General MAC Frame Formats

MAC frame formats:
MAC frame (MPDU) frame consists of the following basic components :
– a MHR, which comprises frame control, sequence number, address information, and security-related information.
– a MAC payload, of variable length. which contains information specific to the frame type.
– a MFR, which contains a FCS.

f41.jpg

Frame Control :
The frame control field is 2 octets in length and contains information defining the frame type, addressing fields,
and other control flags.
f42.jpg

Frame Type subfield :
The frame type subfield is 3 bits in length and shall be set to one of the nonreserved values listed in the
following table. :
t79.jpg
Security Enabled Subfield :
The security Enabled subfield is 1 bit in length, and it shall be set to one if the frame is protected by the MAC
sublayer and shall be set to zero otherwise.

Frame Pending subfield :
The frame pending subfield is 1 bit in length and shall be set to one if the device sending the frame has more data
for the recipient. This subfield shall be set to zero otherwise.

Acknowledgment Request subfield :
The acknowledgment request subfield is 1 bit in length and specifies whether an acknowledgment is required from the
recipient device on receipt of a data or MAC command frame. If this subfield is set to one, the recipient device
shall send an acknowledgment frame only if, upon reception, the frame passes the third level of filtering. If this
subfield is set to zero, the recipient device shall not send an acknowledgment frame.

Destination Addressing Mode Subfield :
All devices operating on a network shall have unique 64 bit extended address. This address can be used for direct
communication within the PAN, or it can be exchanged for a short address allocated by the PAN coordinator when the
device associates.
fig42-table80.jpg

Sequence Number Field :
The sequence number field is 1 octet in length and specifies the sequence identifier for the frame.
for the beacon frame, the sequence number field shall specify a BSN (beacon sequence number). For a data,
acknowledgment, or MAC command frame, the sequence number firld shall specify a DSN (data sequence number) that is
used to match an acknowledgment frame to the data or MAC command frame.

Destination PAN identifier field :
The destination PAN identifier field is 2 octets in length and specifies the unique PAN identifier of the intended
recipient of the frame. A value of 0xfffff in this field shall represent the broadcast PAN identifier.

Destination Address field :
The destination address field is either 2 octets or 8 octets in length, according to the value specified in the
Destination Addressing Mode subfield of the Frame Control Field.

Source PAN Identifier field :
the source PAN identifier field is 2 octets in length and specifies the unique PAN identifier of the originator of
the frame.

Source Address Field :
The source address field is either 2 octets or 8 octets in length, according to the value specified in the source
addressing mode subfield of the frame control field and specifies the address of the originator of the frame.

Auxiliary Security Header field :
The Auxiliary security header field has a variable length and specifies information required for security
processing, including how the frame is actually protected.

Frame Payload field :
The frame payload field has a variable length and contains information specific to individual frame types. If the
security enabled subfield is set to one in the frame control field, the frame payload is protected as defined by the
security suite selected for that frame.

FCS field :
Frame Check Sequence (FCS) is 2 octets in length and contains a 16-bit ITU-T CRC (Cyclic Redundancy Check). The FCS
is calculated over MHR and MAC payload parts of the frame.

Reference :
IEEE Standard for Information technology, Specifications for WPANs 802.15.4

Boring Winter Vacation,

January 27 2008 – Winter Vacation,
Taipei City
High Speed Network Lab

Udin Harun

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