Investigation and Implementation of Dicode Pulse Position Modulation Over Indoor Visible Light Communication System

A visible light communication (VLC) system with green technology is available and enables users to use white LEDs for illumination as well as for high data rate transmission over wireless optical links. In addition, LEDs have advantages of low power consumption, high speed with power efficiency and low cost. Therefore, a great deal of research is considered for indoor VLC, as it offers huge bandwidth whilst using a significant modulation technique. This thesis is concerned with the investigation and implementation of the dicode pulse position modulation (DiPPM) scheme over a VLC link using white LED sources. Novel work is carried out for applying DiPPM over a VLC channel theoretically and experimentally including a comparison with digital PPM (DPPM) in order to examine the system performance. Moreover, a proposal of variable DiPPM (VDiPPM) is presented in this thesis for dimming control. The indoor VLC channel characteristics have been investigated for two propagation prototypes. Two models have been proposed and developed with DiPPM and DPPM being applied over the VLC channel. A computer simulation for the proposed models for both DiPPM and DPPM systems is performed in order to analyse the receiver sensitivity with the effect of intersymbol interference (ISI). Both systems are operating at 100 Mbps and 1 Gbps for a BER of 10-9. An improvement in sensitivity being achieved by the DiPPM compared to the DPPM VLC system. The system performance has been carried out by Mathcad software. The predicted DiPPM receiver sensitivity outperforms DPPM receiver at by -5.55 dBm and -8.24 dBm, at 1 Gbps data rate, and by -5.53 dBm and -8.22 dBm, at 100 Mbps, without and with guard intervals, respectively. In both cases the optical receiver sensitivity is increased when the ISI is ignored. These results based on the received optical power required by each modulation scheme. Further work has been done in mathematical evaluation carried out to calculate the optical receiver sensitivity to verify the comparison between the two systems. The original numerical results show that DiPPM VLC system provides a better sensitivity than a DPPM VLC system at a selected BER of 10-9 when referred to the same preamplifier at wavelength of 650 nm and based on the equivalent input noise current generated by the optical front end receiver. The results show that the predicted sensitivity for DPPM is greater than that of DPPM by about 1 dBm when both systems operating at 100 Mbps and 1 Gbps. Also, it is show that the receiver sensitivity is increased when the ISI is limited. Experimentally, a complete indoor VLC system has been designed and implemented using Quartus II 11.1 software for generating VHDL codes and using FPGA development board (Cyclone IV GX) as main interface real-time transmission unit in this system. The white LEDs chip based transmitter and optical receiver have been constructed and tested. The measurements are performed by using LED white light as an optical transmitter faced to photodiode optical receiver on desk. Due to the LED bandwidth limitation the achieved operating data rate, using high speed LED driver, is 5.5 Mbps at BER of 10-7. The original results for the measurements determined that the average photodiode current produced by using DiPPM and DPPM optical receivers are 8.50 μA and 10.22 μA, respectively. And this in turn indicates that the DiPPM receiver can give a better sensitivity of -17.24 dBm while compared to the DPPM receiver which gives is -16.44 dBm. The original practical results proved the simulation and theoretical results where higher performance is achieved when a DiPPM scheme is used compared to DPPM scheme over an indoor VLC system

Performance of Di-code Pulse Position Modulation Technique in Diffuse Indoor Wireless Optical Communication Systems

The bandwidth of the indoor optical wireless Pulse Position Modulation (PPM) system can be exploited to improve the receiver sensitivity by using Di-code Pulse Position Modulation (Di-PPM) technique. This paper analysis the receiver sensitivity of indoor optical wireless Di-PPM systems, over a slightly dispersive channel, uses a bandwidth-limited PIN-bipolar (PINBJT) optical receiver, zero guard interval and pre-detection filter based on a simple third-order Butterworth filter, that authorizes the receiver to operate over channels with bandwidth as low as 1.2 times the bit rate. The received pulse shape is a convolution between the impulse response of a diffuse optical wireless link in a ceiling bounce model and rectangular waveform, the operating bit-rate chosen is 100Mbit/s. In this paper the performance analysis is extended in order to include the effects of intersymbol interference (ISI) on error probability and some important errors: wrong slot, erasure and false alarm. A mathematical model is then presented showing how the transfer function of the indoor optical wireless Di-PPM receiver can be calculated. Results are obtained and the pulse shape at input of receiver decision device is illustrated by using MathCAD software

