2 PHY Layer Introduction

The physical layer contains the transceiver specific functionalities as mentioned in the requirements of IEEE 802.15.4 specification. It provides an interface to the MAC core layer which is independent of the underlying transceiver.

The PHY layer provides a set of APIs that can be used to interface with a basic application.

The following are the components of Physical Layer:
  • Frame Transmission Unit (including automatic frame retries)
  • Frame reception unit (including automatic acknowledgment 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 them to the PHY incoming frame queue.

The PHY layer manages the incoming frames and invokes the receive callback function of the upper layer (Application or MAC). The PHY layer is controlled by the PHY state machine. The CSMA module is used for channel access. The PIB attributes related to PHY are stored in the PHY PIB storage.