In the present paper performance analysis and a comparative study is reported for channels using receive diversity ( 1X2 ) , transmit diversity ( 2X1 ) and transmit-receive diversity( 2X 2) with maximum Likelihood detection technique. The channel is assumed to be flat Rayleigh fading channel and noise samples are independent with zero mean complex Gaussian random variable. The Alamouti Space Time Block codes with modulation techniques BPSK, QPSK 8-PSK and 16-QAM are used to obtain the bit error rate performance under different SNR scenarios. The results reported in this paper suggest substantial improvement in the system performance by incorporating multiple input multiple output techniques in order to improve the link quality.

1. Carmela Cozzo, and Brian L. Hughes, “ Space Diversity in Presence of Discrete Multipath Fading Channel” IEEE Transactions On Communications, Vol. 51, No. 10, October 2003
2. Hamid Jafarkhani ” Space-Time Coding Theory And Practice “, university Of California, Irvine
3. G. J. Foschini and M. J. Gans, “On limits of wireless communication in a fading environment when using multiple antennas,” Wireless Pers. Communication., vol. 6, no. 3, pp. 311–355, Mar. 1998.
4. S. M. Alamouti, “A simple transmitter diversity scheme for wireless communications,” IEEE J. Select. Areas Commun., vol. 16, pp. 1451–1458, Oct. 1998.
5. A. J. Paulraj, D. A. Gore, R. U. Nabar, and H. Bölcskei, “An overview of MIMO communications-A key to gigabit wireless,” Proc. IEEE, vol. 92,no. 2, pp. 198–218, Feb. 2004
6. V. Tarokh, N. Seshadri, A. R. Calderbank, “Space-Time Codes for High Data Rate Wireless Communication: Performance Criterion and Code Construction”, IEEE Transactions on Information Theory, vol. 44, no. 2, pp. 744-765, March 1998.
7. Troels Emil Kolding, Klaus Ingemann Pedersen, Jeroen Wigard, Frank Frederiksen, Preben Elgaard. Mogensen, “High Speed Downlink Packet Access (Hsdpa): W-Cdma Evolution”, IEEE Vehicular Technology Society News, February, 2003.
8. Vibhav Kumar Sachan, Ankur Gupta , Dr. Avinash Kumar ,”Performance analysis of MIMO space diversity technique for wireless communications “ Krishna Institute of Engineering & Technology, Ghaziabad, INDIA 978-1-4244-3328-5/08/$25.00 ©2008 IEEE.
9. A. F. Naguib, V. Tarokh, N. Seshadri, and A. R. Calderbank, “A space time coding modem for high data rate wireless communications,” IEEEJ. Select. Areas Commun., vol. 16, no. 8, pp. 1451–1458, Oct.1998.
10. A. Maaref and S. Aïssa, “Shannon capacity of STBC in Rayleigh fading channels,” IEEE Electron. Lett., vol. 40, no. 13, pp. 817–819, June 2004.
11. A. J. Paulraj and B. C. Ng, “Space–time modems for wireless personal communications,” IEEE Pers. Commun. Mag., pp. 36–48, Feb. 1998
12. Agilent Application Note 5989-8973EN,” Agilent MIMO Channel Modeling and Emulation Test Challenges” , June 6, 2006.

Channel state information (CSI) Phase Shift Keying (PSK) Bit Error Rate (BER) Signal-to-Noise Ratio (SNR) Space Time Block codes (STBC) Quadrature Amplitude Modulation (QAM)