KF7031 - Wireless Networks And Security - IT/Computer Science Assignment Help

Assignment Task

Question 1 

a) Critically analyse the impact of Reflection in evaluating the performance of legacy 802.11 a/b/g WLAN technologies.

b) Explain how scattering occurs in RF signals. What is the result of scattering on the quality and strength received signal?

c) What is Multipath in RF transmission? Analyse the effects of multipath propagation in WLANs.
Question 2 (10 + 5 Marks): 

a) Assume you are working as a Network Engineer and your task is to estimate the feasibility of a 5 km link between two buildings, with one access point and one client radio. The access point is connected to an antenna with 10 dBi gain, with a transmitting power of 20 dBm and a receive sensitivity of -89 dBm.  The client is connected to an antenna with 14 dBi gain, with a transmitting power of 15 dBm and a receive sensitivity of -82 dBm. The cables in both systems are short, with a loss of 2dB at each side at the 2.4 GHz frequency of operation.
(10 Marks)
b) What recommendation you would make to improve the link margin for the system deployed in part a above?

Question3 (15 Marks)
a) You have been assigned to perform a wireless site survey of CIS Building at Northumbria University. You are expected to make a recommendation to improve the quality and coverage of wireless networks throughout the building. Describe the key steps you would consider conducting the survey. The building consists of Computer Laboratories and large lecture theaters. What factors you need to consider when producing the survey outputs to make the design recommendations
b) In a role as Network Design Engineer, which factors would you consider when choosing an antenna. List and briefly explain at least four). 
Question 4 (15 Marks)

a) Assume that you have a wireless channel with a bandwidth has a of roughly 100MHz. We would like to transmit information at a bit rate of 500Mbps. Is a signal-to-noise ratio of 30dB enough to reliably transmit this much information? Why or why not?                                        

b) Briefly explain the concept of Voltage Wave Standing Ration (VSWR). What are the effects of VSWR on a wireless system?                            

Question 5 (15 Marks)
a) Wireless transmission suffer from the “Hidden Node” problem. With the help of a diagram explain the hidden node problem.                           
b) Give 2 possible causes of wireless nodes experiencing the hidden terminal problem.                           

c) Would CSMA/CD which was designed for wired Ethernet LAN work for LAN and why? 
d) How does the CSMA/CA use the control packets to overcome the problem hidden node in wireless LANs?

Question 6 

a) In IEEE 802.11 DCF, various mechanisms are introduced to reduce collisions, however, these mechanisms also provide the vulnerability for denial of service (DoS) attacks.  Critically analyse how 802.11 medium contention can be compromised by a DoS attack?
b) Assume that you are working as a Network Engineer that has hired you to look after wireless local area networks. You are assigned a task to ensure each WLAN user is properly authenticated. The existing network infrastructure is only configurable with three options: a) open system authentication with WEP, b) shared key authentication, and c) 802.1X/EAP authentication. Which one these authentication methods is most secure. Justify your answer.
c) You learned in lectures that WEP implementation uses an initialization vector (IV). Explain the purpose of IV in WEP. Critically analyse the vulnerability posed using IV in WEP. 
d) Assume Bob is using RC4 Cipher to send encrypted messages to Alice. Bob sends an encrypted message to let her know the time for the next meeting. Bob wishes to meet Alice at 13:15 hrs. Assume that this time could be written by a string of 4 numbers (ignore the :), where each number is represented by 3 bits. If the key is [1 2 3 4], using a state vector of size 8, find out the encrypted message. Show the process for each iteration. 
Question 7
Name and critically explain at least five (05) security mechanisms that are important for wireless communications.
 

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