ID 原文 译文
4763 该方法首先采用平滑伪 Wigner-Ville 分布算法获取跳频信号时频图，并经过二维维纳滤波去除时频图背景噪声，提高低信噪比条件下时频图清晰度； Firstly, the time-frequency diagram of the frequency hopping signal was obtained bysmoothed pseudo Wigner-Ville distribution, and the background noise of the time-frequency diagram was removed bytwo-dimensional Wiener filtering to improve the resolution of the time-frequency diagram under low SNR conditions.
4764 然后采用连通域检测算法提取每跳信号的时频能量谱并将其转化为时频灰度图，计算其直方图统计特征和灰度共生矩阵特征组成 22 维特征向量； Then, the connected-domain detection algorithm was used to extract the time-frequency energy spectrum of each hopsignal and convert it into a time-frequency gray-scale image. The histogram statistical features and the gray-scaleco-occurrence matrix feature were combined to form a 22-dimensional eigenvector.
4765 最后通过参数优化后的支持向量机分类器对特征集进行训练、分类和识别。 Finally, the feature set was trained,classified and identified by optimized support vector machine classifier.
4766 仿真实验表明，所提取的多维特征向量具有较强的表征能力，避免了由单一特征相似性引起的误判问题，在信噪比为−4 dB 的条件下，对跳频信号 BPSK、QPSK、SDPSK、QASK、64QAM 和 GMSK共 6 种调制方式的平均识别正确率达到 91.4%。 Simulation experiments show that the mul-ti-dimensional feature vector extracted by the algorithm has strong representation ability and avoids the misjudgmentcaused by the similarity of single features. The average recognition accuracy of the six modulation methods of frequencyhopping signals BPSK, QPSK, SDPSK, QASK, 64QAM and GMSK is 91.4% under the condition of −4 dB SNR.
4767 针对超密集无线网中的信息泄露和传输覆盖效率问题，提出了基于频率正交时间反演的虚拟覆盖方法。 To solve the problem of information leakage and coverage efficiency in ultra-dense wireless network, the or-thogonal frequency-time reversal virtual coverage scheme was proposed.
4768 首先，以正交子载波区分各信道，降低相关度； At first, different wireless reversal channelswith lower correlation were distinguished by orthogonal carries.
4769 其次，进行时间反演，让各目标信号在目的用户附近空间聚焦； Next, after time reversal, the space focusing of each tar-get signal was realized around the terminal.
4770 然后，研究推导出覆盖范围与信号干扰噪声比理论表达式并进行论证； Then, theoretical expressions of the signal coverage and the sig-nal-interference-to-noise ratio were derived and proved.
4771 最后，在确保用户覆盖需求的基础上，无关用户的覆盖范围缩小，形成了虚拟覆盖。 Ultimately, the virtual coverage was shaped, meeting the re-quirements of users. The coverage of unrelated user not belonging to system was reduced.
4772 仿真表明，在不增加功率和天线情况下，虚拟覆盖增加了接收信号难度，提升了可靠传输的安全速率和系统容量。 The results show that thoseunrelated users are difficult to receive the target signal because of virtual coverage. In addition, the system has higher ca-pacity and security rate of reliable transmission without any more power or antennas.