Gilen Tell

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8 years, 5 months ago.

Is LBT implemented in libmdot?

Hi,

I have read in LoRa MAC Specification v1.0 this paragraph:

"Prior to transmission, the end device uses Listen Before Talk (LBT) to assess that the intended transmission channel is free. A channel is considered free if the instantaneous signal strength measured is smaller than RSSI_FREE_TH. If the channel is not free, the end device changes to another channel and repeats the LBT procedure."

I suspect that it's not implemented. When I put a mDot with SF12 transmiting every 3 minutes and another mDot with SF7 transmiting every 15 seconds simultaneously and near the gateway, the PER (Packet Error Rate) of the SF12 node is extremely incresed to about 40-55%.

The change log of libmdot last version (1.0.8) says that it's LoRaWAN 1.0 Certified. Is this LBT requirement implemented in libmdot just now?

If the mDot uses LBT, I will have to search the cause of this PER in the MultiTech Conduit gateway.

Thank you an cheers,

Gilen

Question relating to:

Last updated: 09 Nov 2021
The MultiConnect® mDot™ offers significantly longer range and improved radio performance compared to traditional wireless solutions—resulting in greater transmission range and reduced capital expense.

2 Answers

Jason Reiss
8 years, 5 months ago.

The specification in use is today LoRaWAN 1.0.

LoRaMAC was a predecessor with specification versions up to v3.1. It appears you are looking at an old spec.

The LoRaWAN protocol exclusively uses duty-cycle to manage access to the medium.

From LoRaWAN 1.0

7 7.1.2 EU863-870 ISM Band channel frequencies ... 14 In order to access the physical medium the ETSI regulations impose some restrictions such 15 maximum time the transmitter can be on or the maximum time a transmitter can transmit per 16 hour. The ETSI regulations allow the choice of using either a duty-cycle limitation or a so- 17 called Listen Before Talk Adaptive Frequency Agility (LBT AFA) transmissions 18 management. The current LoRaWAN specification exclusively uses duty-cycled limited 19 transmissions to comply with the ETSI regulations.

Anthony Huy
8 years, 5 months ago.

Jason, is this specification that you listed -

"The current LoRaWAN specification exclusively uses duty-cycled limited 19 transmissions to comply with the ETSI regulations"

enforced

(1) in the libmdot api (2) OR by the conduit via the LoRaWan protocol (3) OR by the user application that uses LoRa

Also, is this just a Europe spec? Does it apply to North America?

Thanks.