PSMP is an action frame introduced in 802.11n, which is a management frame used to share TXOP obtained by AP through EDCA among STAs.
The PSMP payload does not include the MAC HEADER and has the following two parts, one is the PSMP parameter set field, the other is the STA info field.
The STA info filed is the AID of each STA that is triggered (scheduled), and the respective UTT and/or DTT time allocation.
STA can be divided into three types: BC, MC, Individual. Each has its own STA info field format.
The PSMP parameter set field can specify whether there are subsequent PSMP frames, how many STAs are in STA_info, and the duration/id of the PSMP sequence.
The detailed format is as follows:
filed category action PSMP parameter set STA info
length 1 1 2 8
value '7' ‘2’ - -
meaning HT PSMP indicators, utt/dtt allocation for each STA
The format of the PSMP parameter set is as follows:
fieldd N_STA MORE_PSMP PSMP sequence duration/id
length 5 1 10
value - - (8 us unit, max 8.184ms)
meaning number of sta in sta_info more PSMP PSMP sequence duration
STA info varaint for individual-addressed(IA):
filed STA_info type PSMP-DTT start offset PSMP-DTT duration STA_ID PSMP-UTT start offset PSMP-UTT duration reserved
length 2 11 8 16 11 10 6
value '0' (4us unit) (16us unit) AID (4us unit) (4us unit)
meaning IA relative to PSMP end relative to PSMP end
STA info varaint for multicast-:
filed STA_info type PSMP-DTT start offset PSMP-DTT duration Multicast_ID
length 2 11 8 43
value '1' (4us unit) (16us unit)
meaning multicast relative to PSMP end
STA info varaint for broadcast-:
filed STA_info type PSMP-DTT start offset PSMP-DTT duration reserved
length 2 11 8 43
value '2' (4us unit) (16us unit)
meaning broadcast relative to PSMP end