e wireless medium cannot be as readily constrained as a wired LANs connect nearby computers together SO that they connection. Wireless links are much noisier and less re- can exchange data. Ethernet, by far the most popular liable in general than wired links. The MAC and PHY LAN technology today, was invented by Bob Metcalfe of layers of a wireless network must therefore deal with Xerox Palo Alto Research Center in 1973, in connection a number of issues that are rare or absent from the pro- with the prescient work on personal computers then vision of a wired link: being done at Palo Alto Research Center. Ethernet is an Getting connected: Wireless stations by default are asynchronous technology: there are no fixed time slots likely to be mobile. How does a wireless station let assigned to users. There is also no central control of access other mobile or fixed stations know it is present and to the transmitting medium. Instead, Ethernet exploits wants to join the network? This is the problem of three basic ideas to minimize the impact of two or more associating with the network. A closely related stations trying to use the medium at the same time; two problem is the need of portable mobile stations to of them depend on the ability of a station to listen to the save power by shutting down when they have no voltages on the cable while it sends its message. Carrier traffic, without losing their associated status; the sensing is used by each station to make sure no one is using network coordinator must remember who is awake the medium before beginning a transmission. (Note that and who is asleep, allow new stations to join, and in fact the most popular forms of Ethernet use baseband figure out that a station has left. signaling, that is, the voltages on the cable correspond directly to binary bits and are not modulating a high- Authentication: In wired networks, a station plugs into frequency carrier, SO there's no carrier to sense. Why did a cable placed by the network administrator. If you expect it to make sense?) C