Table 2.

A comparative analysis of blockchain-based 6G services.

	Author	Year	6G Application	Objective	Implication of Blockchain	Methodology	Remarks
Network slicing	Abdulqadder et al. [39]	2022	NFV and SDN	Context-aware authentication handover.	The proposed scheme tackle security, QoS guarantee, and improper resource utilization challenges through network slicing and load balancing.	Generative adversarial network and DAG-blockchain.	Not focused on the privacy threats of the 6G.
	He et al. [40]	2021	NFV and SDN	Multi domain network slicing.	Offers end-to-end network slice orchestration services and privacy-preserving scheme for private network.	CoNet consensus algorithm.	The scheme does not consider time complexity for multiparty computation.
	Chen et al. [41]	2020	IoT	Optical network slices for user.	To provide user’s data security and trust.	Blockchain-based optical network slicing approach.	Does not consider other performance evaluation parameters such as throughput, scalability.
Spectrum sharing	Liu et al. [48]	2021	IoT, cloud	Radio spectrum resource sharing -tructure in eURLLC.	Integrate blockchain with hybrid cloud to register and manage the information of IoT devices.	Reinforcement learning.	Does not discuss energy efficiency.
	Zhang et al. [49]	2021	IoT	To manage a large-scale IoT network with heterogeneous devices.	DAG-blockchain for user-autonomy spectrum sharing.	A dynamic tip selection and swarm intelligence method.	Focused on the unlicensed bands.
	Manogaran Manogaran et al. [50]	2020	MTC	Secure reliable service delegation in 6G.	Incorporates blockchain with security measure that provide access control, security, and privacy-preserving for the resources and the users.	Q-learning.	The proposed scheme focused on the virtual resource sharing.
Data sharing	Khowaja et al. [51]	2022	VSN	Efficient and secure data sharing.	The scheme proposed Hyperledger Fabric for data-sharing security.	Stacked autoencoders and density-based clustering method.	The presented scheme is not able to handle broadcasting security issues.
	Zhang et al. [52]	2021	FL	State-channel-based distributed data sharing for sandbox.	They proposed permissioned blockchain with FL for data sharing.	Fine-grained data access control model.	Does not take time complexity and computation overhead.
	Li et al. [53]	2020	VANET	Distributed data storage for vehicles and fine-grained access for VANET data.	They integrated blockchain with ciphertext-based attribute encryption.	HECP-ABE algorithm.	Does not consider data security in term of level of anonymity and stateless access.
Resource management	Li et al. [58]	2022	MEC and IoT	Intelligent resource allocation.	They incorporate practical Byzantine fault tolerance protocol for the data privacy.	Collective reinforcement learning.	Does not consider the user’s privacy and task offloading scenario when the user is outside of the covered area.
	Jain et al. [59]	2021	IoE	Optimal resource allocation.	Introduced blockchain for system’s monitoring, assuring safety, managing, and sharing resources effectively.	Metaheuristic with blockchain.	The proposed scheme does not talk about the computation overhead of the system.
	Yang et al. [60]	2020	MEC and IIoT	To optimize the IIoT device’s energy allocation.	They combined blockchain with MEC to solve the joint optimization problem.	Deep Q-learning.	They do not focus on the network access scenario when large-scale devices are connected.