Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diod...Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diodes （LEDs） are used in Li-Fi as visible light transmitters, therefore, only intensity modulated direct detected modulation techniques can be achieved. Single carrier modulation techniques are straightforward to be used in Li-Fi, however, computationally complex equalization processes are required in fre- quency selective Li-Fi channels. On the other hand, multiearrier modulation techniques offer a viable solution for Li-Fi in terms of power, spectral and computational efficiency. In particular, orthogonal frequency division multiplexing （OFDM） based modulation techniques offer a practical solution for Li-Fi, especially when direct current （DC） wander, and adaptive bit and power loading techniques are considered. Li-Fi modulation techniques need to also satisfy illumination requirements. Flickering avoidance and dimming control are considered in the variant modulation techniques presented. This paper surveys the suitable modulation techniques for Li-Fi including those which explore time, frequency and colour domains.展开更多
Li-Fi, or known as light fidelity, is a new technology that could alleviate some network congestion for the ever-increasing internet of things (IOT). The patent for Li-Fi was created by German physicist Harald Haas in...Li-Fi, or known as light fidelity, is a new technology that could alleviate some network congestion for the ever-increasing internet of things (IOT). The patent for Li-Fi was created by German physicist Harald Haas in 2011 around visible light communication. The purpose of the following research includes the capabilities of Li-Fi Technologies and how the implementation of a Li-Fi network can improve network infrastructure. A main point is to highlight the advantages that Li-Fi technology brings to the table in comparison to traditional Wi-Fi networks like the increased bandwidth frequency, faster transmission speeds, as well as not being affected by network latency due to high traffic. Benefits that Li-Fi technologies provide to network infrastructure include the use of less energy, the need for fewer components to operate, as well as the simplicity of only needing a light source to provide high-speed internet traffic. Some of our research shows the implementation of these systems and how they can provide different benefits to different types of needs of the consumer. The research gave a complete idea about hybrid indoor systems based on Li-Fi and Wi-Fi that indicates how Li-Fi technology raises the possibilities to fulfill the technological demand in the future. Also, the part explained the security concerns of Li-Fi technology and we can consider this technology secure by updating some system protocols. At present day, Li-Fi lacks the infrastructure that Wi-Fi has, which makes replacement unideal. Rather, Li-Fi can be seen as complementary to Wi-Fi and used to improve current technology.展开更多
The fidelity of light with arbitrary polarizations stored in a warm STRb atomic vapor at different storage time is studied. The exponential decay of regeneration efficiency with the storage time is observed and a dete...The fidelity of light with arbitrary polarizations stored in a warm STRb atomic vapor at different storage time is studied. The exponential decay of regeneration efficiency with the storage time is observed and a detectable signal at 300-us storage time is still existed. The storage fidelity at different storage time is well maintained in our experiment.展开更多
基金support by the UK Engineering and Physical Sciences Research Council(EPSRC)under Grants EP/K008757/1 and EP/M506515/1
文摘Modulation techniques for light fidelity （Li-Fi） are reviewed in this paper. Li-Fi is the fully networked solution for nmltiple users that combines communication and illumination simultaneously. Light emitting diodes （LEDs） are used in Li-Fi as visible light transmitters, therefore, only intensity modulated direct detected modulation techniques can be achieved. Single carrier modulation techniques are straightforward to be used in Li-Fi, however, computationally complex equalization processes are required in fre- quency selective Li-Fi channels. On the other hand, multiearrier modulation techniques offer a viable solution for Li-Fi in terms of power, spectral and computational efficiency. In particular, orthogonal frequency division multiplexing （OFDM） based modulation techniques offer a practical solution for Li-Fi, especially when direct current （DC） wander, and adaptive bit and power loading techniques are considered. Li-Fi modulation techniques need to also satisfy illumination requirements. Flickering avoidance and dimming control are considered in the variant modulation techniques presented. This paper surveys the suitable modulation techniques for Li-Fi including those which explore time, frequency and colour domains.
文摘Li-Fi, or known as light fidelity, is a new technology that could alleviate some network congestion for the ever-increasing internet of things (IOT). The patent for Li-Fi was created by German physicist Harald Haas in 2011 around visible light communication. The purpose of the following research includes the capabilities of Li-Fi Technologies and how the implementation of a Li-Fi network can improve network infrastructure. A main point is to highlight the advantages that Li-Fi technology brings to the table in comparison to traditional Wi-Fi networks like the increased bandwidth frequency, faster transmission speeds, as well as not being affected by network latency due to high traffic. Benefits that Li-Fi technologies provide to network infrastructure include the use of less energy, the need for fewer components to operate, as well as the simplicity of only needing a light source to provide high-speed internet traffic. Some of our research shows the implementation of these systems and how they can provide different benefits to different types of needs of the consumer. The research gave a complete idea about hybrid indoor systems based on Li-Fi and Wi-Fi that indicates how Li-Fi technology raises the possibilities to fulfill the technological demand in the future. Also, the part explained the security concerns of Li-Fi technology and we can consider this technology secure by updating some system protocols. At present day, Li-Fi lacks the infrastructure that Wi-Fi has, which makes replacement unideal. Rather, Li-Fi can be seen as complementary to Wi-Fi and used to improve current technology.
基金supported by the National Natural Science Foundation of China(No.10834007)the Key Program of the Chinese Academy of Sciences(No. KJCX2-SW-T12)
文摘The fidelity of light with arbitrary polarizations stored in a warm STRb atomic vapor at different storage time is studied. The exponential decay of regeneration efficiency with the storage time is observed and a detectable signal at 300-us storage time is still existed. The storage fidelity at different storage time is well maintained in our experiment.
