基于大气信道的混合FSO/RF系统自动切换的研究
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摘要
本文介绍了自由空间光通信(FSO)和射频通信(RF)的基本理论、研究现状和发展趋势。为了保证自由空间光通信的传输质量,针对大气信道的恶劣环境造成的可靠性下降问题,引入了一种减小FSO传输信号衰减的混合FSO/RF通信系统,并对该系统中两条链路的自动切换性能进行了分析研究,结果表明混合系统的可用性高于单链路。
本文根据最新的ITU-R建议,深入分析大气衰减效应和大气湍流效应对信号传输的影响,尤其是云、雾、雨的散射衰减作用,初步构建混合FSO/RF通信系统信道的物理和数学模型,拟定了自由空间光通信的流程图,并依据该流程图进行性能仿真。该流程的物理意义清楚,形式简单。另外通过对大气衰减信道和湍流信道的分析仿真,模拟出两种信道光斑的差异,得出一个重要的结论:大气衰减信道适合用接收功率来描述,而大气湍流信道适合用接收光斑来描述。
本文在对接收功率与误码率性能分析的基础上,推导出两个具体的链路切换门限值,提出了一种新的切换方案:利用DSP来进行判断处理,通过矩阵切换开关来实现切换功能。另外,将混合FSO/RF系统的性能与前人的实测结果比较,两者基本吻合。
The basic theories, state-of-the-art and development of free space optical (FSO) and radio frequency (RF) communication are introduced in this paper. In order to ensure the transmission quality of FSO, a hybrid FSO/RF system used to decrease the attenuation of FSO transmission signals is presented for the problem of decreasing reliability owing to the severe environment of the atmospheric channel. Then the automatic switchover performance of the two links of the system is analyzed and researched, and the results show that the availability of the hybrid system is better than the single link.
According to the newest recommendation of ITU-R, the effects on signal transmission caused by atmospheric attenuation and turbulence are deeply analyzed, especially clouds, fog and rain scattering. The physical and mathematical model of hybrid FSO/RF system is designed, the flow chart of FSO communication is provided and the link performance is simulated. The physics meaning of the flow chart is clear, and its format is simple. Moreover, by performance simulation of the atmospheric attenuation channel and the turbulence channel, the differences between light spots of two channels are simulated and an important conclusion is concluded that the received power is suitable for describing the atmospheric attenuation channel while the received light spots are suitable for describing the atmospheric turbulence channel.
Based on the performance analysis of the received power and bit error rate (BER), two certain thresholds for link switchover are deduced and a new switchover scheme is put forward. Digital signal processor (DSP) is used for judgment and a matrix on-off is used for implementing switchover. In addition, by comparing the simulation performance with the former experimental results of hybrid FSO/RF system, the results show that they are similar with each other.
本文根据最新的ITU-R建议,深入分析大气衰减效应和大气湍流效应对信号传输的影响,尤其是云、雾、雨的散射衰减作用,初步构建混合FSO/RF通信系统信道的物理和数学模型,拟定了自由空间光通信的流程图,并依据该流程图进行性能仿真。该流程的物理意义清楚,形式简单。另外通过对大气衰减信道和湍流信道的分析仿真,模拟出两种信道光斑的差异,得出一个重要的结论:大气衰减信道适合用接收功率来描述,而大气湍流信道适合用接收光斑来描述。
本文在对接收功率与误码率性能分析的基础上,推导出两个具体的链路切换门限值,提出了一种新的切换方案:利用DSP来进行判断处理,通过矩阵切换开关来实现切换功能。另外,将混合FSO/RF系统的性能与前人的实测结果比较,两者基本吻合。
The basic theories, state-of-the-art and development of free space optical (FSO) and radio frequency (RF) communication are introduced in this paper. In order to ensure the transmission quality of FSO, a hybrid FSO/RF system used to decrease the attenuation of FSO transmission signals is presented for the problem of decreasing reliability owing to the severe environment of the atmospheric channel. Then the automatic switchover performance of the two links of the system is analyzed and researched, and the results show that the availability of the hybrid system is better than the single link.
