FAQ for FMLR LoRaWAN® -RF-Modules and SensorsThis is an ever growing collection of frequently asked questions around our family of LoRa and LoRaWANmodules and sensors. It is meant to help prospective costumers get a deeper understanding of theadvantages and pitfalls of LoRaWAN-based IoT systems.

1 LoRaWAN basics

1.1 LoRaWAN or LoRa?

LoRa and LoRaWAN are often used interchangeably. But in fact its two different things. LoRa is a spreadspectrum radio technology optimized for long range and low power consumption. LoRaWAN is a networkprotocol layer on top of LoRa, specified be the LoRa Alliance.

1.2 What is the Commissioning data?

It is the keys and EUIs you get from your service provider. Depending on the joining procedure (ABP or OTAA), you either need at least:

• OTAA

◦ Device EUI

◦ Application EUI

◦ Application key

• ABP

◦ Device address

◦ Network session key

◦ Application session key

1.3 What does ABP (Activation by Personalization) mean?

"In some cases you might need to hard code the DevAddr as well as the security keys in the device. This means

activating a device by personalization (ABP). This strategy might seem simpler, because you skip the join

procedure, but it has some downsides related to security." - hdtvisser, www.thethingsnetwork.org/forum

1.4 What does OTAA (Over-the-Air Activation) mean?

"Over-the-Air Activation (OTAA) is the preferred and most secure way to connect with The Things Network.

Devices perform a join-procedure with the network, during which a dynamic DevAddr is assigned and security

keys are negotiated with the device." - hdtvisser, www.thethingsnetwork.org/forum

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The most common FMLR LoRaWAN modules available

If possible, you should choose OTAA, mostly because of the improved security. You also get feedback uponjoining, and usually more available channels to use on that specific network.

1.5 What is the data rate? How much data can I transmit and how often?

In Europe, there is a duty cycle limitation per transmitting device for the used radio frequencies (section 7.2.3 ofthe ETSI EN300.220 standard), which limit the time on air allowed. In most cases it’s 1%, but the LoRaWAN stackhandles that for you. So in the worst case, you’re able to send around 50 bytes every few minutes. Butdepending on your provider your limited even more. Some commercial providers allow you 144 messages perday max.

1.6 Why should I avoid using confirmed messages?

Since the duty cycle explained in 1.5 also applies to the gateways, their allowed duty cycle would be used pretty fast, if every node always wants a confirmation.

1.7 What does ADR mean?

Adaptive Data Rate (ADR) is a mechanism for optimizing data rates, and therefore the duty cycle and energyconsumption of your node. The LoRaWAN standard defines different data rates, namely different spreadingfactors and bandwidths. The data rate has a direct impact on the duty cycle and energy consumption of yournode. As a rule of thumb: The lower the data rate, the slower the speed and the longer the range.

1.8 How can I set the Data Rate parameter?

We developed a small AT interface to set commission data. Depending on your product configuration, you can also set other parameters like transmitting interval, attached sensors and the like. See our FMLR AT Interface Guide.

1.9 How long does the battery last?

This highly depends on the length of your payload, on the transmit interval and on your data rate. With ourmodule, just sending data you can estimate the following theoretical values. Keep in mind that batteries have ashelf lifetime and temperature dependency that can effect the lifetime as well. We could do more accuratecalculations based on your sensors and battery types.

Data rate Payload Size Messages per day Battery life AA LTC cell Battery life AA alkaline cell

DR0 (SF12BW125) 1 byte 1 44 years 25 years

DR0 (SF12BW125) 1 byte 12 26 years 14 years

DR0 (SF12BW125) 1 byte 144 (every 10 min) 4.4 years 2.5 years

DR0 (SF12BW125) 1 byte 360 (every 3 min, worstcase maximum)

1.8 years 1 years

DR0 (SF12BW125) 1 byte 1000 250 days 144 day

DR0 (SF12BW125) 50 bytes 1 41 years 23 years

DR0 (SF12BW125) 50 bytes 12 17 years 10 years

DR0 (SF12BW125) 50 bytes 144 2.2 years 1.2 years

DR0 (SF12BW125) 50 bytes 360 330 days 190 days

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DR0 (SF12BW125) 50 bytes 1000 123 days 70 days