MATLAB Simulation for DiPPM over Diffuse Optical Wireless Communications

In this paper computer simulation is presented for dicode pulse position modulation (DiPPM). DiPPM system offers good performance and operates at only twice the original PCM, thus it is very simple to implement in comparison to other PPM modulations. This makes DiPPM an extremely attractive modulation scheme for indoor optical wireless applications. MATLAB/Simulink has become the universal mathematical and modelling tool in most universities and research laboratories around the world. Studying complex models in optical link communications may be simplified by using simulation models so that real and industrial applications can be approached. The DiPPM is implemented over a diffuse optical wireless link using an LED at a wavelength of 1550nm and data rate of 1Gb/s. The data sequence, coded by using DiPPM coder, is convolved with the diffuse optical link then received and decoded by DiPPM coder to get the original data signal. The indoor diffuse channel model which considers additive white Gaussian noise (AWGN) model as more appropriate for significant background light has been simulated and bit error rate (BER) has been calculated

Optimum reed solomon code using with dicode pulse position modulation system

Dicode Pulse Position Modulation (DiPPM) has been proposed as a more advantageous format than digital PPM with one of its main advantages being that the line rate is twice that of the original data rate, a significant reduction in speed compared to digital PPM. This paper describes the performance of a DiPPM system using a Reed Solomon (RS) code to enhance the sensitivity. Theoretical results are presented at an original data rate of 1Gbit/s, in terms of transmission efficiency, bandwidth expansion, and number of photons per pulse. According to simulation results the Reed Solomon error correction coded system offers an improvement over uncoded DiPPM of 5.12dB, when operating at the optimum code rate of approximately 3/4 and a codeword length of 25 symbols

Improving error performance of dicode pulse position modulation system using forward error correction codes

Dicode pulse position modulation (DiPPM) has been considered as a solution for the bandwidth consumption issue that other existing pulse position modulation (PPM) formats suffer from. This is because it has a line rate that is twice that of the original data rate. This paper considers for the first time forward error correction (FEC) Reed Solomon (RS) codes to improve the error performance of a DiPPM. The results show that the error performance in the system can be improved by using FEC code when the RS is working at its optimum parameters. The error performance of the uncoded DiPPM system has been compared with a RS coded DiPPM system and one using maximum likelihood sequence detector (MLSD) in terms of the number of photons per pulse, transmission efficiency, and bandwidth expansion. The DiPPM with RS code offers superior performance compared to the uncoded DiPPM and DiPPM using MLSD, requiring only 4.5 × 103 photons per pulse, when operating at a bandwidth equal or above to 0.9 times the original data rate. This is with an optimum code rate of approximately ¾, and a codeword length of 25

VLC system performance using Dicode Pulse Position Modulation over an indoor diffuse link

Dicode Pulse Position Modulation (DiPPM) has been proposed as an alternative modulation scheme to digital PPM over optical fibre channels. This paper, for the first time, analyses the receiver sensitivity of the DiPPM system on a diffuse indoor Visible Light Communication (VLC). The system operates at a bit rate of 1Gbit/s and λ = 0.65 μm. A mathematical model of the VLC using DiPPM is presented. The results show the degradation in sensitivity as normalized delay spreads increase. It is shown that with a typical delay spread of 5 ns, the DiPPM system can achieve a sensitivity of -36.47 dBm and -37.5 dBm for the error rates of 10-9 and 10-6, respectively. This represents a sensitivity improvement over a comparable digital PPM system by 3.47 dB and 3.5 dB

Cyber Defense in the 5+5 area : prospect for cooperation / João Assis Barbas ... [et al.]

Estudo académico realizado no âmbito da iniciativa 5+5, destacando as perspetivas de cooperação em termos de defesa do ciberespaço. Três eixos ou tópicos principais foram identificados e abordados: análise do ambiente cibernético, ameaças e riscos cibernéticos e gestão de questões relevantes no ciberespaço. O relatório apresenta conclusões de cada eixo e um capítulo com a síntese de recomendações no âmbito da cooperação 5+5.info:eu-repo/semantics/publishedVersio