Wireless Communications Assignment: Questions and Instructions

Question 1: Mitigating Unauthorized Access Points Threat

· There are FIVE questions on this assignment paper. Please answer ALL questions. Thisassignment is marked out of 50 marks. It is worth 50% of the total marks for this module.

· Write your answers in the Answer book template available on the Referral Assignmentsubmission link on eLP. Clearly write your name and students ID on the cover page. Donot write (or copy) the text from questions in the answer book.

· All answers except known formulas and equations should your own work. If you arusing other sources, make sure these cited properly. Any text taken as verbatim should

be in inverted quotes and properly cited. All submission will be processed via Turnitin,therefore you should aim for a similarity score of less than 15%.

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· Your final submission file should be saved as word or PDF in the following format:<Last_Name><studentID>.Expected size of the submission:Your report must use a font size no smaller than 10 and be less than 1500 words excludingappendices and references.Academic Integrity Statement: You must adhere to the university regulations on academicconduct. Formal inquiry proceedings will be instigated if there is any suspicion of plagiarismor any other form of misconduct in your work. Refer to the University’s AssessmentRegulations for Taught Awards if you are unclear as to the meaning of these terms. The latest copy is available on the University website.

QUESTION 1

Note: Word limit for this question is 300 words excluding references,equations, tables and diagrams.Unauthorized access points (APs) pose a serious security threat to wireless LANs. Inmost cases an adversary clones a legitimate access point AP and exploits autoselection technique to trick wireless clients into associating with the unauthorizedAP. You are required to present and analyse one strategy which could mitigate thissecurity threat.

Hint: You may think about the authentication framework of IEEE802.11 and proposea simple modification in the authentication mechanism (or protocol).

QUESTION 2

Note: Word limit for this question is 300 words excluding references,equations, tables and diagrams.IEEE 802.11ac introduced few significant enhancements to the previous version(802.11n) by introducing a number of new features. Critically analyse how theseenhancements resulted in achieving much higher data rates?

QUESTION 3

Note: Word limit for each question part is 150 words excluding references,diagram, and equations.

(a)Assume you are working as a wireless device designer and your task is to estimatthe value of maximum power of this device to cover 4.2 km area of cell. The devicecan send its signal to a receiver at the border of the cell with a sensitivity of -90 dBmand has 5 dBi antenna gain. Your device will be connected to an antenna gain with10 dBi and operate at frequency 10 GHz. Assume that he total system loss is 10 dB.

(b)Your goal is to save energy consumed in transmitting wireless messages. Whatrecommendations would you make to reduce the maximum power in the abovesystem with the same ability to send the signal to that receiver successfully?

QUESTION 4

Note: Word limit for each question part is 150 words excluding references, diagram, and equations.

(a) A wireless channel can transmit information with a bit rate 10 Mbps. Compute the required signal-to-noise ratio in dB to transmit with the same bit rate when the channel bandwidth varies as 10 MHz, 5 MHz, and 2 MHz?

(b) What are the differences between Binary Phase Shift Keying (BPSK) and Quadrature Phase Shift Modulation (QPSK)? Critically analyse which one is better to increase the data rate?

QUESTION 5

Note: Word limit for this question is 300 words excluding references, equations, tables and diagrams.\

Consider three stations A, B and C transmitting data to a destination over a shared medium access using CSMA-CA mechanism in IEEE 802.11a network. Suppose each station can get access to the shared medium at each attempt with probability p. We call an attempt by a station for data transmission over the shared medium is unsuccessful if another station gets access to the medium at the same time and therefore, the current station should defer its data transmission with the whole time duration until the backoff period (this whole time duration is called access defer).

Compute the average waiting time until station A starts the transmission of its data under the following assumptions.

- Station A gets immediately (without backoff period) access to the shared medium in attempt.

- The duration of backoff period is fixed at 2 time slots in every unsuccessful attempt.

- The size of RTS, CTS, Data and Ack are respectively 1, 1, 2 and 1 time slots.

- Use the typical values for CSMA-CA parameters in IEEE 802.11a network.

- Note that your solution should be in terms of and p. (END)