DCO-OFDM Implementation for Visible Light Communication Systems

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Resource Overview

Single-Input Single-Output (SISO) DCO-OFDM code for Visible Light Communication (VLC) systems based on DC-biased OFDM methodology. The core implementation involves converting bipolar OFDM signals to unipolar signals by adding a DC bias (BDC) using the transformation x(t) = X₀(t) + BDC, followed by clipping operations. Key implementation challenges include managing clipping noise caused by Gaussian-distributed signal peaks and optimizing BDC selection to balance between linear modulation range and noise performance. Critical algorithmic considerations involve power management, signal distribution analysis, and clipping level calculations relative to subcarrier count.

Detailed Documentation

In visible light communication systems, Single-Input Single-Output (SISO) DCO-OFDM code implements a DC-biased OFDM methodology. The fundamental algorithm processes the OFDM signal by adding a DC bias component BDC through the mathematical operation x(t) = X₀(t) + BDC. Following this transformation, the resulting signal x(t) undergoes clipping operations. However, since the original signal X₀(t) exhibits Gaussian-distributed peak amplitudes, the clipping process inevitably generates clipping noise. The selection of BDC becomes critical in code implementation - excessive BDC values cause signal levels to exceed the linear operating range of M-Z modulators, leading to distortion, while insufficient BDC increases clipping noise and deteriorates the system's Bit Error Rate (BER). Therefore, optimal BDC selection must be constrained within appropriate boundaries during system parameter configuration.

System design implementations typically face constraints from average transmitted optical power, while BER performance depends on the electrical signal-to-noise ratio after photodetection. For signal x(t), due to intensity modulation and square-law detection implementations, optical power P_op is determined by E{x}, and electrical power P_ele is governed by E{x²}. Consequently, optoelectronic power conversion efficiency depends on the time-domain signal distribution characteristics. Unlike ACO-OFDM implementations, DCO-OFDM's clipping levels exhibit dependency on the number of subcarriers, requiring additional algorithmic adjustments in multi-carrier configurations.

Since OFDM signals follow Gaussian distribution profiles, inadequate BDC values prevent proper conversion of negative peaks to positive signals, resulting in clipping operations that generate clipping noise N_c. When BDC decreases in implementation, N_c increases and affects all subcarriers uniformly, requiring careful signal conditioning in the preprocessing stage.

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