Recognition method for cognizing radio signal modulation modes under low-signal-to-noise-ratio condition

Abstract

The invention discloses a recognition method for cognizing radio signal modulation modes under the low-signal-to-noise-ratio condition. Processing signal-to-noise ratios of received signals are improved by adoption of segmental frequency domain filtering, and according to M power sine wave generation characteristics of four modulation signals including FSK, BPSK, MSK and QPSK, the modulation modes are identified and converted to detection of the number of sine waves. Simulation experiment proves that the method has a good recognition effect, and under the condition that the signal-to-noise ratio is not smaller than minus 1dB, recognition rate of the four signals can be up to over 90%.

Description

technical field [0001] The invention relates to the field of communication technology, in particular to a method for identifying modulation modes of cognitive radio signals under low signal-to-noise ratio conditions. Background technique [0002] Due to the increasing usage of wireless mobile services, radio spectrum resources are facing an increasingly insufficient situation. The use of cognitive radio (CR, Cognitive Radio) technology can improve the utilization of radio spectrum, which provides an effective way to solve this problem. The core idea of ​​CR is that the system detects the use status of the surrounding spectrum. When the authorized user does not use the allocated spectrum, the unlicensed user adjusts its transmission parameters in real time and opportunistically accesses the frequency band. Once the authorized user re-accesses , unauthorized users quickly vacate the channel. In order to fully understand the use status of spectrum resources, identifying the si...

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Problems solved by technology

Literature [7] Reichert, J. (1992). Automatic classification of communication signals using higher order statistics, IEEE proposed for the first time the carrier frequency, Under the condition of prior information such as the symbol rate, the modulation mode is distinguished by using the M-th power line spectrum generation characteristics of the signal, and a statistical detection method for distinguishing the line spectrum and the continuous spectrum is proposed. However, due to the high-order nonlinearity of the signal After calculation, the signal-to-noise ratio decreases. This method requires the signal-to-noise ratio to meet a certain threshold value to achieve a satisfactory recognition rate. For example, for QPSK signals, when the recognition rate reaches 99.8%, the required receiving signal-to-noise ratio is not less than 7.3dB

In addition, the algorithm proposed in this method to judge whether there is a line spectrum in the signal spectrum is vague in description, and the calculation is complicated

Literature [8] Fan Haibo, Yang Zhijun, Cao Zhigang. Automatic identification of common modulation modes in satellite communication [J]. Journal of Communications, 2004, 25(1): 140-149 for the modulation modes commonly used in satellite communication, such as ASK, FSK, MSK, BPSK, QPSK, etc., extract a set of characteristic parameters that are robust to signal-to-noise ratio and modulation parameters, such as the single-frequency component detection value, flatness index, and number of spectral peaks of the signal power spectrum, square spectrum, and quartic spectrum , to identify the modulation pattern of the signal under the condition that the prior information of the signal is not required, and the overall recognition rate is over 98% when the signal-to-noise ratio is greater than 5dB, but this method also has higher requirements on the signal-to-noise ratio

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