Optimization of spreading code and estimation of channel capacity in multi-code CDMA downlink

Abstract

Transmission of multimedia data was one of the primary goals of the 3G cellular radio system. This necessitated very high-speed data links and the accommodation of the maximum possible number of users where the multipath delay spread encompassed many symbol intervals. Thus we saw that there was an urgent requirement to find more effective methods to combat the problems and channel impairments of the cellular radio system. Limiting Walsh sequence usage to class I data links eliminates the limitation of orthogonal code and class II links using PN sequences. Finally, self recovering (blind) channel estimation is adopted as no training sequence is required for initial adjustment of the equalizer coefficients, thus saving bandwidth. In this approach, sub-banding techniques are proposed for blind equalization. The sub-banding is carried out and the correlation between the method adopted and the accrued improvement in channel estimates is utilized.