Abstract: An apparatus for sampling clock recovery (SCO) and methods for estimating and compensating SCO are provided. The apparatus comprises a symbol timing adjustment module for shifting forward or backward symbol timing of the transmitted OFDM symbols; a discrete Fourier transform (DFT) processor for performing DFT to an output from the symbol timing adjustment module; a channel estimator for undertaking a channel frequency response estimation based on a channel estimation sequence; a SCO phase rotator for receiving and performing phase shift on the transmitted OFDM symbols of a frame header and a frame payload; an SCO estimation stage for undertaking an SCO estimation based on a pilot-subcarrier-related output of the SCO phase rotator and the CFR estimation; and an SCO compensation distributor for dividing the SCO estimation into integer and fractional portions and then distributing them into the symbol timing adjustment module and the SCO phase rotator, respectively.

Abstract: A multi-stage CFR estimation method for multi-band OFDM-based UWB systems is provided. The method includes obtaining a CFR estimation ?r(1) by performing LS estimation using a channel estimation sequence from a received OFDM-UWB frame; obtaining a CFR estimation ?r(2) by applying a frequency-domain smoothing to the CFR estimation ?r(1) with a first smoothing factor; obtaining a frame header which contains OFDM symbols transmitted with frequency-domain spreading on each OFDM symbol, and detecting signal signs based on a combination of two spread signals of the same OFDM symbol in the frame header with a decision directed mode and the CFR estimation ?r(2) assisted; obtaining a CFR estimation ?r(3) by using the signs and a finite-alphabet feature of the detected transmitted signals; obtaining a CFR estimation ?r(4) by applying a frequency-domain smoothing to the CFR estimation ?r(3) with a second smoothing factor; and obtaining a CFR estimation ?r by averaging the CFR estimations ?r(2) and ?r(4).

Abstract: Method and apparatus for receiving coded signals with the aid of CSI are provided. The method comprises: performing channel estimation to obtain a CFR estimation vector; computing a squared magnitude of the CFR estimation vector, and obtaining a normalization factor ? by averaging the squared magnitudes of CFR estimations on all N subcarriers; finding a norm-shift operand m satisfying the condition that ?0=2m is a power of 2 number closest to the normalization factor ?; performing a CSI-aided one-tap channel equalization on an output signal vector from a DFT processor by using the norm-shift operand m; performing constellation demapping; and performing channel decoding. The method further comprises obtaining a weighting factor vector by right shifting m bits of the squared magnitude of the CFR estimation vector so that the constellation demapping can use the weighted decision boundary values in case that its input signal is sensitive to both amplitude and phase.

Abstract: A system for performing LS equalization on a signal in an OFDM system comprises a receiver stage for receiving a modulated signal, a demodulation stage for demodulating the received modulated signal to produce a demodulated signal, a channel estimation stage for processing the demodulated signal to provide an output signal corresponding to a channel frequency response and an equalization stage arranged to process the output signal from the channel estimation stage to produce a channel state information signal. The equalization stage is arranged to use the channel state information signal to operate on the demodulated signal from the demodulation stage to produce an equalized demodulated output signal. There is also disclosed a method for performing LS equalization on a signal in an OFDM system.

Abstract: An apparatus for sampling clock recovery (SCO) and methods for estimating and compensating SCO are provided. The apparatus comprises a symbol timing adjustment module for shifting forward or backward symbol timing of the transmitted OFDM symbols; a discrete Fourier transform (DFT) processor for performing DFT to an output from the symbol timing adjustment module; a channel estimator for undertaking a channel frequency response estimation based on a channel estimation sequence; a SCO phase rotator for receiving and performing phase shift on the transmitted OFDM symbols of a frame header and a frame payload; an SCO estimation stage for undertaking an SCO estimation based on a pilot-subcarrier-related output of the SCO phase rotator and the CFR estimation; and an SCO compensation distributor for dividing the SCO estimation into integer and fractional portions and then distributing them into the symbol timing adjustment module and the SCO phase rotator, respectively.

Abstract: A method for demapping dual carrier modulated COFDM signals comprises normalizing an estimated channel state information signal to obtain a normalized channel state information signal, determining a Y-domain weighting factor from the normalized channel state information signal, determining an X-domain weighting factor from the normalized channel state information signal, performing equalization on a received data OFDM signal to obtain an equalized data signal, weighting an equalized data signal using the Y-domain weighting factor and the X-domain weighting factor to generate a weighted input signal of a demapper and performing linear demapping of the weighted input signal in the demapper. There is also disclosed an apparatus for demapping dual carrier modulated COFDM signals and a receiver comprising such an apparatus.

