Exam Regulations and Questions on 5G Networks, Line-Codes, Speech Coding, Entropy, ISI, and Noise

Question 1 and 2 on 5G Networks, Line-Codes, and Speech Coding

Reminder of exam regulations:

· The work you submit must be entirely your own and carried out by you and you alone.

· Any form of communication with other candidates is strictly prohibited.

· By submitting your answers to this examination, you are confirming your agreement and conformity with the above conditions. You further agree that where this is subsequently deemed not to be the case, that you will be subject to an investigation under the University’s academic misconduct regulations.

Question 1.

a. 5G networks are expected to carry many new types of traffic including eMBB, URLLC, eRAC and mMTC.

i. For each of the above, describe the main uses and scenarios of each traffic type.

ii. Based on the uses in part i, discuss two technical requirements which are important for each traffic type.

iii. Given that a single 5G network is expected to carry each traffic type, outline and explain some of the conflicting requirements from part ii which may arise from this situation.

b. An MPSK system is to operate with 2n symbols on a channel allocation of 200 kHz. The required data rate is 2 Mbps.

i. Calculate the required Carrier to Noise Ratio (CNR) to maintain a Bit Error Rate BER of better than 10-6

Question 2.

a. Explain the main characteristics of a signal, which should be considered when selecting an appropriate line-code. Your discussion should refer to RZ and HDB3 coding.

b. Discuss the performance of speech coding systems. In particular, you should focus on the relationship between bit rate, voice quality and coder complexity.

c. A discrete memoryless source produces messages with the following probabilities:

i. Calculate the Entropy of each message.

ii. Calculate the Entropy of the source.

iii. How many bits are needed to represent this information using a fixed length code? What is the efficiency of the fixed length code?

iv. Design a Huffman code for this source.

v. What is the average code word length for this code?

vi. What is the efficiency for this code?

Question 3.

a. i. Explain what is meant by Intersymbol Interference (ISI). You should discuss the causes of ISI, and the effect it has on the pulse train.

ii. Outline one technique to reduce the effect of ISI.

b. Discuss the sources of physical (thermal and non-thermal) noise. In each casediscuss how temperature and bandwidth effect the noise power, and what can be done to change this affect.

Question 4.

a. Errors that occur on communication channels can be addresses by using ARQ (Automatic Repeat Request), or FEC (Forward Error Correction). Discuss the implications of choosing how to deal with this situation.

b. Outline the main characteristics of linear group codes and their significance.

c. For the Convolutional coder shown below (fig. q4), answer the following:

i. Draw the trellis diagram.

ii. What is meant by the rate of a coder? Discuss the effect of different rates, and how they can be changed.

iii. What is meant by the constraint length of a coder? Discuss the effect of different constraints.

Candidates will need to answer ALL questions on the examination paper, irrespective of any other instructions which candidates may previously have seen.

· Candidates will be awarded a percentage mark for their examination based on the total number of marks available from ALL questions on the paper. Therefore, candidates missing out or not answering some questions, will receive a lower overall percentage mark.

· Candidates’ answers to questions can be prepared in a single Word document, using the equation editor as appropriate. The Word document should be converted to a PDF format, prior to final submission in Canvas.

· Candidates may also prepare handwritten answers to examinations if they wish. These must be clear and legible. Illegible answers will not be marked. Handwritten answers must then be scanned and saved as PDF format, prior to final submission in Canvas.