Question

i need help on wireless problem 4 please explain each steps so i can understand properly

Consider an OFDM system with total bandwidth B = IMHz assuming B - -0. A single-carrier system would have symbol time T, -1/B-1 us. The channel has a maximum delay spread of T. 5 us, so with T. - Ius and T'm = 5us there would clearly be severe ISI. Assume an OFDM system with MQAM modulation applied to each subchannel. To keep the overhead small, the OFDM system uses N - 128 subcarriers to mitigate ISI. SO TN NT: 128 us. The length of the cyclic prefix is set to 4-8 > TWTto ensure no ISI between OFDM symbols. For these parameters, find the subchannel bandwidth, the total transmission time associated with each OFDM symbol, the overhead of the cyclic prefix, and the data rate of the system assuming M-16.

Answer 1

6 given B-1 MH or 8-o- To = 1 / - ilisec & Imassec N=128 Tuin Ts = 128 usec. M = 87 I'm = length of cyclic prefit, Subchannel Bandwidth BNET s e x 106 -7812.5 Br. = 7.8125 143) Coherence B. w- 7 = 200kHz - Bc BNLC Berso negligibe ISI is there. Total transmission time for each Symbo = I=INTUTS = (28+8 = 136 sec) overhead = = 16 = 6287

For MQ Am with M=16 og each sub carrier transmits 20g 14 bits every T seconds Bit Rate = 1Z 8x4X13 z = 3.7647 mbps 24 Mbips because of the over head. due to cyclic pretix.