The mobility provided by wireless networks has made a huge difference in the lives of most citizens of the internet. However, several challenges have to be overcome by a wireless link layer to make that promise into a reality. Primary among them is the lack of collision detection due to receiver shutdown during transmission. The hidden terminal problem also means that collisions are not apparent to all hosts on a link. This lecture will examine the collision avoidance mechanisms that are key to 802.11 wireless protocols.
By the end of this lesson, the student will be able to:
explain the challenges of a wireless subnet, including those caused by range limits, mobility, receiver shutdown, noise, multi-path, hidden terminal, and exposed terminal problems.
describe the CSMA/CA algorithm and how it helps overcomes some of the wireless challenges.
describe the use of channel reservations to avoid collisions.
explain some features of the 802.11 standard (do not memorize features of the variants). Such features include operating modes, security, frame format, power management and rate adaptation.