Random Acces in LoRa Devices (ADR)


(Z1gm4) #1

Hi to everyone,
i want to ask to anyone who knows about the random access of lora devices,
this is because i'm working on a lora simulator in my university for my degree project, and i'm stuck in that point because i don't know how it works that function of the LoRa Devices.
I have read the LoRa specification of devices and the MAC specification and no get any answers there, but i have two theories.
a) the LoRa endpoint checks every single channel until receives an ack package, this results in some collisions, but less than if just one channel available.
b) The LoRa Gateway notify to the entire network in broadcast, the available channels on the run, so the next receive window beacon the hosts will send the upstream data by those channels (this notify advice triggers in every receive data from a channel, and in the same way, when a upstream link is done and the channel is available).


(Hylke Visser) #2

I assume that you already found our Wiki page about LoRaWAN?

The channels that can be used are specified (by the LoRaWAN spec), statically configured in the node (out of band), or dynamically configured in the node (during the Over the Air Activation procedure).

After this, for each transmission, the node picks a random channel, checks if it's allowed to transmit on that channel (based on the duty cycle) and then transmits. The downlink (response) channel is determined based on the uplink channel (in the first receive window) or specification/configuration (in the second receive window).


(Z1gm4) #3

Thanks for your quick reply,
According to your answer, yes i saw the wiki of LoRaWAN, but i still don't get it how the nodes knows which channels are available at the first receive window time, because, for the default the first communication is using the SF7 according to the specs, but in the next uplink transmissions from the node to the gateway, how the node know which channels he must to test to connect to. Or this "array" of channels is negotiate in the pair phase? That's my doubt


#4

You can also get detailed explanation of LoRaWAN here: http://sakshamaghoslya.blogspot.in/p/how-does-lorawan-nodes-changes-their.html


(Norhane) #5

Hi,

I am currently on project where i have to improve the quality of service in IoT by using LoRa technologie, i would ask you a question:

can i make duty cycle of LoRaWAN dynamic, i mean that if one node need to use less then 1% duty cycle for transmit data and it's not necessary to atribute it all 1% DC, i want decrease this DC when we have low data traficfor exemple i use DC=0,5% and in nother node which have to transmit long data trafic i use DC=1,5% it means that i distribut this DC between nodes.

it is possible to do this experience ?


(Jose Marcelino) #6

No, the duty cycle regulations apply to each product individually.


(Norhane) #7

So, how i improve quality of service for lora technologie ? Which parameter i have to study ? Have you an idea ? Can you help me ?


(Z1gm4) #8

I think that you must to check the data sheet of the lora node, and see what are the minimum dc that needs to work properly. If that 0.5% of DC is into that limit, i think that it's possible, but always check the specs.
In the other question about the quality of service, the lora technologie in my opinion has been designed to assure connectivity between two points in a defined distance, so you could assign the packet loss rate like quality meassure unit.


(Norhane) #10

Hi,

have you idea about Adaptive data rate ? how we can improve the quality of service using this parameter ? how work this mecanism ?


(Hylke Visser) #11

Did you see our wiki page about ADR?

https://www.thethingsnetwork.org/wiki/LoRaWAN/ADR


(Norhane) #12

this is the algorithm used in LoRa , how we can improve it ? have you an idea for the contribution of ADR in the improvement of quality of service in LoRaWAN ?

thanks for your help


(Hylke Visser) #13

Yes, this algorithm only works for LoRa modulation.

TTN's implementation is currently only used in our Europe region. The implementation based on an algorithm proposed by Nicolas Sornin (Semtech). This algorithm is probably not the most optimal algorithm, but it provides a good baseline.

If you're interested in this, please help us improve it.


(Norhane) #14

i am working about improvement of Mac Layer of LoRa, so, i am intersting about the amelioration of algorithm of ADR


(Norhane) #15

hello,
please i woule ask you questions about ADR ,

  • why in the algorithm of ADR we devide by 3 SNR margin ?

  • when we look at this : " If the number of steps < Nstep, the remainder is used to decrease the TXpower by 3dBm per step, until TXmin is reached. TXmin = 2 dBm for EU868 ", what is the difference betweek number of steps and Nstep ???

thanks for your help


(Norhane) #16

Hello,

in simulation of lora i would select a device which has a heigher data rate , how can i do this ?

thank you