# Blockchain Interoperability for Future Telecoms
## 3 Literature Review
### Essential Design Requirements  
The blockchain-based interoperability architecture can cover the aforementioned use cases for future 6G telecoms. The essential design requirements for future telecoms are outlined below, based on the existing literature and popular projects:  
* Single Point of Failure: According to [PERSON] et al. [53], intermediaries such as notary schemes and sidechains introduce an SPoF into interoperability designs. In such a design approach, the interoperability of cross-chain communication is not operational when the intermediary goes down. This is a typical SPoF issue, as no alternative or backup solution exists. * Decentralization: This is the most famous feature of blockchain technology. Blockchain promises to eliminate any authority or intermediary that may rule the interoperability process and make decisions when executing transactions. [PERSON] [54] discussed government-owned processes and asked whether such intermediary processes arenecessary. As asserted in [54], blockchain technologies represent a disintermediation process that can remove intermediary state-owned processes. [PERSON] even mentioned the state or governing authorities causing an SPoF, as they cannot necessarily respond to the rapidly changing needs of society and face scalability challenges in delivering services. According to [PERSON] et al. [55], decentralized enterprise models create new opportunities in this context. Similarly, [PERSON] et al. [56] indicated that blockchain cryptocurrencies' existing mining consensus models allow large miners to dominate the mining process. The authors of both studies suggested that centralized architectures or models be eliminated. As discussed in [38], the third frequency range of sixth-generation (6G) communication systems (FR3) requires meticulous channel modeling. This requirement is critical for the effective use and sharing of the available spectrum. If dynamic and agile spectrum sharing is centralized through a process established by a regulatory authority and facilitated by an intermediary application, this centralization may hinder the efficiency of spectrum sharing and introduce delays into the process. * Safety of Access Management and Policies: Every independent permissioned blockchain has specific user-access management rules and policies. The rules, such as consensus mechanisms and executed smart contract-based rules, are particular to the blockchain network. When an interoperability architecture is offered, there is an expected tendency to synchronize and unify both blockchains' access management functions. [PERSON] et al. [57] have proposed a framework that preserves patient privacy in a national health system while using blockchain to manage private patient data access. According to [PERSON] et al., patient data confidentiality must be maintained if external access is required. [PERSON] et al. [6] stated that the user identity and data can be detected when a trusted intermediary is used for interoperability. Therefore, intermediaries should be avoided, and trustless decentralized approaches should be chosen to keep users' identities safe. * Sovereignty: In contrast to these approaches, [PERSON] et al. [58] provided a cross-network identity framework that manages DIDs in an interoperability network. The self-sovereignty of blockchains in a multi-network architecture allows each blockchain to choose which users and groups can access their distributed ledger technologies (DLTs) from other chains and which functions they can execute through cross-chain communications. DIDs provide users with self-sovereignty. However, unified access management and policies for interoperated blockchains can introduce unexpected access leakages. These statements indicate that the user rights, access policies, and data are preserved and isolated. In such cases, DIDs with minimum user extensions can have much more secure and minimally affected interoperability. * Core Blockchain Process Isolation: [PERSON] et al.