Wireless LAN Basics

This assignment comprises 4 questions based on the work you have completed in your semester 1 laboratory exercises. Some questions may also require you to carry out further research to give complete answers. Include annotated print-outs of protocol decode traces, flow graphs or other diagrams (as required) clearly indicating which question they refer to.

Answer all questions.

(6 marks)

(b) (i) Summarise the results you obtained for Part D of lab 1 regarding the effects on received signal strength for each transmitter antenna type and orientation. Discuss the results with reference to the antenna specifications given in Appendix 2.

was -96 dBm, calculate (showing your working) the:

(i) signal/noise ratio in dBs

(i) Analyse the spectrum, discuss your findings and identify the most active channels/frequencies used during the lab period.

(ii) Identify the time when the video sender was active in the lab and submit a screen shot showing this period.

(a) With the aid of diagrams, distinguish between the WLAN architectures IBSS, BSS and ESS and explain how the wireless nodes belonging to each service set are identified.

(6 marks)

(i) Much higher between a wireless station and a wired computer than between two wireless stations.

(ii) Higher between two wireless stations on a ad-hoc network than two wireless stations on an infrastructure network.

Figure Q2d

Explain the network operation and describe the tests you performed to confirm the function of the APs when:

(7 marks)

3. This question relates to Lab3 'IEEE 802.11 Wireless LAN Frame Types and Formats'

Figure Q3a

(b) Submit protocol decode printouts of a beacon and a probe response frame with the SSID of the network your client has been configured to associate with, highlighted.

(i) Explain how Kismet is able to identify cloaked or hidden networks.

(ii) Submit the extract from a Kismet scan report showing a hidden SSID

(ii) Create a Flowgraph diagram from relevant captured frames using the Wireshark statistics feature to show the frame interchange that took place when your client connected to the BSS

(iii) With the aid of the Flowgraph diagram explain the steps involved in network connection.

(iii) State the Wireshark post capture filter used to display RTS and CTS frames only.

(iv) Explain why the use of RTS/CTS might adversely impact throughput on some networks?

Figure Q4a

(i) Describe, with the aid of Wireshark decodes, how you confirmed the correct bridging operation between the two LAN segments.

(10 marks)

(b) Figure Q4 b shows a wireless PtP bridge link employing Cisco 1300 outdoor Bridges with a clear Fresnel zone operating in the IEEE 802.11g ISM band Channel 6.

1. Total Link loss if the path length is 20 miles

2. Received signal power in dBm

(c) The IEEE 802.11n standard offers many improvements over legacy WLAN technology.

(i) Explain why multiple antennas may improve received signal strength in both 802.11n and legacy WLANs.