| Since 2020,the fifth-generation mobile communication systems(5G)achieve large-scale commercial deployment worldwide.To meet the network requirements of unlimited connectivity,green low carbon,and high reliability in 2030 and beyond,academia,industry,and governments are now engaged in research and development of the sixth-generation mobile communication systems(6G).6G will support the 100 billion-scale intelligent connection of all things,and will generate massive amounts of wireless data.A large number of new applications require the network to be comprehensively improved in terms of peak rate,latency,mobility,and positioning capabilities.The complexity of resource allocation and scheduling is extremely high,and the security and privacy of users’ personal information are threatened in more aspects.The introduction of blockchain technology into 6G ensures the privacy and security of users,reduces infrastructure and maintenance costs,thereby realizing the organic combination of mobile communication and blockchain technology.However,the introduction of blockchain technology will bring problems such as limited computing and storage resources,poor scalability,and high cost of communication services to mobile communication systems.To alleviate the above-mentioned problems,this thesis cooperates with mathematical methods such as game theory and optimization,and conducts in-depth research on the theory and key technologies of edge computing-based mobile blockchains.Firstly,for blockchain-enabled Internet of Things(IoT)systems,we propose the computation offloading method in untrusted mobile edge computing(MEC)-aided mobile blockchains,which solves the issue on the trust of the MEC server.An untrusted MEC proof of work(PoW)scheme is initially proposed where plenty of nonce hash computing demands can be offloaded to the MEC server.Then,we design a nonce ordering algorithm for this untrusted MEC PoW scheme to provide fairer computing resource allocation.By using the non-cooperative game and repeated game,we analyze that the nonce selection strategy of individual users and the cooperation behavior is unsuitable for blockchain-enabled IoT devices.Subsequently,the blockchain’s difficulty adjustment mechanism is designed to ensure stable block times during a long period of time.The simulation results show that compared with the traditional weighted round-robin algorithm,our proposed nonce ordering algorithm can provide fairer computation resources for all users.Additionally,for delay-limited mobile blockchain systems,we propose the MEC-assisted computation offloading model and algorithm,which reduces communication costs and maintains stable block times.First,three computation offloading models are introduced,namely the local computation model,the full computation offloading model,and the hybrid computation offloading model.We also derive the individual delay and revenue of mining a new block under these three models,respectively.Considering the PoW consensus mechanism,we formulate the delay-limited computation offloading strategy as a non-cooperative game,where revenues of the individual user are maximized.The non-cooperative game problem can be divided into multiple sub-game optimization problems to obtain final solutions for all users.Moreover,we design an alternating iterative algorithm based on the continuous relaxation and greedy rounding to achieve the Nash equilibrium(NE)of this game.Based on the above offloading strategies,we also derive the optimal transmit power for an individual user within the maximum mining delay range.The simulation results confirm the effectiveness of the proposed algorithm,and compared with other algorithms,the proposed algorithm can achieve a reasonable balance in terms of offloading,revenue,and delay.Subsequently,for resource-constrained IoT devices,we elaborate the blockchain storage and computation offloading architecture for collaborative edge computing,which relieves the computing and storage pressure of IoT devices.To enable more IoT devices for participating in the PoW mining process of public blockchains,a cooperative MEC-aided blockchain network is first proposed,in which IoT devices can offload computation-intensive PoW mining tasks to base stations and store their block data to the cloud service provider.Then,we formulate the joint computation offloading,block storage,and resource service pricing problem as a three-stage Stackelberg game.We analyze the sub-game optimization problem in each stage and propose an iterative algorithm based on backward induction to achieve the NE of the Stackelberg game.Furthermore,we derive the upper bound of the ergodic throughput of the cooperative scheme and the maximum number of IoT devices connected to the network.The experimental results verify that proposed cooperative MEC-aided blockchain network can significantly improve the system throughput and serve more IoT devices in comparison with other non-cooperative schemes.Finally,for heterogeneous cellular systems,we propose blockchain storage,computation offloading,and user association architecture,which solves the problem of poor quality of wireless links.Specifically,a blockchain-enabled heterogeneous cellular network is first introduced,in which IoT devices store block data to the cloud service provider,offload the PoW mining tasks to base stations,and associate with the macro-cell base station or small-cell base stations.Then,we discuss the user association problem,computation offloading problem,and block storage problem.We also design corresponding algorithms to solve these problems.Furthermore,in view of the phenomenon of data congestion at base stations,based on the obtained computation offloading and block storage strategies,we propose a modified user association algorithm.The numerical simulation results reveal the effectiveness of our proposed algorithms for computation offloading and block storage,and the proposed modified user association algorithm has a significantly great advantage compared with the traditional nearest base station association algorithm in terms of avoiding data congestion. |
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