Method for sensing OFDM spectrum under conditions of time asynchronization and known cyclic prefix length

Abstract

The invention discloses a method for sensing an OFDM (Orthogonal Frequency Division Multiplexing) spectrum under conditions of time asynchronization and known cyclic prefix length. The processing procedure of the method comprises the following steps: at first, sampling a receipt signal from a monitoring channel to obtain a sampled signal; then, computing an autocorrelation function of the sampled signal according to the sampled value in the sampled signal; next, computing test statistic according to an autocorrelation coefficient in the autocorrelation function of the sampled signal under the condition of time asynchronization; and at last, judging whether the monitoring channel is in the idle state or not according to the test statistic and the judgment threshold. The method has the advantages that the spectrum sensing can be carried out by directly using the sampled signal, without the need of time synchronization, so that the computation complexity is reduced effectively. During the process of computing the test statistic, due to the use of the nonnegative characteristic of the autocorrelation coefficient corresponding to the cyclic premix part of the OFDM signal in the autocorrelation function of the sampled signal, the spectrum sensing performance of the OFDM signal is improved effectively.

Description

Technical field [0001] The present invention relates to a spectrum sensing technology in a cognitive radio system, in particular to an OFDM spectrum sensing method under the condition that time is asynchronous and the cyclic prefix length is known. Background technique [0002] With the rapid development of various wireless communication services, the importance and scarcity of spectrum resources have become increasingly prominent. A large number of studies have shown that the current shortage of spectrum is not due to the physical shortage of frequency resources, but mainly due to the low spectrum utilization rate caused by the fixed spectrum allocation management mechanism. Cognitive radio is just trying to solve the problem of increasingly scarce wireless communication resources by improving spectrum utilization. It can perceive the surrounding communication environment in real time, identify available idle channels, and then adaptively adjust the system parameters of the cog...

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Problems solved by technology

In "Autocorrelation-Based Decentralized Sequential Detection of OFDM Signals in Cognitive Radios" in 2009, Chaudhari et al. proposed the use of the autocorrelation feature of the cyclic prefix, Spectrum sensing is realized by calculating the autocorrelation function of the received signal, but this method does not take into account the non-stationary characteristics of the autocorrelation function

In response to this problem, Axell et al. in 2011 in "Optimal and Sub-Optimal Spectrum Sensing of OFDM Signals in Known and Unknown Noise Variance (OFDM Optimal and Suboptimal Spectrum Sensing Method when Known and Unknown Noise Variance)" A new spectrum sensing method based on the autocorrelation function of the received signal is proposed. Compared with the method proposed by Chaudhari et al., this method has better detection performance, but this method requires time synchronization

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