According to the newest recommendation of ITU-R, the effects on signal transmission caused by atmospheric attenuation and turbulence are deeply analyzed, especially clouds, fog and rain scattering. The physical and mathematical model of hybrid FSO/RF system is designed, the flow chart of FSO communication is provided and the link performance is simulated. The physics meaning of the flow chart is clear, and its format is simple. Moreover, by performance simulation of the atmospheric attenuation channel and the turbulence channel, the differences between light spots of two channels are simulated and an important conclusion is concluded that the received power is suitable for describing the atmospheric attenuation channel while the received light spots are suitable for describing the atmospheric turbulence channel.
Based on the performance analysis of the received power and bit error rate (BER), two certain thresholds for link switchover are deduced and a new switchover scheme is put forward. Digital signal processor (DSP) is used for judgment and a matrix on-off is used for implementing switchover. In addition, by comparing the simulation performance with the former experimental results of hybrid FSO/RF system, the results show that they are similar with each other.
引文
[1] http://www1.pudong-edu.sh.cn/netapp/show.asp?id=6807
[2] 陈如明.全球无线通信发展走势.人民邮电报,2000.3
[3] 苏磊.无线光通信技术及应用[J].光通信技术,2002,26(4):22-25
[4] 毛天棚,胡涛,周东方,胡松.微波降雨衰减计算模型及特性分析[J].信息工程大学学报, 2004.6,5(2):125-127
[5] H. H. Refai, J. J. Sluss, Jr., H. H. Refai and M. Atiquzzaman, “Transporting RF Signals over Free-Space Optical Links”, Free-Space Laser Communication Technologies XVII, Proc.SPIE,5712,pp.46-54,2005
[6] 李珊.FSO——本地接入市场新焦点.世界电信,2001,12:37-40
[7] 张英海,霍泽人,王宏.自由空间光通信的现状与发展趋势.泰尔网,2004.12
[8] http://media.ccidnet.com/media/ciw/1136/c0902.htm
[9] A. Akbulut, H. G. Ilk and F. Ari, "Design, Availability and Reliability Analysis on an Experimental Outdoor FSO/RF Communication System", Proceedings of 2005 7th International Conference on Transparent Optical Networks, Vol.1, pp.403-406, Jul.2005
[10] M. Achour, P. D,“Simulating Atmospheric Free-Space Optical Propagation, Part II: Haze, Fog and Low Clouds Attenuations ” , Optical Wireless Communications V, Proc. SPIE, 4873,pp.1-12, 2002
[11] Recommendation ITU-R P. 1621, “Propagation data required for the design of Earth-space systems operating between 20THz and 375 THz”, 2003
[12] 中国科学院大气物理研究所微波遥感组.中国晴空和云雨大气的微波辐射和传播特性.国防工业出版社,1982
[13] H. Wu,B. Hamzeh,M. Kavehrad,“Availability of Airborne Hybrid FSO/RF Links ”, Digital Wireless Communications VII and Space Communication Technologies, Proc. SPIE, 5819, pp.89-100, 2005
[14] M. Achour, P. D,“Simulating Atmospheric Free-Space Optical Propagation, Part I: Rainfall Attenuation”, Free-Space Laser Communication Technologies XIV, Proc. SPIE,4635, pp.192-201, 2002
