IEEE Std 1900.7-2015 pdf download – IEEE Standard for Radio Interface for White Space Dynamic Spectrum Access Radio Systems Supporting Fixed and Mobile Operation.
5. PHY layer 5.1 PHY layer service specification The PHY layer provides an interface between the MAC sublayer and the physical radio channel. The PHY layer conceptually includes a management entity called the PLME. This entity provides the layer management service interfaces through which layer management functions may be invoked. The PHY layer provides the following two services:  The PHY data service and the PHY management service interfacing to the PHY layer management entity (PLME) service access point (SAP) (known as the PLME-SAP).  The PHY data service (PD) enables the transmission and reception of PHY protocol data units (PPDUs) across the physical radio channel. 5.1.1 PHY data service The PD-SAP supports the transport of MPDUs between peer MAC sublayer entities. 5.1.1.1 PD-DATA.request The PD-DATA.request primitive requests the transfer of an MPDU from the MAC sublayer to the local PHY entity (i.e., PHY service Data UnitPSDU).
The receipt of the PD-DATA.request primitive by the PHY entity will cause the transmission of the supplied PSDU to be attempted. Provided the transmitter is enabled (TX_ON state), the PHY will first construct a frame, and then transmit the PPDU. When the PHY entity has completed the transmission, it will issue the PD-DATA.confirm primitive with a status of SUCCESS. If the PD-DATA.request primitive is received while the receiver is enabled (RX_ON state) the PHY entity will discard the PSDU and issue the PD-DATA.confirm primitive with a status of RX_ON. If the PD- DATA.request primitive is received while the transceiver is disabled (TRX_OFF state), the PHY entity will discard the PSDU and issue the PD-DATA.confirm primitive with a status of TRX_OFF. If the PD- DATA.request primitive is received while the transmitter is already busy transmitting (BUSY_TX state) the PHY entity will discard the PSDU and issue the PD-DATA.confirm primitive with a status of BUSY_TX.