Frame Format of IEEE 8011
IEEE 802.11 MAC layer data frame consists of 9 fields:
Frame Control
It is 2 bytes long and defines type of frame and control information. The types of fields present in FC are:
- Version: Indicates the current protocol version.
- Type: Determines the function of frame i.e. management(00), control(01) or data(10).
- Subtype: Indicates subtype of frame like 0000 for association request, 1000 for beacon.
- To DS: When set indicates that the destination frame is for DS(distribution system).
- From DS: When set indicates frame coming from DS.
- More frag (More fragments): When set to 1 means frame is followed by other fragments.
- Retry: If the current frame is a re-transmission of an earlier frame, this bit is set to 1.
- Power Mgmt (Power Management): It indicates the mode of a station after successful transmission of a frame. Set to ‘1’ field indicates that the station goes into power-save mode. If the field is set to 0, the station stays active.
- More data: It is used to indicate to the receiver that a sender has more data to send than the current frame.
- WEP: It indicates that the standard security mechanism of 802.11 is applied.
- Order: If this bit is set to 1 the received frames must be processed in strict order.
Duration / ID
It contains the value indicating the period of time in which the medium is occupied (in µs).
Address 1 to 4
These fields contain standard IEEE 802 MAC addresses (48 bit each). The meaning of each address is defined by DS bits in the frame control field.
SC (Sequence Control)
It consists of 2 sub-fields i.e. sequence number (12 bits) and fragment number (4 bits). Sequence number is used to filter duplicate frames.
Data
It is a variable length field which contains information specific to individual frames which is transferred transparently from a sender to the receiver.
CRC (Cyclic Redundancy Check)
It contains 32 bit CRC error detection sequence to ensure error free frame.
Note: To know more about the features of IEEE 802.11 MAC frame visit this article.
IEEE 802.11 Architecture
The IEEE 802.11 standard, commonly known as Wi-Fi, outlines the architecture and defines the MAC and physical layer specifications for wireless LANs (WLANs). Wi-Fi uses high-frequency radio waves instead of cables for connecting the devices in LAN. Given the mobility of WLAN nodes, they can move unrestricted within the network coverage zone. The 802.11 structure is designed to accommodate mobile stations that participate actively in network decisions. Furthermore, it can seamlessly integrate with 2G, 3G, and 4G networks.
The Wi-Fi standard represents a set of wireless LAN standards developed by the Working Group of IEEE LAN/MAN standards committee (IEEE 802). The term 802.11x is also used to denote the set of standards. Various specifications and amendments include 802.11a, 802.11b, 802.11e, 802.11g, 802.11n etc.
Table of Content
- Important Terminologies of IEEE 802.11 Architecture
- IEEE 802.11 Architecture and Services
- Services provided by the WLAN
- Frame Format of IEEE 802.11
- WiFi Alliance
- Advantages and Disadvantages of IEEE 802.11 Architecture
- Applications of IEEE 802.11 Architecture
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