802.11ag Packet Formats

What is the general structure of an 802.11a/g packet?

It consists of a Physical Layer Convergence Protocol (PLCP) preamble and header, followed by the MAC Protocol Data Unit (MPDU).

What is the PLCP preamble in 802.11a/g?

The PLCP preamble helps receivers synchronize and prepare to receive the frame; it consists of training symbols.

How long is the PLCP preamble in 802.11a?

The short preamble duration is 16 microseconds, while the long preamble is 20 microseconds.

What is included in the PLCP header?

The header contains information about the data rate, length of the frame, and error checking for synchronization.

What is the MAC Protocol Data Unit (MPDU)?

MPDU includes the MAC header, payload (data), and Frame Check Sequence (FCS) for error detection.

What fields are in the MAC header?

The MAC header contains Frame Control, Duration/ID, Addresses (up to 4), Sequence Control, and QoS Control fields (if applicable).

How many address fields can a MAC header have?

Up to four address fields can be present, used for source, destination, transmitter, and receiver addresses.

What is the purpose of the Frame Control field?

It specifies the frame type, subtype, protocol version, and control flags like retry and power management.

What is the Duration/ID field used for?

It carries information for network allocation vector (NAV) to reserve the medium and avoid collisions.

What is the Sequence Control field?

It contains the fragment number and sequence number to support fragmentation and reassembly.

What does the Frame Check Sequence (FCS) do?

FCS provides error detection using a cyclic redundancy check (CRC) to ensure data integrity.

Are there different types of frames in 802.11a/g?

Yes, management, control, and data frames, each with specific formats and purposes.

What is unique about management frames?

Management frames handle network organization tasks like association, authentication, and beaconing.

What is the function of control frames?

Control frames assist in medium access control, such as acknowledgments (ACK) and Request to Send (RTS) frames.

How is QoS support reflected in packet formats?

QoS control field is added in the MAC header in QoS data frames (802.11e extension) to prioritize traffic.

What is the maximum size of an 802.11a/g MAC frame?

The maximum MPDU size is typically 2304 bytes, but fragmentation can be used for larger data.

How does fragmentation affect packet format?

Large frames are divided into fragments, each with its own MAC header and FCS for independent transmission.

How are packet formats standardized for interoperability?

Strict adherence to IEEE 802.11a/g PLCP and MAC frame definitions ensures devices from different vendors communicate correctly.

Topics in this section,

  • In this section, you are going to learn

  • Terminology

  • Version Info

  • setup

  • Reference links