What is LoRaWAN and how does it differ from raw LoRa?

LoRa (Long Range) is a physical layer modulation technique based on Chirp Spread Spectrum (CSS), developed by Semtech. It defines how bits are encoded onto radio waves in the sub-GHz ISM bands (868 MHz EU, 915 MHz US, 433 MHz Asia). LoRa provides configurable tradeoffs between range, data rate, and power through parameters like Spreading Factor (SF7-SF12), Bandwidth (125/250/500 kHz), and Coding Rate (4/5 to 4/8). A raw LoRa radio is essentially a modem — you can build point-to-point or star links, define your own packet format, and implement custom networking logic. Raw LoRa gives maximum flexibility and is used in proprietary industrial systems, agriculture, and custom sensor networks where you control both endpoints.

LoRaWAN is a MAC layer and network architecture specification maintained by the LoRa Alliance that sits on top of the LoRa PHY. It defines a complete network stack: device classes (A, B, C), packet formats with headers and frame counters, AES-128 encryption (network session key and application session key), Adaptive Data Rate (ADR) to automatically select the best SF/BW for each device, over-the-air activation (OTAA) and activation by personalization (ABP), and a star-of-stars topology where end devices communicate with gateways that forward packets to a centralized Network Server via IP backhaul. The Network Server deduplicates packets received by multiple gateways, manages device sessions, and routes application data to the appropriate Application Server.

The key differences: raw LoRa is peer-to-peer with no network management, no standardized security, and no cloud integration — you build everything yourself. LoRaWAN provides a managed, secure, scalable network with built-in device management, but imposes constraints: Class A devices (the most power-efficient) can only receive downlink data in two short windows immediately after an uplink transmission, limiting bidirectional communication. LoRaWAN also enforces regional duty cycle limits (1% in EU868, frequency hopping in US915) that restrict how often a device can transmit. For an interview, emphasize that LoRa is the radio, LoRaWAN is the network — and that choosing raw LoRa over LoRaWAN makes sense when you need low latency, custom protocols, or cannot deploy gateway infrastructure, while LoRaWAN makes sense when you need to scale to thousands of devices with centralized management and standard security.