TV band cognitive system interference cancellation based on spread spectrum LDPC codes

In the cable television covered area, the CUs (cognitive users) will face the problem of TV signals interference in TV band; it means the CU cannot effectively utilize the spectrum hole of TV band. In order to solve this problem, this paper proposes an interference cancellation method for cognitive system based on spread spectrum LDPC codes. In the cable television covered area, a small-scale cognitive system has eliminated the need for receiving TV signals; the CUs can use the TV band to communicate by using the proposed scheme. Protograph LDPC codes and spread spectrum are applied to cognitive system in the proposed scheme, the information transmission can be of the anti-interference ability and error correcting capability through channel coding and spread spectrum mapping, which can cancel TV signals interference and channel noise interference. The simulation results in Rayleigh flat-fading channel show that, comparing with cognitive system without the proposed method, the proposed approach can effectively cancel TV signals interference and channel noises interference, and obtain about 11dB coding gain.