ENGN4536/ENGN6536 - Wireless Communications
Assignment 1
Release date: 2 August 2024
Due date: 11:55pm, 18 August 2024
Cut-off date: 11:55pm, 23 August 2024
Brief Requirement for Submission:
• Submit an electronic copy of your solution as a single PDF file in Wattle. In the submitted PDF file, please use the assignment coversheet provided in Wattle as the front page.
• Provide sufficient and professional descriptions for mathematical derivations. Students may lose marks if the tutor cannot follow the derivation, even if the final answer is correct.
• Add references, following the IEEE Citation Reference format, when necessary. Students are expected to use publicised materials (e.g. books, research papers, reports, theses and online articles), rather than course lecture slides, for referenc-
ing.
• Show a good command of language and avoid grammar mistakes and other errors that can be easily overlooked.
• A typed version of solutions is preferred. If a typed version is not available, a handwritten version is also acceptable, provided that it is clear and easy to read.
• Submission by the due date does not incur any penalty. Late submission prior to the cut-off date is allowed, but at a penalty of 5% of the maximum mark per working day. No submission is allowed after the cut-off date.
• Serious penalties apply to plagiarism. Assessment Criterion:
• The assignment will be marked out of 50. Your mark will be then converted into a scale of 100 and posted in Wattle.
• Your mark (in the scale of 100) worths 7% of the final mark if you are an under- graduate student, and 6% of the final mark if you are a postgraduate student.
Question 1 (12 marks):
In this question, we consider the design of the optimal reuse factor for diamond cells without and with sectorisation. A simplified path loss model is assumed with a path loss exponent of η = 3. Recall that for diamond cells, the number of first-tier co-channel cells is 8.
1. For acceptable performance at mobile users, a signal-to-interference ratio (SIR) of at least α dB is required. Through this question, please use α = 17 if the last digit of your Uni ID is an even number, i.e., 0, 2, 4, 6, 8, but use α = 18 if the last digit of your Uni ID is an odd number, i.e., 1, 3, 5, 7, 9. Determine the minimum reuse factor that can guarantee this SIR requirement using omni- directional antennas at the base stations (i.e. the transmitters).
2. Assume the optimum reuse factor computed in Question 1.1 is now used. If a total of 1440 channels are uniformly distributed to each cell in a cell cluster and assuming a GoS (measured in terms of blocking probability in an Erlang B system) of 1%, how much Erlang of traffic can each cell support?
3. Now we assume that the base station in each cell uses 90。directional antennas with 4 sectors per cell. How many interfering cells (i.e. cells causing interfer- ence) are there in the first tier of the co-channel cells? Please show the sectoring under your consideration.
4. To achieve the same SIR requirement, i.e., a minimum SIR of α dB, determine the minimum reuse factor with 90。sectoring (i.e. 4 sectors per cell).
5. Assume 90。 sectoring and the optimum reuse factor computed in Question 1.4 is now used. The network still has a total of 1440 channels that are evenly dis- tributed to each cell in a cell cluster. Assume that the channels assigned to one cell are uniformly distributed to each sector and a GoS of 1% is required for each sector. How much Erlang of traffic can each sector support? How much Erlang of traffic can each cell support? Why does each cell supports higher traffic with the use of sectorisation?
▶ Please keep two digits after decimal point.
▶ Please use the fullErlang B table uploaded in Wattle for solving this question.
Question 2 (11 marks):
A cellular network provider currently has 16 channels dedicated per cell and offers a GoS (measured in terms of the blocking probability in an Erlang B system) of 0.5% to its clients. But according to a recent survey, customers are not happy with this GoS and demand a GoS of 0.1% or lower.
The network provider decides to allocate more channels per cell such that with the current number of users, a GoS of 0.05% is offered, and then gradually increase the number of users in the system until a GoS of 0.1% is reached.
Use the Erlang B table uploaded in Wattle and answer the following questions:
1. What is the current average amount of traffic generated by the users per cell (measuredinErlangs)?
2. How many additional channels does the network provider have to allocate per cell to reach a GoS of 0.05% with the current number of clients but a doubled traffic generation (i.e. supporting the twice traffic)?
3. With these additional channels in place, how many more users per cell can the system accommodate with a GoS of 0.1%, comparing to the system with a GoS of 0.05%. Assume that each user requests an average of five calls per hour and holds each call for an average duration of 1 minute.
▶ Please keep two digits after decimal point.
Question 3 (12 marks):
A cellular system is operating at the carrier frequency of 2.1 GHz with base station transmitter power equal to 1 W and transmitter antenna gain of 3 dB. The receiver antenna gain at the mobile user is unity. Assume that until the distance d0 = 100 m, signal propagation follows a free space propagation model. Beyond the distance d0 = 100 m, the path loss exponent switches to η = 4 and the transmitted signal also experiences log-normal shadowing with standard deviation of 8 dB. For satisfactory performance, the received power at the mobile terminal should be at least −90 dBm. A communication outage occurs when the received power falls below this threshold value.
Assume a disk-shape cell and find the answers to the following questions:
1. The received power in dBm at distanced0 .
2. The general expression for the received power in dBm at distance d > d0 . This expression would be a function of d and the shadowing random variable xdB .
3. The maximum cell radius that ensures a mobile terminal at the cell boundary experiences an outage probability less than 0.1%.
4. The cell coverage (in percentage), assuming the maximum cell radius found in Question 3.3 is used.
▶ Please keep two digits after decimal point.
▶ Please use the Q function table uploaded in Wattle or an online Q function calculator for solving this question.
Question 4 (4 marks):
Is each of the following statements TRUE or FALSE? If the statement is true, write “True” as your answer and the explanation is not necessary (but you can still provide an explanation if you believe there is a necessity). If the statement is false, write “False” as your answer and the explanation is needed. Please write your explanation with no more than two sentences.
1. Co-channel cells with distances larger than the reuse distance do not cause inter- ference to each other.
2. The use of smart antennas in cellular networks causes significantly more han- dover.
3. The path loss effect explains why the received power is different at different locations.
4. Although the shadowing effect is typically modelled using a log-normal distri- bution, this effect can also be expressed in the linear scale and used in a linear model for combined path loss and shadowing.
Question 5 (6 marks):
The deployment of commercial 5G wireless networks is in progress across different countries. The high density of base stations is a key feature in this deployment, e.g. the average density of base stations in 5G is anticipated to be much higher (such as 3 times) than that of 4G. From your perspective, what is the reason for this feature?
• You may conduct some research, e.g. reading related scientific/industrial articles (such as, but not limited to, those uploaded in Wattle), to better understand the (anticipated) benefits of 5G networks.
• Please indicate word count (150 words or less) together with your answer and cite references where necessary. There is no minimum word count for this question.
• Please answer this question based on your understanding and using your own language. Note that straightforward copying and pasting (even with referencing) is considered to be plagiarism.
Presentation (5 marks):
Requirement for Presentation
• The assignment coversheet is used as the front page. – 1 mark
• The language used for descriptions and explanations is grammarly correct and professional. – 2 marks
• The IEEE Citation Reference format is correctly and consistently used for refer- ences. – 2 marks