802.11 Reference Design: MAC

Overview

The MAC implementation is based on the DCF (distributed coordination function) protocol specified in section 9.3 of the 802.11-2012 standard. This design does not implement the PCF (point coordination function) in section 9.4 of the standard. It also does not implement the EDCA (enhanced distributed channel access) in section 9.2.4.2 of the standard.

Frames: The MAC specification defines many frame formats in section 8 of the 802.11-2012 standard. Our implementation supports a sub-set of these frames.

Data/ACK: Data and ACK frames are of course supported.

Management Frames: The following management frames are supported:

• Beacon
• Probe Request
• Probe Response
• Authentication
• Deauthentication
• Association Request
• Association Response
• Reassociation Request
• Reassociation Response
• Disassociation

Handshakes: The standard defines many inter-node handshakes for many combinations of ad-hoc and infrastructure networks. Our current MAC implementation supports the common association handshake required for a STA (node) to join the network of an AP. This handshake consists of:

STA	Direction	AP
Probe Request	→	↓
↓	←	Probe Response
Authentication	→	↓
↓	←	Authentication
Association Request	→	↓
•	←	Association Response

RTS/CTS: The RTS/CTS access mechanism is fully supported by the reference design.

Architecture

The MAC implementation is split into two pieces:

• The Upper-level MAC is responsible for inter-packet behaviors that are not time critical
• The Lower-level MAC is responsible for intra-packet behaviors that are time critical