Research On Blockchain-Enabled Dynamic Spectrum Access

The radio spectrum resources are limited and precious.However,under the static and fixed spectrum allocation mechanism,since the spectrum license holders will not always use the spectrum bands for transmission,the spectrum resources are shown to be under-utilized.To this end,dynamic spectrum access(DSA)is proposed to allow the spectrum access from the unlicensed users(secondary users,SUs)on the premise that the licensed users(primary users,PUs)are prioritized.Conventionally,there are two main models in DSA,namely,opportunistic spectrum access(OSA)and secondary spectrum auction.In OSA,the SUs need to first acquire the information of the spectrum bands which are currently not used by the PUs before spectrum access.On the other hand,in secondary spectrum auction,the PUs offer their idle spectrum resources to the SUs through the auction mechanism.There exist several deflects and challenges in DSA.For example,in OSA,there lacks a compulsory record of the spectrum access from the SUs,which impairs the interests and security of the PUs.In addition,in OSA,the SUs can perform cooperative spectrum sensing(CSS)to improve the performance of individual Spectrum Sensing(SS),so as to better capture the spectrum availability and better protect the PUs.In this case,to avoid the interference,the detected idle spectrum resources through CSS should be fairly and orderly allocated.To achieve these,the SUs are required to cooperate with each other.However,there lacks an efficient incentive mechanism for such cooperation.On the other hand,in secondary spectrum auction,the security and the non-repudiation of the auction need to be improved,and the frauds from the SUs or the PUs should be prevented.In recent years,blockchain,as an open,distributed and secure ledger,has been applied to the digital cryptocurrency,the management of the Io T devices and resources.To this end,this paper aims to apply the blockchain to DSA to tackle its aforementioned challenges,so as to more efficiently and securely use the spectrum resources.In this paper,we first discuss the application of blockchain to OSA and secondary spectrum auction.By being compared with the traditional methods,the proposed blockchain-enabled DSA has shown its advantages,and the challenges to implement such applications are also discussed.Then,we propose the blockchain-enabled OSA system and design the strategy for the SUs in such a system,so as to optimize their transmission rate and energy efficiency.On the other hand,since time consumption of blockchain will result in the decrease of the time on spectrum sensing and access,we jointly optimize the sensing time,the block mining time and the spectrum access time,so that to maximize the achievable throughput of the secondary system.Finally,to improve the scalability of blockchainenabled secondary spectrum auction,we propose the hierarchical blockchain architecture.Through discussions,mathematical modeling and simulations,we prove the effectiveness of blockchain to reduce the cost the communication and storage of blockchain.After that,we propose and analyze the profit ratio maximization problem in the hierarchical blockchain-enabled secondary spectrum auction,and then use the deep reinforcement learning to optimize such a problem.