Sidelobe Characteristics Of Spread Spectrum Multiple Access Communication System Description

The direct spread spectrum system is widely applied into multiple access communication, satellite-based navigation-position systems and radar systems. The correlation side-lobes have effect on detection performance of signal and make side-lobe loss as a result.This article is based on the two-star-position systems, the key project of nation defense. The character of correlation side-lobes is mainly discussed and the difference effect on system between the auto-correlation and cross-correlation is given.In the first part, the properties of correlation side-lobes are discussed. The equivalent side-lobes are given so as to simplify the calculation and analysis in the end of this part.In the second part, the side-lobes effect on detection performance is analyzed under the condition of coherent and un-coherent receiver. The analysis is based on m sequence, small Kasami sequence and truncation code and compared with the definite time delay. The side-lobes loss given is helpful to the analysis of channel capacity. In the end, this article considered the side-lobes with Doppler frequency as definite side-lobes and has studied the effect on detection performance and the side-lobes loss.In the third part, the status of the multiple access interference (MAI) and the relationship between the cross-correlation and MAI are introduced. In order to meet the need of the practical project, without the perfect power control, this article set up the model for multiple access communication under the condition of coherent and un-coherent receiver and considered the MAI which is determined by range, cross-correlation and phase as the correlation side-lobes.The result of this article is to be used to the PN code choice in the project of long pseudo-noise code capture in the satellite-based navigation-position systems.