3. (a) (i) Ethernet networks use collision detection to mitigate the problem of frames colliding during transmission. Explain why wireless networks cannot use collision detection. (ii) In place of collision detection, many wireless network standards exploit short messages known as handshakes to protect longer data transmissions. What are the roles of the RTS and CTS messages, and why are they an effective approach to managing network capacity? (iii) In CSMA-CA wireless networks, three different inter-frame spacings are commonly used as part of the MAC algorithm. List the three spacings in terms of duration from longest to shortest and explain how they enable efficient access to the available bandwidth to be managed by the point controller. (b) (i) A student living in a block of flats is configuring his home wireless access point as part of a 2.4 GHz 802.11b network. Explain why he may be better choosing one of the overlapping channels rather than one of those guaranteed to not overlap with each other (i.e. why there may be an advantage to the student in avoiding channels 1, 6, & 11).

(ii) 802.11 networks allow nodes to enter sleep states, thus conserving power. Explain the role of the power management bit and beacon frames in this process. (c) (i) An 802.15.1 (Bluetooth) network is being used in a kitchen to wirelessly connect a set of speakers. Explain why signal quality may be a problem in this environment, and how the division of the 2.4GHz spectrum by the 802.15.1 standard is used by devices to mitigate this risk.