Sequence Design And Multiple Access Technology In Complex Electromagnetic Environment

The actual electromagnetic environment is increasingly complex with the rapid development of electronic technology,and traditional communication methods can not play a good role to keep communication performance,thus a series of new communication technologies have came into being.Cognitive radio(CR)has became a promising research direction of wireless communication,which can take the initiative to understand the electromagnetic environment around,continue to learning,and greatly improving the reliability of the wireless communication in complex electromagnetic environment.Sequence design and multiple access technology under complex electromagnetic environment are investigated in this thesis.Since the traditional correlation sequences are designed based on the assumption that the entire spectrum bins are available,the correlation of the traditional sequences is destroyed by the spectrum hole constraint and traditional sequence turns into a new sequence,which can not satisfy actual demand.Therefore,the design of sequence which displays low correlation sidelobes property under arbitrary spectrum hole constraint is required.Firstly,some typical sequence design schemes based on different optimization goals are introduced.On the basis,apart from designing sequences with good correlation properties,they also need to satisfy some spectral hole constraints,which called “cognitive sequence”.Then,according to the shortcomings of the cognitive sequence,corresponding improvement scheme is given,and the improved sequence has better correlation degree and spectra limit performance.Afterwards,we choose multiple-input multiple-output(MIMO)system under complex electromagnetic environment as the application scenario,and adopt the cognitive sequence proposed in this thesis as the pilot signal to implement channel estimation.Compared with traditional zero correlation zone(ZCZ)sequence,the estimation results based on cognitive sequence are more accurate.As new types of wireless transmission technology for cognitive radio applications,transform domain communication system(TDCS)and non-continuous orthogonal frequency division multiplexing(NC-OFDM)can satisfy the challenges of complex electromagnetic environment and have unique advantages respectively.In the view of their respective system model and structure characteristic,this thesis provides the corresponding scheme to improve the multiple access capability.For TDCS,because the system communication performance is closely related with the design of the basic modulation waveform,thus the improved structure based on sequence design and spread phase coding is provided.For NC-OFDM,it is combined with high-performance interleave divison multiple access(IDMA)technology to miantain the advantages of two structures and achieve better communication performance.