| In this work we study the downlink transmission of Code Division Multiple Access (CDMA) systems using the Alamouti code in order to provide space time diversity.; We will propose a novel spreading signature assignment technique for space-time coded single rate CDMA system, which, compared to other signature assignment methods, allows to reduce the number of spreading signatures necessary in order to solve the channel ambiguity problem while performing blind channel estimation. This encoding method is called "rolling signatures".; We also introduce a new method for combining the Alamouti space-time code with multi-rate CDMA. Instead of block coding entire CDMA symbols we will apply Alamouti coding at the chip-level. Such a coding method is called "chip-level" block coding. We present for our chip-level coding technique, various linear decoding structures both joint and disjoint. In the case of joint decoding, space-time and CDMA filtering at the mobile's end is done simultaneously by a single linear receiver. In the case of disjoint decoding, there are two dedicated receive filters, one performing space-time decoding and the other CDMA filtering. We also introduce a blind channel estimation technique and provide a thorough performance analysis of our estimator, in the form of mean-square-error performance analysis. Finally, we provide the Cramer-Rao Bound for our channel estimator. |
