面向2G/3G/4G/WLAN融合接入应用的光载无线分布式天线

、2.3 GHz的LTE-FDD 64QAM信号和2.412 GHz的WLAN 802.11g 64QAM信号。

CO：中心局
CWDM：粗波分复用
LD：直调激光器
RAU：远端天线单元
PD：光电探测器
VSA：矢量信号分析器
VSG：矢量信号发生器
图11 基于SCM-CWDM技术的ROF-DAS性能测试原理图

图12给出了测得的每种业务传输的误差向量幅度(EVM)值，包括使用SCM技术和未使用SCM技术的情况。由图12可以看出，上、下行链路的性能之间没有明显差别，同时四种业务的EVM曲线是相似的。在射频输入功率较低时，随着功率的增加，EVM性能得到提高，当功率增加到一定值是，由于非线性的引入，EVM性能会随着功率的增加而恶化。在4 dBm的输入功率，802.11g 64QAM、LTE-FDD 64QAM、WCDMA和EDGE实现了最好的EVM值，分别是0.75%、0.9%、1.1%和0.5%，符合无线标准的相关规定。表明基于SCM-WDM技术的光载无线分布式天线网络能够实现多制式无线业务上下行链路的高性能传输。

(a)802.11g 64QAM
(b)LTE-FDD 64QAM
(c)WCDMA
(d)EDGE
EVM：误差向量幅度
QAM：正交幅度调制
SCM：副载波复用
图12 实验测得的EVM值

5 结束语

本文主要介绍了低成本、高性能、宽带光载无线系统的几项关键技术：低成本、宽带的光收发模块电路设计与研制，链路中光损耗和受激布里渊散射效应对信号传输性能的分析。针对面向2G/3G/4G/WLAN四网融合接入的应用需求，本文提出了副载波复用结合波分复用的技术，实现了多制式无线业务点到多点的分布式混合传输。为光载无线分布式天线系统的广泛应用提供了有力的支撑和推动。

6 参考文献

[1] 王少波, 冯传奋, 付宏志, 等. GSM/TD与WLAN网络深度融合方案研究[J]. 电信工程技术与标准化, 2011(2):32-35.
[2] Seeds a j, Williams k j. Microwave Photonics [J].Journal of Lightwave Technology, 2006, 24(12): 4628-4641.
[3] Tavik G C, Hilterbrick c l, Evins J B,et al. The advanced multifunction RF concept [J]. IEEE Transactions on Microwave Theory and Techniques, 2005,53(3-2): 1009-1020.
[4] Sauer M, Kobyakov a. Low-cost radio-over-fiber links [C]//Proceedings of the 20th Annual Meeting of the IEEE Lasersand Electro-optics Society (LEOS’07), Oct 21-25, 2007, Lake Buena Vista,FL,USA.Piscataway, NJ,USA: IEEE, 2007:333-334.
[5] SUN Xiaoqiang, XU Kun, SHEN Xi, et al. New hierarchical architecture for ubiquitous wireless sensing and access with improved coverage using CWDM-ROF links [J]. IEEE/OSA Journal Optical Communications Networking, 2011,3(10): 790-796.
[6] Zhang Xiupu, Liu Baozhu, Yao jianping, et al. A novel millimeter-wave-band radio-over-fiber system with dense wavelength-division multiplexing bus architecture [J]. IEEE Transactions on Microwave Theory and Techniques, 2006, 54(8): 929-937.
[7]Le Bras h, Moignard m, Charbonnier b. Brillouin scattering in radio over fiber transmission [C]//Proceedings of the Optical Fiber Communication Conference& Exposition Optical Fiber Communication Conference (OFC’07), Mar 25-29, 2007, Anaheim, CA,USA. Piscataway, NJ,USA: IEEE, 2007:3p.
[8] SUNXiaoqiang, XU Kun, PEI Yinqing, et al. Characterization of SBS gain and loss spectra using  Fresnel reflections and interaction of two sidebands [C]//Proceedings of the Optical Fiber Communication/National Fiber Optic Engineers Conference(OFC/NFOEC’10),Mar 21-25, 2010, San Diego,CA,USA. Piscataway, NJ,USA: IEEE, 2010:3p.
[9]Attar a, Li h, Leung v C M.Applications of fiber-connected distributed antenna systems in broadband wireless access [C]//Proceedings of the International Conference on Computing, Networking and Communications(ICNC’12), Jan 30- Feb 2, 2012, Maui, HI,USA.Piscataway, NJ,USA: IEEE, 2012:623-627.
[10]Morant m, Quinlan t, Llorente r, et al. Full standard triple-play bi-directional and fullduplex CWDM transmission in passive optical networks [C]//Proceedings of the Optical Fiber Communication/National Fiber Optic Engineers Conference (OFC/NFOEC’11), Mar 6-11, 2011,Los Angeles, CA,USA.Piscataway, NJ,USA: IEEE, 2011:3p.

作者：徐