RSSI & SNR in LoRa Wireless Wide Area Network

 

INTRO
•In this tutorial I will explain what RSSI and SNR are. By the end of this tutorial you come to know the importance of RSSI and SNR in LoRa signal strength description, then because of this tutorial you can make your own research with LoRa WAN.
RSSI
•The Received Signal Strength Indication (RSSI) is the received signal power in milliwatts and is measured in dBm. This value can be used as a measurement of how well a receiver can “hear” a signal from a sender.

RSSI & SNR in LoRa

SNR & RSSI 1

• The RSSI is measured in dBm and is a negative value.
The closer to 0 the better the signal is.
• Typical LoRa RSSI values are:
RSSI minimum = -120 dBm.
If RSSI=-30dBm: signal is strong.
If RSSI=-120dBm: signal is weak.

Hence Make sure your RSSI must be in between Typical RSSI values to get better signal strength.

for more information: https://en.wikipedia.org/wiki/Received_signal_strength_indication

SNR
• Signal-to-Noise Ratio (SNR) is the ratio between the received power signal and the noise floor power level.
• The noise floor is an area of all unwanted interfering signal sources which can corrupt the transmitted signal and therefore re-transmissions will occur

SNR & RSSI2 in LoRa

• Normally the noise floor is the physical limit of sensitivity, however LoRa works below the noise level.

SNR & RSSI3

Typical LoRa SNR values are between: -20dB and +10dB
• A value closer to +10dB means the received signal is less corrupted.
• LoRa can demodulate signals which are -7.5 dB to -20 dB below the noise floor.

so, Make sure your SNR is between typical values to get more  LoRa signal strength.

for more information: https://en.wikipedia.org/wiki/Signal-to-noise_ratio

5 simple rules to guarantee a successful LoRa Wide Area Network coverage test:

1. Aim high: Understand the the power of the gateway (antenna) height
2. Do not take your test results for granted:
Radio performance is subject to many different influences – and many of them can change over time (we cover this in detail somewhere else, currently only available in German). This means that what you measure, or not measure, today can be quite different tomorrow, next month or next year.
3. Test over a longer period of time
4. Know the details about your RSSI values
5. Add as much metadata as possible:
Any at least semi-serious test will result in a a big amount of data. You won’t end up with just a simple data point telling you what the RSSI value at a specific time was. You most likely will have several data points with RSSI values at different times. Such a dataset will make it difficult to exactly differentiate where the value was recorded and under which circumstances.So, as a result make sure you follow five rules to make your LoRa coverage is sufficient for you.

 

1 Comment

Leave a Reply

Your email address will not be published. Required fields are marked *

%d bloggers like this: