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2D-OFDM for Optical Camera Communication

 

OFDM is well-known for LiFi; however, it is still fresh advanced waveform for OCC. This post shares an implementation of 2D-OFDM for Screen-to-Camera communication system in which a massive number of display cells brings a great advantage for communication.

  • A full journal version of this topic is available online at IEEE Access.

Video demonstration:

 

System Features:

  • MIMO-OFDM screen-camera
    • MIMO channel with sub-channels consisting of subcarriers for reliable communication.
    • Configurable size of Tx, with OFDM symbols based on experimentally verifying the channel in conjunction with the channel analysis
  • The new design of Tx that jointly supports critical functionalities
    • 360-degree rotation support.
    • Asynchronous communication with frame rate variation support.
    • Correction of perspective distortion.
  • Complete system architecture and detailed implemental guidance.
    • OFDM symbol creation and Tx post-processing (2D-cyclic prefix insertion and clipping processes).
    • Scaling and DC-bias control.
    • 2D pilots design and channel equalization.
    • PHY frame format PPDU co-existent to 802.15 standards.
    • Effective FEC.
  • Comprehensive Rx processing and decoding guidance
    • Specific decoding processes are given based on implemental results, significantly including
    • Spatial downsampling and the correction of perspective distortion,
    • Temporal downsampling to deal with frame rate variation, and
    • Rotation correction
Figure 1 – Reference Architecture for the Screen-Camera DFT-OFDM system

The transmitter design:

  • The bolder area: to support the detection and extraction of the code.
  • The rotation tracking corners: to determine the rotation.
  • Clock cells at the surrounding of the code: to support the Rx determining the proper sampling ratio under the presence of perspectivedistortion.
Figure 2 – Allocation of multiple-OFDM symbols into Tx

 

Experiment setup: