Explain LoRaWAN architecture and its use in IoT.

LoRaWAN is a Low Power Wide Area Network protocol built on LoRa modulation, designed for long-range IoT applications. Architecture: End devices (sensors) communicate with gateways via LoRa. Gateways connect to network server via IP (Ethernet, cellular). Network server manages devices, deduplication, routing. Application server handles business logic. Key features: Range up to 15km rural, 5km urban. Battery life of years on coin cell. Data rate: 0.3-50 kbps (trade-off with range). Star-of-stars topology (all gateways hear all devices). Device classes: Class A (lowest power, uplink-initiated). Class B (scheduled receive windows). Class C (continuous receive, highest power). Security: AES-128 encryption, device and application keys. Use cases: Smart metering, agriculture, asset tracking, environmental monitoring. Limitations: Low data rate, fair-use policies, no real-time capability.