1.2 Physical Layer (PHY Layer)

The Physical Layer (PHY Layer) contains the transceiver-specific functionalities as mentioned in the requirements of the IEEE 802.15.4 specification. It gives the interface to the MAC core layer which is independent of the underlying transceiver.

Besides that, the PHY layer provides the set of APIs which can be used to interface a basic application.

The following are the components of the PHY layer:
  • Frame transmission unit (including automatic frame retries)
  • Frame reception unit (including automatic acknowledgement handling)
  • State machine
  • PHY PIB storage
  • CSMA module
  • Energy detection
  • Power management
  • Interrupt handling
  • Initialization and Reset
The PHY layer uses the services of PAL layer for its operation. The frame transmission unit generates and transmits the frames. The frame reception unit reads incoming frame and uploads in to the PHY incoming frame queue.

The PHY layer handles the incoming frame and invokes the receive callback function of the upper layer (application or MAC). The PHY state machine controls the PHY layer. The PHY PIB storage stores all the PIB attributes related to PHY.