微波通讯链路监测降水和水汽的研究

With the development of wireless communication technology, the fourth generation wireless communication networks have been widely deployed around the world, and the research on the technologies for the fifth generation wireless communication networks has ready begun. There has been significantly increasing recognition that millimeter waves from 30 GHz to 300 GHz as carriers for future 5G cellular networks. This is good for high speed, line-of-sight communication, potentially using very densely deployed infrastructure involving many small cells. High resolution, continuous and accurate monitoring of environmental conditions, such as rainfall and water vapor are of great important to meteorology, hydrology (e.g. flood warning), agriculture, environmental policy (e.g. pollution regulation) and weather forecasting. However, in many parts of the world, the density of surface rainfall and precipitation gauging networks is even rapidly declining. This situation can potentially be counteracted by using the received signal level data from the enormous number of links used worldwide in commercial cellular communication networks. The aim of this project is to study the potential of using millimeter wave based radio links to monitor environmental conditions including rainfall and water vapor. We will build a transmission link modeling at millimeter frequency (25GHz) at our research institute in central Beijing, and the radio signals propagate from the transmitter to a receiver. We will conduct long term measurement to record the received signal strength at different time of the day, different seasons, and in different weather conditions. Rain induced attenuation, and subsequently, rain rate can be retrieved from the signal’s attenuation between transmitter and receiver. We will also evaluate the potential of millimeter wave based transmission link for other meteorological factors, including water vapour, temperature, and air pressure etc. By comparing the results with the data from weather radar and rain gauage, we will analyze the possibility, accuracy, reliability of this method. Another novelty of the project is to incorporate the measurement results into a 3D ray tracing model recently developed by University of Bristol for modeling millimeter wave propagation of all significant spatial and temporal multipath components between a transmitter and receiver. The outcome of the project can potentially improve the accuracy of the 3D ray tracing model to correspond to reality.

密集的，实时的，准确的降水以及水汽等环境监测，对气象，水文，农业，地质，污染，洪涝等自然灾害的监测和预警都有重大的意义。随着第四代通讯网络在世界范围内已经广泛覆盖，第五代无线通讯技术的研究已经开始。近期的研究表明，毫米波无线电频谱将是未来的5G通讯网络重要组成部分。 本项目的创新是将调研一种新的通过未来高密度5G通讯网络将采用的毫米波信号在大气中传播的实验来测量降雨和水汽等天气状况的方法的可行性。 我们将搭建一个模拟未来5G通讯使用的毫米波信号的链路，对接收信号受降雨和水汽密度进行长期观测，并且通过毫米波信号的衰减来反演这些数值。通过和雷达以及雨滴谱仪等的观测数值的差别，从而揭示这种检测方法的准确性和可靠性。本项目的另一个创新是将毫米波信号受天气变化的测量结果首次用于模拟未来5G通讯信道的3D射线跟踪建模中，用于评估气候变化对未来5G毫米波信号和网络的影响。

传统近地面的气象观测网存在的问题是密度不足,气象数据的时空分辨率有待提高，尤其是在农村和地形复杂的地区观测覆盖有限。本项目探索了一种利用无线蜂窝网络中基站与基站之间的毫米波链路来监测降水和水汽等气象要素的新的微波遥感探测技术。第五代通讯网络，智慧城市以及物联网等新兴技术将广泛地使用毫米波的链路用于城市宽带数据传输。随着商用无线通信系统和网络使用频段向毫米波频段扩展，降雨的影响越来越严重，这一影响在通信领域是需要尽量避免并消除的。若将其应用到气象观测和研究中，基于电磁信号的强度因为某些天气条件，特别是雨水而减弱，可以用于观测降雨。本项目通过在北京的外场实验和理论研究展示了利用微波链路（特别是在毫米波频段范围内）测量降水方面的潜力。.项目组和包括以色列特拉维夫大学等多个国际和国内的课题组建立了合作研究的联系。到目前为止，通信链路已经在20 多个国家被证明可以作为雨量计和雷达网络测量近地面降雨方法的有效补充，本课题组也是其中一个团队。在本基金的支持下，我们在北京3年夏天的开展长期外场实验数据(信号频率是25GHz到38GHz),通过数据后期处理和计算，反演获得了降雨强度，与雨滴谱仪实测降雨强度的相关性系数在0.6-0.9之间，有效的验证了毫米波链路在中国用于降雨监测的准确性。此外，项目组基于瑞典的71-86GHz的2017年6月13日到7月 13日一个月份的链路数据，反演获得水汽密度数值并与附近的气象站实测数据进行对比，相关性系数超过0.9。本结果验证了利用毫米波链路，与现有的水汽密度监测方法相比，可以为现有的天气监测网络提供额外的丰富的数据源。.除此之外，项目组在降水反演算法优化上、毫米波MIMO、短距离通信资源优化理论模型、信道编码等方面开展了理论研究。.项目组取得丰富的成果，已接收和发表的标注基金号的成果共24项: 包括11篇SCI、3篇中文核心期刊及普刊2篇；工程索引（EI）文章6篇；已获授权发明专利 2 件，在实审中的专利4项。