[15] 胡晟,艾勇.自由空间光通信中气象因素影响分析[J].光学与光电技术,2003.8,1(3):16-20
[16] I. I. Kim, B. McArthur and E. Korevaar, “Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications”, Optical Wireless Communications III, Proc. SPIE,4214,pp.26-37, 2001
[17] Recommendation ITU-R P.1622,“Prediction methods required for the design of Earth-space systems operating between 20THz and 375THz”, 2003
[18] 许昌武.半导体激光通过大气随机信道的二维实时显示与研究,电子科技大学, 2001
[19] M. Gebhart, E.Leitgeb, S. S. Muhammad, B.Flecker,C.Chlestil. “Measurement of Light attenuation in dense fog conditions for FSO applications”, Atmospheric Optical Modeling Measurement and Simulation, Proc. SPIE,5891,2005
[20] M. A. Naboulsi, H.Sizun and F. de Fornel, “Fog attenuation prediction for optical and infrared waves”, Society of Photo-Optical Instrumentation Engineers, Vol.43, No.2, pp.319-329, Feb. 2004
[21] 徐涛.机场、发射场云层激光反射特性分析,西北工业大学,2005
[22] 中国气象局.《地面气象观测规范》, ISBN :7-5029-3690-4, 气象出版社, 2004
[23] M. S. Salisbury, P. F. McManamon, D. Petrovich, L. J. Barnes and J. Schmoll, “Cloud Penetration Laser Radar Experiments”, IEEE Proceedings on Aerospace Conference, Vol.3,pp.3/1507-3/1512,Mar.2001
[24] 王铮,丁金宏.理论地理学概论.科学出版社,2004
[25] 赵振维.水凝物的电波传播特性与遥感研究.西安电子科技大学,2001
[26] 王丽黎,柯熙政,席晓莉.激光在雨中传输的分析与计算[J].光散射学报, 2005.7,17(2):148-153
[27] J. Lee, P. Yang,A. E. Dessler, B. A. Baum and S. Platnick, “The Influence of Thermodynamic Phase on the Retrieval of Mixed-Phase Cloud Microphysical and Optical Properties in the Visible and Near-Infrared Region”, IEEE Geoscience and remote sensing letters, Vol.3, No.3,pp.287-291,Jul.2006
[28] S.S. Muhammad, P. Kuhldorfer and E. Leitgeb, “Channel Modeling for Terrestrial Free Space Optical Links”, Proceedings of 2005 7th International Conference on Transparent Optical Networks,Vol.1,pp.407-410,Jul.2005
[29] 吕宏强.自由空间光技术及其在宽带接入中的应用[J].电视技术,2003,No.5:89-90
[30] 辛培泉.星载 SAR 系统设计中的雨衰估算[J].现代雷达, 2004.9,26(9):15-19
[31] A. Dissanayake,J. Allnutt,F. Haidara,“A Prediction Model that Combines Rain Attenuation and Other Propagation Impairments along Earth-Satellite Paths”,Online J. Space Comm.,Issue No.2,2002
[32] 何宁,陈名松,敖发良,张德琨.蓝绿激光对潜通信光信道的研究[J].广西科学,2001.11,8(4):253-255,278
[33] L. D. Emiliani, J. Agudelo, E. Gutierrez, J. Restrepo, and C. Fradique-Mendez, “Development of Rain-Attenuation and Rain-Rate Maps for Satellite System Design in the Ku and Ka Bands in Colombia”,IEEE antennas and Propagatio Magazine,Vol.46,No.6,pp.54-68, Dec.2004
[34] I. I. Kim and E. Korevaar, “Availability of Free Space Optics (FSO) and hybrid FSO/RF systems”, Optical Wireless Communications IV,Proc. SPIE,4530, pp.84-95,2001
[35] 张杰,宋成杰,张昌雷,崔一平.大气激光通信影响因素分析及信道建模[J]. 电子器件, 2004.3, 27(1):202-205,216
[36] 邓方林,张翼飞,杨辉.云对激光引信测高性能的影响分析及解决方案[J].激光杂志,2005,26(3):74-76
[37] T. Ho,S. Trisno,A. Desai,J. Llorca,S.D. Milner,C.C. Davis, “Performance and Analysis of Reconfigurable Hybrid FSO/RF Wireless Networks”, Free-Space Laser Communication Technologies XVII,Proc. SPIE,5712,pp.119-130,2005
