Home › Previous year questions › GATE 2016 EC (EC2) › Question 59GATE 2016 EC (EC2) – Question 59 Communications · Digital Communications · 2 marks · Numerical answer
A 500–2000 Hz ideal band-pass channel carries 4800 bits/s using 16-QAM. A raised-cosine pulse spectrum uses the entire channel bandwidth. Its roll-off factor is ________.
Practise this question in The GATE Grind →
Show answer and explanation Correct answer: 0.24 to 0.26
Explanation Sixteen QAM symbols carry 4 bits each, so $R_s=4800/4=1200$ symbols/s. The available passband width is 2000−500=1500 Hz.
For raised-cosine QAM the passband width is $(1+\alpha)R_s$. Hence $1500=(1+\alpha)1200$, giving **$\alpha=0.25$**.
More Digital Communications questions GATE 2016 EC (EC3) Q33 – A binary baseband system transmits the pulse p(t)=cases1/T s,&0 t T s,\\0,&otherwise.cases… GATE 2016 EC (EC3) Q61 – A memoryless binary symmetric channel has bit error probability 10-5. If 105 bits are… GATE 2026 EC Q22 – Consider a discrete memoryless source with an alphabet of four source symbols. s(t) is a… GATE 2026 EC Q32 – A wireless digital transmission scheme is using 16-QAM over an additive white Gaussian… GATE 2026 EC Q44 – A QPSK modulated signal from an additive white Gaussian noise (AWGN) channel is received… GATE 2026 EC Q63 – The average bit error rate at the input of a (7, 4, 1) Hamming decoder is 0.10. The… All Digital Communications questions →