Hierarchic Method for CDMA Synchronization

A hierarchic algorithm for delay estimation, called ACM-MUSIC, which has earlier been developed in context with sinusoidal frequency estimation is introduced, andSimulations show that the new methods outperform standard MUSIC.

Abstract

CDMA (Code Division Multiple Access) is a multiple access technique based on spread spectrum methods. To estimate the delay parameters appearing in the data model, several authors have proposed subspacebased solutions. Unfortunately, these methods, for example the eigenvector-based MUSIC method yields poor results at low signal-to-noise ratios. On the other hand, theoretically optimal maximum likelihood method is computationally too demanding in practice. In addition, when the number of users or propagation paths is unknown, the model order should be estimated accurately. To this end, one can use relatively simple Minimum Description Length (MDL) criterion, but it fails when the signal-to-noise ratio (SNR) is not sufficiently high. In this paper, we introduce a hierarchic algorithm for delay estimation, called ACM-MUSIC, which has earlier been developed in context with sinusoidal frequency estimation. We also use ACM-MUSIC type algorithm for estimating the model order using a new criterion. Simulations show that the new methods outperform standard MUSIC.