As a promising implementation model of payment channel network (PCN), payment channel hub (PCH) could achieve high throughput by providing stable off-chain transactions through powerful hubs. However, existing PCH schemes assume hubs preplaced in advance, not considering payment requests' distribution and may affect network scalability, especially network load balancing. In addition, current source routing protocols with PCH allow each sender to make routing decision on his/her own request, which may have a bad effect on performance scalability (e.g., deadlock) for not considering other senders' requests. This paper proposes a novel multi-PCHs solution with high scalability. First, we are the first to study the PCH placement problem and propose optimal/approximation solutions with load balancing for small-scale and large-scale scenarios, by trading off communication costs among participants and turning the original NP-hard problem into a mixed-integer linear programming (MILP) problem solving by supermodular techniques. Then, on global network states and local directly connected clients' requests, a routing protocol is designed for each PCH with a dynamic adjustment strategy on request processing rates, enabling high-performance deadlock-free routing. Extensive experiments show that our work can effectively balance the network load, and improve the performance on throughput by 29.3% on average compared with state-of-the-arts.

翻译：作为支付通道网络（PCN）的一种有前景的实现模式，支付通道枢纽（PCH）通过强大的枢纽节点提供稳定的链下交易，能够实现高吞吐量。然而，现有PCH方案假设枢纽预先部署，未考虑支付请求的分布情况，可能影响网络的可扩展性，尤其是网络负载均衡。此外，当前基于PCH的源路由协议允许每个发送方自主决定其请求的路由，由于未考虑其他发送方的请求，可能对性能可扩展性（如死锁）产生不良影响。本文提出了一种新型的多PCH高可扩展性解决方案。首先，我们首次研究了PCH部署问题，通过权衡参与者间的通信成本，将原NP-hard问题转化为超模技术可求解的混合整数线性规划（MILP）问题，并针对小规模和大规模场景分别提出了最优/近似解以实现负载均衡。随后，基于全局网络状态和本地直接相连客户端的请求，为每个PCH设计了一种路由协议，并结合请求处理速率的动态调整策略，实现了高性能的无死锁路由。大量实验表明，我们的工作能有效均衡网络负载，与现有最优方法相比，吞吐量平均提升29.3%。