What are the main IoT wireless technologies?

LPWAN (Low Power Wide Area Network) technologies dominate long-range IoT: LoRa/LoRaWAN operates in unlicensed sub-GHz bands (868 MHz EU, 915 MHz US). Uses CSS (chirp spread spectrum) modulation with spreading factors SF7 to SF12. SF12 achieves minus 137 dBm sensitivity at 250 bps. Range: 5 to 15 km rural, 2 to 5 km urban. Power: 25 mA TX, 1.5 microamp sleep. Battery life: 10 plus years on AA. NB-IoT operates in licensed cellular bands using 180 kHz bandwidth (one LTE resource block). Achieves minus 164 dBm with repetition (20 dB MCL improvement over LTE). Deep indoor penetration. Downlink available. Carrier managed. LTE-M (Cat-M1): 1.4 MHz bandwidth, 1 Mbps, supports handover and VoLTE. Better for mobile IoT (asset tracking). Short-range technologies: BLE 5.0 (2 Mbps, coded PHY for 4x range), Zigbee (mesh, 250 kbps, 2.4 GHz), Thread/Matter (IP-based mesh), Wi-Fi HaLow (802.11ah, sub-GHz, 1 km range). Each technology makes different tradeoffs between range, data rate, power, latency, and cost.

How does LoRa achieve such extreme range?

LoRa uses chirp spread spectrum (CSS) modulation, where each symbol is an up-chirp spanning the full bandwidth. The spreading factor (SF) determines how many chips represent each symbol: SF7 uses 128 chips per symbol, SF12 uses 4096 chips per symbol. Processing gain = SF times log2(SF) approximately. At SF12: processing gain is approximately 20 dB. This allows the receiver to decode signals well below the noise floor. The link budget calculation: TX power: 14 dBm (25 mW, typical for EU). Antenna gain: 2 dBi. FSPL at 868 MHz, 10 km: 32.44 plus 20 plus 58.8 = 111.2 dB. Receiver sensitivity at SF12, 125 kHz BW: minus 137 dBm. Link budget: 14 plus 2 minus (minus 137) = 153 dB. Margin after FSPL: 153 minus 111.2 = 41.8 dB margin at 10 km. This enormous margin accounts for building penetration, fading, and non-line-of-sight propagation. The tradeoff: higher SF means lower data rate. SF7: 5.5 kbps, time-on-air 36 ms for 10 bytes. SF12: 250 bps, time-on-air 1.3 s for 10 bytes. European regulations limit duty cycle to 1 percent, meaning an SF12 device can send approximately 30 messages per hour.

What RF design challenges are unique to IoT?

Battery life: IoT devices must operate for 5 to 10 plus years on a single battery (coin cell: 200 to 600 mAh). This requires sleep current below 1 microamp, fast TX/RX wake-up (less than 1 ms), efficient duty cycling, and minimal protocol overhead. The RF transceiver's sleep current dominates total power consumption. Antenna miniaturization: IoT devices are often small (sensor nodes, wearables), requiring electrically small antennas that are inherently inefficient and narrow-band. A quarter-wave antenna at 868 MHz is 8.6 cm; in a small sensor, a chip antenna or PCB trace antenna may have minus 5 to minus 15 dBi gain and 10 to 30 percent efficiency. This gain penalty directly reduces range and must be compensated in the link budget. Coexistence: with billions of devices sharing unlicensed spectrum (especially 2.4 GHz), interference management is critical. Listen-before-talk, frequency hopping (BLE uses 40 channels), and spread spectrum (LoRa) provide interference mitigation. Cost: IoT transceivers must cost less than 1 dollar in volume. This drives integration (SoC with transceiver plus MCU plus memory), elimination of external components (on-chip matching, LNA, PA), and use of CMOS PA (lower efficiency but cheaper than GaAs).

Wireless Connectivity

IoT

/eye-oh-tee/ — Internet of Things

Billions of connected devices. LPWAN: LoRa (CSS, SF7-12, −137 dBm, 10+ km), NB-IoT (−164 dBm, deep indoor), LTE-M (1 Mbps, handover). Short: BLE 5.0 (2 Mbps), Zigbee (mesh), Wi-Fi HaLow (sub-GHz). Battery: 10+ yr on coin cell (<1μA sleep). Antenna: miniaturized (−5-15 dBi). Cost: <$1 SoC. Coexistence: FH, CSS, LBT.

LoRa: −137 dBm

NB-IoT: −164 dBm

Battery: 10+ yr

Understanding IoT RF

IoT represents a fundamentally different design philosophy from traditional wireless communications. Instead of maximizing data rate (cellular, Wi-Fi), IoT optimizes for three things: battery life, range, and cost. This leads to radically different design choices: extremely low data rates (250 bps for LoRa SF12), aggressive duty cycling (transmit for 1 second, sleep for 1000 seconds), and spreading or repetition to achieve sensitivity well below the noise floor.

The RF challenge is clear: connect a coin-cell-powered sensor 10 km away, through building walls, for 10 years, using a $1 radio. Every dB of link budget matters; every microamp of sleep current matters.

IoT Technology Comparison

Technology	Range	Rate	Power	Spectrum
LoRa	10-15 km	0.25-50 kbps	25 mA TX	Unlicensed
NB-IoT	10+ km	26-127 kbps	120 mA TX	Licensed
LTE-M	10+ km	1 Mbps	200 mA TX	Licensed
BLE 5.0	100-400 m	2 Mbps	8 mA TX	2.4 GHz ISM
Zigbee	100 m	250 kbps	18 mA TX	2.4 GHz ISM

Common Questions

Frequently Asked Questions

Technologies?

LPWAN: LoRa (CSS, sub-GHz, unlicensed, 10+km, −137dBm). NB-IoT (licensed, −164dBm, deep indoor, cellular managed). LTE-M (1 Mbps, handover, VoLTE). Short: BLE 5.0 (coded PHY 4× range), Zigbee (mesh, 250 kbps), Thread/Matter, Wi-Fi HaLow. Each trades range/rate/power/cost differently.

LoRa range?

CSS modulation: chirps spanning full BW. SF7: 128 chips/sym, 5.5 kbps. SF12: 4096 chips, 250 bps, ~20 dB processing gain. Receiver decodes below noise floor. 14 dBm TX + 2 dBi − 111 dB FSPL @10km: 42 dB margin for building penetration and fading. Tradeoff: higher SF = lower rate + higher ToA + duty cycle limit.

Design challenges?

Battery: <1μA sleep, fast wake (<1ms), minimal protocol overhead. Antenna: small devices = chip/trace antenna (−5 to −15 dBi, 10-30% eff). Coexistence: billions in 2.4 GHz = interference. FH (BLE 40ch), CSS (LoRa), LBT. Cost: <$1 SoC, CMOS PA, on-chip everything. Every dB and μA counts.

Related Terms

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