本项目研究移动通信中FDD信道密钥生成方法，利用FDD信道中上下行传播路径的高度相似性，提取或构建互易的信道特征参数，将之转换为通信双方所需的对称密钥，加解密经过该无线信道的数据，达到保护空口安全传输的目的。该方案具有高安全性及无需密钥分配的优点，更适合大规模移动通信用户的保密通信应用。.本项目结合移动通信中安全密钥分发的需求，建立FDD无线信道多径传输模型，研究FDD信道密钥生成方法。开创性地提出了基于多径分离和频率修正相结合的对称信道参数提取方法，基于多轮传输协议的互易复合信道参数构建方法以及最大化生成速率的优化密钥生成方法。将理论研究与系统实验相结合，构建基于无线信道特性密钥的OFDM FDD点到点保密通信原型系统，形成FDD模式系统中无线信道密钥生成理论体系，取得一些专利成果，为我国未来移动通信原创技术的形成添砖加瓦。

This project focuses on secret key generation from frequency division duplex (FDD) channels for mobile communications. Taking advantage of high similarity between the uplink and downlink wave propagation paths in FDD channels, extract or construct the reciprocal channel parameters from the received signals on both communication sides, and then convert the channel parameters to symmetric keys. The data via the wireless channel are encrypted/decrypted using the symmetric key. Thus the aim to protect the wireless air interface can be achieved. The proposed scheme has the advantage of high security performance and needless of key distribution. It is more appropriate for securing communication for large scale mobile users...Combining the requirement of security key distribution for mobile communications, this project builds up a multipath model of the FDD wireless channel and studys the secret key generation methods based on FDD channels. A novel approach is proposed to extract symmetric channel parameter based on the combination of multipath separation and frequency adjustment. A multiple round transmission protocal is designed to construct reciprocal composite channel parameters. To gain maximal secret key rate, the optimization key generation methods are proposed. This project will also combine the theoretical methods with experiments, and build up an OFDM FDD prototype system for point to point secure communications. It will form the theory of secret key generation from wireless channel in systems using FDD, and will obtain some invention patents. It will make contributions to the formation of Chinese original technology for future mobile communications.