A Novel Timing Synchronization Method for DCO-OFDM-Based VLC Systems

Abstract

Being sensitive to synchronization errors, symbol timing synchronization is a key factor affecting the performance of orthogonal frequency division multiplexing (OFDM) -based visible light communication (VLC) systems. A novel timing synchronization method based on odd-even symmetry for direct current biased optical OFDM (DCO-OFDM) is investigated in this paper. The proposed method produces an excellent pulse-like timing metric, resulting in a sharper peak at the correct place, while the values of other parts are negligible. The performance of the proposed timing synchronization approach is assessed by measuring the root mean squared error (RMSE) and mean absolute error (MAE) of timing offset estimation and bit error rate (BER) performance by computer simulation. The simulation results show that this novel symbol timing synchronization approach is superior to the typical methods for DCO-OFDM, such as the Park method and Guerra method, in various channel environments.

Novel Unipolar Optical Modulation Techniques for Enhancing Visible Light Communication Systems Performance

“…The noise cancellation block is used not only to enhance the system performance by minimizing the system clipping distortion noise but also to restore the original transmitted special even data from the clipped samples. Figure (15), shows the noise cancellation technique is based on three stages, the first stage is splitting the received 𝑦 𝑠𝑝𝑒𝑐𝑖𝑎𝑙 (𝑛) ̅̅̅̅̅̅̅̅̅̅̅̅̅̅ into four parts each of size (N/4) and storing them as represented in (38),…”

“…So, different modified OFDM systems were under investigation taking into consideration SE, power efficiency (PE), bit error rate (BER), and nonlinearity distortion. Previous studies introduced different techniques like DC-biased optical-OFDM (DCO-OFDM) [14,15], which main merit is achieving the maximum data rate ratio (DRR) of (50%) in the VLC systems at the cost of adding a DC bias that leads to power inefficiency and degrading the system BER performance [16]. Asymmetrically clipped optical (ACO)-OFDM [17,18], FLIP-OFDM [19,20], and unipolar OFDM (U-OFDM) [11,21], schemes have a low DRR of (25%), but better BER system performance compared to DCO-OFDM system.…”

“…The first stage is to extract 𝑦 𝑒𝑣𝑒𝑛 (𝑛) from the received signals represented in(18), and(19) taking into consideration 𝑦 𝑒𝑣𝑒𝑛 𝑁𝐶 (𝑛), and 𝑦 𝑒𝑣𝑒𝑛 𝑃𝐶 (𝑛) are the received signals for 𝑥 𝑒𝑣𝑒𝑛 𝑁𝐶 (𝑛) illustrated in(14), and 𝑥 𝑒𝑣𝑒𝑛 𝑃𝐶 (𝑛) illustrated in(15), respectively. Therefore 𝑦 𝑒𝑣𝑒𝑛 (𝑛) can be obtained through subtracting 𝑦 𝑒𝑣𝑒𝑛 𝑃𝐶 (𝑛) from 𝑦 𝑒𝑣𝑒𝑛 𝑁𝐶 (𝑛) as shown in (34),…”

Design and Implementation of Spectrally Efficient Frequency Division Multiplexing Receiver

“…Accordingly, there exists a large estimation error for S&C algorithm. Aiming at reducing the estimation error, several timing synchronization methods, such as Minn algorithm, Park algorithm, etc., were applied in OFDM system [22], [23], [25], [26], [31]. By designing appropriate timing synchronization preamble and synchronization metric function, the peak of timing metric curve became more sharp and recognizable, thus leading to an improve timing synchronization accuracy.…”

“…By designing appropriate timing synchronization preamble and synchronization metric function, the peak of timing metric curve became more sharp and recognizable, thus leading to an improve timing synchronization accuracy. In particular, the methods in [22], [23], [25], [26], [31] can also be adopted in SEFDM system by setting an SEFDM symbol preamble. However, the above algorithms need two parts of preamble, which reduces the throughput especially under small signal to noise ratio (SNR).…”