Method for recognizing subcarrier modulation modes of orthogonal frequency division multiplexing signal in wireless communication

Abstract

The invention relates to a method for recognizing subcarrier modulation modes of an orthogonal frequency division multiplexing signal in wireless communication, belonging to the field of wireless communication signal processing. The method comprises the following steps of: firstly; preprocessing a received radio-frequency signal by a receiving end of a wireless communication system; extracting N symbols from the received orthogonal frequency division multiplexing signal; respectively carrying out complementation, blind channel estimation and balance on the N symbols to acquire a modulation signal on a data subcarrier so that the modulation signal is matched with the planispheres of all the subcarrier modulation modes of the orthogonal frequency division multiplexing signal; and selecting the modulation mode with the maximum matching degree as a recognition result. An OFDM (Frequency Division Multiplexing) robust blind channel estimation algorithm when a virtual subcarrier exists is adopted in the method of the invention, which is suitable for a time-varying multi-path environment for balancing a non-ideal channel and has the advantages of simple flows, little amount of calculation, short observation time and time-varying channel environment suitability.

Description

technical field [0001] The invention relates to a method for identifying subcarrier modulation modes of orthogonal frequency division multiplexing signals in wireless communication, and belongs to the field of wireless communication signal processing. Background technique [0002] Orthogonal frequency division multiplexing (hereinafter referred to as OFDM) technology is widely used in many official commercial communication protocols due to its high spectrum utilization, resistance to frequency selective fading channels and low complexity equalization, such as the European digital Broadcasting, IEEE 802.11 and IEEE 802.16 standards, etc., are also one of the indispensable technologies for the fourth generation mobile communication system. [0003] Signal modulation recognition technology has a wide range of applications in the fields of military reconnaissance, electronic countermeasures and information security. In the field of cognitive radio, which has attracted widesprea...

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Problems solved by technology

However, when the OFDM signal contains virtual subcarriers, spatial smoothing cannot solve the lack of rank problem of the frequency domain signal matrix, so the performance drops sharply

[0006] Communications Conference Proceedigs, 1999, 1: 432-436." The modulation recognition algorithm based on high-order cumulants cannot work in a time-varying environment because of its long observation time

Non-ideal channel equalization leads to phase and amplitude jitter of the subcarrier modulation signal, and the constellation diagram of the modulation signal is very deformed at low SNR

Therefore, in the document "K.Woo, C.Kok, Clustering based distribution fitting algorithm for automatic modulation recognition [C]. IEEE ISCC, 2007: 13-18." and the document "S.Barbarossa, A .Swami, B.Sadler.Classificaiton of digital constellations under unknown multipath propagationcondition[C].Proc.SPIE, 2000, 4045(175):175-186."The symbol matching algorithm (Alphabet MatchedAlgorithm) based on the constellation diagram cannot work normally Work

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