[38] J. Llorca, A. Desai, E. Baskaran, S. Milner and C. Davis, “OPTIMIZING PERFORMANCE OF HYBRID FSO/RF NETWORKS IN REALISTIC DYNAMIC SCENARIOS", Free-Space Laser Communications V, Proc. SPIE, 5892, 2005
[39] 郑旨良.RF 路由切换矩阵[J].有线电视技术,2003,No.15:92-93
[40] 蒋丽娟,朱道伟.近地实用激光大气通信系统设计[J].光通信技术,2000,24(3):219-222
[41] 万玲玉.气象条件对近地视距光通信链路的影响研究.广西大学,2002
[42] E. Leitgeb, S. S. Muhammad, C. Chlestil, M. Gebbart and U. Birnbacher,“Reliability of FSO Links in Next Generation Optical Networks”, Proceedings of 2005 7th International Conference on Transparent Optical Networks, Vol.1, pp.394-401,Jul.2005
[2] 陈如明.全球无线通信发展走势.人民邮电报,2000.3
[3] 苏磊.无线光通信技术及应用[J].光通信技术,2002,26(4):22-25
[4] 毛天棚,胡涛,周东方,胡松.微波降雨衰减计算模型及特性分析[J].信息工程大学学报, 2004.6,5(2):125-127
[5] H. H. Refai, J. J. Sluss, Jr., H. H. Refai and M. Atiquzzaman, “Transporting RF Signals over Free-Space Optical Links”, Free-Space Laser Communication Technologies XVII, Proc.SPIE,5712,pp.46-54,2005
[6] 李珊.FSO——本地接入市场新焦点.世界电信,2001,12:37-40
[7] 张英海,霍泽人,王宏.自由空间光通信的现状与发展趋势.泰尔网,2004.12
[8] http://media.ccidnet.com/media/ciw/1136/c0902.htm
[9] A. Akbulut, H. G. Ilk and F. Ari, "Design, Availability and Reliability Analysis on an Experimental Outdoor FSO/RF Communication System", Proceedings of 2005 7th International Conference on Transparent Optical Networks, Vol.1, pp.403-406, Jul.2005
[10] M. Achour, P. D,“Simulating Atmospheric Free-Space Optical Propagation, Part II: Haze, Fog and Low Clouds Attenuations ” , Optical Wireless Communications V, Proc. SPIE, 4873,pp.1-12, 2002
[11] Recommendation ITU-R P. 1621, “Propagation data required for the design of Earth-space systems operating between 20THz and 375 THz”, 2003
[12] 中国科学院大气物理研究所微波遥感组.中国晴空和云雨大气的微波辐射和传播特性.国防工业出版社,1982
[13] H. Wu,B. Hamzeh,M. Kavehrad,“Availability of Airborne Hybrid FSO/RF Links ”, Digital Wireless Communications VII and Space Communication Technologies, Proc. SPIE, 5819, pp.89-100, 2005
[14] M. Achour, P. D,“Simulating Atmospheric Free-Space Optical Propagation, Part I: Rainfall Attenuation”, Free-Space Laser Communication Technologies XIV, Proc. SPIE,4635, pp.192-201, 2002
[15] 胡晟,艾勇.自由空间光通信中气象因素影响分析[J].光学与光电技术,2003.8,1(3):16-20
[16] I. I. Kim, B. McArthur and E. Korevaar, “Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications”, Optical Wireless Communications III, Proc. SPIE,4214,pp.26-37, 2001
[17] Recommendation ITU-R P.1622,“Prediction methods required for the design of Earth-space systems operating between 20THz and 375THz”, 2003
[18] 许昌武.半导体激光通过大气随机信道的二维实时显示与研究,电子科技大学, 2001
[19] M. Gebhart, E.Leitgeb, S. S. Muhammad, B.Flecker,C.Chlestil. “Measurement of Light attenuation in dense fog conditions for FSO applications”, Atmospheric Optical Modeling Measurement and Simulation, Proc. SPIE,5891,2005
