TDoA algorithm Implementation

Osman · March 2, 2018, 4:25pm

Thanks a lot @brocaar. If it is the default packet forwarder, then how it could possibly give us nano second resolution.

Because in the source

it is bound to give microseconds. Could you kindly clarify this ?

About modification

I have read one document where source (lora-packet-forwarder) has been modified and cross compiled using linux toolchain.

toolchain

Could we do similar work for our multitech conduits ?

brocaar · March 3, 2018, 4:39pm

Sorry, I might not have been clear on this. I never claimed that the packet-forwarder is providing nanosecond precision timestamp, only that the LoRa Gateway Bridge is using the ns timestamp formatting of the Go time package (which is able to parse the packet-forwarder timestamp format, even when less digits are provided):

RFC3339Nano = "2006-01-02T15:04:05.999999999Z07:00"

Of course the LoRa Gateway Bridge can’t make it more accurate than what you feed it

BadBane · April 30, 2018, 3:13pm

Hello, I also was trying to figure out how to get nanosecond precision for using TDoA techniques on LoRa. I’ve also read this thesis with changing of the uSeconds to nanoseconds. Did you manage to find a solution for getting nanoseconds resolution after all? I’ve been struggling for days to find a good approach on that!
Thanks a bunch!

brocaar · April 30, 2018, 3:32pm

You need a gateway with fine-timestamp support. You also need to license the key to decrypt this fine-timestamp as it is encrypted.

BadBane · April 30, 2018, 4:23pm

Thanks a lot for the quick answer! Any suggestions on Gateways that support precise timestamping? Above you stated that conduit ones don’t really support that.

Osman · April 30, 2018, 4:48pm

No, unfortunately i did not try it till now. But as mentioned in the thesis document, we need to cross compile the packet forwarder with the changes mentioned (replace %06 with %09 and remove division by 1000).
@brocaar If i want to do the above changes in your created packages listed here, what steps do i need to follow?
My understanding is to download the LoRa default packet forwarder on a liux machine and compile it by making the above mentioned changes. However, i am not sure about this. Could you kindly guide me in this regard?

Thanks for your help

brocaar · April 30, 2018, 6:05pm

This is the recipe I’m using for the Conduit packet-forwarder package (you can add your own patch there):

github.com

brocaar/loraserver-yocto/blob/master/layers/meta-semtech/recipes-lora/lora-packet-forwarder/lora-packet-forwarder_4.0.1.bb

DESCRIPTION = "LoRa Packet Forwarder"
HOMEPAGE = "https://github.com/lora-net/packet_forwarder"
PRIORITY = "optional"
LICENSE = "BSD"
LIC_FILES_CHKSUM = "file://LICENSE;md5=22af7693d7b76ef0fc76161c4be76c45"
DEPENDS = "lora-gateway"
PR = "r5"

SRCREV = "v${PV}"
SRC_URI = "git://github.com/Lora-net/packet_forwarder.git;protocol=git \
           file://lora-packet-forwarder-ap1.init \
           file://lora-packet-forwarder-ap2.init \
           file://global_conf.json.MTAC-LORA-H-868.basic \
           file://global_conf.json.MTAC-LORA-H-868.gps \
           file://global_conf.json.MTAC-LORA-H-915.basic \
           file://global_conf.json.MTAC-LORA-H-915.gps \
           file://lora-packet-forwarder-add-spi-dev-path.patch \
"

S = "${WORKDIR}/git"

This file has been truncated. show original

brocaar · April 30, 2018, 6:06pm

Kerlink is one of the vendors that have gateways with support for precise timestamps.

BadBane · May 1, 2018, 9:01pm

Perfect thanks, I’ll give it a look and report my findings!

1kastner · May 23, 2018, 10:31pm

Have you made any progress? I was also interested in geopositioning and I have read all the way you have already taken. I am very interested in whether you have found a solution and if so, how you did it. Did you find hardware with the fine nanosecond timestamps? Could you enable that granularity as well? Thanks a lot in advance!

