Electrical and Electronic Engineering - Research Publications
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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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ItemNo Preview AvailableIndoor infrared optical wireless localization system with background light power estimation capability(Optica Publishing Group, 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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ItemAn Efficient Resource Allocation Mechanism for LTE-GEPON Converged Networks(SPRINGER, 2014-07)
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ItemMAC protocol for indoor optical wireless networks(Institution of Engineering and Technology, 2019-11-03)Optical wireless communication has emerged as a promising candidate for future high data rate indoor applications such as virtual reality. Even though physical layer of optical wireless networks has rapidly developed during last decade, upper layer architecture that harness the physical layer capabilities has not yet been developed in the same pace. To this end, the authors develop a novel contention-based medium access control (MAC) protocol that accompanies a service differentiation mechanism and a dynamic contention window tuning algorithm. The proposed service differentiation mechanism can identify the diverse traffic types and facilitate their throughput and delay requirements. To add more robustness to the contention-based MAC protocol which depends on contention windows to avoid collisions, the authors also propose an algorithm that dynamically changes the contention window sizes to suit the congestion level. They analyse the performance of the proposed MAC protocol under diverse network configurations and they show that it is far more effective to use end-user network metrics such as throughput in dynamic adaptation algorithms in addition to collision rate due to the wide range of traffic types present in the network. The proposed results demonstrate that the proposed MAC protocol can handle next-generation traffic types and their stringent latency requirements in an effective manner.
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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.
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Item5G C-RAN With Optical Fronthaul: An Analysis From a Deployment Perspective(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2018-06-01)
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ItemAn unusual case of implantable cardioverter-defibrillator inhibition(AUSTRALASIAN MED PUBL CO LTD, 2015-04-06)
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ItemNo Preview AvailableDigitized RF over fiber systems(OSA, 2014-01-01)
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ItemNo Preview AvailableExperimental demonstration of free-space based 120 Gb/s reconfigurable card-to-card optical interconnects(OPTICAL SOC AMER, 2014-10-01)In this Letter, we propose and experimentally demonstrate a free-space based reconfigurable card-to-card optical interconnect architecture with 16-carrierless-amplitude-phase modulation. Experimental results show that up to 120 Gb/s (3×40 Gb/s) flexible interconnection can be achieved for up to 30 cm distance with a worst-case receiver sensitivity of -9.70 dBm.
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ItemDigitized RF-over-fiber technique as an efficient solution for wideband wireless OFDM delivery(Optica Publishing Group, 2012-05-24)