Method for sensing OFDM signal frequency spectrum under condition of time synchronization

Abstract

The invention discloses a method for sensing an OFDM (Orthogonal Frequency Division Multiplexing) signal frequency spectrum under condition of time synchronization. The method comprises the following processing procedures: sampling a received signal from a supervisory channel to obtain a sampled signal; calculating autocorrelation function of the sampled signal according to a sampled value in the sampled signal; selecting the first to the Ncth autocorrelation coefficients from the autocorrelation function under the condition of time synchronization, and calculating test statistics through utilizing the selected Nc autocorrelation coefficients, wherein Nc denotes the length of cyclic prefix of the OFDM signal; and judging whether the supervisory channel is at idle condition according to the sizes of the test statistics and of a judgment threshold. The method has the advantages that under the condition of time synchronization, the test statistics can be calculated with a plurality of autocorrelation coefficients of which the number is the same as the length of the cyclic prefix, so that the calculation complexity is greatly reduced; and during calculation of the test statistics, the non-negative property of the autocorrelation coefficients corresponding to the cyclic prefix is utilized, so that the sensing ability of the OFDM signal frequency spectrum is effectively increased.

Description

technical field [0001] The invention relates to a spectrum sensing technology in a cognitive radio system, in particular to an OFDM signal spectrum sensing method under the condition of time synchronization. Background technique [0002] Broadband wireless communication services require the support of a large number of spectrum resources. The existing static spectrum allocation method results in a very low utilization rate of spectrum resources, which leads to the phenomenon of lack of spectrum resources. The proposal of cognitive radio provides a feasible idea for improving spectrum utilization. In order to avoid interference to the existing wireless communication system, the cognitive radio system must be able to determine whether the channel is idle or not. Spectrum sensing can be used to determine whether the channel is idle, so spectrum sensing is one of the key technologies in cognitive radio. [0003] Orthogonal frequency division multiplexing (OFDM) technology has...

AI Technical Summary

Problems solved by technology

In the case of time synchronization, compared with the method proposed by Chaudhari et al., the method proposed by Axell et al. has better detection performance, but the method proposed by Axell et al. does not take advantage of the non-negative properties of the cyclic prefix autocorrelation function. Detection performance is still not very good

Images