I thought that in order to be a great writer, he should be born with a great talent in that area. Now, I realze that there is another way to be a great writer. Almost anybody can be like that if he practice a lot in one area. Practice make people different. One can be a great writer. One cen be a great artist. One can be a great scientist.

I also realize that good mathematician can be created by his long time effort with pleasure. If he like an area and practice a lot he will have a great potential to be a fomus person in that area almost regardless of his inhererent talent.

## Basics of Communication Theory

The capacity of a communication system can be wirtten as

- $ C = \log_2 \left(1+ \text{SNR} \right) $

where SNR is the signal to noise ratio. The signal-to-noise-ratio is defined as

- $ \text{SNR} = \frac{P_s}{N_0} $

where $ P_s $ is the signal power and $ N_0 $ is the noise spectral density.