IEEE 802.11 standard
802.11 defines a Basic Service Set (BSS) comprising of two or more fixed, portable, and/or moving nodes or stations that can communicate with each other in a limited geographical area. There are two configurations:- Infrastructure mode: at least one central access point (AP) connected to the wired network
- Ad hoc or peer-to-peer mode: a set of wireless stations communicate directly with one another without requiring a central access point or a wired connection
802.11 define the physical layer and medium access (MAC) layer. There are three radio frequency (RF) physical layers that operate at the 2.4 GHz ISM band, namely frequency hopping spread spectrum (FHSS), digital sequence spread spectrum (DSSS) and infrared (IR).
In WLAN, CSMA/CD is unsuitable due to the hidden station problem. Refering to the figure below, let's say A and C are not within transmission range of each other. C is currently transmitting to B. Using CSMA/CD, when A wants to transmit to B, it has to listen to determine if there is currently any ongoing transmission. Because C is not within A's transmission range, it is unable to detect C's transmission. When A starts transmitting to B, it results in a collision at B.
