868 MHz LoRa temperature sensors: range, limits and when they are worth it
The same LoRa hardware reached over 15 km in open terrain and roughly 100 metres inside a building in university measurements. That spread is not a measurement error — it is the single most important thing to understand before choosing wireless monitoring.
EnviSensor Team
In short
- In Europe the 863–870 MHz band is governed by ETSI EN 300 220-2: in the sub-bands LoRaWAN uses, power is limited to 25 mW e.r.p. and transmission time to 1% duty cycle — 36 seconds per hour.
- Range measured by the University of Oulu: over 15 km on land and close to 30 km over water with a tower-mounted antenna — yet the same researchers recorded roughly 2.6 km in built-up areas and about 100 m indoors.
- Each increase of the spreading factor doubles airtime and energy per message, but improves receiver sensitivity — from −123 dBm at SF7 to −136 dBm at SF12.
- LoRaWAN data rates in Europe range from 250 bit/s to 5.5 kbit/s, with an application payload of 51–222 bytes. It is a technology for measurements, not for images or files.
- Installation quality decides range, not the datasheet: the researchers attributed the gap between 15 km and 100 m to less than ideal indoor deployment, hardware and antennas.
Why 868 MHz, and what is allowed in Europe
The 868 MHz band is the European counterpart of the American 915 MHz. The difference is regulatory rather than physical: in Europe the conditions for using 863–870 MHz are set by the harmonised standard ETSI EN 300 220-2, linked to a European Commission implementing decision.
The standard splits the band into sub-bands with different power limits and different permitted channel occupancy:
| Range | Max power e.r.p. | Medium access |
|---|---|---|
| 863–865 MHz | 25 mW | duty cycle ≤ 0.1% or polite spectrum access |
| 865–868 MHz | 25 mW | duty cycle ≤ 1% or polite spectrum access |
| 868.000–868.600 MHz | 25 mW | duty cycle ≤ 1% or polite spectrum access |
| 868.700–869.200 MHz | 25 mW | duty cycle ≤ 0.1% or polite spectrum access |
| 869.400–869.650 MHz | 500 mW | duty cycle ≤ 10% or polite spectrum access |
LoRaWAN in Europe uses three mandatory channels — 868.1, 868.3 and 868.5 MHz — 125 kHz wide, with a default 16 dBm EIRP and a duty cycle below 1%. The LoRa Alliance specification states plainly that LoRaWAN meets the ETSI requirements exclusively through duty-cycle limitation, not through listen-before-talk.
What a 1% duty cycle means in practice
One percent is 36 seconds of airtime per hour in a given sub-band. This is a legal limit, not a hardware one — and it, rather than gateway processing power, usually sets the ceiling for network growth. For comparison, FCC rules in the United States allow up to 30 dBm but require hopping across at least 50 channels and cap a single transmission at 400 ms.
What the range really is
The most frequently quoted figures come from a measurement campaign by the University of Oulu. At 14 dBm, SF12 and a base station on a tower roughly 24 metres high, the measured range was over 15 km on land and close to 30 km over water.
It is worth looking at link quality rather than maximum distance alone:
| Distance | Packets lost |
|---|---|
| 0–2 km | 12% |
| 2–5 km | 15% |
| 5–10 km | 33% |
| 10–15 km | 74% |
| 15–30 km (over water) | 38% |
Beyond 10 km the link stops being useful for reliable monitoring, even though the range formally exists. A second result matters even more: in an ACM MSWiM paper the same researchers, using the same hardware, achieved about 2.6 km in a rural setting and about 100 metres in dense built-up areas and indoors — describing it as a worst-case deployment caused by less than ideal mounting and antennas.
Inside a building
Indoor measurements at 868 MHz show path loss exponents from 1.96 in partially line-of-sight conditions to 3.01 in heavily shadowed ones. In a comparative study LoRa maintained error-free transmission across roughly 50 metres of corridor where Zigbee was losing every packet at 40 metres.
The practical conclusion is that a range figure without stated measurement conditions carries no information. When planning an installation in a hall or warehouse, what counts is gateway mounting height, metallic obstacles and the number of floor slabs — not the number on a datasheet.
Spreading factor: what airtime buys you
LoRa uses chirp spread spectrum modulation. The spreading factor sets how many chips make up one symbol — two to the power of SF, so 4096 chips at SF12.
Each step up in SF halves the data rate and doubles airtime, and therefore the energy needed to send the same message. In exchange, receiver sensitivity improves:
| Spreading factor | Sensitivity |
|---|---|
| SF7 | −123 dBm |
| SF8 | −126 dBm |
| SF9 | −129 dBm |
| SF10 | −132 dBm |
| SF11 | −133 dBm |
| SF12 | −136 dBm |
The gap between SF7 and SF12 is roughly 13 dB of link budget — a lot. It costs time: a 20-byte packet can occupy the air from 9 milliseconds to 2.2 seconds depending on settings. Against a 36-second hourly allowance, the slowest setting leaves room for only a dozen or so transmissions per hour, which is the real constraint on reporting frequency in large installations.
