802.11an Packet Formats

What is a packet format in IEEE 802.11an?

Packet format defines the structure of data frames at MAC and PHY layers for communication.

How does 802.11an packet format differ from 802.11a?

802.11an adds support for wider channels, MIMO, and higher data rates, impacting frame aggregation and header fields.

What are the main components of an 802.11an MAC frame?

Frame Control, Duration/ID, Address fields, Sequence Control, QoS Control, Frame Body, and Frame Check Sequence.

What is the purpose of the Frame Control field?

It specifies frame type, subtype, protocol version, and control flags.

How many address fields can 802.11an frames have?

Up to four address fields are used for source, destination, BSSID, and receiver/transmitter identification.

What is the QoS Control field used for?

It carries information related to traffic prioritization and scheduling.

What frame types exist in 802.11an?

Management, Control, and Data frames, each with distinct formats.

What modulation technique is used at the PHY layer in 802.11an?

OFDM combined with MIMO spatial multiplexing.

How is the PHY preamble structured in 802.11an?

It includes training sequences for synchronization and channel estimation.

Does 802.11an support frame aggregation?

Yes, it supports A-MPDU and A-MSDU aggregation to improve throughput.

What is the significance of the Sequence Control field?

It manages fragmentation and packet sequencing to ensure data integrity.

How are control frames formatted in 802.11an?

They have shorter formats optimized for quick responses like ACK and RTS/CTS.

What is the Frame Check Sequence (FCS)?

A CRC field for error detection of the entire frame.

How does 802.11an handle variable packet sizes?

Packet sizes vary up to the Maximum Transmission Unit (MTU) supported by aggregation.

Are there any changes to the header size in 802.11an?

QoS Control and HT Control fields may increase header size compared to legacy frames.

How is encryption handled in the packet format?

Encryption headers are added within the MAC frame body depending on security protocols.

What is the role of the HT Control field in 802.11an?

It supports high throughput features like block acknowledgment and beamforming.

How do packet formats support multi-antenna transmissions?

PHY layer signaling includes spatial stream information to coordinate MIMO transmissions.

What mechanisms ensure packet format compatibility across vendors?

Standardized frame structures and fields verified through interoperability testing.

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