PN Acquisition Schemes Using RAKE Structure for DS/SS Systems over a Frequency-Selective Rayleigh Fading Channel 139 PN Acquisition Schemes Using RAKE Structure for DS/SS Systems over a Frequency-Selective Rayleigh Fading Channel

This paper proposes noncoherent PN acquisition schemes that combine the hybrid structure, the RAKE structure, and the double/multiple-dwell technique in order to improve the performance in a frequency-selective fading channel. The hybrid structure reduces the acquisition time compared to a serial scheme. The RAKE structure enhances the received signal strength of a multipath faded signal, while the multiple-dwell technique reduces the acquisition time. The parallel paths of the hybrid structure are used as the RAKE fingers as well, avoiding the need of additional hardware for the RAKE fingers. To further improve the performance, noise-only detection is used in each RAKE finger to nullity the fingers containing only noise in signal combining of the RAKE structure. These helps improve the signal-to-noise ratio at the RAKE output. The performance is evaluated by analysis and simulation. Results show that the proposed schemes significantly outperform other noncoherent PN acquisition schemes with the similar hardware.