Relay Selection And Resource Allocation Of 6G Internet Of Things System Based On Information Freshness

In the era of rapid development of the Internet of Things(Io T),The fifth-generation(5G)mobile communication technology has shown a trend towards large-scale commercial applications.Looking back at the vision of information interaction and connectivity of all things in 5G,“information a finger away,everything in touch” has now turned into “mind-bending,everything at will”.The vision of The sixth-generation(6G)mobile communication technology covers the basic concepts of 5G and proposes higher target requirements.Future communication systems will further develop based on 5G,and 6G Io T technology will surpass current sensor communication to achieve high-speed data transmission for massive Io T devices.In the future 6G Io T system,ensuring the timeliness of delivery status update information is one of the main goals in designing Io T system applications.Considering the freshness of information in the Io T system,this thesis discusses how multi-relay cooperative Io T systems transmit status update information to ensure system freshness,combining relay cooperation technology,Short Packet Communication(SPC),Energy Harvesting(EH)technology,Age of Information(Ao I)theory,and Half-Duplex(HD)and Full-Duplex(FD)relay working modes.The research content of this thesis is specifically focused on the following two points:(1)To address the problem of high information transmission delay caused by limited sensor node energy in traditional relay cooperative Io T systems,this thesis considers a multi-relay cooperative Io T system model with EH and SPC,where relays work in HD decode-and-forward mode,and the system source node and relay nodes need to harvest radio frequency signal energy from dedicated energy stations to ensure the sustainability of information transmission.To make the status update information received by the destination node as fresh as possible,this thesis proposes an earliest partial relay selection scheme and a system node EH scheme,and designs a layered iterative algorithm.This algorithm is a trade-off between the packet length,the number of relay selection and average Ao I on the Source-Relay(S-R)and Relay-Destination(R-D)links.For the HD relay system,firstly,by analyzing the SPC transmission performance,selection combining and Maximal-Ratio Combining technologies are used at the destination node,and the average packet error rate of data packets on the S-R and R-D links is derived.Secondly,combined with the theory of order statistics,the number of packet retransmissions at the system source node and relay nodes are statistically described,and the average Ao I expression of the system is derived based on the update process theory.Finally,the gradient descent method is used to obtain an approximate solution for the average Ao I.The numerical simulation results show that the Maximal-Ratio Combining technology can improve the signal quality received by the destination node and reduce the system’s average Ao I.At the same time,optimizing the number of relay selections and packet length can effectively improve the freshness of system information,verifying the feasibility of the earliest partial relay selection scheme.(2)Considering the freshness issue of information in the multi-relay cooperative Io T system with natural EH,this thesis combines the earliest partial relay selection scheme from the perspective of energy and Ao I trade-off.The average Ao I of FD relaying systems with both Self-Interference and Co-Channel Interference is analyzed.To describe the packet transmission process more intuitively,a new round of packet transmission starts only when the selected FD relay and the destination node both restore to the state before receiving the packet.For the FD relay system,firstly,the average packet error rate is analyzed for different interference conditions on the S-R link by comparing the number of packet retransmissions on the S-R and R-D links.Secondly,the average Ao I of the system in different data transmission stages is discussed,and the total average Ao I of the cooperative Io T system with FD relay is derived.Finally,the numerical simulation analyzes the impact of system parameters on the average Ao I,and by comparing the average Ao I of the HD and FD relay systems,it is demonstrated that the presence of Self-Interference and Co-Channel Interference in the FD system affects the freshness of system state updates.