GCI search & multiple cell location

RE: GCI search & multiple cell location

AndrewKostka — Mon, 01 May 2023 17:57:38 GMT

Hi, Marco: Unfortunately we're not able to give out the exact source of a specific data point. We're going to address this issue within the next couple of months, as part of a larger set of improvements to LTE Location Services.

However, I'd encourage you to test more than just this one data point, as you may get more accurate results from other towers when your device completes handover.

RE: GCI search & multiple cell location

barbiz — Wed, 26 Apr 2023 12:40:46 GMT

Hello,

thanks.

At this point, we are stuck... do you have any idea on when this implementation can be improved?

Or perhaps can you tell us who the location provider is behind?

It's quite anoying to know that the solution is there but cannot access to it...

Marco

RE: GCI search & multiple cell location

AndrewKostka — Tue, 25 Apr 2023 16:24:38 GMT

Hi, Marco: I've looked more into why my initial results were different from what I see now on nrfcloud. We have multiple data sources for some areas, and we continuously do performance evaluation in order to rank those data sources. The environment where I did my initial test had slightly outdated rankings. While these rankings in general improve our success rate, in very specific cases like this it can decrease accuracy.

This edge case has given our team some ideas for improvement of this ranking procedure, including checking SCELL vs. MCELL results for uncertainty decreases. I'm sorry if this isn't the answer you were hoping for, but these cases help us improve our service over time.

RE: GCI search & multiple cell location

barbiz — Fri, 21 Apr 2023 08:29:17 GMT

Hello,

yes I understand that data can change but this seems really a suspicious concidence. Consider I never got improvement by adding multiple cells in this way.

Waiting for updates

Marco

RE: GCI search & multiple cell location

AndrewKostka — Thu, 20 Apr 2023 17:41:27 GMT

Hi Marco:

I now see the same result that you do for that data. It is to be expected that results will sometimes change slightly over time, as data sources get refreshed and updated. However, I'm also seeing what you are seeing, that the second cell no longer changes the accuracy. I'm going to look into this in our data sources to gather more information.

RE: GCI search & multiple cell location

barbiz — Wed, 19 Apr 2023 17:25:02 GMT

Dear Andrew,

first of all, thank you for your detailed explanation!!

I am having too issues in finding my cells in cellmapper. Thay are in the same eNodeb as your example, but in different sectors which are not in the cellmapper database. however, this is what the radio returns.

On other hand, I am unable to reproduce your results with nrfCloud.

For example, this query:

{
 	"lte": [
		{
			"mcc": 222,
			"mnc": 1,
			"tac": 17211,
			"eci": 179200573
		}
	]
}

returns a different result:

{
	"lat": 45.4146033,
	"lon": 11.9093139,
	"uncertainty": 1201.109,
	"fulfilledWith": "SCELL"
}

Also the second query:

{
 	"lte": [
		{
			"mcc": 222,
			"mnc": 1,
			"tac": 17211,
			"eci": 179200573
		},
		{
			"mcc": 222,
			"mnc": 1,
			"eci": 179200575,
			"tac": 17211
		}
	]
}

does not give any accuracy improvement:

{
	"lat": 45.4146033,
	"lon": 11.9093139,
	"uncertainty": 1201.109,
	"fulfilledWith": "MCELL"
}

Can you help me understand why I am getting different results by calling the API?

thanks much,

Marco

RE: GCI search & multiple cell location

AndrewKostka — Mon, 17 Apr 2023 21:59:51 GMT

Hi, Marco: I'm Andrew, I work on the Location Services feature with Cole.
I'd like to offer some more context to the conversation surrounding LTE positioning. First, I think there seems to be a misunderstanding about the term "cell". The term "cell" refers to a specific geographic area that is served by a specific tower, or eNodeB in LTE terminology. Let's look at an example using your original serving tower to see how multicell can improve a position estimate.

