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Frame Header Compression

Date: Jan, 2012. Frame Header Compression. Authors:. Date: 2012-01-16. MAC Frame Header. The typical frame payload of Smart Grid is tens/hundreds bytes. 100 bytes payload frame with 3 MAC addresses has about 30/100=30% MAC header overhead!

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Frame Header Compression

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  1. Date: Jan, 2012 Frame Header Compression Authors: Date: 2012-01-16 Liwen Chu Etc.

  2. MAC Frame Header The typical frame payload of Smart Grid is tens/hundreds bytes. 100 bytes payload frame with 3 MAC addresses has about 30/100=30% MAC header overhead! 300 bytes payload frame with 3 MAC addresses has about 30/300=10% MAC header overhead! The following parts of the MAC header can be compressed: Some MAC address fields, No HT Control field when Reverse Direction (RD) is used, Do we need 2 bytes Sequence Control in a low rate Smart Grid BSS? Date: Jan, 2012 2 6 6 6 2 2 4 Variable 4 Octets: 2 6 Frame Header

  3. Data/Management Frame Header Compression 1 MPDU type (Normal or compressed) should be identified by either the PHY or MAC header. Bit15 in Duration field. PHY PLCP SIG. Other methods. BSSID and one AID are used to identify the transmitter and the receiver of the data and management frames. BSSID field is used to identify whether the frame is in the same BSS. When “From DS” is 1 and “To DS” is 0, BSSID is the transmitter identifier and AID is the receiver identifier. When “From DS” is 0 and “To DS” is 1, BSSID is the receiver identifier and AID is the transmitter identifier. When both “From DS” is 1 and “To DS” is 1, compressed MPDU header is not used. TDLS is not allowed, because two AIDs would be needed. Date: Jan, 2012 2 6 2 2 2 4 Variable 4 Octets: 2

  4. Data/Management Frame Header Compression 1 AID/DASA Identifier field are used for indicating AID and DA/SA. Bit15~Bit13 is the DA Identifier (when “From DS” is 0 and “To DS” is 1) and SA (when “From DS” is 1 and “To DS” is 0). DASA Identification Request/Response action frames are used to match DASA identifier to DASA MAC address. Bit12 ~ Bit0 are used to identify Duration or ID Frame Type/subtype can be used to differentiate which one it is. Date: Jan, 2012 Bit15 Bit12 Bit13 Bit0 AID/DA RA Identifier • RD would be relocated from the HT control field into the Duration/ID/RD/FHC field of the compressed header. Bit14 is the “RDG/More PPDU” subfield. Bit12 to Bit0 are the AID indication. • Frame Header Compression indication would be in the Duration/ID/RD/FHC field of the compressed header. Bit15 is the “FHC” (Frame Header Compression indication) subfield. • FHC is 1 means that the frame header is compressed frame header. Bit15 Bit13 Bit14 Bit0 Duration/ID/RD/FHC • Single Address frames are not allowed to use compressed frame format.

  5. Data/Management Frame Header Compression 2 MPDU type (Normal or compressed) should be identified by either the PHY or MAC header. Bit15 in Duration field. PHY PLCP SIG. Other methods. Partial AID in PHY SIG is used to identify RA. If two STAs in the BSS have the same Partial AID, the STAs that have the same Partial AID are not allowed to use compressed frame by AP (e.g. through management frame). MAC address is used to identify TA. DA/RA identifier identifies DA/SA. RDG/More PPDU can be included in the same byte. Single Address frames are not allowed to use compressed frame format. Date: Jan, 2012

  6. DASA Identification Management A non-AP STA sends DASA Identification Request frame to the AP to indicate the mapping between DASA Identifier and DASA MAC Address. The AP sends DASA Identification Response frame to acknowledge the mapping between DASA Identifier and DASA MAC Address. Date: Jan, 2012 1 1 1 6 1 6 Octets: 1 At most 16 DASA Identifier and DASA MAC Address pairs DASA Identification Request frame Bit6 Bit7 Bit2 Bit3 Bit0 DASA Identifier field 1 1 2 Octets: 1 DASA Identification Response frame

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