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Post-DTF/FFT time tracking algorithm for OFDM receivers

A time tracking and receiver technology, applied in baseband systems, channel estimation, digital transmission systems, etc., to solve problems such as inter-symbol interference

Inactive Publication Date: 2012-01-11
NXP BV
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Problems solved by technology

However, if the channel impulse response is longer than one-half the guard interval, this simple approach essentially results in pulling strong paths into the middle of the guard interval and smaller paths moving out of the guard window, causing inter-symbol interference

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  • Post-DTF/FFT time tracking algorithm for OFDM receivers
  • Post-DTF/FFT time tracking algorithm for OFDM receivers
  • Post-DTF/FFT time tracking algorithm for OFDM receivers

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Embodiment Construction

[0034] figure 1 A simplified schematic block diagram of a part of an OFDM receiver is shown, in which the time tracking proposed according to the present invention can be incorporated. Extract blocks with the same length as the DFT from the received composite digital baseband signal, and separate these blocks with the same length as the DFT by using unused blocks with the same length as the OFDM guard interval (110). DFT processing (120) is performed on each useful block, and each processing generates a vector of received data and pilot symbols in the frequency domain. The pilot symbol is a known transmission symbol, and the pilot symbol is provided to the receiver to realize various parameter estimation tasks including channel estimation (150). The calculated channel estimate of a DFT output vector is used to equalize the data symbols of the vector. The equalized symbols are fed to the QAM demapper (140) and finally to the decoder.

[0035] figure 2 A block diagram of the fir...

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Abstract

A method for time synchronization tracking in an orthogonal frequency division multiplexing (OFDM) receiver is described, the method comprising the steps: obtaining a DFT output vector; determining a sample timing offset indication using reference symbols that are extracted from the DFT output vector; and adapting the OFDM symbol timing using said determined indication. In order to provide an improved post-DFT algorithm for estimating a time tracking error in OFDM receivers such as to allow an effective time tracking even in single frequency networks, and more particular to devise a time tracking algorithm for OFDM receivers that supports longer channel impulse responses without causing inter-symbol interference, said determining step comprises the steps of : (a) estimating (162) the channel transfer function at equidistant frequency positions using said reference symbols, for a first OFDM symbol; (b) determining (163) a plurality of autocorrelations of said channel transfer function at a specific set of small frequency offsets for said OFDM symbol; (c) repeating steps (a) and (b) for a plurality of subsequent OFDM symbols; (d) linearly combining (164,165) said plurality of autocorrelations for said plurality of OFDM symbols obtained in steps (a) through (c), for obtaining said sampling clock offset indication wherein the linear combining uses nonzero weights only. Further described is an orthogonal frequency division multiplexing (OFDM) receiver circuit arrangement performing this method.

Description

Technical field [0001] The invention relates to a method for time synchronization tracking in a broadband transmission system. More specifically, the present invention relates to an algorithm for post-DFT time synchronization tracking in an OFDM receiver. The present invention also relates to a system for performing a time synchronization tracking method in an OFDM receiver. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) has become a popular transmission method for high-speed wireless transmission because it can be used in low-complexity transmitters and receivers and has robustness under harsh multipath conditions. There is a more detailed discussion on OFDM in S.B. Weinstein and P.M. Ebert: Data transmission by frequency-division multiplexing using the discrete Fourier transform. IEEE Trans. Communication Technology, COM-19(5): 628-634, Oct. 1971. [0003] In OFDM, a large number of spatially close orthogonal subcarriers are used to carry data. ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26H04L25/02
CPCH04L25/0232H04L27/2662H04L25/022H04L27/2672
Inventor 安德列亚斯·布里
Owner NXP BV
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