Transmission method of orthogonal frequency division multiplexing of multiple cognitive users based on active interference elimination

Abstract

The invention discloses a transmission method of orthogonal frequency division multiplexing of multiple cognitive users based on active interference elimination. In the transmission method, the critical fact is that a cognitive user inserts some subcarriers used for modulating special weights into a protective frequency section, i.e. two sides of the a main user, wherein the subcarriers are namedas interference cancellation subcarriers and the weights thereof are determined by data sent by the cognitive user; thus the sent data and sidelobes of the interference cancellation subcarriers are enabled to be mutually cancelled, and interferences generated in the protective sections are reduced. The more the inserted interference cancellation subcarriers are, the more obvious the interference inhibition is and the more the paid energy cost is. The cognitive user sequentially increases the quantity of the used interference cancellation subcarriers progressively according to the intensity ofdetected main user signals, so as to protect the main user with the minimum energy cost. The interference cancellation subcarriers are removed at a cognitive user receiving terminal, and different cognitive users insert respective interference cancellation subcarriers into two sides position closely next to the protective section in an overlapping mode, therefore, introduced mutual interferences have no effect on system performance, and the frequency spectrum efficiency of the system is improved.

Description

technical field [0001] The invention relates to the technical field of wireless digital communication, in particular to a cognitive multi-user OFDM transmission method based on active interference cancellation. Background technique [0002] With the increasing number of wireless applications, the available spectrum resources are getting less and less, and the problem of poor spectrum resources is becoming more and more serious. However, research has found that licensed frequency bands are not always occupied by licensed users (primary users), but there are many gaps in the time / frequency dimension, that is, spectrum holes, and the spectrum utilization rate is very low. If unlicensed users (cognitive users) can opportunistically occupy these spectrum holes, the spectrum efficiency can be greatly improved. Cognitive radio technology, with its flexible spectrum usage, has become a potential solution to the contradiction between wireless spectrum supply and demand. This technol...

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Problems solved by technology

[0004] However, since the spectrum of each subcarrier of OFDM presents a Sinc function characteristic, the sidelobe oscillation attenuates slowly, resulting in a huge out-of-band radiation power of the entire power spectrum of the OFDM symbol. Simply turning off / on the subcarrier cannot achieve effective out-of-band Power radiation suppression, so designing an effective method to suppress OFDM signal out-of-band radiation is particularly important for the reliable implementation of cognitive radio systems

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