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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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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ItemNetwork Energy Consumption Assessment of Conventional Mobile Services and Over-the-Top Instant Messaging Applications(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016-12)The rapid growth in the energy consumption of mobile networks has become a major concern for mobile operators. Today’s mobile networks’ usage is dominated by over-the-top (OTT) applications and operators are keen to determine the network energy consumed by these OTT applications. With a recent shift in user behavior towards a preference for instant messaging (IM) applications over conventional mobile services, operators are interested in exploring what impact OTT IM applications such as WeChat will have on the energy consumption of a network when compared to a corresponding conventional mobile service. Here, we present for the first time energy assessment models for mobile services based on real network and service measurements to address this need. Using WeChat as an OTT IM application example, our results show that WeChat consumes more network energy than conventional mobile services for both light users and heavy text users due to the network signaling energy overhead. In comparison, for heavy voice users, WeChat consumes less network energy since voice messages are first recorded and then sent in packet bursts. Our findings provide a quantitative analysis of the energy consumption of mobile services, which should be valuable for mobile operators and OTT application developers to improve the energy-efficiency of mobile applications and services.
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ItemTelecommunications energy and greenhouse gas emissions management for future network growth(ELSEVIER SCI LTD, 2016-03-15)A key aspect of greener network deployment is how to achieve sustainable growth of a telecommunications network, both in terms of operational and embodied energy. Hence, in this paper we investigate how the overall energy consumption and greenhouse gas emissions of a fast growing telecommunications network can be minimized. Due to the complexities in modeling the embodied energy of networks, this aspect of energy consumption has received limited attention by network operators. Here, we present the first model to evaluate the interdependencies of the four main contributing factors in managing the sustainable growth of a telecommunications network: (i) the network’s operational energy consumption; (ii) the embodied energy of network equipment; (iii) network traffic growth; and (iv) the expected energy efficiency improvements in both the operational and embodied phases. Using Monte Carlo techniques with real network data, our results demonstrate that under the current trends in overall energy efficiency improvements the network embodied energy will account for over 40% of the total network energy in 2025 compared to 20% in 2015. Further, we find that the optimum equipment replacement cycle, which will result in the lowest total network life cycle energy, is directly dependent on the technological progress in energy efficiency improvements of both operational and embodied phases. Our model and analysis highlight the need for a comprehensive approach to better understand the interactions between network growth, technological progress, equipment replacement lifetime, energy consumption, and the resulting carbon footprint.
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