Tong Wang

Bio: Tong Wang is an academic researcher from Changchun University of Science and Technology. The author has contributed to research in topics: Free-space optical communication & Base station. The author has an hindex of 1, co-authored 6 publications receiving 4 citations.

Atmospheric Turbulence Suppression Algorithm Based on APD Adaptive Gain Control for FSO Links of 5G Floating Base Stations

Abstract: The data transmission between 5G floating base stations will be an important application area of the free space optical (FSO) link, but the problem of atmospheric disturbance will directly affect the application effect. An atmospheric turbulence suppression algorithm based on avalanche photodiode adaptive gain control (APDAGC) for the laser transmission terminal was proposed to suppress atmospheric turbulence. The given design mechanism and experimental results demonstrate its function to improve the performance of FSO. When APDAGC is over 1 km FSO, the variance of intensity fluctuation is lowered from 0.046 to 0.009, with the bit error rate reduced from 4.82E-6 to 1E-12. Comparatively, as APDAGC is over 6.5 km FSO, the variance of intensity fluctuation is decreased from 1.767 to 0.376, with the bit error rate varying from 4.6E-2 to 2.4E-4. Moreover, it was used for the first FSO transmission of 5G floating base station signals on an airship platform.

2.5 Gbps free-space optical transmission between two 5G airship floating base stations at a distance of 12 km.

Abstract: We experimentally demonstrated a long-range, large-capacity-featured, airship-based, free-space optical transmission system by using key technologies, such as GPS/INS real-time precision laser pointing, coarse and fine compound high-bandwidth laser tracking, avalanche photodiode detector adaptive control turbulence channel compensation, and the aurora laser fifth-generation (5G) interface protocol, to solve the problems of laser tracking and targeting based on an airship motion platform, high-speed signal transmission under atmospheric channel perturbation, and interface protocol between a wireless laser link and 5G base station signal, respectively. To the best of our knowledge, the first FSO transmission of 5G base station signals between airship platforms with a rate of 2.5 Gbps and a distance of 12 km was realized, and channel turbulence jitter was also recorded for laser links of different altitudes, from 200 to 1000 m, which provides technical and data support for the application of wireless laser links in 5G floating base stations.

Blimp-Borne Laser Communication Technology Based on Space Dynamic Base Station

Abstract: Space dynamic communication base stations are characterized by high mobility, flexible deployment and wide coverage. It has a wide range of needs in the fields of emergency communication, earthquake relief and island communication. To solve the problem of a limited number of users due to the limited bandwidth of space base stations, so we should improve the reliability and efficiency of data transmission between space mobile base stations. According to the characteristics of the airship platform, a blimp-borne laser communication terminal applied to space dynamic base stations is designed to meet the demand for bi-directional transmission of 5G signal laser carriers in space between airships. The experimental results show that the blimp-borne laser communication terminal achieves an overall technical index of capture probability is better than 98%, the average capture time is 5s, the tracking accuracy is better than 6–15 μrad, the communication rate is 2.5 Gbps and BER is 1E-7. In order to realize the real-time evaluation of the performance of laser communication system under the turbulent channel and guide the research of anti-turbulence fading method, a real-time test method of communication channel turbulence characteristics based on the principle of light intensity scintillation is proposed. And the real-time test of turbulence characteristics of airship inclined link and the horizontal link is completed. The research results play a positive role in promoting the development of 5G mobile technology and space optical communication technology.

Design and evaluation of a high-sensitivity digital receiver with the finite impulse response filter algorithm for free-space laser communication

Abstract: We discuss the design of a digital laser communication receiver and its sensitivity test process. Laser communication is especially suitable for long-distance low-power micro–nano satellite links due to its narrow beam width, but the electro-optical noise situation of the micro–nano satellite platform is complicated and bad. Hence, it is necessary to introduce a digital laser communication receiver to flexibly suppress interference and noise to improve communication sensitivity. A digital laser communication receiver based on the avalanche photodiode (APD) is designed. Based on the principle of digital communication error probability, a high-sensitivity APD device is selected, and a digital receiving channel based on field programmable gate array is designed. The finite impulse response, the dynamic threshold, the baseband median, and other filtering algorithms are used to optimize the signal-to-noise ratio and enhance the detection sensitivity. At the same time, an 800-nm laser communication receiver sensitivity test experimental architecture is designed and the detection sensitivity experiment is carried out. The experiment indicates that the APD receiver achieves detection sensitivity at an Mbps rate better than −60 dBm. The digital filtering algorithm provides a filtering signal-to-noise ratio improvement of about 15 dB, which supplies a reference for the receiver design of micro–nano satellite laser communication.

