Today I had an hour long meeting with Prof. A. S. Ranade. It was the first official meeting where we discussed the project. I started off from point 0 – explaining what MIMO is. Then we moved on to ‘Diversity’- i.e. in a nutshell- sending replicas of signal to achiever better performance, which is the main idea behind mimo. Space Diversity being the area of interest in this project, we discussed what physical ways of achieving it are. Following that we discussed the two techniques of Maximum Ratio Combining and Selective Ratio Combining. Then we had a lengthy detailed discussion on the Alamouti encoding-decoding. Then we tried to discuss the qualitative effect on the code under various impairments. In that we talked about what kind of fading and path gain coefficients the channel can have, the ‘worst case ideal scenario’ where the modulation is BPSK(the symbols are negation of each other) and as a result diversity will result in complete cancellation of the two symbols in first time slot (assuming noiseless channel and unit path gains). But because the second time slot also involves sending manipulated same symbols, the original data can still be recovered. Still a complete qualitative explanation of the Alamouti code under various effects needs to be studied and understood. Prof Ranade has recommended books written by Krauss who gives very good qualitative analysis and explanations of the phenomena related to antennas. This will help in knowing exactly what is happening physically as it is difficult to visualize the phenomenon by considering mere mathematical equations.

Another detailed discussion we had was on that the diversity helps in providing better SNR and Noise Performance, which ‘may’ lead to reduction of total power transmitted if we don’t want any improvement of noise performance compared to the case where no diversity is used. On the other side, better noise performance will mean that we can go for more no of symbols per constellation and thus more no of bits per symbol and ultimately higher data rate.

Next immediate goal- to simulate Alamouti decoding and compare the results with that of simple siso transmission without using any diversity.

Next meeting on Friday, 8th March 2009.