Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation
Abstract
:1. Introduction
1.1. State of the Art Regarding FFT-OFDM and DWT-OFDM
1.2. Frame Work
2. System Model
2.1. The Transmitter
- 1.
- Firstly, the series input information is separated into N streams (according to N-transmitters), the positions of the LED modules are listed in Table 1. The data stream is converted from the data line to the data array, via a serial-to-parallel (S/P) converter.
- 2.
- The data is mapped to symbols by using quadrature amplitude modulation (QAM). The transmitter utilizes a 64 QAM digital modulation to map the serial bits into the OFDM symbols as N is the LED modules number and while s is the number of the parallel data stream.
- 3.
- Then, Hermitian symmetry (HS) is enforced to produce real values data.
- 4.
- 5.
- Wavelet transform for modulation is performed. As shown in Figure 1, the block named IDWT is a function in the MATLAB toolbox which utilizes Low Pass Filter (LPF) and High Pass Filter (HPF). WT utilizes filters like a vector of approximation coefficient (CA) and a vector of detail coefficients (CD). The signal is divided into sub-bands which are divided into low and high frequencies. OFDM symbol 〖Χ〗_N (i) is converted from parallel to serial. It has a vector YY that may be transposed into CA as represented in Figure 2 which is called approximated coefficients.
- A parallel-to-serial (P/S) operation is performed to obtain the time domain signal.
- Pre-SDE is implemented by normalizing all data streams to ensure that the detected N-data have the same value of SNR. The Pre-SDE concept of an optical DCO-OFDM system is based on the VLC-MIMO N-channel imaging technique. The output optical power and the modulation index for every LED are Popt and ξ, respectively. Pre-SDE is performed by using power allocation matrix A = diag (a1; a2; ⋯⋯; aN) which adjusts all electrical powers modulating data.
2.2. Channel Estimation
2.2.1. White Gaussian Noise Estimation
2.2.2. Non-Imaging LOS Channel Gain
2.2.3. Non-Imaging LOS Channel Matrix
2.3. The Receiver
- An A/D conversion is utilized to convert the analog signals to digital. The 3-dB modulation bandwidth of LED is adjusted as 50 MHz.
2.3.1. Received Wavelet-OFDM Data
2.3.2. Pre-SDE Equations
2.3.3. SNR Estimation
2.3.4. Received Data Estimation
3. Simulation Results and Discussion
3.1. Simulation Parameters
3.2. Simulation Results of Dmey Wavelet-OFDM and Discussion
4. Conclusions
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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N = 1 | (2.5, 2.5, 3) |
N = 2 | (1.5, 2.5, 3) (3.5, 2.5, 3) |
N = 3 | (1.5, 1.5, 3) (3.5, 1.5, 3) (2.5, 3.5, 3) |
N = 4 | (1.5, 1.5, 3) (3.5, 1.5, 3) (1.5, 3.5, 3) (3.5, 3.5, 3) |
Room dimensions (width × length × height) | 5 × 5 × 3 m3 |
Number of LED modules = N | 4 |
Number of receivers = M | 1 |
Receiving plane height | 0.85 m |
Half power semi angle (Ψ1/2) | 60 deg |
LED optical output power (Popt) | 10 W |
Modulation index (ξ) | 0.3 |
Gain of optical filter (μ) | 1 |
Lens gain (η) | 1 |
Active area of PD (APD) | 19.6 mm2 |
Photodiode responsivity (R) | 0.53 A/W |
Background current (Ibg) | 190 μA |
Bandwidth (B) | 50 MHz |
QAM | 64 |
FOV of detector | 150 deg |
Number of carriers (QAM) | 64 |
Number of frames = Number of symbols for each carrier (S) | 1 |
Wavelet used (w) | ‘Dmey’ |
Number of symbols | 1000 |
Number of data | 64 |
Parameters | FFT-OFDM [22] | Present Work DWT-OFDM | ||
---|---|---|---|---|
Common requirements | Number of subcarriers | 64 | 64 | |
Total number OFDM symbols | 1000 | 1000 | ||
Transmitter | Input binary data | 1 × 64,000 | 1 × 64,000 | |
QAM data | 1 × 64,000 | 1 × 64,000 | ||
Parallel data transmitted | 1000 × 64 | 1000 × 64 | ||
Parallel to serial data transmitted | 1 × 64,000 | 1 × 64,000 | ||
Normalized transmitted data | 1 × 64,000 | 1 × 64,000 | ||
Receiver | Normalized received data | 1 × 64,000 | 1 × 64,000 | 1 × 64,000 |
1 × 128,000 | ||||
Serial data received | 1 × 64,000 | 1 × 64,000 | ||
Serial to parallel data received | 64 × 1000 | 64 × 1000 | ||
De-QAM data | 1 × 64,000 | 1 × 64,000 | ||
Output binary data recovery | 1 × 64,000 | 1 × 64,000 |
Comparison Parameters | FFT-OFDM (Ref. [22]) | DWT-OFDM (Present Work) | |
---|---|---|---|
Coverage contour | Diameter of the coverage contour employing only Pre-FDE ImADR (m) | 3.4 (52.6%) | 4 (70%) |
Diameter of the coverage contour employing Pre-SDE after Pre-FDE ImADR (m) | 4.2 | 4.7 | |
Diameter of the coverage contour employing only Pre-FDE ImR (m) | 2 (20%) | 2.3 (25%) | |
Bit rate | 983.6 Mbps | 1.049 Gbps | |
BER (along X direction) | Less than 10−5 | Less than 5 × 10−6 |
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Badawi, W.K.; El-Hossary, M.G.; Aly, M.H. Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation. Symmetry 2021, 13, 270. https://doi.org/10.3390/sym13020270
Badawi WK, El-Hossary MG, Aly MH. Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation. Symmetry. 2021; 13(2):270. https://doi.org/10.3390/sym13020270
Chicago/Turabian StyleBadawi, Waleed K., Marwa G. El-Hossary, and Moustafa H. Aly. 2021. "Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation" Symmetry 13, no. 2: 270. https://doi.org/10.3390/sym13020270