Spread spectrum LDPC for cognitive systems working in TV frequency band

In the cable television covered area, the cognitive users (CUs) will face the problem of TV signals interference from TV station, so that CUs cannot effectively utilize the spectrum hole of TV band. To solve this problem, the spread spectrum LDPC (SSLDPC) code for cognitive system has been proposed by us to cancel the TV interference recently. These papers extended and deepen the results of SS-LDPC, developed the algorithms of soften-coding and soft-decoding, removed classical spreading and despreading circuits, simplified the transmitters and receivers of CUs. The cognitive system with SS-LDPC need not withdraw the TV signals, and the CUs can use the TV band to communicate with base-station (BS). The construction, encoding and decoding approaches of SS-LDPC are provided. The information transmission of cognitive system with SS-LDPC can be of the anti-interference ability and error correcting capability. The simulation results in Rayleigh flat-fading channel show that, comparing with cognitive system without SS-LDPC, the proposed approach can effectively cancel TV signals interference.