DR5 (SF7BW125) 1 byte 1 45 years 26 years

DR5 (SF7BW125) 1 byte 12 36 years 21 years

DR5 (SF7BW125) 1 byte 144 10 years 6.1 years

DR5 (SF7BW125) 1 byte 360 5 years 2.8 years

DR5 (SF7BW125) 1 byte 1000 1.9 years 400 days

DR5 (SF7BW125) 50 bytes 1 45 years 26 years

DR5 (SF7BW125) 50 bytes 12 35 years 20 years

DR5 (SF7BW125) 50 bytes 144 9.5 years 5.4 years

DR5 (SF7BW125) 50 bytes 360 4.3 years 2.4 years

DR5 (SF7BW125) 50 bytes 1000 1.6 years 340 days

1.10 How often should I get a GPS fix?

Since getting a GPS fix is very power-consuming, you should really think about how often you want do get a fix. Acquiring a fix more than once a day typically makes the GPS the predominant consumer of battery power.

1.11 100km (62 miles) Range – are you serious?

There is a project, called ttnmapper.org, which measures the coverage of the things network, a communityowned and operated LoRaWAN service provider. The data of the last few days can be visualized on a map.People also use it to make real live range tests, like the one shown below:

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Screenshot from ttnmapper.org September 21th 2017, showing a range test from a mountain top using EU868 DR5 (SF7BW125).The receiving gateways were 138 km away.

1.12 We want to cover a whole city of about 5 km radius with one LoRaWAN gateway. Is this possible?

In principle yes. Place a 3-sector antenna on a 5-10m mast on top of the highest building in the center. Thissetup can provide outdoor coverage for the whole city. Depending on the building type, many will have indoorcoverage as well.

1.13 Do the FMLR modules and Gateway support the relevant frequency plan?

Since we follow the LoRaWAN implementation from STMicroeletronics we support the regional settings they support. The regional settings are fragmented into a plethora of frequencies, and we can test using EU868 and US915-Hybrid. Depending on the frequencies used, the antenna should also be tuned. So order the correct regional version for your case.

Note: According to this blog a gateway for the full LoRaWAN FCC 902-914 MHz Upstream band would require 8x SX1301 with 2xSX1257 each (called sub-bands 1-8):

“Since Semtech’s SX1301 concentrator operates in hybrid mode and provides 8 x 125kHz + 1 x

downstream channels, you can see that a “full” gateway will require 8 SX1301 concentrators thus

making it relatively complex and expensive in comparison to European counterpart.”

Current gateway designs with 1 SX1301 and 2 SX1257 and most LoRaWAN modules are therefore configured to LoRaWAN 915 MHz Hybrid mode and sub-band 1 at 902.3 MHz. Output power density is limited to +8 dBm / 3 kHz or 21 dBm.

2 Design and developed based on FMLR modules

2.1 Are there special design rules for the placement of the FMLR modules?

Yes, there are normal ERC rule checks that need to be followed. If the modules do include an antenna, then RF matching should be taken into account for the rest of the board. The check can be implemented when you use our Altium lib rarie s .

2.2 Can FMLR modules run our own apps and how do I develop such an app?

We provide development tools and free Open Source sample apps. Development can be done using SW4STM32 and ST-Link or Segger J-Link.

3 LoRaWAN technological background

3.1 Are 14 dBm output power enough given the 14 dBm ETSI Limit?

Our module version with integrated chip antenna provides full transmit power because the higher output powercompensates the negative gain of the chip antenna. Furthermore, higher transmit power is allowed undermultiple circumstances. This results in better range and stability.

The longer answer is a bit more complicated: Under ETSI regulations the output power limit is not 14 dBmexactly. The license free ISM band used by LoRaWAN in Europe is the 863 to 870 MHz band. The general limit inthis band is 14 dBm ERP which means Radiated Power compared to a dipole with 2.15 dBi gain. Compared to anisotropic radiator this is 16.15 dBm. That means that a device is allowed to radiate with up to 16.15 dBm in any

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direction compared to the isotropic radiator. So if your device uses an external antenna which is worse than anideal dipole (real gain is lower than 2.15 dBi) than you can compensate that by increasing the output power bythe difference. Our unique FMLR modules with integrated chip antenna makes use of this advantage. Thisenables our customers to build tiny sensors without compromise and with full RF performance despite of havinga small chip antenna in a less than ideal housing. Additionally, ETSI provides the G3 Band with up to 27 dBmoutput power. So depending on the application and the region customers products benefit from higher outputpower (14 dBm is 25 mW and 20 dBm is 100 mW), potentially doubling the range.

