The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detect...The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.展开更多
Fast growth of mobile internet and internet-of-things has propelled the concept formation and research on 5G wireless communications systems which are to be standardized around 2020(IMT-2020).There will be diverse app...Fast growth of mobile internet and internet-of-things has propelled the concept formation and research on 5G wireless communications systems which are to be standardized around 2020(IMT-2020).There will be diverse application scenarios expected for 5G networks.Hence,key performance indicators(KPIs) of 5G systems would be very diverse,not just the peak data rate and average/edge spectral efficiency requirements as in previous generations.For each typical scenario,multiple technologies may be used independently or jointly to improve the transmission efficiency,to lower the cost,and to increase the number of connections,etc.Key enabling technologies are discussed which include massive MIMO,ultradense deployment specific techniques,nonorthogonal transmission,high frequency communications,etc.展开更多
In view of the probability dilution problem of the existing quantitative indexes of rendezvous trajectory safety performance using collision probability,this paper proposes a new quantitative index of rendezvous traje...In view of the probability dilution problem of the existing quantitative indexes of rendezvous trajectory safety performance using collision probability,this paper proposes a new quantitative index of rendezvous trajectory safety performance by well combining collision probability with warning threshold.The proposed new index increases monotonously as the position errors of the chaser spacecraft increase,therefore it can effectively overcome the problems of the reduction in the largest performance value and the advancement in the most dangerous time induced by the probability dilution.The proposed new index is applied to the safety design of close range rendezvous missions.The mission’s safety requirements for initial navigation precision and the safe region of initial and final keeping points’positions with a certain navigation precision are analyzed,and several valuable conclusions about the relation between position navigation precision and velocity navigation precision as well as the relation between keeping points’positions and navigation precision are obtained.展开更多
基金supported by National Natural Science Foundation of China under Grand No.61671183
文摘The majority of existing papers about spectrum sensing have the assumption that secondary users(SUs) are stationary. However,mobility is an essential feature of mobile communications networks. In this paper,the detection performance of spectrum sensing by mobile SUs was analyzed. Three performance metrics,i.e.,detection probability,miss detection probability and false alarm probability,were thoroughly investigated. In our analysis,a critical variable was the real-time received primary user signal power by a mobile SU. Its probability distribution and mathematical expectation were analytically derived. Moreover,the three performance metrics in single-node spectrum sensing and multi-node collaborative spectrum sensing systems were also derived. Extensive simulations were performed. The results are consistent with the theoretical analysis. And it is concluded that SU mobility has a significant impact on the detection probability and the miss detection probability,but not on the false alarm probability.
文摘Fast growth of mobile internet and internet-of-things has propelled the concept formation and research on 5G wireless communications systems which are to be standardized around 2020(IMT-2020).There will be diverse application scenarios expected for 5G networks.Hence,key performance indicators(KPIs) of 5G systems would be very diverse,not just the peak data rate and average/edge spectral efficiency requirements as in previous generations.For each typical scenario,multiple technologies may be used independently or jointly to improve the transmission efficiency,to lower the cost,and to increase the number of connections,etc.Key enabling technologies are discussed which include massive MIMO,ultradense deployment specific techniques,nonorthogonal transmission,high frequency communications,etc.
基金supported by the National Natural Science Foundation of China(Grant No.11222215)the National Basic Research Program of China("973" Program)(Grant No.2013CB733100)Hunan Provincial Natural Science Foundation of China(Grant No.13JJ1001)
文摘In view of the probability dilution problem of the existing quantitative indexes of rendezvous trajectory safety performance using collision probability,this paper proposes a new quantitative index of rendezvous trajectory safety performance by well combining collision probability with warning threshold.The proposed new index increases monotonously as the position errors of the chaser spacecraft increase,therefore it can effectively overcome the problems of the reduction in the largest performance value and the advancement in the most dangerous time induced by the probability dilution.The proposed new index is applied to the safety design of close range rendezvous missions.The mission’s safety requirements for initial navigation precision and the safe region of initial and final keeping points’positions with a certain navigation precision are analyzed,and several valuable conclusions about the relation between position navigation precision and velocity navigation precision as well as the relation between keeping points’positions and navigation precision are obtained.
