Synchronization method and apparatus for orthogonal frequency division multiplexing system

Active Publication Date: 2010-09-30
APPLE INC
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Benefits of technology

[0021]Based on the above-mentioned descriptions, the exemplary embodiments of the present invention provide the synchronization method, the synchronization apparatus of the OFDM system, and the OFDM system, so that the precision of estimating a timing offset value and a frequency offset value can be enhanced. Namely,

Problems solved by technology

However, the OFDM system is sensitive to a timing offset and a frequency offset which easily result in crosstalk among carriers.
However, since the above-mentioned two methods are both affected by cyclic prefix (CP) which results in large timing estimation errors, Minn proposed another method of timing synchronization and frequency synchronization as a modification to Schmidl's approach (referring to Minn H, Zeng M, Bhargava V K. On Timing Offset Estimation for OFDM System [J].
Since the Schmidl's method sets a timing point corresponding to the maximum function value in the Schmidl decision function M2(d) as a timing synchronization point, the Schmidl method leads to uncertainty of the timing estimation and results in significant timing estimation errors so as to affe

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Example

[0029]refer to FIG. 2A. FIG. 2A is a flow chart of a synchronization method according to an exemplary embodiment of the present invention. The synchronization method is suitable for being used in a receiving terminal of an OFDM system. As shown in FIG. 2A, the synchronization method of the exemplary embodiment of the present invention mainly includes the following steps. First, an OFDM training symbol is received by the receiving terminal, wherein the OFDM training symbol includes a plurality of sample points (step S102). Next, a plurality of first function values are calculated according to the sample points by using a first function (step S104). In the exemplary embodiment of the present invention, the first function is a Park decision function M1(d). However, it is apparent that one of ordinary skills in the art can choose another type decision function as the first function according to other embodiments of the present invention, such as a Schmidl decision function.

[0030]Thereafter

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Abstract

A synchronization method used in a receiving terminal of an orthogonal frequency division multiplexing (OFDM) system is illustrated. The synchronization method includes following steps: (a) receiving an OFDM training symbol at the receiving terminal, wherein the OFDM training symbol includes many sample points; (b) calculating first function values according to the sample points by using a first function; (c) selecting D timing points from many timing points corresponding to the first function values, wherein D first function values of the D timing points are larger than a first threshold value; (d) calculating D second function values of the D timing points by using a second function; and (e) selecting a first timing point from the D timing points, and setting the first timing point as a timing synchronization point, wherein the second function value of the first timing point is a first one greater than a second threshold value.

Description

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Claims

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Application Information

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Owner APPLE INC
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