Hybrid Carrier Communication System Resistance Against Multi-path Fading And Narrowband Interference

Weighted fractional Fourier transform (WFRFT) is a generalized form of theFourier transform, which has many excellent mathematical properties. With theimprovement of the theory, more and more scholars apply WFRFT into the field ofsignal processing, especially the hybrid carrier technology based on WFRFT. It canprovide the mode of signal both in time domain and frequency domain, andintegrate traditional single/multi carrier technology into a unified systemframework, establishing a real hybrid carrier modulation technology. This papermainly researches the hybrid carrier system based on WFRFT, analyzing theperformance of system under the multi-path fading channel and narrowbandinterference. Besides, the traditional carrier modulation technologies have beencompared with it.Firstly, we introduced the definition and mathematical properties of WFRFT,focusing on the analysis of the relationship between WFRFT domain andtime/frequency domain. Then, the basic structure and working principle of thehybrid carrier modulation system were introduced, to prepare for the theoreticalstudy of the below.As a broadband wireless modulation technique, hybrid carrier system musttake into account the channel multipath fading problem. Firstly, the mathematicalmodel of the system performance is established. Then use the theory of concave toanalyze the mathematical priority of this model. Combined with distribution rule ofreal-time signal to noise ratio in each sub-channel, the development trend of thesystem performance can be derived. At this point, we can compare the performanceof single/multi carrier modulation technique system and hybrid carrier technologysystem both from theory prove and system simulation.On the other hand, the narrowband interference suppression also should beconsidered in the hybrid carrier technology system. Compared with the traditionalsystem, the hybrid carrier system can change the energy distribution of interferencesignal by adjusting the transform order, so that decrease the bit error ratio to theleast. Firstly, the principle of interference suppression in hybrid carrier system is introduced, and then the criteria of optimal fractional domain transform areanalyzed. At last, the optimal order analytic expression is derived.