How many sensors one gateway handles
The answer depends on configuration more than on hardware. In a simulation grounded in validated measurements, a typical urban deployment with default static LoRaWAN settings sustained around 120 nodes across 3.8 hectares at a delivery ratio above 90%.
The same study showed that dynamic transmission parameter selection or an additional gateway improves this markedly — for 200 nodes the delivery ratio rose from 0.51 to 0.80. The authors put it plainly: scalability is usually limited by duty-cycle regulation, not by technical limitations.
Environmental monitoring operates in a far gentler regime than city-wide deployments — a temperature sensor typically reports every few or few dozen minutes rather than every few seconds. Real installations in halls and warehouses therefore stay well inside the limits, provided the reporting interval was chosen deliberately.
LoRa, WiFi or cable — how to choose
The three technologies answer three different problems. The comparison below rests on figures verifiable in specifications and published research.
| Criterion | LoRa 868 MHz | WiFi | Ethernet / PoE |
|---|---|---|---|
| Data rate | 250 bit/s – 5.5 kbit/s | megabits | megabits |
| Payload per message | 51–222 bytes | no practical limit | no practical limit |
| Airtime restriction | 1% (36 s/h) | none | none |
| Range of a single link | hundreds of metres to a few kilometres | tens of metres | up to 100 m per run |
| Sensor power | battery | mains | over the cable (PoE) |
| Infrastructure | gateway | access points | structured cabling |
A practical rule: choose LoRa where pulling a cable costs more than replacing a battery — large halls, high-bay warehouses, dispersed sites, locations without power. Where cabling already exists or is easy to run, Ethernet or PoE gives higher reliability, no airtime restriction and power over the same cable.
Radio energy use is worth remembering too: the transceiver draws roughly 0.2 microamperes in sleep and around 87 milliamperes while transmitting at 17 dBm. Battery life is therefore governed mainly by how rarely and how briefly the device transmits — that is, by reporting interval and spreading factor.
Common mistakes when planning a radio installation
- Taking the datasheet range at face value. Marketing figures come from open terrain with a mast-mounted antenna. A hall is a completely different environment.
- Mounting the gateway at floor level or inside a metal cabinet. A gateway belongs high up, with as few obstacles around the antenna as possible.
- Reporting too often. An interval of a few seconds at a high spreading factor exhausts the airtime allowance and drains batteries without improving monitoring quality.
- Ignoring conductive obstacles. Metal racking, cold room enclosures and reinforced slabs attenuate the signal far more than partition walls.
- Skipping a range test before final mounting. A handful of check measurements at the planned sensor locations costs an hour and saves weeks of rework.
Frequently asked questions
What is the range of an 868 MHz LoRa sensor?
In open terrain with a base antenna about 24 metres high, University of Oulu measurements recorded over 15 km on land and close to 30 km over water. The same hardware achieved about 2.6 km in built-up areas and about 100 metres indoors. Range depends primarily on mounting conditions and obstacles rather than on the standard itself.
What is duty cycle and why does it limit monitoring?
Duty cycle is the share of time a device is permitted to transmit. In the sub-bands LoRaWAN uses in Europe it is 1%, or 36 seconds per hour. It limits the number and length of transmissions and, at high spreading factors, the reporting frequency as well.
LoRa or WiFi for temperature monitoring?
LoRa suits sites without power and cabling where distances are large — halls, warehouses, dispersed facilities. WiFi or Ethernet is the better choice where infrastructure already exists and frequent readings matter, because neither is subject to airtime limits and both offer far higher throughput.
How many sensors can one LoRa gateway handle?
In published research a typical deployment with default settings sustained around 120 nodes at a delivery ratio above 90%. That number rises with dynamic transmission parameters, longer reporting intervals or an additional gateway. In environmental monitoring, where readings are taken every few minutes, the limit is rarely a problem.
Is LoRa fast?
No, and it is not meant to be. LoRaWAN data rates in Europe run from 250 bit/s to 5.5 kbit/s, and a single message carries 51 to 222 bytes. That is enough for temperature and humidity readings, but not for images or file transfer.
Sources
- ETSI EN 300 220-2 V3.2.1 (2018-06) — urządzenia bliskiego zasięgu w pasmie 25–1000 MHz, Aneks B
- LoRa Alliance, LoRaWAN Regional Parameters v1.0.3revA
- Petäjäjärvi i in., Uniwersytet w Oulu — On the Coverage of LPWANs: Range Evaluation and Channel Attenuation Model for LoRa Technology (ITST 2015)
- Bor, Roedig, Voigt, Alonso — Do LoRa Low-Power Wide-Area Networks Scale? (ACM MSWiM 2016)
- Badanie propagacji wewnątrz budynków w paśmie 868 MHz (Sensors, PMC)
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