Let's take the following request and look at its corresponding cell on CellMapper:

{
 	"lte": [
		{
			"mcc": 222,
			"mnc": 1,
			"tac": 17211,
			"eci": 179200573
		}
	]
}

Finding the corresponding cell on CellMapper means deriving the eNodeB, or tower, ID from the Cell ID. The eNodeB ID here is '700002', and the Sector (or cell) ID is '61'. This is what that cell looks like:

The result we get from nRF Cloud for that data is here:

{
	"lat": 45.4181242,
	"lon": 11.9116044,
	"uncertainty": 796
}

Which correlates to this position:

Now, let's add another nearby cell. Adding another cell from the same eNodeB makes our request:

{
 	"lte": [
		{
			"mcc": 222,
			"mnc": 1,
			"tac": 17211,
			"eci": 179200573
		},
		{
			"mcc": 222,
			"mnc": 1,
			"eci": 179200575,
			"tac": 17211
		}
	]
}

Here's our new cell in CellMapper:

We can see that while this cell has the same serving tower, it is geographically located further to the southwest than our first cell. So, how does this change our results?

{
	"lat": 45.40624738,
	"lon": 11.8985796,
	"uncertainty": 568
}

We can see our new position is over a kilometer further to the southwest, which makes sense given the geographic location of the cells. Additionally, our uncertainty has reduced by about 230M, suggesting we are more confident about the result position.

Unfortunately I wasn't able to find information about the specific cells in your original request on CellMapper, so I can't confirm the location of the actual cells.

RE: GCI search & multiple cell location

barbiz — Mon, 10 Apr 2023 21:33:20 GMT

Dear Cole,

I understand, but I honestly think this is an oversimplified explanation.

The cases I am spotting out are very simple: the radio finds three cells, I can spot them on cellmapper and draw the best intersection and provide, manually, a better location than the single cell would allow.

I could do this, theoretically, by a script querying the cloud N times and then making the average.

My question is: why the locations services does not do that? Is there any reason? Or is there any plan to do that?

Or maybe I am wrong: can you please spot out an example where the cloud is actually providing better accuracy with GCI search? (not normal search, we already know that 99% of the cases normal search does not give any further cells)

This would help us to understand how the thing works.

Thanks

Marco

RE: GCI search & multiple cell location

Cole Hafner — Mon, 10 Apr 2023 18:34:52 GMT

Hi Alex and Marco,

Multi cell accuracy depends on a variety of factors: cell density of the area (rural or urban), which cells the SIM carrier is allowed to connect to (irrelevant in 1.3.4), signal strength etc. Sometimes single cell accuracy is just as good, in other cases multi cell is better.

The "uncertainty" response is an estimate of where your device may be relative to the location of the tower, here are some docs. We are working on docs that better explain the details of this.

Alex, will you pass me your device details in a private message? I would like to investigate your specific use case.

Best Regards,

Cole

RE: GCI search & multiple cell location

amessner — Thu, 06 Apr 2023 16:00:56 GMT

Hi everyone,

We actually ran into the exact same issue.

We use Soracom in Alberta, Canada and when using the GCI search types and mfw_v1.3.4 we do get additional cells as expected. However, when injecting these additional cells into the "nmr" section of the a location request to the nRF Cloud we don't see any improvement on the location either.

Currently we are only evaluating the recent improvements on multicell, so we send the requests directly from the device using a service key.

Thanks
Alex

RE: GCI search & multiple cell location

barbiz — Mon, 20 Mar 2023 08:33:17 GMT

Hi Cole,

did you get any news from the vendors?

thanks

Marco

RE: GCI search & multiple cell location

Cole Hafner — Wed, 15 Mar 2023 05:47:14 GMT

Hi Marco,

This is very odd indeed. I am passing your findings onto our vendors and will get back to you.