Atmospheric Laser Communication Technology Based on Detector Gain Factor Regulation Control

Abstract: Space laser communication, with its strong anti-jamming capability, high transmission rate and good adaptability, offers hope for the establishment of 5G mobile networks in areas that are not conducive to the erection of cables, such as islands and remote land areas. Turbulent scintillation effect is one of the important factors affecting the performance of laser communication, which can lead to the increase of communication BER and even communication interruption. Based on the working principle of the photoelectric detector in atmospheric turbulence, an optical communication receiving system based on the detector gain factor regulation control is designed, which calculates the scintillation variance according to the received signal in real time, establishes the function conversion relationship between the scintillation variance and the gain factor, realizes the closed-loop regulation control of the detector gain factor, and improves the SNR of the receiving system. A ground-based 13km static laser communication experiment was set up to test the reception performance, and the test results show that the system reduces the communication BER by more than two orders of magnitude and can be kept at 1E-6 under medium to weak turbulence (discriminated by flash variance) at a communication rate of 2.5Gbps. The technology was applied to the test of laser 5G signal transmission between the airship and the ground, and for the first time, the mobile communication (access network) signal transmission with a downlink speed of 1.230Gbps and an uplink speed of 76.4Mbps is realized, which verified the performance of mobile signal transmission between the mobile base station and the fixed station on the ground.

2.5 Gbps free-space optical transmission between two 5G airship floating base stations at a distance of 12 km.

Abstract: We experimentally demonstrated a long-range, large-capacity-featured, airship-based, free-space optical transmission system by using key technologies, such as GPS/INS real-time precision laser pointing, coarse and fine compound high-bandwidth laser tracking, avalanche photodiode detector adaptive control turbulence channel compensation, and the aurora laser fifth-generation (5G) interface protocol, to solve the problems of laser tracking and targeting based on an airship motion platform, high-speed signal transmission under atmospheric channel perturbation, and interface protocol between a wireless laser link and 5G base station signal, respectively. To the best of our knowledge, the first FSO transmission of 5G base station signals between airship platforms with a rate of 2.5 Gbps and a distance of 12 km was realized, and channel turbulence jitter was also recorded for laser links of different altitudes, from 200 to 1000 m, which provides technical and data support for the application of wireless laser links in 5G floating base stations.

A Survey of Hybrid Free Space Optics (FSO) Communication Networks to Achieve 5G Connectivity for Backhauling

Abstract: Increased capacity, higher data rate, decreased latency, and better service quality are examples of the primary objectives or needs that must be catered to in the near future, i.e., fifth-generation (5G) and beyond. To fulfil these needs, cellular network design must be drastically improved. The 5G cellular network design, huge multiple-input multiple-output (MIMO) technology, and device-to-device communication are all highlighted in this comprehensive study. Hence, free-space optics (FSO) is a promising solution to address this field. However, FSO standalone is insufficient during turbulent weather conditions. FSO systems possess some limitations, such as being able to be disturbed by any interference between sender and receiver such as a flying bird and a tree, as it requires line-of-sight (LOS) connectivity. Moreover, it is sensitive to weather conditions; the FSO performance significantly decreases in bad weather conditions such as fog and snow; those factors deteriorate the performance of FSO. This paper conducts a systematic survey on the existing projects in the same area of research such as the hybrid FSO/Radio frequency (RF) communication system by listing each technique used for each model to achieve optimum performance in terms of data rate and Bit Error Rate (BER) to be implemented in 5G networks.

Blimp-Borne Laser Communication Technology Based on Space Dynamic Base Station

Abstract: Space dynamic communication base stations are characterized by high mobility, flexible deployment and wide coverage. It has a wide range of needs in the fields of emergency communication, earthquake relief and island communication. To solve the problem of a limited number of users due to the limited bandwidth of space base stations, so we should improve the reliability and efficiency of data transmission between space mobile base stations. According to the characteristics of the airship platform, a blimp-borne laser communication terminal applied to space dynamic base stations is designed to meet the demand for bi-directional transmission of 5G signal laser carriers in space between airships. The experimental results show that the blimp-borne laser communication terminal achieves an overall technical index of capture probability is better than 98%, the average capture time is 5s, the tracking accuracy is better than 6–15 μrad, the communication rate is 2.5 Gbps and BER is 1E-7. In order to realize the real-time evaluation of the performance of laser communication system under the turbulent channel and guide the research of anti-turbulence fading method, a real-time test method of communication channel turbulence characteristics based on the principle of light intensity scintillation is proposed. And the real-time test of turbulence characteristics of airship inclined link and the horizontal link is completed. The research results play a positive role in promoting the development of 5G mobile technology and space optical communication technology.