Devices with different radios (Zigbee 12 m, Z-Wave 14 m, Wi-Fi 22 m, BLE 8 m) can relay only to the same protocol within range, forming isolated islands. The gateway connects to every device inside its own range and translates between protocols.
route = BFS over same-protocol links (+ gateway links)
latency = sum(hop_ms) + 30 ms per translation
hop_ms: ZB 15, ZW 20, WiFi 5, BLE 25
Messages between random device pairs are routed; delivered share is the interoperability score.