The LoRa Technology can be used in any wireless and IoT application world wide. Even the popular LoRaWAN isstandardized for different frequency bands all over the world. For example there is the popular 902 to 927 MHzBand in the US and Canada under FCC regulation with up to 4 Watts or 36 dBm output power. Don't hesitate toask for details as well if you find the numbers uncommon. Wireless is our business.

3.2 Are there other options to increase the range dramatically?

One option is having a high gain directional antenna at the gateway pointing into the direction of the sensornode. If the nodes are all distributed into one direction seen from the gateway then a single directional antennais the right solution. Tested designs are Yagi, Helical, Panel or Log-N. If your sensors are distributed over the full360 degrees range with respect to the gateway, then a combination of 3 sector antennas is the best solution.Every sector antenna overlooks a range of 120 degrees.

3x 120° Sector Antenna

Yagi-Antenna Log-N-Antenna Patch-Antenna

High Gain Antenna Types

Another very important step to get ultra long ranges like 50-100km and more is to have the antennas installed

on a high mast. Best locations for antenna masts are on roofs of high buildings or even better on a nearby hill ormountain. In the end, radio waves in the UHF range travel comparably to visible light. That means that they canonly extend about 10-15% behind the visible horizon. One should never forget that Earth’s shape is spherical,not flat. To get the idea just have a look at GSM or TV-Broadcast antennas in your area. They use about the samefrequencies and underlay the same physical principles.

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3.3 Is it possible to simulate even better if terrain is taken into account?

Yes, we can simulate link quality for your environment. Have a look the picture below. It shows the simulation of a60 km link from Zurich to the Swiss mountain Säntis. As you can see on the right the receiving signal strength is about -107 dBm which provides a huge margin to LoRa's sensitivity limit of -137..143 dBm. Just ask for support.

3.4 Why can't I have a LoRaWAN based tracking device without an integrated GPS receiver?

Despite the fact that Semtech and the LoRa Alliance have announced plans to integrate localization functionalityinto LoRaWAN without the need for a dedicated GPS, we are not convinced of its real world use. Mostcustomers and applications want to have high accuracy tracking functionality for valuable goods, animals or evenhumans. This corresponds to an accuracy of 5 meters or better. Try using smartphone to show your position onGoogle Maps. Most of the time, you will see that even with its superior configuration based on GPS, GLONASS,EGNOS plus WiFi access points in proximity, and its large battery power budget, its accuracy is often worse then10 meters. We do not believe that LoRaWAN will provide high accuracy localization functionality. However, itsusability solely depends on the accuracy an application requires. Now let's look at two current sources ofprofound information about LoRaWAN:

LinkLabs is an early adopter of LoRa Technology and develops gateways1

“According to this report on localization released by Semtech, the 10% error rate for a single packet using 11 gateways in an urban environment is just over 500 meters. To draw a circle your location will be within 90% of the time, it would be just over 1km in diameter.”

Microwave Journal is a leading source for information about RF and Microwave technology2:

1 https://www.link-labs.com/lora-localization/

2 http://www.microwavejournal.com/articles/27357-lora-a-radio-approach-towards-iot-geo-localization

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“When B is the bandwidth of the radio transmit signal, the achievable temporal resolution is in the order of 1/B

with an estimator using a correlation approach, which is the basic mechanism for TDoA estimations. For a LoRa

system with 500 kHz bandwidth, this results in precision of about 600 m. This number can be interpreted as a

worst case threshold. When the signal of the direct path is significantly stronger than the signal of the echoes,

the results will be better. With other estimators, which exploit the radio channel information (the channel delay

spread or, better, an estimate of the channel impulse response) in addition to the pure signal correlation

characteristics, better results can also be achieved. However, LoRa based localization will never directly

compete with the precision of GPS, which is several meters down to centimeters when applying differential

GPS. This will have to be reflected in the application domain.”

3.5 Do you have SAR radiation values? Are animals safe when LoRa is used?

At 868/915 MHz and 14 dBm the safe distance for humans (with the R&TTE / RED / EN 62479 limit of 4.35 W/m²) is 2cm from the antenna's most powerful direction.

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