Scalable Routing in a City-Scale Wi-Fi Network for Disaster Recovery

TL;DR

MapMesh tackles the problem of maintaining intra-city communications during wide-area Internet outages by introducing a scalable, building-map-driven routing approach for a city-scale DFN. The method replaces per-device control messaging with a flat, decentralized mesh that uses a postbox abstraction, conduits, waypoints, and grid-based addressing to route across millions of devices. Key contributions include a building-graph path metric with $w=d^{k}$, a conduit-based forwarding model, hierarchical grid addressing with precomputed routes, and suppression mechanisms that dramatically reduce transmissions while preserving deliverability; simulations across 60 cities show high delivery rates with compact routing state. The work demonstrates that leveraging up-to-date building maps enables resilient, scalable disaster-response networks that operate with modest overhead and without new hardware deployment.

Abstract

In this paper, we present a new city-scale decentralized mesh network system suited for disaster recovery and emergencies. When wide-area connectivity is unavailable or significantly degraded, our system, MapMesh, enables static access points and mobile devices equipped with Wi-Fi in a city to route packets via each other for intra-city connectivity and to/from any nodes that might have Internet access, e.g., via satellite. The chief contribution of our work is a new routing protocol that scales to millions of nodes, a significant improvement over prior work on wireless mesh and mobile ad hoc networks. Our approach uses detailed information about buildings from widely available maps--data that was unavailable at scale over a decade ago, but is widely available now--to compute paths in a scalable way.

Figures (13)

• Figure 1: Impact of transmission range on AP connectivity within a city.
• Figure 2: Converting a transformed map to Building Graph
• Figure 3: "Conduit" that defines the boundary within which devices should rebroadcast a given packet. The conduit, bounded by waypoints, simplifies the route a packet should follow.
• Figure 4: Grid-based addressing and routing table. Addresses are assigned based on buildings' location. Source S stores all (destination building, next waypoint) pairs in the routing table.
• Figure 5: Condensed routing table of source S. We can combine destination entries by specifying a coarser gridID if all destinations in that coarser grid have the same next waypoint.