Wipro Techno Centre (singapore) Pte. Ltd.

Oki Techno Centre (singapore) Pte Ltd

Agency for Science, Technology and Research

Oki Techno Center (singapore) Pte Ltd.

Zhongjun Wang

Masayuki Tomisawa

Yanxin Yan

Lee Guek Yeo

Wenzhen Li

Yujing Ting

Zhi Ping Li

Yu Jing Ting

Saigui Hu

Xiaodan Gan

Qi Jun Xu

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.

Apparatus and methods for estimating and compensating sampling clock offset

A multi-stage CFR estimation method for multi-band OFDM-based UWB systems is provided. The method includes obtaining a CFR estimation &#x125;by performing LS estimation using a channel estimation sequence from a received OFDM-UWB frame; obtaining a CFR estimation &#x125;by applying a frequency-domain smoothing to the CFR estimation &#x125;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 &#x125;assisted; obtaining a CFR estimation &#x125;by using the signs and a finite-alphabet feature of the detected transmitted signals; obtaining a CFR estimation &#x125;by applying a frequency-domain smoothing to the CFR estimation &#x125;with a second smoothing factor; and obtaining a CFR estimation &#x125;by averaging the CFR estimations &#x125;and &#x125;.

CFR estimation method for multi-band OFDM-based UWB systems

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 &#x3b1; by averaging the squared magnitudes of CFR estimations on all N subcarriers; finding a norm-shift operand m satisfying the condition that &#x3b1;=2is a power of 2 number closest to the normalization factor &#x3b1;; 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.

Method and apparatus for receiving coded signals with the aid of channel state information

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.

System and method for performing LS equalization on a signal in an OFDM system

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.

Method, apparatus and receiver for demapping dual carrier modulated COFDM signals

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. The first and second radix-4 butterfly elements are arranged to perform a butterfly operation on the complex input signal to generate and deliver one or more components of a processed signal to the fourth stage. The fourth stage is arranged to process the processed signal received from the first stage according to a Fast Fourier Transform processing procedure to produce an output signal. There is also disclosed a method for performing a Fast Fourier Transform and/or Inverse Fast Fourier Transform of a complex input signal.

Processor and method for performing a fast fourier transform and/or an inverse fast fourier transform of a complex input signal

A method for channel response estimation for an OFDM communication system based on a certain normal training symbols plus one virtual training symbol begins with receiving at least one preamble symbol of a transmitted data frame. A first channel state information is estimated from the at least one preamble symbol. At least one signalling symbol is then received and equalized and a rate factor and a length factor are extracted from the at least one signalling symbol. A virtual training symbol is formed from the rate factor and the length factor. A second channel state information is estimated from the at least one preamble symbol and the virtual training symbol. The data symbols are equalized by performing channel correction on data symbols with the second channel estimation and pilot sub-carriers in each of the plurality of data symbols.

Growing community of inventors

Singapore, Singapore

Zhongjun Wang