LoRa Questions

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Why my LoRa module shows RF96? what frequency is it?

The RF96 mark means this module is the HopeRF RFM95W-868-S2 or RFM95W-915-S2 module. Both modules use the Semtech SX1276 IC on it.

Meanwhile, if the LoRa module has a RF98 mark, which means it is hopeRF RFM98W-433-S2 module and use the sx1278 chip.

What is the frequency range of the Dragino LoRa products?

The Dragino LoRa products base on SX127x solution normally has three version: 433, 868 and 915. This means the device is best tuned at this frequency. The exactly work frequency is set in the software.

Below is the table shows the model info:

Version LoRa IC Support Frequency Best Tune Frequency
433Mhz Semtech SX1278 Band2(LF): 410 ~525Mhz

Band3(LF): 137 ~175Mhz

868Mhz Semtech SX1276 Band1(HF): 862 ~1020Mhz 868Mhz
915Mhz Semtech SX1276 Band1(HF): 862 ~1020Mhz 915Mhz

Some countries may need different frequency such as ~920Mhz. In this case, User can choose the 915Mhz version, the performance is similar.

I have a Dragino LoRa product with 868Mhz, Can i use it in 915Mhz?

Yes, in our product, the 868Mhz and 915Mhz module use the SX1276 HF Radio path, the difference of these two modules are 3 inductors which can let the module work best in 868MHz or 915Mhz.

So if user use the 868Mhz model as 915Mhz, the software is complete the same. the difference will be the Radio performance which is not siganificant between 868Mhz and 915Mhz.

I have a Dragino LoRa product with 868Mhz, Can i use it in 433Mhz?

No,in hardware side, the 433Mhz module use the LF Radio path in hardware(410 ~525Mhz ), and 868Mhz use the HF radio path (862 ~1020Mhz ) of LoRa chip. To save space and support PA mode, there is no radio path for LF in the 868Mhz module. So use 433Mhz in 868 module won't work, (actually it might work if you put both transmit and receive device very very close)

How can i increase the distance for two LoRa devices?

Check the use environment

First , User should notice: Radio link quality and performances are highly dependent of environment.
Better performances can be reached with:

  • Outdoor environment.
  • No obstacles.
  • No high level radio interfere in the ISM band you use.
  • At least 1 meter above the ground.

Radio performances are degraded with:

  • Obstacles: buildings, trees...
  • Inner buildings environments.
  • High ISM band usage by other technologies.
  • Radio communication are usually killed with bad topographic conditions. It is usually not possible to communicate through a hill, even very small.

Check the Antenna

  • Check if the Antenna has a good connection to the Antenna connector
  • Check if the Antenna has the good performance in the require frequency. (need special device, so may not possible to check in most case.)

Check the Frequency Setting in Software

  • Check if in the software, the correct frequency is set.

Check the Modem Setting in Software

Check if the modem is set to the correct modulation, Different modem setting will affect heavily in the distance and datarate. User can refer How Modem Config Affect Distance to see how it works.

user can download a modified version from Dragino Modified Radiohead Lib which add extra function to support change the LoRa Radio in a friendly way. Examples calls is as below:

  //Different Combination for distance and speed examples: 
  Example 1: Bw = 125 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Default medium range
  Example 2: Bw = 500 kHz, Cr = 4/5, Sf = 128chips/symbol, CRC on. Fast+short range
  Example 3: Bw = 31.25 kHz, Cr = 4/8, Sf = 512chips/symbol, CRC on. Slow+long range
  Example 4: Bw = 125 kHz, Cr = 4/8, Sf = 4096chips/symbol, CRC on. Slow+long range

How can i change the Bandwidth of the LoRa Radio

User can change the LoRa Bandwidth in the LoRa Radio. the detail of bandwidth description can be found at the Semtech Sx1276 datasheet. Changing Bandwidth will effect the distance for LoRa Radio, detail please check this link: How Modem Config Affect Distance.

In case User use the RadioHead Library, user can download a modified version from Dragino Modified Radiohead Lib which add extra function to support change the Bandwidth in sketch. Examples calls is as below:


What is the difference between LG01 single channel gateway and a 8-channel LoRaWAN gateway?

Here we talk about the difference on the LoRa and LoRaWAN part, which are the general difference due to hardware limited. other system features like connecting to the IoT Server depends on the software design.

