Wi-Fi Modem for Smart Meters

I need a purpose-built Wi-Fi modem that can sit in the field, discover and manage between twenty and thirty of my smart prepaid electric meters at once, then forward their information to a third-party server.

Core requirements
• Meter side: maintain a stable local link to each prepaid electric meter, poll at configurable intervals, queue data when the Wi-Fi link is down, and reconcile immediately after reconnection.
• Network side: connect via standard 2.4 GHz Wi-Fi, authenticate securely (WPA2 minimum), and push three distinct data streams—usage statistics, diagnostics snapshots and real-time alerts—through the API endpoints I will supply.
• Throughput: normal operating load is small, but latency for real-time alerts must stay below two seconds under full meter count.

Deliverables
1. Hardware design: schematic, PCB layout, parts list with lead times.
2. Firmware: well-commented source, build instructions, and flash image.
3. Integration demo: a working prototype proven with at least ten meters, showing data flowing to a test server I host.
4. Documentation: setup guide, API call sequence, and test report validating 20‒30-meter scalability.
5. Full code and all necessary things handover

Acceptance criteria
• Stable operation for 72 hours with thirty meters, zero data loss.
• Secure Wi-Fi reconnection in under ten seconds after dropout.
• All three data categories reach the server and are ACKed.

Feel free to propose the most suitable local meter interface (RS-485, PLC, or other) as long as it meets the above performance targets and keeps BOM costs reasonable.