1kastner · May 28, 2018, 6:48am

Have you found a good source for nanosecond-accurate gateways? Kerlink offers more than one gateway nowadays and I was searching for an appropriate hardware solution.

brocaar · May 28, 2018, 8:43am

I believe the iBTS (Compact) gateway from Kerlink does provide the fine timestamp I hope to have one myself soon for testing and better integration (as this gateway also supports multiple antennas and modules).

Osman · May 28, 2018, 9:57am

Hi,

Actually, i was unable to find gateways that are designed for TDoA algorithm. And the one i purchased (Multitech LoRa conduit) are rather poor for Geolocation. Therefore, my results are not encouraging. The clocks are highly unreliable in terms of precision. I am using clocks with micro second resolution and the achieved accuracy in terms of distance is above 500 meters (for ideal cases). As a result, i would try to integrate RSSI alongwith TDoA and see if it improves the performance. Because as of now, the system is highly unreliable and unstable.
If you are going for Kerlink gateways, they have their own TDoA solver as well but i guess you need to pay more.
Please read the following article “TDoA-Based Outdoor Positioning with Tracking Algorithm in a Public LoRa Network” where the authors have used the Kerlink gateways and their TDoA solver. The results in the paper are encouraging as the authors have made improvements in the algorithm itself. But the basic TDoA solver was provided by Kerlink

Osman · May 28, 2018, 10:08am

You can also look here for more information about Kerlink gateways and their TDoA solver.

Best Regards,

Usman

BadBane · May 30, 2018, 12:58pm

Hello everyone,

No progress on the Gateway + Fine timings but I am doing research on implementing gps modules on Gateways so I can take advantage of their fine timing because the Kerlink Gateway are way too expensive. I still couldn’t confirm any gps that provide this timing. Plus you will need a way to keep this timing with an external clock afterwards.

barillaro · August 30, 2018, 9:29pm

Dear LoRaServer friends,

I am following your steps. I am also willing to deploy a geolocation solution based on lora Geolocation capability. I am still trying to find a gateway vendor. So far, Kerlink is offering a big package with hardware + software (bloatware?). MAXIIoT said that their hardware support Geolocation, but theyr never have heard nothing about a fee nor have tested Geolocation by thyself.
Do you know if that fee for fine timings is based on messages, devices, monthly, or what?

With best regards

Sebastian

brocaar · September 12, 2018, 1:31pm

In the next LoRa Server release support will be added to integrate with an external geolocation server. An open-source geolocation server which integrates with the Semtech Collos platform will also be released

Support for this has already been merged into the LoRa Server master branch. LoRa Server will also support the decryption of the fine-timestamp (given a decryption-key has been configured).

Jeryl_Cook · September 15, 2018, 5:16pm

The ‘external geolocation server’ you mentioned already exists? if so what is it.

Also,
I sadly cannot find any fully compatible Gateway for the United states(915Mhz) with network-based LoRa native geolocation…

if anyone has a suggestion of a LoRa gateway with fine-timestamp support and a license the key to decrypt and encrypted the payload…it would be greatly appreciated for the US.

As someone above suggested Kerlink…
The BTS (Compact) gateway from Kerlink seems to be only offered for EU, and not for the United States yet.

Thanks.

brocaar · September 16, 2018, 9:37am

The ‘external geolocation server’ you mentioned already exists? if so what is it.

Please see GitHub - brocaar/chirpstack-geolocation-server: LoRa Geo Server is a geolocation server part of the LoRa Server project. This will be announced in the next release and also added to the docs You’ll find a preview here: https://www.loraserver.io/lora-geo-server/overview/.

I sadly cannot find any fully compatible Gateway for the United states(915Mhz) with network-based LoRa native geolocation…

I think that Kerlink does have an US915 model of their iBTS gateway, but please contact them for more information. Other vendors that sell gateways with geolocation capability (there might be more) are: Tektelic and Cisco.

pooja.mittal · June 10, 2019, 12:11pm

Hey @Osman, hope you’re doing well!

I would like to know that after achieving FineTimeStamp with nanosecond precision (with v1 Gateway), were you able to successfully encrypt it inside the v1 gateways(which are without FPGA) ?

And send it successfully to the LoRa Server, which later decrypts it and forwards it to LoRa Geo Server?

If yes, then can you kindly share how?

Thank you!