Electrical and Electronic Engineering - Research Publications
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ItemNo Preview AvailableReconfigurable optical crosshaul architecture for 6G radio access networks(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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ItemNo Preview AvailableEvolution of Short-Range Optical Wireless Communications(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2023-02-15)
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ItemDemonstration of Spatial Modulation Using a Novel Active Transmitter Detection Scheme with Signal Space Diversity in Optical Wireless Communications(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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ItemNo Preview AvailableSecure multiple access for indoor optical wireless communications with time-slot coding and chaotic phase(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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ItemGigabit/s Optical Wireless Access and Indoor Networks(OSA - Optical Society of America, 2020)Optical wireless networks are being explored as a wireless alternative for provision of multi gigabits/second wireless and this paper presents an overview of recent progress and outstanding challenges. and technologies.
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ItemPerformance Analysis of Repetition-Coding and Space-Time-Block-Coding as Transmitter Diversity Schemes for Indoor Optical Wireless Communications(Institute of Electrical and Electronics Engineers (IEEE), 2019-10-15)The benefits of 2 × 1 multiple-inputs-single-output scheme for transmitter diversity in the infrared indoor optical wireless communication link are theoretically investigated. The performance of repetition-coding (RC) and Alamouti-type real-valued space-time-block-coding (STBC) as effective transmitter diversity schemes is systematically compared under conditions of channel gain variation caused by the degradation in the received optical power due to the blocking of one optical beam of the optical wireless channel. It is shown that the linear addition of channel gains in the RC scheme outperforms the root-sum-square of channel gains in the STBC scheme with regards to the bit-error-rate (BER) performance. Proof-of-concept experiments are carried out with both schemes under emulated scenarios of channel blockage. The RC scheme exhibits better BER performance when observed experimentally, validating the proposed theoretical model for the two spatial diversity schemes. To understand the performance of RC and STBC schemes against the optical delay caused by the two optical channel path difference within one-bit interval, both schemes are experimentally investigated using on-off-keying modulation, and results show that RC still outperforms STBC. Both theoretical and experimental results indicate that RC has better robustness to channel blockage and differential channel paths induced optical delay.