| Ultra reliable low latency communications(URLLC)is one of the three typical application scenarios of the 5th Generation mobile networks,5G),which puts forward very strict requirements for the delay and reliability of the mobile communication system.In the cellular network,the Base Station(BS)and User Equipment(UE)exchange information such as round-trip acknowledgement/non-acknowledgement handshake,automatic re-transmission request,authentication and authentication,etc.,to complete channel allocation,power control and other behaviors.This complex closed-loop control mode leads to signaling storm,which results in huge transmission delay.The technology of Proactive Mobile Network(PMN)breaks the traditional closed-loop communication mode of network(namely centralized control and interaction)and adopts open-loop communication mode and proactive association technology to minimize the air interface latency of the network.Its core is that UE actively associates multiple Access points(APs)to form a virtual cell,and then uses resources in virtual cell without applying to the network side,directly and independently occupies channel transmission;The network side autonomously detects the environment and information in real time,and configures intelligent resources according to the network status and user needs.Although PMN can reduce the air interface latency of wireless communication to the extreme,the lack of closed-loop control process leads to the lack of information such as channel status.This almost blind channel selection method for data transmission inevitably leads to radio resource conflict or serious interference,which significantly reduces network reliability.Proactive multi-association transmission uses spatial diversity and joint decoding technology to improve the probability of successful connection between users and virtual cells and the probability of successful joint decoding,thus significantly improving network reliability.Therefore,based on proactive multi-correlation transmission technology,this paper studies high reliability optimization technology of PMN.The main innovative contributions of this paper are as follows:1)Aiming at the trade-off problem between high reliability and high system capacity in proactive multi-association transmission,an association optimization algorithm of the best AP in virtual cell based on Stackelberg game is proposed.By setting the reliability of the user side as the leader and the capacity of the network side as the follower,the follower maximizes the income of the net utility function according to the decision of the leader until Nash equilibrium is reached.The concave-convex analysis of the net utility function of the network side and the user side is made mathematically,and it is proved that the network based on Stackelberg game has Nash equilibrium solution.The experimental results reveal that the optimal number of AP actively associated by users is 4,and the method based on Stackelberg game can achieve more than 99.999%high reliability while maintaining a large system capacity.2)Further,we consider that the phenomenon of building occlusion and forest occlusion in the actual network will lead to the failure to reach the ideal number of APS in the virtual community,resulting in a sharp decline in the reliability of active multi-association transmission.To address this issue,we propose an active multi-association transmission scheme with Unmanned Aerial Vehicle(UAV)relay and RIS-assisted communication.The mechanism of UAV relay location,transmission block length and the number of RIS reflection units on network reliability is analyzed,and the mathematical formula of active multi-association network reliability is derived.The simulation results show that the reliability of a single RIS-assisted virtual cell can reach 99.999%when the transmission power of RIS is greater than 5dBm.And the network reliability increases with the increase of the number of UAV relays,and the reliability of virtual cell is sensitive to the location of UAV relays. |
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