在认知超宽带(cognitive ultra-wideband,CUWB)通信系统中,检测与躲避(detection and avoidance,DAA)策略通过感知首要用户(primary user,PU)所处频段,然后用脉冲波形设计等方法来规避所占频段以获得共存通信的效果。提出了一种新的DAA-CUWB共存通信方案,首先设计多尺度的宽带频谱检测算法来感知PU所用频段,粗细尺度结合的检测方式保证频谱的准确检测和较低的复杂度,进而提出基于多通道正交频域编码的脉冲成形设计算法,来避开被PU占据的频段,最大化CUWB的频谱利用率。利用理论分析和仿真测试验证了所提出的DAA算法的特性,并通过性能仿真进一步论证了共存方案的有效性,实验结果表明CUWB和PU都能保证各自系统性能,并最大化地共享了频率资源。
提出一种基于超宽带(ultra wideband,UWB)信号到达时间估计(time of arrival,TOA)/到达角度估计(angle of arrival,AOA)联合估计的无线传感器网络(wireless sensor networks,WSNs)定位方案,只需要一个参考节点就可以实现对其他传感器节点的2D相对定位,并且不需要时钟同步,适合于传感器网络节点的低成本设计需求.利用往返时间(round trip time,RTT)进行TOA估计,给出了基于多径检测的TOA估计算法;利用到达时间差估计(time difference of arrival,TDOA)进行AOA估计,因而无需借助复杂的天线波束赋形技术.同时,分析了定位误差模型对定位性能的影响,并通过IEEE802.15.4a信道下的仿真实验进行了验证,结果表明了所提方案的有效性.
Two-tier heterogeneous networks(HetNets),where the current cellular networks,i.e.,macrocells,are overlapped with a large number of randomly distributed femtocells,can potentially bring significant benefits to spectral utilization and system capacity.The interference management and access control for open and closed femtocells in two-tier HetNets were focused.The contributions consist of two parts.Firstly,in order to reduce the uplink interference caused by MUEs(macrocell user equipments) at closed femtocells,an incentive mechanism to implement interference mitigation was proposed.It encourages femtocells that work with closed-subscriber-group(CSG) to allow the interfering MUEs access in but only via uplink,which can reduce the interference significantly and also benefit the marco-tier.The interference issue was then studied in open-subscriber-group(OSG) femtocells from the perspective of handover and mobility prediction.Inbound handover provides an alternative solution for open femtocells when interference turns up,while this accompanies with PCI(physical cell identity) confusion during inbound handover.To reduce the PCI confusion,a dynamic PCI allocation scheme was proposed,by which the high handin femtocells have the dedicated PCI while the others share the reuse PCIs.A Markov chain based mobility prediction algorithm was designed to decide whether the femtocell status is with high handover requests.Numerical analysis reveals that the UL interference is managed well for the CSG femtocell and the PCI confusion issue is mitigated greatly in OSG femtocell compared to the conventional approaches.