[20] M. A. Naboulsi, H.Sizun and F. de Fornel, “Fog attenuation prediction for optical and infrared waves”, Society of Photo-Optical Instrumentation Engineers, Vol.43, No.2, pp.319-329, Feb. 2004
[21] 徐涛.机场、发射场云层激光反射特性分析,西北工业大学,2005
[22] 中国气象局.《地面气象观测规范》, ISBN :7-5029-3690-4, 气象出版社, 2004
[23] M. S. Salisbury, P. F. McManamon, D. Petrovich, L. J. Barnes and J. Schmoll, “Cloud Penetration Laser Radar Experiments”, IEEE Proceedings on Aerospace Conference, Vol.3,pp.3/1507-3/1512,Mar.2001
[24] 王铮,丁金宏.理论地理学概论.科学出版社,2004
[25] 赵振维.水凝物的电波传播特性与遥感研究.西安电子科技大学,2001
[26] 王丽黎,柯熙政,席晓莉.激光在雨中传输的分析与计算[J].光散射学报, 2005.7,17(2):148-153
[27] J. Lee, P. Yang,A. E. Dessler, B. A. Baum and S. Platnick, “The Influence of Thermodynamic Phase on the Retrieval of Mixed-Phase Cloud Microphysical and Optical Properties in the Visible and Near-Infrared Region”, IEEE Geoscience and remote sensing letters, Vol.3, No.3,pp.287-291,Jul.2006
[28] S.S. Muhammad, P. Kuhldorfer and E. Leitgeb, “Channel Modeling for Terrestrial Free Space Optical Links”, Proceedings of 2005 7th International Conference on Transparent Optical Networks,Vol.1,pp.407-410,Jul.2005
[29] 吕宏强.自由空间光技术及其在宽带接入中的应用[J].电视技术,2003,No.5:89-90
[30] 辛培泉.星载 SAR 系统设计中的雨衰估算[J].现代雷达, 2004.9,26(9):15-19
[31] A. Dissanayake,J. Allnutt,F. Haidara,“A Prediction Model that Combines Rain Attenuation and Other Propagation Impairments along Earth-Satellite Paths”,Online J. Space Comm.,Issue No.2,2002
[32] 何宁,陈名松,敖发良,张德琨.蓝绿激光对潜通信光信道的研究[J].广西科学,2001.11,8(4):253-255,278
[33] L. D. Emiliani, J. Agudelo, E. Gutierrez, J. Restrepo, and C. Fradique-Mendez, “Development of Rain-Attenuation and Rain-Rate Maps for Satellite System Design in the Ku and Ka Bands in Colombia”,IEEE antennas and Propagatio Magazine,Vol.46,No.6,pp.54-68, Dec.2004
[34] I. I. Kim and E. Korevaar, “Availability of Free Space Optics (FSO) and hybrid FSO/RF systems”, Optical Wireless Communications IV,Proc. SPIE,4530, pp.84-95,2001
[35] 张杰,宋成杰,张昌雷,崔一平.大气激光通信影响因素分析及信道建模[J]. 电子器件, 2004.3, 27(1):202-205,216
[36] 邓方林,张翼飞,杨辉.云对激光引信测高性能的影响分析及解决方案[J].激光杂志,2005,26(3):74-76
[37] T. Ho,S. Trisno,A. Desai,J. Llorca,S.D. Milner,C.C. Davis, “Performance and Analysis of Reconfigurable Hybrid FSO/RF Wireless Networks”, Free-Space Laser Communication Technologies XVII,Proc. SPIE,5712,pp.119-130,2005
[38] J. Llorca, A. Desai, E. Baskaran, S. Milner and C. Davis, “OPTIMIZING PERFORMANCE OF HYBRID FSO/RF NETWORKS IN REALISTIC DYNAMIC SCENARIOS", Free-Space Laser Communications V, Proc. SPIE, 5892, 2005
[39] 郑旨良.RF 路由切换矩阵[J].有线电视技术,2003,No.15:92-93
[40] 蒋丽娟,朱道伟.近地实用激光大气通信系统设计[J].光通信技术,2000,24(3):219-222
[41] 万玲玉.气象条件对近地视距光通信链路的影响研究.广西大学,2002
[42] E. Leitgeb, S. S. Muhammad, C. Chlestil, M. Gebbart and U. Birnbacher,“Reliability of FSO Links in Next Generation Optical Networks”, Proceedings of 2005 7th International Conference on Transparent Optical Networks, Vol.1, pp.394-401,Jul.2005