OverlapShard: Overlap-based Sharding Mechanism

The sharding-based protocols provide an effective solution on scaling decentralized blockchains. However, the performance of a sharding-based blockchain protocol can be greatly degraded by the existence of cross-shard transactions. This paper proposes an overlap-based sharding mechanism for sharding protocols, OverlapShard, to weaken the adverse impact of cross-shard transactions by mapping each node into multiple actual shards. The virtual shards composed of overlapping nodes can be used to process cross-shard transactions. The results of empirical analysis show that when a transaction contains 2 inputs and 2 outputs, the consensus overheads of OverlapShard account for 25% of that of the nonoverlapping mechanism, and OverlapShard's communication overheads are reduced by about 33.3 %. The evaluation results show that the average communication overhead of OverlapShard is reduced by 63.30%. And the average cross-shard transaction ratio of overlap-based sharding model with 3-layer virtual shard structure is 43.76% lower than that of the non-overlapping sharding model.