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：作为一种有前景的支付通道网络（PCN）实现模型，支付通道枢纽（PCH）可通过强大的枢纽提供稳定的链下交易，从而实现高吞吐量。然而，现有PCH方案假设枢纽被预先部署，未考虑支付请求的分布情况，这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根据自身请求独立做出路由决策，由于未考虑其他发送方的请求，可能对性能可扩展性产生负面影响（例如死锁）。本文提出了一种具有高可扩展性的新型多PCH解决方案。首先，我们首次研究了PCH部署问题，并通过权衡参与者间的通信成本，将原始的NP难问题转化为通过超模技术求解的混合整数线性规划（MILP）问题，提出了面向小规模和大规模场景的负载均衡最优/近似解。然后，基于全局网络状态与本地直接相连客户端的请求，为每个PCH设计了路由协议，并采用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，与现有最优方案相比，吞吐量平均提升29.3%。