LiFi Physical Layer Basics: PHY-I, PHY-II, and PHY-III Types

This page describes the fundamentals of the LiFi physical layer, complete with a block diagram. It also explores the different versions of the LiFi physical layer: PHY-I, PHY-II, and PHY-III, detailing their features and modulation code rates.

The LiFi Physical Layer provides the following functions:

• Provides services to the upper layer.
• Employs FEC (Forward Error Correction) techniques like Convolution encoding and RS encoding at the receiver to correct errors.
• Activates and deactivates the VLC (Visible Light Communication) transceiver.
• Provides WQI (Wireless Quality Indicator) for all received frames.
• Facilitates synchronization at the receiver by using a preamble incorporated in the frame structure.
• Inserts a header (PHR - Physical Layer Header) at the transmitting end, which is then decoded at the receiving end to determine the length field of the PSDU (PL Service Data Unit).
• Enables channel selection based on specific requirements.
• RLL (Run Length Limited) Encoding aids in correcting DC balance, clock recovery, and flicker mitigation.

Different LiFi physical layers exist to cater to varying data rate needs and application scenarios, whether indoor or outdoor.

LiFi PHY-I

The LiFi PHY-I version is designed to meet low data rate requirements, ranging from 12 to 267 Kbps. It’s primarily intended for outdoor applications.

Fig-1: LiFi Physical Layer Transmitter (version: PHY-I)

Table-1: LiFi PHY-I Operating Modes (Modulation, Code rates)

LiFi PHY-II

The LiFi PHY-II version is developed to meet moderate data rate requirements, ranging from 1.25Mbps to 96 Mbps. It is ideally used for indoor applications.

Fig-2: LiFi Physical Layer Transmitter (version: PHY-II)

Table-2: LiFi PHY-II Operating Modes (Modulation, Code rates)

LiFi PHY-III

The LiFi PHY-III version is designed to meet data rate requirements from 12 Mbps to 96 Mbps. It’s particularly suited for systems utilizing color sources based on RGB and detectors.

Fig-3: LiFi Physical Layer Transmitter (version: PHY-III)

Table-2: LiFi PHY-III Operating Modes

Note: The information presented on this page is based on the IEEE 802.15.7-2011 draft version. Read latest standard specifications published by IEEE for any updates.