A Disaster Mesh Communications Budget for a Town Without Grid or Towers: Coverage, Traffic, Power and Price for the First Week

A LoRa-class mesh of solar relay nodes plus household handsets is designed and priced for the first week after a disaster removes grid power and cellular towers from a stated town of 10.0 km by 6.0 km with 7500 households. Link budgets over three terrain classes, hexagonal node spacing and count under a double-coverage requirement, ALOHA delivery probability and latency under a stated coded-message load (welfare checks, clinic requests, water-point status; 11,796 messages per day), and battery/solar sizing through a stated seven-day storm profile are computed in one integrated budget. The design gives 8 relays at 4.64 km spacing, 0.989 end-to-end delivery, 2.57 s mean latency, 43.2 Wh per relay per day, and $42.91 per covered household. Failure regimes are printed at full size: shadowed terrain is out of range at the design rate and is served only by 24 m relays at the slowest rate, and the single-channel relay backhaul falls below 90% delivery above 29,057 messages per day. SIMULATED, NOT MEASURED.