Research Output
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PublicationMedical healthcare M2M system using the VLC system( 2020-01-08)The RF communication has suffered from the interference and excessive latency issues. It is required a separated setup for transmission and reception of RF waves. To overcome this problem, the VLC system is a chosen technique due to high bandwidth and immunity to interference from electromagnetic sources. In this project, Optisystem Software version 15 has been chosen to study the perfomances of the VLC system in directed LOS. The performance results will be displayed on BER analyser and the simulation that has been done is iterating continuously in order to get the acceptable results. The result indicates that the reading of simulation of 1 user for both bit rate 155Mbps and 622Mbps shows the best result compared to 4 users. Without using any kind of OCDMA system, the number of users will reach the limitations which is not more than 4 users. The number of users influences the performance of the system and the result shows the decrement of BER reading which is lower than 10-9.
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PublicationA novel zero cross correlation code for optical code division multiple access system( 2012)Optical Code Division Multiple Access (OCDMA) techniques have shown outstanding capabilities in sharing multiple users simultaneously in access network. The purpose of this study was to develop a new spectral amplitude coding (SAC) in OCDMA code. In particular, we tried to minimize multiple access interference (MAI), consequently diminish the phase induced intensity noise (PIIN) by using this new code with the main characteristic of zero cross correlation in its property. This code was investigated and analyzed for its performance in the network system. Another aim was to find out the components and parameters used in order to optimize the performance of the code. Finally, the analysis was validated by comparing theoretical studies with the simulation results. The method of combinatorial matrix was applied in developing this zero cross correlation (ZCC) code. By using SAC incoherent OCDMA techniques, we were able to mitigate the PIIN effect in the system performance. The study of system performance methodology in ZCC code was conducted and used to generate the mathematical derivation for the code performance theoretically.The simulation was conducted with optimization of the parameters involved to obtain the best performance in the system. The validation of the theoretical results was confirmed through this simulation analysis. The great contribution of ZCC code was that there was no overlapping of bit ‘1’ among users and absolutely orthogonal for any number of users and weights. The code structure was very flexible especially in changing code parameter such as the number of users and the number of weight. The code demonstrated an excellence in signal security due to the random code structure. Our performance analysis showed ZCC code has a better performance compared to other codes in the same class of SAC. It could also accommodate a higher number of users simultaneously. This system could support 110 users simultaneously with a permissible bit error rate of 10-9. Power required was lower at the photo detector which means the detection system required less power by applying this code. Direct detection technique used in the ZCC coding system reduced the number of filters, thus led to less system cost. The results showed that employing ZCC coding technique achieved higher bit rates up to 10 Gigabits per second compared to other coding techniques. The principal conclusion was that by the invention of the new ZCC code, it contributed to the solution of many issues in OCDMA such as reduction of MAI, increased the number of users accommodated, increased effective power at the detector, higher bit rates being transmitted, enhanced security and reduced the complexity by using a direct detection technique.
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PublicationA study and investigation of small antenna efficiency measurement using reverberation chamber( 2006)Numbers of small antennas were designed and various kind of antennas were tested for measurement. Amplitude fluctuations in signals received over mobile radio channels are typically modeled by Rayleigh distribution. The field statistics in the volume of the enclosure are shown to correspond to the Rayleigh statistics found in properly functioning reverbration chambers when a sufficiently large number of modes are excited. The purpose of this paper is to show that the antenna efficiency can be measured accurately in much faster, easier and cost effectively reverberation chamber using three different antennas (two monopole antennas with attenuator and surface mount resistor, and modified folded monopole patch antenna). It also gives an investigation of the statistical characteristics in Rayleigh communications channels by using reverberation chamber. Scattering parameters taken from the measurement of the antenna radiation efficiency using reverberation chamber is implemented into Rayleigh Probability Density Function (PDF) model and it really shows that they are in good agreement with those of theoritically predicted Rayleigh model.
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PublicationDiscrete multiwavelet critical-sampling transform-based OFDM system over Rayleigh fading channels( 2015)Discrete multiwavelet critical-sampling transform (DMWCST) has been proposed instead of fast Fourier transform (FFT) in the realization of the orthogonal frequency division multiplexing (OFDM) system. The proposed structure further reduces the level of interference and improves the bandwidth efficiency through the elimination of the cyclic prefix due to the good orthogonality and time-frequency localization properties of the multiwavelet transform. The proposed system was simulated using MATLAB to allow various parameters of the system to be varied and tested. The performance of DMWCST-based OFDM (DMWCST-OFDM) was compared with that of the discrete wavelet transform-based OFDM (DWT-OFDM) and the traditional FFT-based OFDM (FFT-OFDM) over flat fading and frequency-selective fading channels. Results obtained indicate that the performance of the proposed DMWCST-OFDM system achieves significant improvement compared to those of DWT-OFDM and FFT-OFDM systems. DMWCST improves the performance of the OFDM system by a factor of 1.5–2.5 dB and 13–15.5 dB compared with the DWT and FFT, respectively. Therefore the proposed system offers higher data rate in wireless mobile communications.
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