# Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation
## 3 Simulation Results and Discussion
### Simulation Parameters
Since the spatial positions of the channels vary, they are uneven. This affects the channel overall behavior, and consequently the system BER. Figure 8: Bit Error Rate (BER) performances along width-direction (X) and length Y = 1.5 m of (**a**) N = 1, (**b**) N = 2, (**c**) N = 3, and (**d**) N = 4. Lastly, the DWT communication contour at \(10^{-3}\) BER target for N = 1, 2, 3, and 4 is calculated, for the N- channel imaging VLC-MIMO technique. The coverage with Pre-FDE ImADR is larger than that of the Pre-FDE ImR as shown in Figure 9. For N = 1, as shown in Figure 9a, the coverage is almost identical for both Pre-FDE individually and for Pre-SDE after Pre-FDE ImR. In addition, for ImADR, it is identical for both Pre-FDE individually and for Pre-SDE after Pre-FDE. For N = 2 and 3, the contour coverage is increased, performing the Pre-FDE after Pre-SDE ImADR coverage is greater than that of the Pre-FDE after Pre-SDE ImR coverage. The ImADR coverage for N = 4 for Pre-FDE individually or before Pre-SDE is like a circle. We can calculate the coverage area by calculating the areas of the circles. The diameters for Pre-FDE individually or before Pre-SDE ImADR are 4 and 4.7 m, respectively, and for ImR are 2.3 and 3 m, respectively. The coverage along the direction of X is increased while it has no difference along the direction of Y. This is because the SNR of channel 1 is almost the same as channel 2. The SNR for all numbers of LED modules is the same whenever Pre-SDE is applied with Pre-FDE ImADR. Furthermore, X is the width, as well as, Y is the length of the room, respectively, as shown in Table 2. Coverage always increases and improvement achieved when Pre-SDE is applied with Pre  
used the Pre-FDE under FFT-OFDM conditions for all number of LED modules. For N = 4, the coverage contour is improved by 70% when replacing the FFT-OFDM by DWT-OFDM over the system which uses the Pre-FDE only. Following this, the coverage contour is improved by 17.4% when replacing the FFT-OFDM by DWT-OFDM at a target \(10^{-3}\) BER over the system which uses Pre-SDE after Pre-FDE for N = 4, at which the improvement remains the same when N = 1. The improvement is changed with a different number of LED modules. This makes the average percentage of the improvement of the 4- LED modules equals 20% over the system which uses Pre-SDE after Pre-FDE. According to the simulation that has been performed in Ref. [22] to the conventional OFDM, Table 3 shows the matrix-valued comparison between conventional-OFDM and our suggested wavelet-OFDM system whenever the hybrid space-frequency domain pre-equalization scheme is used. The results show that the received data of wavelet-OFDM is doubled. This is because of the use of two filters. For DWT-OFDM, it is required to double FFT-OFDM data. This is because the wavelet transmitter might have zero-padding components. The main disadvantage of FFT-OFDM is that the adding of CP by 6.25% of its data which does not contain any useful information and is just used to avoid the ISI and ICI [22]. The DWT inherently avoids the ISI and ICI. In the FFT-OFDM simulation, the IFFT/FFT size was 256 [22]. Table 3 indicates that the simulation parameters comparison between FFT-OFDM [22] and DWT-OFDM seem to be similar except in the parameter of the normalized received data of wavelet-OFDM which is doubled. The reason for this is the use of two filters in proposed system which is based on DWT-OFDM. For DWT-OFDM, it is required to double FFT-OFDM data, because the DWT-OFDM transmitter might have zero-padding components. Hence, this is the reason to duplicate the normalized received data parameter in the proposed system compared to other systems based on FFT-OFDM. The system modulation bandwidth (BW) is 50 MHz. So, the AWG sampling rate for the system equals (1/BW) = 200 \(\times\)\(10^{6}\) samples/sec. The bit rate for the overall system