LoRa under cover

This time we put LoRa underground, reading water meter 2 meters below the surface. Other technologies including cellular data and 2.4GHz had already proven to fail with this task. Let LoRa proof its capabilities.

Well located at parking lot.

It this test, a water meter is located in an infrastructure well located at parking lot. The well has heavy cast iron lid and also all-metal collar for depth of 25 cm. Walls of the well are made with concrete rings. The water meter is at the bottom of the well, approx. 2 meters in depth. 

Water meter at the bottom of the well.

We build a demo setup with Multitech Conduit LoRa gateway, and mDot integrated with Raspberry Pi and M-BUS master interface, all put in an IP-classified plastic box. The box is well over-sized, but there is good space for battery. The LoRa transmitter in the "shoe-box" is interfaced with the meter over wired M-BUS. RF transmit power is 14dBm and spreading factor 12.

LoRa transmitter and gateway.

The transmitter was located next to the meter at the bottom of the well. The LoRa gateway was located in a meeting room inside a nearby building. The line of sight between meeting room and the well was blocked by a storage wing covered by metal plates.

Building where the gateway was located.

Distance of the well and the building is approx 25 meters. For realistic condition, the lid was closed tightly and a van was parked above the well. In the direct line between transmitter and receiver, there is several meters of soil, metal cage, brick wall and concrete floor.

Diagram of the test setup

And the results? Excellent!

Received signal strength is approx. -105dBm, which gives wide margin left. The gateway could be located much further away. We also tested signal coverate inside the office building and got it all covered from the same gateway location, 100 meters through several steel reinforced concrete floors and brick walls.

What's the meaning of all this? In an automated meter reading application, whether water, electricity or other types of meters or sensors, even a large complex with outdoor environment and difficult locations like basements and underground locations, it all can be covered with a single gateway located pretty freely in most convenient location. Outdoor wall installation or other difficult to reach position is not necessary.

This time we didn't tested the maximum distance from the well where the signal can be detected, as the results were good enough for the purpose of the trial.

New challengers entering IoT connectivity market

IoT connectivity market is far from mature. New challengers are popping up every now and then. The latest was announced Today, when Intel, Nokia and Ericsson released their co-op in a new mobile radio technology called Narrow-Band (NB) LTE-M for Low Power Wide Area IoT communication.

Like the name says, NB LTE-M is narrow-band version of the LTE-M. NB uses 200 kHz band where as the normal LTE-M consumes 1.4MHz. Both versions can co-exists without interfering each others. The purpose of the narrower band is to reduce end-device power consumption and cost. Intel says it will launch low-cost and low-power chips for IoT market using the new technology. What does that mean in numbers remains to be seen.

LPWA IoT Connectivity Overview
Nokia White Paper - LTE-M – Optimizing LTE for the Internet of Things

Technologies listed in the comparison above are all intended for public networks. LoRa is the only one which is available for private network applications also. That means you can set up a LoRa gateway of your own just like using WiFi. Sigfox is closed and propriterary technology, and use of licensed frequency bands means you got to be an operator to get the license in hand.

The greatest weakness of LoRa technology is the use of unlicensed frequency band. In Europe, the duty-cycle limitation is only 1%. That's regulatory not technology limitation. It does not affect much the downlink or uplink of many IoT applications, but over-the-air firmware updates are very difficult, next to impossible. It would take awfully long time to transfer any reasonable sized firmware. Perhaps some clever delta (diff) technology for patching the device firmware image could work.

 The above comparison is missing energy consumption. It seems to be difficult to find comparable numbers for real energy (J) consumption per delivered payload with different technologies. Mobile data suffers from significant overhead in terms of channel opening, handshaking, etc. Most of the energy is consumed by other functions than transmitting/receiving the actual payload data. As an opposite, LoRa introduces very low overhead. Any technology can provide battery life of over 10 years, it's only question of how much batteries you need.

LoRa is available as of Today. For LTE-M, first device and network manufacturers must introduce new products, then operators must upgrade their base stations. I don't believe LTE-M is really in place next year. Once it's there, the deployment of the technology will be fast for sure.

No convergence of IoT connectivity technologies is visible within the foreseeable future. There are different use cases for different types of radios. Main categories are short range radios (Bluetooth, Wifi, etc), Low Power Wide Area (LoRa, UNB), and cellular data. They have all different nature and no single technology will rule them all.

Conduit LoRa gateway and Espotel LoRa device supporting ThingPark

Multitech MultiConnect Conduit is latest LoRa gateway supporting Actility's ThingPark LoRa Network Server. I just got one of the very first setups.

Conduit gateway connected to ThingPark.

Recently Actility and Multitech created a custom firmware for Conduit to provide connectivity to ThingPark backend. Thanks to that, now there exists cost-efficient alternative gateway available for LoRa networks operated with ThingPark network management solution. Conduit may improve indoor coverage of public LoRa networks, or it can be used in private network installations. Later this year Multitech will introduce outdoor installation kit with IP-classified chassis and optional solar power pack.

Multitech and Kerlink gateways listed in my ThingPark account.

Espotel recently joined Actility's ThingPark certification program. The aim is to provide end-devices compliant with the ThinkPark network management solution. Espotel is now finalizing it's own LoRa reference design, nickname "ELMO" (Espotel LoRa Modem), which is Arduino form-factor compatible prototyping device.

Espotel LoRa Modem "ELMO"

ELMO will be LoRaWAN certified and tested against Actility's requirements. Right at the moment our engineers are working to introduce ELMO as public platform in ARM mbed development environment.

ELMO has dual Arduino-pinheaders. This enables function as a master or slave. ELMO can be used as LoRa-shield for external MCU boards, like STM32-Nucleo, Freescale FRDM, or Arduino. ELMO also supports integration of application software and protocol stack into one and running them both directly in ELMO's own MCU without external MCU needed. In both scenarios, 3rd party shields can be used to provide additional interfaces and sensors.