Suppose that we want to transmit a digital TV signal at 4 Mbits/sec using coherent QPSK modulation scheme. Assume further that the required Eb/NO (the energy per bit to noise power spectral density ratio) is 9.9 dB. i) Calculate the symbol rate. ii) Calculate Es/NO (the energy per symbol to noise power spectral density) in dB. iii) If we use a raised cosine pulse shaping filter with rolling- off factor of 0.8, what is the null-to-null bandwidth for this scheme? iv) Derive an expression to calculate the average probability of the symbol error using complementary Gaussian error function. A communication system transmits data using QPSK modulation at a rate of R. = 8 Mbps over an ideal bandlimited bandpass channel with centre frequency f-390 MHz. To remove inter-symbol interference (ISI), a raised-cosine spectrum with roll-off factor a=0.2 is employed. i) Determine the values of symbol rate R (symbols per second) and required channel bandwidth B. ii) Sketch carefully the overall raised-cosine spectrum X() of this system. Q3. A digital communication system employs 16-QAM modulation. The amplitude spectrum of the transmitted bandpass square-root raised cosine (SRRC) pulse is shown in Figure 2. Derive the bitrate of this system. 1/40 1/80 IG(f) | 15 20 25 30 35 40 45