An OFDM system with a passband bandwidth of 10 MHz and carrier frequency of 1 GHz is used in an outdoor environment with a maximum delay spread of 15 microseconds
a- What is the cyclic prefix length?
b- What is the efficiency if 1024 subcarriers are used
c- If number of subcarriers are fixed, show how the efficiency changed as function of bandwidth
d- For the OFDM subcarriers to be orthogonal, the channel must be fixed for the duration of the OFDM symbol. What is the maximum number of OFDM subcarriers such that the OFDM symbol will not lose its orthogonality assuming that the maximum speed is 30 meters/sec