Scalable video coding(SVC)has been widely used in video-on-demand(VOD)service,to efficiently satisfy users’different video quality requirements and dynamically adjust video stream to timevariant wireless channels.Und...Scalable video coding(SVC)has been widely used in video-on-demand(VOD)service,to efficiently satisfy users’different video quality requirements and dynamically adjust video stream to timevariant wireless channels.Under the 5G network structure,we consider a cooperative caching scheme inside each cluster with SVC to economically utilize the limited caching storage.A novel multi-agent deep reinforcement learning(MADRL)framework is proposed to jointly optimize the video access delay and users’satisfaction,where an aggregation node is introduced helping individual agents to achieve global observations and overall system rewards.Moreover,to cope with the large action space caused by the large number of videos and users,a dimension decomposition method is embedded into the neural network in each agent,which greatly reduce the computational complexity and memory cost of the reinforcement learning.Experimental results show that:1)the proposed value-decomposed dimensional network(VDDN)algorithm achieves an obvious performance gain versus the traditional MADRL;2)the proposed VDDN algorithm can handle an extremely large action space and quickly converge with a low computational complexity.展开更多
Covert communication aims to prevent the warden from detecting the presence of communications,i.e.with a negligible detection probability.When the distance between the transmitter and the legitimate receiver is large,...Covert communication aims to prevent the warden from detecting the presence of communications,i.e.with a negligible detection probability.When the distance between the transmitter and the legitimate receiver is large,large transmission power is needed,which in turn increases the detection probability.Relay is an effective technique to tackle this problem,and various relaying strategies have been proposed for long-distance covert communication in these years.In this article,we first offer a tutorial on the relaying strategies utilized in covert transmission.With the emergence of reflecting intelligent surface and its application in covert communications,we propose a hybrid relay-reflecting intelligent surface(HR-RIS)-assisted strategy to further enhance the performance of covert communications,which simultaneously improves the signal strength received at the legitimate receiver and degrades that at the warden relying on optimizing both the phase and the amplitude of the HR-RIS elements.The numerical results show that the proposed HR-RIS-assisted strategy significantly outperforms the conventional RIS-aided strategy in terms of covert rate.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.61801119。
文摘Scalable video coding(SVC)has been widely used in video-on-demand(VOD)service,to efficiently satisfy users’different video quality requirements and dynamically adjust video stream to timevariant wireless channels.Under the 5G network structure,we consider a cooperative caching scheme inside each cluster with SVC to economically utilize the limited caching storage.A novel multi-agent deep reinforcement learning(MADRL)framework is proposed to jointly optimize the video access delay and users’satisfaction,where an aggregation node is introduced helping individual agents to achieve global observations and overall system rewards.Moreover,to cope with the large action space caused by the large number of videos and users,a dimension decomposition method is embedded into the neural network in each agent,which greatly reduce the computational complexity and memory cost of the reinforcement learning.Experimental results show that:1)the proposed value-decomposed dimensional network(VDDN)algorithm achieves an obvious performance gain versus the traditional MADRL;2)the proposed VDDN algorithm can handle an extremely large action space and quickly converge with a low computational complexity.
基金supported in part by the National Natural Science Foundation of China(Nos.62001116,62271150,62171134,U22A2002 and 62071234)the Natural Science Foundation of Fujian Province under Grant(Nos.2020J05106 and2022J01081)+1 种基金the Major Science and Technology plan of Hainan Province under Grant ZDKJ2021022the Scientific Research Fund Project of Hainan University under Grant KYQD(ZR)-21008
文摘Covert communication aims to prevent the warden from detecting the presence of communications,i.e.with a negligible detection probability.When the distance between the transmitter and the legitimate receiver is large,large transmission power is needed,which in turn increases the detection probability.Relay is an effective technique to tackle this problem,and various relaying strategies have been proposed for long-distance covert communication in these years.In this article,we first offer a tutorial on the relaying strategies utilized in covert transmission.With the emergence of reflecting intelligent surface and its application in covert communications,we propose a hybrid relay-reflecting intelligent surface(HR-RIS)-assisted strategy to further enhance the performance of covert communications,which simultaneously improves the signal strength received at the legitimate receiver and degrades that at the warden relying on optimizing both the phase and the amplitude of the HR-RIS elements.The numerical results show that the proposed HR-RIS-assisted strategy significantly outperforms the conventional RIS-aided strategy in terms of covert rate.