  • Both gateways use LoRa for physic layer transmit/receive. but the LG01/OLG01 supports only 1 channel frequency transmit or receive at one time. while 8 channels gateway can handle 8 channels at the same time.
  • The LoRaWAN is a software stack runs on LoRa technology. In LoRaWAN protocol, the end node will send data at different frequency at different time. So the gateway is required to run at different frequency channels to make sure it can get all data sent from the LoRa End device. The single channel gateway such as LG01 due to hardware limitation, it is not fully compatible with LoRaWAN protocol, because it can't receive data sent from different frequency at the same time. Assume a end device send data in eight different frequency, the LG01 can only get 1 of 8 due to this limitation.
  • Some LoRaWAN devices now can work with LG01 but some not.Now LG01 can't support OTAA LoRa Devices. Here is a reference link (Connect to TTN LoRaWAN example) for how to use the LG01-P and LoRaWAN ABP device. It also shows how to send the end device to work at only one single channel.
  • Due to channel limitation, the LG01 can't support too many devices, in a lab test, we see packet lost if there are more than 50~60 LoRaWAN devices if each device sent a LoRa packet at each 10 minutes. this is far below a real LoRaWAN gateway can support. By using private LoRa protocol, it is possible to support several hundreds LoRa devices in LG01, the LoRa devices in this case will be in polling mode in most of the time, so not good for low power use. For the LG01-P single channel gateway, each packet will need to take 2~3s to process. So we can consider the packet capacity is 20~30/minutes.

What is the difference between LoRa, LoRaWAN and RadioHead?

  • LoRa is an innovation Wireless Technology developed by Semtech. It offer long range, low power consumption and secure data transmission.Public and private networks using this technology can provide coverage that is greater in range compared to that of existing cellular networks. It is one of the most promising technology used for IoT solutions.
  • LoRaWAN is a protocol specification built on top of the LoRa technology developed by the LoRa Alliance. It uses unlicensed radio spectrum in the Industrial, Scientific and Medical (ISM) bands to enable low power, wide area communication between remote sensors and gateways connected to the network. This standards-based approach to building a LPWAN allows for quick set up of public or private IoT networks anywhere using hardware and software that is bi-directionally secure, interoperable and mobile, provides accurate localization, and works the way you expect. The specification is available for free to download from the LoRa Alliance website today.
  • RadioHead is a Packet Radio library for embedded microprocessors. It provides a complete object-oriented library for sending and receiving packetized messages via a variety of common data radios and other transports on a range of embedded microprocessors. It supports LoRa chip as well.

LoRaWAN and RadioHead both are software protocol run on top of LoRa and they have below difference.

  • LoRaWAN provides a standard for communication , Different vendors' LoRa devices , LoRa Gateway can communicate with each other if all these devices follow the LoRaWAN standard. LoRaWAN design for a nationalwide network scale to support millions devices.
  • Radiohead library provide a fast way to evaluate the LoRa technology. It only provide the base connection for LoRa. The library itself doesn't provide mechanism to support large scale network. and different vendors devices can't communicate with each.

Can Dragino devices communicate with LoRa Devices from other vendor?

If both devices have the same Radio Settings in LoRa: Frequency, Spread Factor, Bandwidth, Preamble length and SyncWord. Both devices can communicate with each via LoRa. There are some things need to be considered:

  • It is possible one device has encryption on the LoRa data, so even the other device receive its packet, it will be encrypted.
  • If the Device is using the standard LoRaWAN protocol, first check if the device is running in OTAA or ABP mode.
    • For ABP mode, according to LoRaWAN protocol, the end node will send data on different frequency, for example: send first data on 868.1Mhz , send second data on 868.3Mhz ,,etc. So if we use single channel gateway (LG01) or other LoRa node such as LoRa Shield to receive the data, we have to set the receive device at one match frequency, it will only get the data sent in that frequency, if the device send out data on unmatch frequency, the LG01 won't get it.
    • For OTAA mode, the software support is still under developing in LG01.

Above info is suitable for all Dragino LoRa Products.

How many LoRa client node can LG01/OLG01 support?

The LG01/OLG01 LoRa Gateway is a single channel gateway, it can receive one packet at a time. for example, if there are two LoRa packet arrives the gateway at the same time. one will be ignored. When discuss the capacity for LG01, we can use packets/minute to see how many packet it can process and calculate how many nodes it can support. The packets / minute here not only include the rx time in lora, but also include the LG01 avr part to pass this data to Linux and call a linux command. Packets/minute will be different if user use different software in the LoRa part. but it normally takes 2~3 seconds to process a packet, so we can consider 20~30 packets/minutes.