Abstract: An apparatus for sampling clock recovery (SCO) and methods for estimating and compensating SCO are provided. The apparatus comprises a symbol timing adjustment module for shifting forward or backward symbol timing of the transmitted OFDM symbols; a discrete Fourier transform (DFT) processor for performing DFT to an output from the symbol timing adjustment module; a channel estimator for undertaking a channel frequency response estimation based on a channel estimation sequence; a SCO phase rotator for receiving and performing phase shift on the transmitted OFDM symbols of a frame header and a frame payload; an SCO estimation stage for undertaking an SCO estimation based on a pilot-subcarrier-related output of the SCO phase rotator and the CFR estimation; and an SCO compensation distributor for dividing the SCO estimation into integer and fractional portions and then distributing them into the symbol timing adjustment module and the SCO phase rotator, respectively.

Abstract: A processor for performing a Fast Fourier Transform and/or an Inverse Fast Fourier Transform of a complex input signal comprises a first stage for passing the input signal to a second stage when a Fast Fourier Transform procedure is to be performed and for swapping the real and imaginary components of the complex input signal before passing the signal to the second stage if an Inverse Fast Fourier Transform procedure is to be performed. The second stage has first and second radix-4 butterfly elements. A third stage is arranged to switch between first and second operating modes, the second operating mode being for processing a complex conjugate symmetrical input signal. A fourth stage has a plurality of processing units, one or more of the processing units comprising a radix-2 pipelined Fast Fourier Transform processor.

Abstract: An apparatus for sampling clock recovery (SCO) and methods for estimating and compensating SCO are provided. The apparatus comprises a symbol timing adjustment module for shifting forward or backward symbol timing of the transmitted OFDM symbols; a discrete Fourier transform (DFT) processor for performing DFT to an output from the symbol timing adjustment module; a channel estimator for undertaking a channel frequency response estimation based on a channel estimation sequence; a SCO phase rotator for receiving and performing phase shift on the transmitted OFDM symbols of a frame header and a frame payload; an SCO estimation stage for undertaking an SCO estimation based on a pilot-subcarrier-related output of the SCO phase rotator and the CFR estimation; and an SCO compensation distributor for dividing the SCO estimation into integer and fractional portions and then distributing them into the symbol timing adjustment module and the SCO phase rotator, respectively.

Abstract: A multi-stage CFR estimation method for multi-band OFDM-based UWB systems is provided. The method comprises obtaining a CFR estimation ?r(1) by performing LS estimation using a channel estimation sequence from a received OFDM UWB frame; obtaining a CFR estimation ?r(2) by applying a frequency-domain smoothing to the CFR estimation ?r(1) with a first smoothing factor; obtaining a frame header which contains OFDM symbols transmitted with frequency-domain spreading on each OFDM symbol, and detecting signal signs based on a combination of two spread signals of the same OFDM symbol in the frame header with a decision directed mode and the CFR estimation ?r(2) assisted; obtaining a CFR estimation ?r(3) by using the signs and a finite-alphabet feature of the detected transmitted signals; obtaining a CFR estimation ?r(4) by applying a frequency-domain smoothing to the CFR estimation ?r(3) with a second smoothing factor; and obtaining a CFR estimation ?r by averaging the CFR estimations ?r(2) and ?r(4).

Abstract: Method and apparatus for receiving coded signals with the aid of CSI are provided. The method comprises: performing channel estimation to obtain a CFR estimation vector; computing a squared magnitude of the CFR estimation vector, and obtaining a normalization factor ? by averaging the squared magnitudes of CFR estimations on all N subcarriers; finding a norm-shift operand m satisfying the condition that ?0=2m is a power of 2 number closest to the normalization factor ?; performing a CSI-aided one-tap channel equalization on an output signal vector from a DFT processor by using the norm-shift operand m; performing constellation demapping; and performing channel decoding. The method further comprises obtaining a weighting factor vector by right shifting m bits of the squared magnitude of the CFR estimation vector so that the constellation demapping can use the weighted decision boundary values in case that its input signal is sensitive to both amplitude and phase.

Abstract: An encoder system for encoding a signal according to any number of FEC and/or channel codes comprises a shift register, an array of MOD/XOR stages, and a generator matrix stage for controlling the connections between the shift register and the MOD/XOR stages and altering these connections according to a coding format selected by an encoder selection stage. There is also disclosed a decoder system for decoding a signal encoded according to a number of FEC and/or channel codes comprising a decoding stage, and a generator matrix stage for configuring the decoding stage to a decoding code format to be applied an incoming encoded signal. A decoder selection stage is coupled to the generator matrix stage and selects the decoding code format to be used in the decoding process. The decoder selection stage instructs the generator matrix stage to configure the decoding stage according to the selected decoding code format. There is also disclosed a method for encoding and decoding.

