Frame aggregation
Encyclopedia
Frame aggregation is a feature of the IEEE 802.11e and 802.11n wireless LAN standards that increases throughput by sending two or more data frames in a single transmission.
Every frame transmitted by an 802.11 device has a significant amount of overhead, including radio level headers, Media Access Control
(MAC) frame fields, interframe spacing, and acknowledgment of transmitted frames.
At the highest data rates, this overhead can consume more bandwidth than the payload data frame.
To address this issue, the draft 802.11n standard defines two types of frame aggregation: MAC Service Data Unit (MSDU) aggregation and MAC Protocol Data Unit (MPDU) aggregation. Both types group several data frames into one large frame. Because management information needs to be specified only once per frame, the ratio of payload data to the total volume of data is higher, allowing higher throughput.
frames to be transmitted to a single destination and wraps them in a single 802.11n frame. This is efficient because Ethernet headers are much shorter than 802.11 headers.
Every frame transmitted by an 802.11 device has a significant amount of overhead, including radio level headers, Media Access Control
Media Access Control
The media access control data communication protocol sub-layer, also known as the medium access control, is a sublayer of the data link layer specified in the seven-layer OSI model , and in the four-layer TCP/IP model...
(MAC) frame fields, interframe spacing, and acknowledgment of transmitted frames.
At the highest data rates, this overhead can consume more bandwidth than the payload data frame.
To address this issue, the draft 802.11n standard defines two types of frame aggregation: MAC Service Data Unit (MSDU) aggregation and MAC Protocol Data Unit (MPDU) aggregation. Both types group several data frames into one large frame. Because management information needs to be specified only once per frame, the ratio of payload data to the total volume of data is higher, allowing higher throughput.
MSDU aggregation
MSDU aggregation relies on the fact that most mobile access points and most mobile client protocol stacks use Ethernet as their "native" frame format. It collects EthernetEthernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
frames to be transmitted to a single destination and wraps them in a single 802.11n frame. This is efficient because Ethernet headers are much shorter than 802.11 headers.
MPDU aggregation
MPDU aggregation also collects Ethernet frames to be transmitted to a single destination, but it wraps each frame in an 802.11n MAC header. Normally this is less efficient than MSDU aggregation, but it may be more efficient in environments with high error rates, because of a mechanism called block acknowledgement. This mechanism allows each of the aggregated data frames to be individually acknowledged or retransmitted if affected by an error.See also
- Packet aggregationPacket aggregationIn a packet-based communications network, packet aggregation is the process of joining multiple packets together into a single transmission unit, in order to reduce the overhead associated with each transmission....
- Block acknowledgementBlock acknowledgement-Block Acknowledgment:Block Acknowledgment was initially defined in IEEE 802.11e as an optional scheme to improve the MAC efficiency. Recently ratified amendment 802.11n enhances this BA mechanism then made it as mandatory to support by all the HT devices...
- IEEE 802.11n-2009
- IEEE 802.11IEEE 802.11IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...