Wavelet Based Cognitive UWB Sensors for Smart Tunnels

拟议的研究项目的目标是加强地铁隧道和地下采矿环境的安全，并使用超宽带(UWB)传感器网络保持列车司机或矿工与控制器之间的不间断数据传输。由于超宽带的频带范围很广，会与其他无线服务(如IEEE 802.11 a)产生相互干扰，因此将开发认知能力来缓解超宽带带宽内的干扰，并提高监测性能。采用频谱感知的认知无线电可以解决频谱紧缺问题，在不对授权用户造成有害干扰的情况下有效利用频谱空洞。认知特性使提出的超宽带传感器网络能够检测干扰信号源，并在基于小波的发射机中避免干扰。该功能使系统能够消除对隧道环境中客户端各种无线服务的干扰；例如，移动设备、PC和Wi-Fi的用户在地铁通勤时可以享受不间断的服务。同样，矿井中的无线通信也受到严重的环境噪声和信道损害的影响。大型矿用机电设备功率大、启动频繁，会产生加性高斯白噪声和脉冲干扰，对超宽带网络造成干扰。提出的UWB网络能够感知隧道环境，决定和缓解干扰用户对数据传输的影响。该项目将小波无线电作为UWB传感器网络的一个组成部分。在多载波调制(MCM)方面，基于小波的MCM可以提供更高的频谱效率，并增强了传统OFDM系统对噪声和固有干扰的鲁棒性。基于小波的隧道UWB信道建模与基于傅里叶变换的方法相比，具有较高的时频局部化程度，减少了信道表示所需系数的数量。针对地下隧道的复杂性，提出了一种协作频谱感知技术来缓解阴影和多径衰落对UWB传感器网络的影响。

The goal of the proposed research project is to enhance the safety of the subway tunnels as well as underground mining environment and to maintain an uninterrupted data transmission between train driver or miners and the controllers using Ultra Wide-Band (UWB) sensor network. Since UWB's wide range of frequency band causes mutual interference with other wireless services such as IEEE 802.11 a, cognitive capabilities will be developed to mitigate the interference within the UWB bandwidth and enhance the monitoring performance. Cognitive radio equipped with spectrum sensing can deal with spectrum scarcity and utilize the spectrum holes without causing harmful interference to the licensed users. Cognitive features enable the proposed UWB sensor network to detect the sources of interfering signals and avoid them in the wavelet based transmitter. Such feature enables the system to eliminate interference with various wireless services of clients in a tunnel environment; e.g. users of mobile devices, PCs and Wi-Fi can enjoy uninterrupted services while commuting in subway. Likewise, wireless communication in underground mines suffer from serious environmental noise and channel impairments. The large mining and electromechanical equipment, with high power and frequent starts, produce additive Gaussian white noise and pulse jamming leading to interference with UWB network. The proposed UWB network can sense the tunnel environment, decides and mitigates the impacts of interfering users on the data transmission. This project incorporates wavelet radio as an integrated part of the UWB sensor network. In terms of multicarrier modulation (MCM), wavelet based MCM can offer more spectrum efficiency and enhance the robustness against noise and inherent interference of conventional OFDM system. Wavelet based UWB channel modeling of tunnels can reduce the number of required coefficients of channel representation with high degree of time-frequency localization compared to the Fourier based method. Due to the complex nature of underground tunnels, cooperative spectrum sensing is proposed to alleviate the effects of shadowing and multipath fading on the UWB sensor network.