Multipath time delay estimation by super-resolution PN correlation method

Multipath propagation severely degrades the performance of broadband digital radio communication systems, and various methods have been used to measure the multipath delay profiles. The most general is the PN correlation method, which estimates the impulse response by using a pseudo-noise (PN) sequence having a sharp autocorrelation function. This method, however, cannot resolve paths with a time delay difference shorter than the chip length of the PN code. In order to increase the resolution, a super-resolution PN correlation method (SPM) is proposed. This method applies the MUSIC algorithm and spatial smoothing, to the ordinary PN correlation method. Although its performance is good, the details of its resolution characteristics have not been reported. This paper therefore describes a detailed evaluation of SPM by computer simulation and experiments. It is shown in both computer simulations and experiments that SPM can resolve time delays shorter than the sampling interval of delay profiles, the computer simulation showed that for a sampling interval of 0.2 Tc, SPM can resolve two paths having a time delay difference of 0.04 Tc with an estimated error of only 5%. In the experiments using the delay simulator, the resolution at 5% estimated error degraded to 0.15 Tc.