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Method and apparatus for estimating modulation accuracy of OFDM_TDD system

A modulation accuracy and adjusted technology, applied in the direction of multi-frequency code system, multi-carrier system, baseband system components, etc., can solve the influence of nonlinear products, the distortion of the amplitude-frequency characteristics of the channel filter, and the EVM of the OFDM_TDD system is not given test methods etc.

Active Publication Date: 2009-08-05
DATANG MOBILE COMM EQUIP CO LTD
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Problems solved by technology

[0004] 1. The amplitude of the input I and Q signals is unbalanced;
[0005] 2. Quadrature modulator phase shift error, that is, I and Q phase imbalance;
[0006] 3. Carrier leakage;
[0007] 4. The amplitude-frequency characteristics of the channel filter are distorted;
[0008] 5. Distortion of the phase-frequency characteristics of the channel filter;
[0009] 6. The influence of the phase noise of the local oscillator;
[0010] 7. Influence of nonlinear products
[0023] The prior art does not provide a test method for the EVM of the OFDM_TDD system, and there is no ready-made device that can be used to measure the EVM of the OFDM_TDD system

Method used

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  • Method and apparatus for estimating modulation accuracy of OFDM_TDD system

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Embodiment Construction

[0044] The embodiment of the present invention proposes a method and device for measuring EVM aiming at an OFDM-TDD system. This method only uses the collected IQ data to complete EVM analysis, and does not need to perform channel decoding. The basic flow is as follows figure 1 shown, including the following steps:

[0045] Step 101: filter and extract the collected I-channel and Q-channel signals;

[0046] Step 102: Perform various corrections on the signal, including time offset correction, frequency offset correction, frequency amplitude correction, phase offset correction, etc., to reduce the influence of the channel on the signal;

[0047] Step 103: extracting a measurement signal and a reference signal from the signal;

[0048] Step 104: subtracting the measurement signal from the reference signal to obtain an error signal, and then calculating the EVM according to the error signal and the reference signal.

[0049] In order to make the purpose, technical solutions an...

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Abstract

The invention discloses a method for estimating the precision modulation of an orthogonal frequency division multiplexing (OFDM_TDD) system of time division multiplexing. The method comprises the following steps: received I and Q path signals are filtered and extracted, and the time shift and frequency shift of the extracted signals are adjusted; the the adjusted signals are demodulated to generate measurement signals; hard decision is carried out to the measurement signals, and the measurement signals after hard decision is adjusted to generate reference signals; error signals are obtained by decreasing the reference signals from the measurement signals and an error vector magnitude (EVM) is obtained through calculation according to the error signals and the reference signals. The invention also discloses a device for estimating the modulation precision of the OFDM_TDD system of time division multiplexing. The application of the method is capable of obtaining the EVM without the processing of channel decoding by generating the reference signals and the measurement signals after the signals are adjusted. The method is a proposal for the estimation of the modulation precision applicable to the OFDM_TDD systems.

Description

technical field [0001] The invention relates to the technical field of mobile communication, in particular to a method and a device for estimating the modulation precision of an Orthogonal Frequency Division Multiplexing (OFDM_TDD) system of time division multiplexing. Background technique [0002] Error vector value (EVM), also known as correlation constellation error, is an important indicator for measuring modulation quality in digital communication systems. The third generation mobile communication system, including Wideband Code Division Multiple Access (WCDMA), CDMA2000, Time Division-Synchronous-Code Division Multiple Access (TD-SCDMA), etc. , and the Worldwide Interoperability Microwave Access (WIMAX) protocol stipulate that the modulation accuracy is measured by EVM. [0003] The EVM indicators that affect the output signal mainly include the following factors: [0004] 1. The amplitude of the input I and Q signals is unbalanced; [0005] 2. Quadrature modulator ...

Claims

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Application Information

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IPC IPC(8): H04L25/03H04L25/06H04L27/26H04L27/38
Inventor 熊军王策柴旭荣张亮倪慧娟王胜勇顾伟陈茂云张俪武占宇
Owner DATANG MOBILE COMM EQUIP CO LTD
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