Numerical Question Bank
Q1. Calculate the required bandwidth if in a communication channel the signal power is 10W
and the information transmission rate is 10 Kbps.
Q2. It is required to transmit a data at a rate of 64 kbps over a 3 KHz telephone channel.
What is the minimum SNR required to accomplish this?
Q3. Given a 10-but sequence 1010011110 and a divisor 1011. Find the CRC. Check your
answer.
Q4. A pure Aloha network transmits 200 bit frames on shared channel of 200 kbps. What is
the through put if the system (all station together) produces 250 frames per second?
Q5. Consider the use of 10 K-bit size frames on a 10 Mbps satellite channel with 270 ms
delay. What is the link utilization for Stop-and-Wait ARQ technique assuming P=10-3.
Q6. Construct the Polar, NRZ-L and NRZ-I schemes for the following data: 01001110.
Q7. If a 7-bit hamming code received as 1110101, show that the code has error. Also rectify
error in this code.
Q8. A bit stream 10011101 is transmitted using x3+1 generator polynomial. Generate the
CRC code word for this message.
Q9. Encode the data stream 10011010 using the following encoding scheme:
(i) Unipolar (ii) Bipolar NRZ-L (iii) Biploar NRZ-I (iv) RZ (v) Machester (vi)
Diffrential Machester (vii) AMI
Q10. Assume we want to send a data from S to R and there are 2 routers in between. What
will be the total time taken if total number of packets are 5. Data is like:
Tp=0 msec, Data size=1000 bytes, Bandwidth=1 mbps, header of the packet=100 bytes.
Q11. Measurement of slotted ALOHA channel with infinite number of users show that the 10
percent of slots are idle.
(i) What is the channel load?
(ii) What is the throughput?
Q12. A slotted ALOHA network transmits 400-bit frames on a shared channel of 400 kbps.
What is the throughput if the system (all stations together) produces-
(i) 1000 frames per second
(ii) 500 frames per second
(iii) 250 frames per second
Q13. If a binary signal is sent over a 3 KHz channel. Whose signal to noise ratio is 20 dB.
What is the maximum achievable data rate?
Q14. A channel has a bit rate of 20 Kbps. The stop and wait protocol with frame size 4500
bits is used. The delay for error detection and sending ACK by the receiver is 0.25 seconds
because of a fault. Find the maximum efficiency of the channel is 2.8*10 8 m/sec. Find the
decrease in efficiency due to the fault.
Q15. Sender’s data D=11010, CRC generator polynomial=x3+x+1. Apply CRC algorithm and
perform calculation both at sender and receiver end.
Q16. Calculate the total number of transmissions that are required to send 10 data packets
through GBN-3 and every 5th packet is lost.
Q17. Define the relationship between transmission delay and propagation delay, if the
efficiency is at least 50% in STOP N WAIT protocol.
Q18. Find out the window size and minimum sequence number in sliding window protocol, if
Transmission delay (Tt)=1 msec, Propagation delay (Tp)= 24.5 msec.
Q19. Sketch the Manchester and Differential Manchester encoding for the bit stream:
0001110101.
Q20. Perform the subnetting of the following IP address 160.11.X.X. Original subnet mask
255.255.0.0 and number of subnets is 6 (six).
Q21. Given the IP address 180.25.21.172 and the subnet mask 255.255.292.0, what is the
subnet address.
Q22. The IP network 200.198.160.0 is using subnet mask 255.255.255.224. Design the
subnets.
Q23. If a class B network on the Internet has a subnet mask of 255.255.248.0, what is the
maximum number of hosts per subnet?
Q24. The IP network 200.198.160.0 is using the subnet mask 255.255.255.224. draw the
subnets.
Q25. What is the transmission time of a packet sent by a station if the length of the packet is
2 million bytes and the bandwidth of the channel is 300 Kbps?
Q26. The following is the dump of a TCP header in hexa decimal format:
05320017 00000001 00000000 500207FF 00000000
(i) What is the sequence number?
(ii) What is the destination port number?
(iii) What is the acknowledgement number?
(iv) What is the window size?
Q27. Using the RSA public key cryptosystem with a=1, b=2 etc.
(i) If p=7 and q=11, list five legal values for d.
(ii) If p=13 and q=31 and d=7, find e.