Cole

RE: GCI search & multiple cell location

barbiz — Tue, 14 Mar 2023 14:41:24 GMT

Dear Cole,

I tried with other SIMs form other providers. But the cells that can be seen do not change much. I managed to add one more cell to the list:

{
	"lte": [
		{
			"mcc": 222,
			"mnc": 1,
			"eci": 52015010,
			"tac": 37560,
			"earfcn": 6254,
			"adv": 65535,
			"rsrp": -78,
			"rsrq": -10
		},
		{
			"mcc": 222,
			"mnc": 1,
			"eci": 179200674,
			"tac": 37560,
			"earfcn": 6254,
			"adv": 65535,
			"rsrp": -78,
			"rsrq": -10
		},
		{
			"mcc": 222,
			"mnc": 1,
			"eci": 179200673,
			"tac": 37560,
			"earfcn": 6254,
			"adv": 65535,
			"rsrp": -78,
			"rsrq": -10
		},
		{
			"mcc": 222,
			"mnc": 10,
			"eci": 9721967,
			"tac": 37560,
			"earfcn": 6354,
			"adv": 64,
			"rsrp": -78,
			"rsrq": -10
		}
	]
}

However, no improvement on the response.

NOTE: I am using Nb-IoT.

I cannot really understand if this is working as expected. The cells in the nearby are actually in a range of 400m (red line on the map)

So I don't understand:

why single cell location give only 2500m accuracy (if the device was 2500 metres away, it would receive other cells)
why multiple cell location does not give any improvement.

Thanks & best

Marco

RE: GCI search & multiple cell location

Cole Hafner — Tue, 14 Mar 2023 04:48:32 GMT

Hi Marco,

I can reproduce the issue. I see that it makes no difference whether the neighbor cells are included. This could be due to available cell towers in the area or that your SIM is locked down to one carrier with only access to certain towers. Do you have a different SIM that you could try? That may get you higher accuracy.

Cole

RE: GCI search & multiple cell location

Cole Hafner — Mon, 13 Mar 2023 16:10:38 GMT

Hi Marco,

I'm looking into this today.

Thanks for your patience.

Cole

RE: GCI search & multiple cell location

barbiz — Mon, 13 Mar 2023 10:37:41 GMT

Hello, any news?

thanks

Marco

RE: GCI search & multiple cell location

barbiz — Tue, 07 Mar 2023 22:44:36 GMT

Team ID is

a918c7d0-ca8f-4738-9c40-7db89aeea4bb

RE: GCI search & multiple cell location

Cole Hafner — Tue, 07 Mar 2023 22:35:31 GMT

Yes, please provide TeamID.

RE: GCI search & multiple cell location

barbiz — Tue, 07 Mar 2023 22:13:14 GMT

You asked me to provide a device ID to look for logs. However, I do not have it because I made a cloud API call without specifyng device id. I can give you team ID maybe?

Anyway, could you try to reproduce it and help me understand why accuracy does not increase?

RE: GCI search & multiple cell location

Cole Hafner — Tue, 07 Mar 2023 20:14:52 GMT

Hi Marco,

[quote userid="114732" url="~/f/nordic-q-a/97089/gci-search-multiple-cell-location/412702"]what is the difference between my formatting and passing an array of cells direcly in the "lte" object?[/quote]

Either way works. Passing an array of cells considers several serving cells (cells with an ECI value) and a group of neighbor cells for each (the nmr property). This can provide more accuracy in some cases.

[quote userid="114732" url="~/f/nordic-q-a/97089/gci-search-multiple-cell-location/412702"]How can I make my call trackable?[/quote]

What do you mean by this?

Cole

RE: GCI search & multiple cell location

barbiz — Tue, 07 Mar 2023 10:30:56 GMT

Hello, any updates?

thanks

Marco

RE: GCI search & multiple cell location

barbiz — Wed, 01 Mar 2023 10:25:02 GMT

Actually, I am directly calling the API cloud-to-cloud so there is no device id. How can I make my call trackable?

Also, I was wondering: what is the difference between my formatting and passing an array of cells direcly in the "lte" object?

RE: GCI search & multiple cell location

Cole Hafner — Tue, 28 Feb 2023 18:34:18 GMT

Hi Marco,

Your formatting is correct. What is the device ID? I can look into the logs and see if I can help you get a better result.

Thanks,

Cole