What is the minimum guard time interval for preventing

Question

Problem 1:

In a certain wireless channel, the delay spread T_D=10µsec and the maximum Doppler spread f_d=0.2 kHz. The maximum propagation attenuation is 40dB.

The total power available at the transmitter is 1.08Watt. (Hint: i.e., the minimum received signal power is 0.108 mWatt.) The total bandwidth is 2 MHz For the OFDM receiver, the received noise power density is 0.1µWatts/MHz. The total intercarrier interference power (for all subcarriers combined) is (f_dT)² mWatts where T is the OFDM symbol duration.

a.) What is the minimum guard time interval for preventing intersymbol interference?

b.) What is the maximum data rate (BPSK signaling) where minimum SINR is 40 (in linear scale)?

Problem 2:

Let the original symbol duration T be 0.1msec and the number of subcarrier is 16 (k=0:15). Guard time T_G for cyclic prefix is 0.02msec. The combined symbol period T_s becomes 0.12msec. Let the OFDM signal go though a time varying channel with the following 2-path model:

a.) For f₁=200Hz and f₂=-200Hz, find the ICI_m at the 8th carrier (k=7) for m=0,1,2, ...,6.

b.) For f₁=600Hz and f₂=-600Hz, find the ICI_m at the 8th carrier (k=7) for m=0,1,2, ...,6