A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 2001

Finally, I very much thank the scholarship donor, the Government of Finland, for Transmitter diversity is an effective technique to reduce the degradation of the signal to noise ratio caused by the fading and the Doppler spread in mobile radio channel. Recently, Multi-Carrier Code Division Multiple Access (MC-CDMA) is proposed as a multi-accessed multi-carrier modulation scheme in which the channel in each sub-carrier can be considered as a flat fading channel. In the thesis, transmitter diversity using a suitable Space-Time code modulation scheme has been studied. MC-CDMA incorporated with Space-Time Codes (STC), designed for high capacity multi-antenna systems, can be used in the frequency selective fading environment. This research applied and discussed a new technique to estimate the channel parameters of a MC-CDMA system for downlink transmission using training symbols inserted at the transmitter. The derived estimator is optimized in the sense of minimizing the mean square error (MSE) based on the received signal and the training signal of all sub-carriers. For the two transmit antenna - two receive antenna MC-CDMA system considered with transmission efficiency 0.1848 bits/s/Hz, the Bit Error Rate (BER) degradation of real channel estimation is 2 - 3dB compared to perfect channel estimation. As seen from the results, the system using a channel interleaver is not sensitive to a number of the accessed users as well as the velocity of Mobile Station (MS). The application of Trellis Coded Modulation (TCM) is also considered. It is shown that the MC-CDMA system of both the real channel estimation and perfect estimation for TCM has a larger degradation than for Space Time Coded Modulation (STCM).