## 2 Literature Survey
The implementation of PFI neither maximizes the total transmit power, nor increases the decoder complexity in the design of the MIMO-VLC system. [PERSON], [PERSON], [PERSON] and Chen, L.K. [21] developed the MIMO-OFDM-VLC system along with a receiver module with angular diversity for improving the BER. The Channel State Information (CSI) evaluated for this VLC system are multiple reflections, LED nonlinearity and modulation bandwidth.The channel of MIMO-VLC is decomposed into independent parallel sub-channels by utilizing the Singular Value Decomposition (SVD). Subsequently, the bit and power loading is utilized for sub channels to enhance the system capacity. An improvement in channel diversity is obtained by using the receiver module with four receiver heads, which are oriented to the optimized polar angle with various azimuthal angles. The system performance is limited when the polar angle is too large. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] [22] presented an Optical Adaptive Precoding (OAP) scheme for the MIMO-VLC downlink systems. The signal-to-interference-plus-noise ratio (SINR) is improved by using the information of transmitted symbols in OAP. The channel matric of VLC is maintained as positive by using the recalling function and On-Off Keying (OOK) modulation. In perfect and outdated CSI conditions, the expressions of BER are derived for the OAP scheme. This helps to mitigate the harmful interference which provides the diversity gain for the receivers. The receiver's diversity gain leads to avoiding the effect of noise enhancement. This OAP-based MIMO-VLC system fails to attempt the higher modulation during data transmission. Besides, the performance of the OAP is improved only when the system uses lesser order modulation. [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] [23] developed two filter bank-based multicarrier techniques for MIMO-VLC. The orthogonal multicarrier signals are created by using the frequency translation and pulse shaping with Square Root Raised Cosine (SRRC)filtering in the development of signal design. The Filter Bank Modulation (FBM) technique is designed by considering the signal design scheme. Additionally, one more FBM method is designed by using the spatial indexing that improves the spectral efficiency and data rate. The throughput of this MIMO-VLC system is reduced, when there is an increment in amount of parallel bit streams in the input. [PERSON] and [PERSON] [24] presented the \(4\times 4\) MIMO-based indoor VLC system. The BER of the indoor MIMO-VLC system is analyzed for three multipath reflections such as LOS, LOS plus first reflection, LOS with 1 st and 2 nd reflection. Here, a random NRZ-OOK bit stream is created and it is transformed into a vector that represents the time domain waveform. Subsequently, these data streams are separated into four equal parallel streams that are transferred after performing the convolution with each LED impulse response. The indoor MIMO-VLC system is affected by the ISI, when there is no equalizer in the system design and the received signal's root mean square delay is higher than the symbol duration.