Method of designing OFDM-TDCS waveform with low PAPR

Abstract

The invention belongs to the communication technology field, and especially relates to a method of designing an OFDM-TDCS waveform with low PAPR (Peak-to-Average Power Ratio) in the field of cognitive radio technology. According to the method, the reasonable design of a pilot frequency pattern prevents all pilot frequencies from being not available due to pilot frequency shifts; through optimization of a pilot frequency sequence, a PAPR value of a signal is reduced, and distortion of the pilot frequency sequence caused by PAPR control is minimized; and the PAPR and outband attenuation of the signal can both meet the requirements of a cognitive radio system by combining noise shaping amplitude limit with outband radiation control.

Description

technical field [0001] The invention belongs to the technical field of communication, and in particular relates to a low peak-to-average power ratio (Peak-to-AveragePowerRatio, PAPR) OFDM-TDCS waveform design method in cognitive radio technology. Background technique [0002] Cognitive Radio (CR) technology was first proposed by Dr. JosephMitolaIII in 1999. Its core idea is to obtain the spectrum available at the current time through spectrum sensing, and use these spectrums for data transmission, thus greatly improving overall Spectrum utilization. [0003] The transform domain communication system (TransformDomain Communication System, TDCS) uses the idea of ​​cognitive radio to dynamically change the spectrum waveform of the transmitted signal within a given spectrum range to avoid interference with authorized users. Document 1 "Addressing the control channel design problem: OFDM-based transform domain communication system informive radio (by Chuan Han, Jun Wang, Yaling ...

AI Technical Summary

Problems solved by technology

First of all, in the OFDM system, the basic idea of ​​the pilot-based channel estimation method is that the transmitter inserts the pilot at an appropriate position, and the receiver recovers the pilot position and pilot sequence through the same pilot generation method; while in OFDM- In the TDCS system, due to the inconsistency of the electromagnetic environment between the transmitter and the receiver, the available spectrum of the transmitter and the receiver is inconsistent. At this time, the pilot position and pilot sequence generated by the transmitter are unknown to the receiver. , if the channel estimation is performed directly, the channel estimation may be completely wrong due to pilot misalignment. The existing OFDM-TDCS channel estimation methods reduce the influence of pilot misalignment by setting equivalent comb pilots. However The time-domain PAPR of the comb pilot is too high, resulting in pilot distortion after PAPR processing, which affects the performance of channel estimation

At the same time, like the OFDM system, the OFDM-TDCS system also faces the problem of high PAPR. Document 2 "Clipping noise cancellation in OFDM systems using oversampled signal reconstruction (by Hamid Saeedi, Masoud Sharif, and Farokh Marvasti. IEEE Communications Letters. 2002, 6(2): 73-75.)" proposed in the OFDM system Using the NoiseSharping-CrestFactorReduction (NS-CFR) method to perform PAPR control on time-domain signals can reduce the number of iterations, but when it is applied to cognitive radio technology, the out-of-band attenuation of the spectrum may cause adjacent Channel interference (AdjacentChannelRejection, ACI)

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