Chip Rate, Symbol Rate and Bit Rate
I would like to understand what is Chip rate, Symbol rate and bit rate.
How is it different ?
Answer
In digital communications, each symbol may encode one or more bits. Very simple modulation schemes, e.g. PSK, just encode one bit per symbol, but more sophisticated schemes can encode several bits per symbol, e.g. QPSK encodes 2 bits per symbol. Hence the symbol rate (symbols per second, aka baud) may be less than bit rate (bits per second).
Chip rate is a term which is specific to spread spectrum communication - a symbol is represented by a number of chips, hence the symbol rate is lower than the chip rate.