Blockchain Consensus Based Unlicensed Spectrum Sharing Strategies In Heterogeneous Wireless Networks

Sharing unlicensed spectrum is considered an important means to increase the capacity and coverage of cellular mobile communication networks.However,cellular networks based on scheduled access may cause continuous congestion in Wi-Fi networks based on carrier sense access,thereby affecting the fairness of cellular networks and Wi-Fi networks in using unlicensed spectrum.Although making cellular networks also adopt carrier sense access can reduce the impact on Wi-Fi network channel access,channel sensing and conflict backoff processes can lead to considerable access delay.Therefore,it is crucial to construct an efficient spectrum sharing collaboration framework and ensure the fairness of cellular network-Wi Fi network in using unlicensed spectrum.The centralized spectrum sharing framework of cellular networks and Wi-Fi networks used in existing research carries the risk of single point failures,and the massive node access demand in future mobile communication networks also imposes an unbearable huge management cost.Although a distributed spectrum sharing framework can effectively alleviate these contradictions,the exchange of collaborative information brings the risk of privacy leakage.Emerging blockchain technology,relying on distributed ledgers,consensus mechanisms,and encryption technology,can ensure the security and privacy protection of transactions in a distributed environment,making it very suitable for implementing fair and reliable collaboration interactions among multiple untrusted entities.Although blockchain technology is considered a powerful tool for implementing distributed spectrum sharing in wireless networks,its application still faces many obstacles.On the one hand,blockchain systems represented by Bitcoin have excessive computational overhead,and the delay of the consensus process and block confirmation may further increase access delay.On the other hand,the consensus capabilities and delay characteristics of chainbased blockchains and Directed Acyclic Graph(DAG)blockchain models are different,making it difficult to choose a single blockchain model to meet the dynamically changing service environment.In response to these problems,this dissertation proposes a spectrum sharing collaboration framework between cellular-Wi-Fi heterogeneous networks using blockchain technology,and designs a spectrum consensus scheme that adapts to different service environment characteristics,thereby using consensus conflicts on the blockchain to replace access conflicts on unlicensed spectrum.The main contributions and innovations of the dissertation can be summarized as follows:1.To solve the interaction problem of distributed spectrum sharing between heterogeneous networks,this dissertation proposes a distributed spectrum sharing framework based on blockchain technology,using the blockchain system to realize information interaction between heterogeneous networks.On this basis,a user privacy protection scheme based on ring signature technology is designed to satisfy the unlinkability between the user’s real identity and the public key,enhancing the privacy protection capability of the framework? a virtual backoff and aligned transmission scheme based on smart contracts is designed to reduce channel access delay,providing a paradigm for subsequent spectrum consensus design.2.To avoid the introduction of a large amount of computational overhead by consensus interaction,this dissertation designs a new lightweight consensus mechanism,which realizes the deep coupling of spectrum sharing optimization problem and distributed consensus,and proves its performance is the same as centralized spectrum sharing using noncooperative game theory? to reduce the impact of consensus delay caused by complex blockchain interactions on throughput,a switching mechanism oriented to spectrum resource demand is designed,realizing the switch between ”contention mode” and ”blockchain mode”,thereby avoiding unnecessary overhead caused by waiting for transaction verification.This dynamic behavior is modeled as an evolutionary game,and the existence and uniqueness of Nash equilibrium are theoretically and simulationally proven.3.To further reduce the impact of consensus delay on access delay,this dissertation proposes a spectrum sharing strategy based on DAG blockchain technology.Different from conventional DAG blockchain systems,in this dissertation,blockchain nodes select blocks based on channel contention conflicts,making the consistent set on the chain equivalent to the conflict-free channel occupancy scheme,realizing the convergence of a single node’s spectrum selection to a global strategy? at the same time,to further reduce access delay,a dynamic block approval mechanism is proposed,allowing the blockchain system to adjust the number of old blocks required for approval of new blocks according to the transaction arrival rate,improving the efficiency of spectrum allocation strategy.4.To solve the problem that consensus delay and consensus efficiency in static blockchain systems are difficult to adapt to different service quality requirements of services,a heterogeneous network spectrum sharing model based on a semi-dynamic dual-layer blockchain system is proposed.By dynamically adjusting the ledger structure and consensus parameters of the blockchain system,the problem that static blockchain systems are difficult to adapt to dynamic,differentiated demands is solved? a mapping relationship between communication delay and block approval delay in the blockchain system is established,coordinating and optimizing the spectrum ratio of wireless blockchain and heterogeneous networks,alleviating the problem of network performance degradation caused by overuse or underuse of spectrum resources by wireless blockchain nodes.