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ECS528U - Communications Systems - 2025/26
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A digital communication systems is using an -ary NRZ bipolar encoding between and , with = 4
By knowing that we are using a bandwidth 1 KHz and that millijoules, determine range where 68% of the AWGN noise value will be. In particular, the range []
Chose the answer closer to value that you obtained.
Considering a BPSK modulation scheme is used to transmit a digital bitstream with a bitrate Kbps. By assuming that the carrier has an amplitude Volt and that a frequency of 1 MHz, calculate the value of .
Imagine your source of information generate the following sequence of symbols:
a b c d c c c c d c b b b a c
Which one is the symbol with lowest information associated?
Imagine that your source emits the following 3 symbols with associate probabilities:
| Symbol | Probability |
| D | 0.45 |
| A | 0.28 |
| C | 0.15 |
| B | 0.12 |
Which of the following reflect the Shannon-Fano Tree encoding:
NOTE: use the convention explained during the lecture where left and right are from the tree perspective
Imagine that we transmit a stream of N=6 bit over a channel where a single bit will be received corrupted with probability . How much is the probability that of these N bit will be received with error (corrupted)?
A PCM based system has 2^N codewords. N=4, and the q value is 0.0125. Evaluate the SQNR in dB if the input signal is a sinusoid of amplitude A=0.1.
Imagine that we are required to transmit a stream of bit using a bit-rate Kbps. In order to prevent the Intersymbol Interference (ISI) which of the following conditions the channel bandwidth MUST respect :
Imagine that we have a 2-bit PCM system used to digitally encode signals that can vary in the range =2 V. Assuming that the power of the signal that we are sampling is 1W, how much is the Signal-to-Quantization noise ratio (SQNR)?
Provide an answer in dB
Suppose to have a SINE wave of 1Hz and Amplitude A=1.5. If we sample it starting
from t=0.25 by using a sampling frequency Hz, the values of the first 4 values will be:
Imagine that we have a signal with a bandwidth kHz.
Which one of the following sampling frequencies respect the sampling theorem?