认知无线电对时分OFDMA主用户系统上下行链路方向的识别

When coexisting with dual-link primary systems, secondary systems in cognitive radios should first distinguish between the pri-mary downlinks and uplinks in order to effici-ently explore their respective spectrum oppor-tunities. Because of the assumptive prior knowledge about the time-frequency lo-cations of primary downlinks and uplinks, this procedure is usually not considered in the design of cognitive radios. In this paper, a cooperative method is proposed for the downlink/uplink identification of time-div-ision duplex-based orthogonal frequency-div-ision multiple access systems. In this method, the power level of the primary link is extracted as the key feature, which also contributes to the subsequent cognitive behaviours. The eff-ects of the primary and secondary systems and the effects of the detection parameters on the identification accuracy are all analysed in detail. The simulation results show that the proposed method can identify the primary links precisely and quickly with low complex-ity.     

车联网关键技术及连通性研究

根据车联网的发展趋势,基于车联网的系统模型和关键技术,着重分析了车联网的连通性,具体研究了在车间通信中传输范围和可达邻接节点对连通性的影响。     

认知无线电系统对TD-LTE主用户系统上下行配置类型的识别

当与时分双工主用户系统共存时,认知无线电系统首先需要识别主用户系统在时间尺度上的传输方向,以便在不同链路上分别设计与执行后续的认知过程,从而优化认知系统的性能。在目前的研究中,均假设认知系统已先验已知主用户系统上下行链路在时间上的交替规律。在普适的认知场景下,该假设并不实际。该文依据双工通信系统上下行发射功率的差异,提出对TD-LTE主用户系统在时间尺度上传输方向的识别算法;基于此初步识别结果,进一步提出对TD-LTE系统上下行配置类型的识别算法。该方法无需主次系统之间的信息交互,实现简单。仿真表明,通过数个次级用户观察10个左右的TD-LTE帧,即可对其上下行配置类型达到95%以上的识别精度。