Adaptive algorithm for the multishot matched filtering multiuser detector in a multipath Rayleigh fading environment

Abstract

CDMA proves to be an attractive method for multiuser communication due to its potential capacity increase and anti-multipath fading capability. However, its performance is limited by the existence of multiple access interference energy (MAI), which results in the so called near-far problem. To reduce the MAI effect, different decorrelating structures for multiuser detection have been proposed. For the asynchronous case, the "one-shot decorrelator" was proposed, based on inversion of the partial correlation matrix, which may however be singular. As an alternative, the so called "multishot decorrelator", which does not suffer from the aforementioned singularities, was also suggested. However, both detectors, based on inversion of some matrix, are not robust to errors in users' relative delays. The application of the adaptive "Bootstrap algorithm" with the one-shot structure proved to easily handle variation in delay estimates and outperform the decorrelating detector. We propose and compare a Bootstrap algorithm suitable for the multishot matched filtering, multiuser detector in a multipath environment, examine its performance, and compare it to that of other detectors. We also propose the extension of the multishot structure to a multistage receiver, by adding an appropriate canceler.