Electrical and Electronic Engineering - Research Publications

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    Investigation on repetition-coding and space-time-block-coding for indoor optical wireless communications employing beam shaping based on orbital angular momentum modes
    Li, J ; Yang, Q ; Dai, X ; Lim, C ; Nirmalathas, A (Optica Publishing Group, 2022-06-06)
    In this paper, we propose a novel beam shaping technique based on orbital angular momentum (OAM) modes for indoor optical wireless communications (OWC). Furthermore, we investigate two spatial diversity techniques, namely repetition-coding (RC) and Alamouti-type orthogonal space-time-block-coding (STBC) for indoor OWC employing the new beam shaping technique. The performance of both diversity schemes is systematically analyzed and compared under different beam shaping techniques using different OAM modes with different power ratios of the modes. It is shown that both RC and STBC can improve the system performance and effective coverage and RC outperforms STBC in all the beam shaping techniques regardless of the power ratios of the different modes. In addition, to further understand the performance of RC and STBC schemes against the signal delays induced during OAM mode conversion, the system tolerance of the two schemes to the delay interval is investigated with different OAM mode-based beam shaping techniques. Numerical results show that higher resistance to the delay interval can be achieved in STBC scheme. The advantage is more obvious when employing OAM0 and OAM1 based beam shaping technique.
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    Few-Mode Based Beam Shaping for Multi-User Indoor Optical Wireless Communications With Time-Slot Coding
    Li, J ; Lim, C ; Nirmalathas, A (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-02-01)
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    IoT Device Integration and Payment via an Autonomic Blockchain-Based Service for IoT Device Sharing
    Dawod, A ; Georgakopoulos, D ; Jayaraman, PP ; Nirmalathas, A ; Parampalli, U (MDPI, 2022-02-01)
    The Internet of Things (IoT) incorporates billions of IoT devices (e.g., sensors, cameras, wearables, smart phones, as well as other internet-connected machines in homes, vehicles, and industrial plants), and the number of such connected IoT devices is currently growing rapidly. This paper proposes a novel Autonomic Global IoT Device Discovery and Integration Service (which we refer to as aGIDDI) that permits IoT applications to find IoT devices that are owned and managed by other parties in IoT (which we refer to as IoT device providers), integrate them, and pay for using their data observations. aGIDDI incorporates a suite of interacting sub-services supporting IoT device description, query, integration, payment (via a pay-as-you-go payment model), and access control that utilise a special-purpose blockchain to manage all information needed for IoT applications to find, pay and use the IoT devices they need. The paper describes aGIDDI's novel protocol that allows any IoT application to discover and automatically integrate and pay for IoT devices and their data that are provided by other parties. The paper also presents aGIDDI's architecture and proof-of-concept implementation, as well as an experimental evaluation of the performance and scalability of aGIDDI in variety of IoT device integration and payment scenarios.
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    Intelligent Radio Resource Allocation for Human-Robot Collaboration
    Feng, Y ; Ruan, L ; Nirmalathas, A ; Wong, E (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-01-01)
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    Dynamic scheduling algorithm for LTE uplink with smart-metering traffic
    Amarasekara, B ; Ranaweera, C ; Evans, R ; Nirmalathas, A (WILEY, 2017-10-01)
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    integrated on a CMOS image sensor
    He, X ; Liu, Y ; Beckett, P ; Uddin, H ; Nirmalathas, A ; Unnithan, RR (OPTICAL SOC AMER, 2021-01-15)
    The CMY colour camera is different from the RGB counterpart where the subtractive colours cyan, magenta and yellow are used. The CMY camera performs better than an RGB camera in low light conditions. However, conventional CMY colour filter technology made of pigments and dyes are limited in performance for next generation image sensors with submicron pixel sizes. This is because the conventional CMY filters cannot be fabricated in nanoscale as they use their absorption properties to subtract colours. This paper presents a CMOS compatible nanoscale thick CMY colour mosaic made of Al-TiO2-Al nanorods forming a total number of 0.82 million colour filter pixels with each filter pixel size of 4.4 µm arranged in a CMYM pattern. The colour mosaic was then integrated on a MT9P031 image sensor to make a CMY camera and colour imaging is demonstrated using a 12 colour Macbeth chart. The developed technology will have applications in astronomy, low exposure time imaging in biology, and photography.
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    Secure multiple access for indoor optical wireless communications with time-slot coding and chaotic phase
    Liang, T ; Wang, K ; Lim, C ; Wong, E ; Song, T ; Nirmalathas, A (OPTICAL SOC AMER, 2017-09-04)
    In this paper, we report a novel mechanism to simultaneously provide secure connections for multiple users in indoor optical wireless communication systems by employing the time-slot coding scheme together with chaotic phase sequence. The chaotic phase sequence is generated according to the logistic map and applied to each symbol to secure the transmission. Proof-of-concept experiments are carried out for multiple system capacities based on both 4-QAM and 16-QAM modulation formats, i.e. 1.25 Gb/s, 2 Gb/s and 2.5 Gb/s for 4-QAM, and 2.5 Gb/s, 3.33 Gb/s and 4 Gb/s for 16-QAM. Experimental results show that in all cases the added chaotic phase does not degrade the legitimate user's signal quality while the illegal user cannot detect the signal without the key.
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    Indoor infrared optical wireless localization system with background light power estimation capability
    Wang, K ; Nirmalathas, A ; Lim, C ; Alameh, K ; Li, H ; Skafidas, E (OPTICAL SOC AMER, 2017-09-18)
    The indoor user localization function is in high demand for high-speed wireless communications, navigations and smart-home applications. The optical wireless technology has been used to localize end users in indoor environments. However, its accuracy is typically very limited, due to the ambient light, which is relatively strong. In this paper, a novel high-localization-accuracy optical wireless based indoor localization system, based on the use of the mechanism that estimates background light intensity, is proposed. Both theoretical studies and demonstration experiments are carried out. Experimental results show that the accuracy of the proposed optical wireless indoor localization system is independent on the localization light strength, and that an average localization error as small as 2.5 cm is attained, which is 80% better than the accuracy of previously reported optical wireless indoor localization systems.
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    An Efficient Resource Allocation Mechanism for LTE-GEPON Converged Networks
    Ranaweera, C ; Wong, E ; Lim, C ; Nirmalathas, A ; Jayasundara, C (SPRINGER, 2014-07-01)
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    Compound nanostructure of metallic nanoholes with 1D photonic crystal for multispectral imaging applications
    He, X ; Liu, Y ; Uddin, H ; Nirmalathas, A ; Unnithan, RR (OSA Publishing, 2020)
    This paper demonstrates a single sensor based multispectral spectral imaging camera using a hybrid RGB colour mosaic made of plasmonic and 1D photonic crystal layers.