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StoriesSystem: LPWAN and mesh

Kilometres on a coin cell

Most environmental sensors send a few bytes a few times an hour. Low-power wide-area networks trade bandwidth for range and battery life; mesh networks trade range for resilience. Both are now international standards12.

Systems
LPWAN, Mesh, Border routers
Toward 2030
Satellite IoT in the cellular standard
Figures
4, data story, simulator, systems diagram, timeline to 2030

Go to the references

01Data story

Spreading factor and airtime.

Each step up in spreading factor roughly doubles the time a packet spends on air, and with it the energy and the share of the duty-cycle allowance it consumes34. The bars are computed with the modem’s published formula for a 20-byte payload.

Figure as text: Time on air by spreading factor, 20 bytes at 125 kHz

A bar chart of LoRa time on air for spreading factors 7 to 12, from about 57 ms to about 1.3 s.

Time on air by spreading factor, 20 bytes at 125 kHz (ms)
Spreading factorTime on air
SF756.6
SF8102.9
SF9185.3
SF10370.7
SF11741.4
SF121,318.9

02Simulator

What the duty cycle allows.

Set the spreading factor, the payload and the duty-cycle limit, and read how many uplinks an hour a device may send. The same arithmetic decides whether a network can add a thousand more sensors.

Figure as text: Uplinks per hour within a duty-cycle limit

A bar chart of time on air for spreading factors 7 to 12 with the chosen factor in red.

Uplinks per hour within a duty-cycle limit, at the starting values
Spreading factor10 SF
Payload24 bytes
Duty-cycle limit1 %
Time on air (125 kHz, CR 4/5)370.7 ms
Uplinks per hour within the limit97
Shortest interval between uplinks37 s

03Systems diagram

A mesh that heals.

In a mesh, each node can forward for its neighbours toward a border router, using a routing protocol designed for lossy, low-power links5. Fail a node and watch the routes find another way, or not.

Figure as text: A low-power mesh with two border routers

A four-tier diagram of leaf sensors, forwarding nodes, border routers and the edge, with red routes from every leaf.

  • Leaf sensors: A, B, C, D, E
  • Forwarders: Node 1, Node 2, Node 3
  • Border routers: Border 1, Border 2
  • Edge: Edge

14 links. Scenarios: All nodes up; Node 2 fails; Border 1 fails; Nodes 1 and 3 fail.

04Timeline to 2030

A family of low-power standards.

Cellular low-power access arrived with NB-IoT and LTE-M in Release 136; sub-gigahertz Wi-Fi extended range for sensors7; the long-range protocol many networks use became an ITU-T recommendation in 20211. Release 17 added satellite access for IoT devices8.

Figure as text: Low-power wide-area and mesh standards

A timeline from 2012 to 2030 with RPL, NB-IoT and LTE-M, 802.11ah, ITU-T Y.4480, IEEE 802.15.4-2020 and IoT over satellite.

  1. 2012-03 RPL routing for lossy networks (RFC 6550). IPv6 routing for low-power meshes.5
  2. 2016 Sub-gigahertz Wi-Fi (IEEE 802.11ah). Long-range, low-power Wi-Fi for sensors.7
  3. 2016-06 NB-IoT and LTE-M. Low-power cellular access in Release 13.6
  4. 2020 Low-rate wireless networks revised (IEEE 802.15.4-2020). The radio beneath many mesh protocols.2
  5. 2021-12 Long-range LPWAN protocol recommended (ITU-T Y.4480). Adopted as an ITU-T recommendation.1
  6. 2022-06 IoT over satellite. Release 17 adds non-terrestrial access for NB-IoT and LTE-M.8

Time on air, 20-byte payload

ms

0

500

1,000

1,500

2,000

SF7

56.6

SF8

102.9

SF9

185.3

SF10

370.7

SF11

741.4

SF12

1,318.9

Figure 1

Data story

Figure 1. Time on air by spreading factor, 20 bytes at 125 kHz. A bar chart of LoRa time on air for spreading factors 7 to 12, from about 57 ms to about 1.3 s.

References

  1. Recommendation ITU-T Y.4480: Low power protocol for wide area wireless networks. International Telecommunication Union, Telecommunication Standardization Sector, 2021.
  2. IEEE 802.15.4-2020: Standard for low-rate wireless networks. IEEE Standards Association, 2020.
  3. SX1276/77/78/79 datasheet, section 4.1.1.7: LoRa time on air. Semtech, 2020.
  4. ETSI EN 300 220-2: Short range devices operating in 25 MHz to 1 000 MHz (duty-cycle limits). European Telecommunications Standards Institute, 2018.
  5. RFC 6550: RPL, IPv6 routing protocol for low-power and lossy networks. Internet Engineering Task Force, 2012.
  6. 3GPP Release 13: NB-IoT and LTE-M. 3rd Generation Partnership Project, 2016.
  7. IEEE 802.11ah: sub-1 GHz Wi-Fi (HaLow), incorporated in IEEE 802.11-2020. IEEE Standards Association, 2016.
  8. Releases: the timeline of 3GPP Releases 17 to 21. 3rd Generation Partnership Project, 2025.

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