# Blockchain Interoperability for Future Telecoms
## 5 Research Challenges and Future Directions
### Future Directions  
It is essential to focus on maintaining the three critical aspects of blockchain technology: decentralization, which spreads control across multiple locations or entities by eliminating intermediaries; immutability, which ensures that information cannot be altered once it is added; and transparency, which allows for the clear visibility of transactions. This literature review highlights four additional areas for future research and discusses why they must be focused on:  
* Side-by-Side Architectures: Weaver offers a side-by-side architecture that eliminates intermediaries. Future research on Weaver and similar approaches should be continued by observing future developments in such projects. Any new solutions are also expected to provide a side-by-side architecture to avoid intermediaries and centralized processes. * High-Security-Oriented Approaches: Interoperability solutions risk introducing vulnerabilities when interoperated blockchain networks are combined with restricted access and privacy policies. Weaver's thin integration layer eliminates such mergingand provides an ideal approach for enhancing security. However, any new design approach must be evaluated to determine whether it aligns with the strict access and privacy policy requirements. * Isolated Mainchain: According to [72], there are three main advantages when a maintain is isolated and integrated with a sidechain. A sidechain can be used to store and process use cases with high transaction requirements. It can also provide more space for transaction storage, faster data access, and higher security. The project for the sidechain proposed in [72] was conducted to safeguard customer privacy regarding medical information in the health sector. Such solutions, designed for customer privacy, can also be applicable to telecoms. A popular review paper [82] provided an in-depth analysis of existing sidechain solutions built for permissionless networks and examined four well-known sidechain solutions, including Loom [83]. This review paper can be considered for future sidechain research. According to [84], smart contracts are essential for deploying sidechain solutions. A smart contract-based layer must be developed and deployed if the mainchain requires integration with the sidechain. When further sidechain solutions, such as those in [80; 85], are analyzed, it is evident that they use permissionless or cryptocurrency-based solutions, such as Ethereum, Ardor, or Loom, which lack strict privacy features. This indicates that more research is required on privately permissioned network-based sidechains. The solution in [86] integrates a sidechain with the mainchain using a cross-chain smart contract architecture. Interoperable networks must consider using smart contracts once the interoperability between heterogeneous networks is required. Considering the existing literature, this research area might bring potential advantages, especially for 5G and 6G interoperability, which requires higher performance and security. * Scalable Architectures: As suggested in this study's final approach, scalable architectures such as sidechains require further analysis to determine their potential for contributing to the research space. In [81], the authors presented a sidechain approach for enhanced efficiency and faster transaction processing in 5G use cases. Most sidechain solutions aim to improve the mainchain's performance by minimizing interactions outside the blockchain network. This method is crucial for future research, and the selected requirements must retain the advantages of private blockchain architectures for an ideal interoperability framework. * Performance: This literature review excludes the performance metrics of blockchain interoperability solutions. The proposed solution, Weaver, is constructed using components from Hyperledger Fabric 2.5. The two selected sources for performance appear to meet the general performance expectations for 6G.