Abstract: A system and method for estimating phase offset between a local oscillator and a transmitted input signal in a communication system comprises a differential detector and a phase compensation stage for compensating for phase errors in an output signal from the differential detector. The output signal from the differential detector is rotated in a decision-based rotation stage coupled to the outputs of the differential detector and the phase compensation stage. The rotation is based on a decision made using the output signal from the phase compensation stage. An accumulation stage accumulates the output signal from the decision-based rotation stage for a number of symbols in the transmitted input signal. A normalization stage normalizes the output signal from the accumulation stage and the normalized output signal corresponds to a phase offset of the local oscillator relative to the transmitted input signal.

Abstract: A method for demapping dual carrier modulated COFDM signals comprises normalizing an estimated channel state information signal to obtain a normalized channel state information signal, determining a Y-domain weighting factor from the normalized channel state information signal, determining an X-domain weighting factor from the normalized channel state information signal, performing equalization on a received data OFDM signal to obtain an equalized data signal, weighting an equalized data signal using the Y-domain weighting factor and the X-domain weighting factor to generate a weighted input signal of a demapper and performing linear demapping of the weighted input signal in the demapper. There is also disclosed an apparatus for demapping dual carrier modulated COFDM signals and a receiver comprising such an apparatus.

Abstract: A processor for performing a Fast Fourier Transform and/or an Inverse Fast Fourier Transform of a complex input signal comprises a first stage for passing the input signal to a second stage when a Fast Fourier Transform procedure is to be performed and for swapping the real and imaginary components of the complex input signal before passing the signal to the second stage if an Inverse Fast Fourier Transform procedure is to be performed. The second stage has first and second radix-4 butterfly elements. A third stage is arranged to switch between first and second operating modes, the second operating mode being for processing a complex conjugate symmetrical input signal. A fourth stage has a plurality of processing units, one or more of the processing units comprising a radix-2 pipelined Fast Fourier Transform processor.

Abstract: A system for performing LS equalization on a signal in an OFDM system comprises a receiver stage for receiving a modulated signal, a demodulation stage for demodulating the received modulated signal to produce a demodulated signal, a channel estimation stage for processing the demodulated signal to provide an output signal corresponding to a channel frequency response and an equalization stage arranged to process the output signal from the channel estimation stage to produce a channel state information signal. The equalization stage is arranged to use the channel state information signal to operate on the demodulated signal from the demodulation stage to produce an equalized demodulated output signal. There is also disclosed a method for performing LS equalization on a signal in an OFDM system.

Abstract: A method of estimating the reliability of decoded message bits in a digital communications system is proposed. Message and tail bits are coded and transmitted across a communications channel. The coded message and tail bits are then decoded and it is determined that the decoded message bits have no error when the decoded tail bits have at least one error.

Abstract: There is provided an apparatus and method for isolating an in-phase component I and a quadrature component Q of a received IF signal and for filtering the received signal. The apparatus comprises a DDC for sampling the received signal at four times the frequency of the received signal, each sample having an order k and a filter for reducing noise outside a required bandwidth. The filter has n taps and comprises a first filter portion for receiving the samples where k is even and for outputting an in-phase component I of the received signal and a second filter portion for receiving the samples where k is odd and for outputting a quadrature component Q of the received signal. The first filter portion has x taps and the second filter portion has y taps and x+y=n.

Abstract: There is provided a method and apparatus for demodulating a received hard limited DPSK signal, which may be an intermediate frequency (IF) signal. The apparatus comprises: a digital down converter for generating an in-phase component I and a quadrature component Q of a received signal; at least one decimator for reducing sampling frequency of the received signal; at least one filter for reducing noise outside a required bandwidth; and a differential decoder for performing differential detection of I and Q over a given symbol span. The method comprises the steps of: generating an in-phase component I and a quadrature component Q from a received signal; reducing sampling frequency of the received signal; reducing noise outside a required bandwidth; and performing differential detection of I and Q over a given symbol span.

Abstract: An automatic gain control system comprises a number of variable gain stages connected in series and a number of sensors, the input of each sensor being connected to a respective output of the variable gain stages. The input of an analogue-to-digital converter is connected to the output of one of the variable gain stages. The input of a control unit is connected to the outputs of the sensors and to the output of the analogue-to-digital converter. The input of a digital-to-analogue converter is connected to the output of the control unit, and the control inputs of each of the variable gain stages is connected to an output of the digital-to-analogue converter. The outputs of the digital-to-analogue converter are used to control the gains of the variable gain stages. Also disclosed is a method for automatically controlling gain in a receiver system.