为了有效利用空间分集对抗多径传播造成的衰落，设计并实现了基于软件无线电平台的分布式天线系统.与传统的方案相比，该系统将各个前端接收到的数据汇聚到另外一台计算机上处理，实现了各个不同的计算机运算量的均衡，适合软件无线电架构.具体而言，以4台计算机与通用软件无线电外设（universal software radio peripheral，USRP）组成的软件无线电平台作为4个不同位置上的内接收机，然后通过交换机与另外一台计算机相连接，该计算机作为外接收机完成译码等操作.此外，利用传输参数信令的空闲比特承载超帧编号，实现内接收机和外接收机之间的同步.该方案实现了内接收机和外接收机的分布式处理，不仅可以实现空间分集，还可以实现运算的均衡，具有较好的实用性与扩展性.在无线场景下的测试结果表明，与单独一台接收机相比，所设计的分布式天线系统能获得一定的分集效果，并改善了系统整体性能.
To utilize the spatial diversity effectively for combating the fading caused by the multipath propagation, a distributed antenna system based on a software-defned radio platform is designed and implemented. Compared with traditional schemes, the system converges the data received by each front-end to another computer, which can equalize the computation load among different computers and is suitable for the software-defned radio architecture. Specifcally, software-defned radio platforms consisting of four computers and universal software radio peripherals (USRP) are used as inner receivers at different positions. In this paper, through a switch, the four inner receivers are connected to an extra computer which is used as an outer receiver for signal decoding and other operations. Besides, superframe number is delivered in the idle bits of transport parameter signaling to achieve the synchronization between inner receivers and outer receiver. The scheme achieves distribution processing of inner receivers and the outer receiver with the capability of realizing the space diversity and the computing balance, accordingly, performing good practicability and expansibility. The test results in the practical wireless scenario show that the distributed antenna system can achieve the spatial diversity and improve the overall performance compared with a single receiver.
[1] Hasna M O, Alouini M S. End-to-end performance of transmission systems with relays over Rayleigh-fading channels[J]. IEEE Transactions on Wireless Communications, 2003, 2(6):1126-1131.
[2] Lozano A, Jindal N. Transmit diversity vs. spatial multiplexing in modern MIMO systems[J]. IEEE Transactions on Wireless Communications, 2010, 9(1):186-197.
[3] 王璟,王燕敏,冯伟,肖立民,周世东. 多小区分布式天线系统高能效协同传输方案[J]. 清华大学学报(自然科学版),2017, 57(1):67-71.Wang J, Wang Y M, Feng W, Xiao L M, Zhou S D. Energy efcient coordinated transmission scheme for multi-cell distributed antenna systems[J]. Journal of Tsinghua University (Science and Technology), 2017, 57(1):67-71. (in Chinese)
[4] Saleh A A M, Rustako A J, Roman R. Distributed antennas for indoor radio communications[J]. IEEE Transactions on Communications, 1987, 35(12):1245-1251.
[5] Zhou S D, Zhao M, Xu X B, Wang J, Yao Y. Distributed wireless communication system:a new architecture for future public wireless access[J]. IEEE Communications Magazine, 2003, 41(3):108-113.
[6] Wang D, Zhao Z, Huang Y, Wei H, Wang X Y, You X H. Large-scale multi-user distributed antenna system for 5G wireless communications[C]//IEEE Proceedings of Vehicular Technology Conference. Boston, USA. 2015:1-5.
[7] Shuo T, Zhao K, Wu H. Wireless communication for heavy haul railway tunnels based on distributed antenna systems[C]//IEEE Proceedings of Vehicular Technology Conference. Nanjing, China. 2016:1-6.
[8] European Telecommunications Standards Institute (ETSI). TR 101190 V1.3.2. Digital video broadcasting (DVB); implementation guidelines for DVB terrestrial services; Transmission aspects[R]. Nice, France:2011.
[9] Ei-Hajjar M, Hanzo L. A survey of digital television broadcast transmission techniques[J].IEEE Communication Survey & Tutorials, 2013, 15(4):1924-1949.
[10] Ladebusch U, Liss C A. Terrestrial DVB (DVB-T):a broadcast technology for stationary portable and mobile use[J]. Proceedings of the IEEE, 2006, 94(1):183-193.
[11] 陈为刚,赵干,李思,杨晋生. 基于USRP的DVB-T接收机实现[J]. 电视技术,2014, 38(9):155-159. Chen W G, Zhao G, Li S, Yang J S. DVB-T receiver implementation based on USRP[J]. Video Engineering, 2014, 38(9):155-159. (in Chinese)
[12] Zheng H, Boyce J. An improved UDP protocol for video transmission over internet-to-wireless networks[J]. IEEE Transactions on Multimedia, 2001, 3(3):356-365.
[13] 吴月敏,陈为刚. 多业务DVB嵌入式接收机的软件实现[J]. 信息技术,2015, 12(1):46-50. Wu Y M, Chen W G. Software implementation of DVB embedded receiver for multi-services[J]. Information Technology, 2015, 12(1):46-50. (in Chinese)
[14] 葛熠,陈为刚. 基于嵌入式USRP的无线通信实现[J]. 电子测量技术,2016, 39(6):167-171. Ge Y, Chen W G. Wireless communication system implementation using embedded USRP[J]. Electronic Measurement Technology, 2016, 39(6):167-171. (in Chinese)
