Bitcoin is undoubtedly a great alternative to today's existing digital payment systems. Even though Bitcoin's scalability has been debated for a long time, we see that it is no longer a concern thanks to its layer-2 solution Lightning Network (LN). LN has been growing non-stop since its creation and enabled fast, cheap, anonymous, censorship-resistant Bitcoin transactions. However, as known, LN nodes need an active Internet connection to operate securely which may not be always possible. For example, in the aftermath of natural disasters or power outages, users may not have Internet access for a while. Thus, in this paper, we propose LNMesh which enables offline LN payments on top of wireless mesh networks. Users of a neighborhood or a community can establish a wireless mesh network to use it as an infrastructure to enable offline LN payments when they do not have any Internet connection. As such, we first present proof-of-concept implementations where we successfully perform offline LN payments utilizing Bluetooth Low Energy and WiFi. For larger networks with more users where users can also move around, channel assignments in the network need to be made strategically and thus, we propose 1) minimum connected dominating set; and 2) uniform spanning tree based channel assignment approaches. Finally, to test these approaches, we implemented a simulator in Python along with the support of BonnMotion mobility tool. We then extensively tested the performance metrics of large-scale realistic offline LN payments on mobile wireless mesh networks. Our simulation results show that, success rates up to %95 are achievable with the proposed channel assignment approaches when channels have enough liquidity.

翻译：比特币无疑是当今现有数字支付系统的绝佳替代方案。尽管比特币的可扩展性长期备受争议，但其第二层解决方案——闪电网络（Lightning Network, LN）已使这一问题不再成为担忧。自诞生以来，闪电网络持续发展，实现了快速、廉价、匿名且抗审查的比特币交易。然而，众所周知，闪电网络节点需要稳定的互联网连接才能安全运行，而这并非始终可行。例如，在自然灾害或停电发生后，用户可能暂时无法访问互联网。因此，本文提出了 LNMesh，它能够在无线 Mesh 网络之上实现离线闪电网络支付。社区或街区的用户可以在无任何互联网连接时，建立无线 Mesh 网络作为基础设施，以支持离线闪电网络支付。为此，我们首先展示了概念验证实现，成功利用低功耗蓝牙（Bluetooth Low Energy）和 WiFi 执行了离线闪电网络支付。对于包含更多用户且用户可移动的大型网络，需要策略性地进行信道分配。因此，我们提出了两种信道分配方法：1）基于最小连通支配集的方法；2）基于均匀生成树的方法。最后，为测试这些方法，我们利用 Python 实现了模拟器，并辅以 BonnMotion 移动性工具。随后，我们对大规模移动无线 Mesh 网络上的现实离线闪电网络支付进行了全面的性能指标测试。模拟结果表明，当信道具备足够流动性时，采用所提出的信道分配方法可实现高达 95% 的成功率。