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Frame synchronization method for burst mode OFDM system

A system frame and sequence technology, applied in the field of frame synchronization of burst OFDM system, can solve the problem of difficult threshold setting at the receiving end

Inactive Publication Date: 2012-07-18
UNIV OF ELECTRONICS SCI & TECH OF CHINA
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0012] On the one hand, due to the existence of the cyclic prefix CP, the time decision variable M SC There will be a platform, and the length of the platform is proportional to the length of the CP. This platform will increase the difficulty of frame detection judgment
On the other hand, the setting of the threshold usually changes according to the change of the signal-to-noise ratio, and the threshold setting at the receiving end is a difficult problem

Method used

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  • Frame synchronization method for burst mode OFDM system
  • Frame synchronization method for burst mode OFDM system
  • Frame synchronization method for burst mode OFDM system

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Embodiment Construction

[0029] The implementation manner of the technical solution of the present invention will be described in detail below.

[0030] In this embodiment, the number of OFDM subcarriers N is 128, the number of effective subcarriers is 116, and the length of the cyclic prefix is ​​N CP It is N / 4, and the symbol interval is 0.25μs. The Doppler frequency is 900Hz, the carrier frequency offset is 1KHz, the OFDM symbol adopts BPSK modulation, and the channel adopts the urban environment (TU) channel model. The training sequence is followed by 25 OFDM symbols. The signal-to-noise ratio is set to 4-16dB. The threshold value is set as Th1=0.02, Th2=0.3.

[0031] Step 1: Generation of training sequences.

[0032] Step 1-1: The selected training sequence in the frequency domain is:

[0033] F=[001010101010-101010-1010-10-10-101010-10-101010-10-10-10-10-10-10-10-1010100000000000-10-10101010-1010-10-10-10101010-10-10 -1010101010-10-1010-10-1010-101010]. Normalize F so that the average pow...

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Abstract

The invention belongs to the synchronous technical field of wireless communication systems, and in particular relates to a frame synchronization method for a burst mode OFDM (Orthogonal Frequency Division Multiplexing) system. The method comprises the following steps: selecting a sequence S with an initial position d and a length N from received data; calculating a related value P of the front half part and the rear half part of the S, as well as a half (E) of an energy value of the S and a normalized related value C; computing time according to the C to judge a variable value M; comparing the M with the small one of two threshold values, if exceeding the threshold value, a maximal circular correlation value Z of the S and a training sequence T is calculated out, otherwise, the d value is updated and the first step is returned; and if the Z exceeds the larger one of the two threshold values, confirming a frame initial position, otherwise, the d value is updated and the first step is returned. According to the method provided by the invention, the influence of a platform effect on the frame synchronization of the burst-mode OFDM system is avoided. Therefore, the method can work under different signal-to-noise ratio conditions.

Description

technical field [0001] The invention belongs to the technical field of synchronization in a wireless communication system, and in particular relates to a frame synchronization method of a burst OFDM system. Background technique [0002] OFDM is a multi-carrier modulation method. It is widely used in standards such as DAB, IEEE 802.11, and IEEE 802.16 because it can resist frequency-selective fading channels, and has the advantages of high spectral efficiency and simple channel equalization. For a burst OFDM system, the first task of the receiver is to detect the starting position of the frame, that is, frame synchronization. At present, there are many literatures on frame synchronization methods, which can be roughly divided into two categories, which are frame synchronization based on training sequence and frame synchronization based on cyclic prefix. Because the performance of frame synchronization based on cyclic prefix is ​​not ideal in multipath fast-changing channels,...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26
Inventor 杨帆邵怀宗蔡星星崔琳莉
Owner UNIV OF ELECTRONICS SCI & TECH OF CHINA
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