Ieee 802.11 Layers Description; The Mac Layer - Alvarion BreezeNET PRO.11 Series User Manual

9.5.2 IEEE 802.11 Layers Description

As in any 802.x protocol, the IEEE 802.11 protocol covers the Media Access
Control Layer (MAC) and Physical Layer (PHY). The Standard currently defines a
single MAC which interacts with three PHYs (all of them running at 1 or 2 Mbit/s)
as follows:
Frequency Hopping Spread Spectrum (FHSS) in the 2.4 GHz Band
Direct Sequence Spread Spectrum (DSSS) in the 2.4 GHz Band, and
InfraRed
Beyond the standard functionality usually performed by MAC Layers, the 802.11
MAC performs other functions that are typically related to upper layer protocols,
such as Fragmentation, Packet Retransmissions, and Acknowledges.

9.5.3 The MAC Layer

The MAC Layer defines two different access methods, the Distributed Coordination
Function and the Point Coordination Function:
9.5.3.1 The Basic Access Method: CSMA/CA
The basic access mechanism, called the Distributed Coordination Function, is
basically a Carrier Sense Multiple Access with Collision Avoidance mechanism
(known as CSMA/CA). CSMA protocols are well-known in the industry, the most
popular being Ethernet, which is a CSMA/ CD protocol (CD standing for Collision
Detection).
A CSMA protocol works as follows: A station desiring to transmit senses the
medium. If the medium is busy (i.e. some other station is transmitting) then the
station defers its transmission to a later time. If the medium seems free then the
station is allowed to transmit.
BreezeNET PRO.11
802.2
802.11 MAC
FH DS IR
9-27
Appendix
Data Link
Layer
PHY Layer
User's
Guide