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A Blockchain Sharding Protocol supporting Dynamic Locality in Mobile Edge Computing

With the proliferation of mobile edge computing (MEC) in 5G networks, there has been growing interest in deploying high performance blockchain sharding protocols over MEC. However, despite numerous blockchain protocols being proposed, most do not consider workload characteristics that exhibit locality and mobility commonly found in MEC environments. We claim that the existing protocols are missing opportunities for performance improvement, e.g., exploiting locality, and have significant performance degradation by not considering dynamically changing locality, e.g., user mobility, resulting in more and more costly cross-shard transactions with remote access in the system. This paper proposes MEC-Chain, a novel blockchain sharding framework that effectively exploits locality and mobility for high performance. MEC-Chain hierarchically organizes sharded local chains, each assigned to state-ownership for locality-aware execution and fine-grained state resharding with the main chain. For exploiting locality, we design a hybrid processing model that allows fast local updates of blockchain state only when its ownership is assigned to the local chain. Otherwise, i.e., the cross-shard transaction is executed and validated against the globally consistent main chain. For handling mobility, we introduce a finegrained state resharding protocol that transfers state ownership dynamically between local chains in a fine-grained way with the help of users. By doing so, our proposal can efficiently handle a common workload that exhibits a high degree of locality that changes gradually over time.