Electrical and Electronic Engineering - Research Publications

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http://hdl.handle.net/11343/362

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Start date: 2010 × Author: Lim, Christina ×

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Now showing 1 - 10 of 32
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    Reconfigurable optical crosshaul architecture for 6G radio access networks
    Tao, Y ; Ranaweera, C ; Edirisinghe, S ; Lim, C ; Nirmalathas, A ; Wosinska, L ; Song, T (Optica Publishing Group, 2023-12)
    The radio access network (RAN) architecture is undergoing a significant evolution to support the next-generation mobile networks and their emerging applications. To realize scalable and sustainable deployment and operations, RAN needs to consider the requirements of 6G and beyond wireless technologies such as ultra densification of cells, higher data rates, ubiquitous coverage, and new radio spectrum in the millimeter-wave band. This calls for a careful redesign of every aspect of RAN, including its crosshaul. The crosshaul is an important network segment in future RAN, capable of transporting diverse traffic types with varying stringent requirements within RAN. The crosshaul towards 6G is envisioned to be highly intelligent, reconfigurable, and adaptable to dynamic service requirements and network conditions. To this end, we propose a software defined network (SDN)-enabled reconfigurable optical crosshaul architecture (ROCA) that supports heterogeneous crosshaul transport technologies and dynamic functional splittings. ROCA enables efficient and intelligent control of the crosshaul data plane. The proposed architecture with a set of the next-generation RAN (NG-RAN) transport interfaces is evaluated using network models built on the ns-3 network simulator. Simulation results demonstrate the strengths and weaknesses of different crosshaul interfaces in agreement with the understanding of respective NG-RAN interfaces from the literature, which validates the modeling accuracy. We then demonstrate the reconfigurability of the architecture using a dynamic scenario with different reconfiguration strategies for meeting the user and network demands. The results indicate that ROCA serves as a scalable and flexible foundation for supporting high-capacity delay-stringent RAN that can be used in 6G and beyond wireless technologies.
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    Joint Beam-and-Probabilistic Shaping Scheme Based on Orbital Angular Momentum Mode for Indoor Optical Wireless Communications
    Li, J ; Yang, Q ; Dai, X ; Lim, C ; Nirmalathas, A (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2023-10-15)
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    Investigation on Orbital Angular Momentum Mode-Based Beam Shaping for Indoor Optical Wireless Communications
    Li, J ; Yang, Q ; Dai, X ; Lim, C ; Nirmalathas, A (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-12-15)
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    Evolution of Short-Range Optical Wireless Communications
    Wang, K ; Song, T ; Wang, Y ; Fang, C ; He, J ; Nirmalathas, A ; Lim, C ; Wong, E ; Kandeepan, S (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2023-02-15)
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    Comparison of Adaptive Equalization Methods for Improving Indoor Optical Wireless Communications Employing Few-Mode Based Uniform Beam Shaping
    Li, J ; Lim, C ; Nirmalathas, A (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-06-15)
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    Demonstration of Spatial Modulation Using a Novel Active Transmitter Detection Scheme with Signal Space Diversity in Optical Wireless Communications
    Song, T ; Nirmalathas, A ; Lim, C (MDPI, 2022-11)
    Line-of-sight (LOS) indoor optical wireless communications (OWC) enable a high data rate transmission while potentially suffering from optical channel obstructions. Additional LOS links using diversity techniques can tackle the received signal performance degradation, where channel gains often differ in multiple LOS channels. In this paper, a novel active transmitter detection scheme in spatial modulation (SM) is proposed to be incorporated with signal space diversity (SSD) technique to enable an increased OWC system throughput with an improved bit-error-rate (BER). This transmitter detection scheme is composed of a signal pre-distortion technique at the transmitter and a power-based statistical detection method at the receiver, which can address the problem of power-based transmitter detection in SM using carrierless amplitude and phase modulation waveforms with numerous signal levels. Experimental results show that, with the proposed transmitter detection scheme, SSD can be effectively provided with ~0.61 dB signal-to-noise-ratio (SNR) improvement. Additionally, an improved data rate ~7.5 Gbit/s is expected due to effective transmitter detection in SM. The SSD performances at different constellation rotation angles and under different channel gain distributions are also investigated, respectively. The proposed scheme provides a practical solution to implement power-based SM and thus aids the SSD realization for improving system performance.
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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)
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    Design of an On-Chip Plasmonic Modulator Based on Hybrid Orthogonal Junctions Using Vanadium Dioxide
    Tanyi, GB ; Sun, M ; Lim, C ; Unnithan, RR (MDPI, 2021-10)
    We present the design of a plasmonic modulator based on hybrid orthogonal silver junctions using vanadium dioxide as the modulating material on a silicon-on-insulator. The modulator has an ultra-compact footprint of 1.8 μm × 1 μm with a 100 nm × 100 nm modulating section based on the hybrid orthogonal geometry. The modulator takes advantage of the large change in the refractive index of vanadium dioxide during its phase transition to achieve a high modulation depth of 46.89 dB/μm. The simulated device has potential applications in the development of next generation high frequency photonic modulators for optical communications which require nanometer scale footprints, large modulation depth and small insertion losses.