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Modulation and demodulation of OFDM signals

A signal and modulator technology, applied in the modulation carrier system, digital transmission system, complex mathematical operations, etc., can solve the problems of increased complexity of digital parts, difference between actual performance and theoretical performance, expensive estimation and compensation, etc.

Inactive Publication Date: 2007-01-24
INT BUSINESS MASCH CORP
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  • Abstract
  • Description
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AI Technical Summary

Problems solved by technology

Estimation and compensation of I / Q imbalance is expensive and leads to discrepancies between actual and theoretical performance
[0008] Disadvantages of digital I / Q modulation are higher sampling rates than analog I / Q modulation and increased complexity of the digital part of the mixing stage

Method used

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  • Modulation and demodulation of OFDM signals
  • Modulation and demodulation of OFDM signals
  • Modulation and demodulation of OFDM signals

Examples

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Embodiment Construction

[0035] exist figure 1 In , a typical implementation of an OFDM modulator according to the prior art is described. The OFDM modulator comprises a modulation mapping unit 3 . The incoming data bit stream S is encoded into multiple complex symbols by using phase shift keying (BPSK, QPSK) or quadrature amplitude modulation (16-QAM, 64-QAM), and is mapped to N subcarriers by the modulation mapping unit 3 on the K data subcarriers in . An extra subcarrier can be reserved for pilot (training) tones, while the DC subcarrier is usually not used to avoid converter offset difficulties. The remaining subcarriers are unused and create spectral guard bands to reduce out-of-band interference and relax the requirements on the wireless front-end filter.

[0036] These so-called subcarrier symbols are then fed into the IFFT unit 4 to perform an N-point Inverse Discrete Fourier Transform (IDFT), thereby generating a complex baseband ( BB) OFDM signal. The inverse discrete Fourier transform ...

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Abstract

The invention relates to a method for modulating sub-carrier symbols to an intermediate-frequency OFDM signal having even and odd samples, including following steps: transforming a number N of the sub-carrier symbols to pre-processed sub-carrier symbols; performing a complex inverse discrete Fourier transformation (IDFT) on the pre-processed sub-carrier symbols to generate complex output symbols; and transforming the complex output symbols to the intermediate-frequency OFDM signal, wherein the sub-carrier symbols are transformed so that the even and odd samples of the intermediate-frequency OFDM signal are given by real and imaginary parts of the complex output symbols.

Description

technical field [0001] The present invention relates to methods and devices for modulating and demodulating OFDM signals. Background technique [0002] Orthogonal Frequency Division Multiplexing (OFDM) has become an attractive signaling scheme for high-speed broadband communication systems. In OFDM-based systems, user data streams are divided into parallel streams with reduced rates. Each obtained substream then modulates a separate subcarrier. By properly choosing the frequency spacing between subcarriers, the carriers are made orthogonal and some spectral overlap between subcarriers is allowed, which leads to high spectral efficiency. Recent wireless standards such as IEEE 802.11a / g, ETSI Hiperlan / 2, and ETSI DAB / DVB-T apply OFDM to cope with multipath fading with moderate receiver complexity, while wired standards such as ANSI xDSL operate on individual subcarriers Leverage the potential of OFDM dynamic bit allocation and power control. [0003] A typical implementati...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H04L27/26G06F17/14
CPCH04L27/265H04L27/2634H04L27/26524
Inventor S·富雷尔J·耶利托W·肖特B·魏斯
Owner INT BUSINESS MASCH CORP
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