Li Feilong, Li Zhiqiang, Li Guangxia, Dong Feihong, Zhang Wei
College of Communication Engineering, PLA University of Science and Technology, 88 Houbiaoying Rd., Nanjing 210007, China.
Sensors (Basel). 2017 Jan 21;17(1):193. doi: 10.3390/s17010193.
The usable satellite spectrum is becoming scarce due to static spectrum allocation policies. Cognitive radio approaches have already demonstrated their potential towards spectral efficiency for providing more spectrum access opportunities to secondary user (SU) with sufficient protection to licensed primary user (PU). Hence, recent scientific literature has been focused on the tradeoff between spectrum reuse and PU protection within narrowband spectrum sensing (SS) in terrestrial wireless sensing networks. However, those narrowband SS techniques investigated in the context of terrestrial CR may not be applicable for detecting wideband satellite signals. In this paper, we mainly investigate the problem of joint designing sensing time and hard fusion scheme to maximize SU spectral efficiency in the scenario of low earth orbit (LEO) mobile satellite services based on wideband spectrum sensing. Compressed detection model is established to prove that there indeed exists one optimal sensing time achieving maximal spectral efficiency. Moreover, we propose novel wideband cooperative spectrum sensing (CSS) framework where each SU reporting duration can be utilized for its following SU sensing. The sensing performance benefits from the novel CSS framework because the equivalent sensing time is extended by making full use of reporting slot. Furthermore, in respect of time-varying channel, the spatiotemporal CSS (ST-CSS) is presented to attain space and time diversity gain simultaneously under hard decision fusion rule. Computer simulations show that the optimal sensing settings algorithm of joint optimization of sensing time, hard fusion rule and scheduling strategy achieves significant improvement in spectral efficiency. Additionally, the novel ST-CSS scheme performs much higher spectral efficiency than that of general CSS framework.
由于静态频谱分配政策，可用卫星频谱正变得稀缺。认知无线电方法已展现出其在频谱效率方面的潜力，可为次要用户（SU）提供更多频谱接入机会，同时为授权的主要用户（PU）提供充分保护。因此，近期的科学文献聚焦于陆地无线传感网络中窄带频谱感知（SS）内频谱复用与PU保护之间的权衡。然而，在陆地认知无线电背景下研究的那些窄带SS技术可能不适用于检测宽带卫星信号。在本文中，我们主要研究基于宽带频谱感知的低地球轨道（LEO）移动卫星服务场景下，联合设计感知时间和硬融合方案以最大化SU频谱效率的问题。建立压缩检测模型以证明确实存在一个能实现最大频谱效率的最优感知时间。此外，我们提出了新颖的宽带协作频谱感知（CSS）框架，其中每个SU的报告持续时间可用于其后续的SU感知。该新颖的CSS框架提升了感知性能，因为通过充分利用报告时隙延长了等效感知时间。此外，针对时变信道，提出了时空CSS（ST-CSS），以在硬判决融合规则下同时获得空间和时间分集增益。计算机仿真表明，联合优化感知时间、硬融合规则和调度策略的最优感知设置算法在频谱效率方面有显著提升。此外，新颖的ST-CSS方案的频谱效率比一般的CSS框架高得多。
