Research On Adapting Technologies Of Fading Channel In Long-distance Wireless TDCS

As a kind of new wireless communication technologies, Transform Domain Communication System (TDCS) has capabilities of interference avoidance and utilization of discontinuous spectrum. On the base of accessing presence information of Channel interference, TDCS transmitter and receiver generate time-domain waveforms without frequency components of interference to carry information. In virtue of presence frequency bands of communication signals and interference being different, It can realize an effective interference avoidance, It is a interference suppression means based on an active avoidance model,so TDCS has a more strong capacity to adapt the interference which has a strong power on the channel. At the same time, TDCS can make use of discrete frequency bands. Therefore, TDCS is a effective techniques means which can achieve the efficient military communications of a complex electromagnetic environment and the the cognitive radio communication of using the spacing of spectrum resources.However,when there is a long-range wireless communication, the channel fading characteristics and the different features of sender and receiver electromagnetic spectrum will reduce the Technical performance of TDCS severely.Due to the problem that TDCS based on a flat rate of forming performance is more sensitive to the characteristics of fading channel and amplitude and phase fading have a large effect to the performance of TDCS system, this paper make use of that the fractional Fourier transform (FrFT) can effectively detect the characteristics of linear frequency modulation (LFM) signal to verificating TDCS of coding rate of forming based on the LFM-FrFT active detecting. By launching LFM trained signals, The system adopts FrFT to detect LFM signal, so as to obtain the information of signal fading characteristics, and uses the means of pre-equalizer to reduce the effects of channel fading characteristics to TDCS system performance.Due to the problem that the different electromagnetic environment of sender and receiver reducing the system performance of TDCS when it is doing long-distance communications,it proposes and demonstrates an improved TDCS system based on information interaction. Through establishing exchange signaling channel, sender and receiver estimate and transmiss the information of channels at the same time, so as to generate basis function at the sender and receiver. and it improves the effect of the electromagnetic environment differences on the system performance in a certain degree.