processing filter (100, 200, 1100, 1308, 1310, 1312, 1346, 1604) maintains a magnitude ordering for successive windows of signal samples. A set of filter density generator values [f1, f2, f3 . . . fj . . . fndensities] are used according to the ordering in a recursion relation that computes successive values of a set function over the set of filter density generator values. The recursion relation involves an adjustable nonlinearity defining parameter ?. The values are normalized by dividing by a largest of the values, and differences between successive values are taken. An inner product between each window of signal values (used in order according to magnitude) and the adaptive differences is a filtered signal sample.

Abstract: A digital signal encoding method and apparatus using a plurality of lookup tables. The method includes: preparing a plurality of lookup tables storing numbers of allocated bits for encoding frequency bands of an input signal according to a characteristic of the input signal in a predetermined number of addresses; dividing an input signal in the time domain into signals in predetermined frequency bands; calculating address values of the frequency bands; selecting one of the plurality of lookup tables according to the characteristic of the input signal; extracting numbers of allocated bits of addresses having the calculated address values from the selected lookup table with respect to the frequency bands and allocating the numbers of bits to the frequency bands; and generating a bitstream by quantizing the input signal according to the numbers of allocated bits.

Abstract: A technique for an equalizer filter with dynamically configurable convolution filter is described. The input to a transmitter chain is modified by an equalizer filter, prior to being applied to the transmitter. The equalizer filter modifies and smoothen the amplitude of the signal. The modified and smoothen signal has its peaks reduced which results in lower Crest Factor. The input to the reconditioning equalizer filter could be a baseband, an intermediate frequency (IF) or radio frequency (RF) signal. In the case of an IF or RF signal, it needs to be down converted to baseband before applied to the equalizer filter.