Problem 1. Consider an OFDM system with total passband bandwidth B = 1.5 MHz with raised-cosine spectrum used for pulse

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Problem 1 Consider An Ofdm System With Total Passband Bandwidth B 1 5 Mhz With Raised Cosine Spectrum Used For Pulse 1 (54.83 KiB) Viewed 71 times

Problem 1. Consider an OFDM system with total passband bandwidth B = 1.5 MHz with raised-cosine spectrum used for pulse shaping. For pulse-shaping filter, assume ß = 0.5. The channel has a maximum delay spread of T'm = 5 μsec. Assume an OFDM system with M-QAM modulation applied to each subchannel. The OFDM system uses N=128 subcarriers to mitigate ISI. Answer the following - (a) What would be the value of the symbol duration Ts if a single carrier system was used? Will there be severe ISI? (¹+= passband bandwidth in case of single- carrier) (b) For the OFDM system, after calculating the OFDM symbol duration (= NTs), find a suitable value of the length of the cyclic prefix to ensure no ISI between OFDM symbols. For this overhead of cyclic prefix, what will be the total duration of the OFDM symbol? (min CP length = Tm/Ts) (c) What is the subchannel bandwidth? (d) What is the final bit rate after addition of the cyclic prefix? Assume M = 16 for M- QAM. (data rate with CP = x data rate without CP) μ+N For more information on cyclic prefix and its effect, check Andrea Goldsmith's book "Wireless Communications"