nRF9160 Bluetooth coexistence Insufficient Documentation

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

ovrebekk — Mon, 05 Dec 2022 14:04:24 GMT

Unfortunately not, this is decided by the network, not the device.

Best regards
Torbjørn

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Fri, 02 Dec 2022 19:43:06 GMT

We are developing drone tracking device, which needs to report its position.
It simply cannot stop reporting the position whenever the modem decides that it whats whole air time.

Is there some configuration of the modem to reduce the amount of data transmitted or retries ?

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

ovrebekk — Fri, 02 Dec 2022 12:20:10 GMT

Hi Tomas

Håkon is currently out of office, so I will help out in the mean time.

[quote user="optical"]What can be done to ensure that the BT will have enough "Air" time to work ?[/quote]

When conditions are this poor you have limited options other than considering whether you can delay the LTE transmission until conditions improve, or somehow reduce the amount of data transmitted to reduce the radio time used by the modem.

As for the Bluetooth link you can adjust the connection parameters in order to make it more robust to these interruptions.

If you use a small connection interval and a long connection supervising timeout then you should be able to keep the link alive even if the radio time is limited.

Data throughput and latency will still be affected though, you will obviously not get the same performance for the Bluetooth link when the radio time is limited.

Best regards
Torbjørn

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Fri, 25 Nov 2022 14:41:53 GMT

Hi Tomas,

Thank you for the update. The signal in the bad scenario is barely any signal at all. The signal in the "good" scenario is quite poor as well. The poor signal conditions are causing CE level 1 to be used, which means worse conditions for coexistence.

I am also discussing this issue with another team and will get back to you over the weekend.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Thu, 24 Nov 2022 09:18:52 GMT

This is result of %CONEVAL when the LTE signal is poor and the modem is taking too much "Air" time for TX operations. You can evaluate the behavior of the COEX pin of nrf9160 down on the screenshots from the analyzer. COEX2=4 Mode.

%CONEVAL: 0,1,5,8,7,19,"000D951F","23003",306,6447,20,0,1,23,32,8,160
%CONEVAL: 0,1,5,8,7,19,"000D951F","23003",306,6447,20,0,1,23,8,8,160
%CONEVAL: 0,1,5,9,9,20,"000D951F","23003",306,6447,20,0,1,24,8,8,159
%CONEVAL: 0,1,5,8,7,18,"000D951F","23003",306,6447,20,0,1,24,8,8,160
%CONEVAL: 0,1,5,8,7,19,"000D951F","23003",306,6447,20,0,1,23,8,8,160
%CONEVAL: 0,1,5,9,9,19,"000D951F","23003",306,6447,20,0,1,24,8,8,159

These are when the modem has good signal.

%CONEVAL: 0,1,5,36,19,29,"000D951F","23003",306,6447,20,0,0,23,32,8,132
%CESQ: 36,1,18,2
%CONEVAL: 0,1,5,37,19,29,"000D951F","23003",306,6447,20,0,0,23,32,1,131
%CONEVAL: 0,1,7,37,21,29,"000D951F","23003",306,6447,20,0,0,23,1,1,131
%CONEVAL: 0,1,7,37,21,29,"000D951F","23003",306,6447,20,0,0,23,1,1,131
%CONEVAL: 0,1,7,37,19,29,"000D951F","23003",306,6447,20,0,0,23,1,1,131

What can be done to ensure that the BT will have enough "Air" time to work ?

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Tue, 08 Nov 2022 11:55:40 GMT

The modem at this point was trying to transmit packets to the server. Is there an option how to configure the maximum number of repetition or some delay between them ?

The Bluetooth operation would definitively be disrupted by this behavior.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Tue, 08 Nov 2022 09:48:38 GMT

[quote user="optical"]I have tested the COEX2=4 mode using logic analyzer. I found out that the the modem TX mode in poor signal conditions is taking a large amount of bandwidth shared of the device. [/quote]

What is the modem doing in this plot? Is it an RRC connection, or just listening for pages?

As you point out, under poor conditions, you probably have multiple repetitions, which will increase the radio usage. Repetitions etc. are configured by the network, so it is limited what you can do. One suggestion is to have a look at %CONEVAL. This command could give the application the information it needs to decide if sending data would cause coexistence issues.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Fri, 28 Oct 2022 14:08:00 GMT

That is implementation for SoftDevice, which is not what i seek. Read the initial ticker description please.

The second this does not answer my question of behavior of nRF9160 COEX pin with poor signal.
How can bluetooth be operation when LTE modem takes more 90% of transmission time. There needs to be some settings inside the modem to limit this. Or there should be support for COEX0 inside the modem.

Could you pass this ticket to HW engineers from modem firmware team ?

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Fri, 28 Oct 2022 14:02:54 GMT

Hi Tomas, sorry for the late reply.

Have you had a look at the description of the 1-Wire coexistence protocol, as well as the Bluetooth External Radio Coexistence examples?

I hope to have a few more comments to you over the weekend.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Wed, 19 Oct 2022 08:04:57 GMT

I have tested the COEX2=4 mode using logic analyzer. I found out that the the modem TX mode in poor signal conditions is taking a large amount of bandwidth shared of the device.

In this state the Bluetooth will became unusable due to limiting the windows for its transmissions. (The image contains both cases for Poor and Good signal, enlarge for view)

The Modem firmware needs to have some option to give the Bluetooth time to transmit required data, or enable the Input functionality of the COEX0

How should we proceed with this ? I believe that the same issue must have been observe, when the Coexistence feature for the SoftDevices controller were developed. How did you solve this issue?

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Fri, 30 Sep 2022 09:09:26 GMT

Hi Tomas,

1. AT%XCOEX0 is a command that can be used to configure the "COEX0" pin as output in our nRF9160 SIP, and to change state based on the used RF frequency.

There is no support, nor will be, in modem FW for supporting coex0 as input.

The states x,y,z are the PIN output states 0 or 1 that can be configured using the AT%XCOEX0. The COEX0 pin can be configured to be either '1' or '0' for a certain frequency range. The following example will configure COEX1 to be '1' (state x) in the range 1570-1580MHz, '1' (state y) in the range 2000-2180MHz and '0' (state z) in the range 600-800MHz, and '0' (state a) in the range 1000-1200MHz.

AT%XCOEX0=4,1,1570,1580,1,2000,2180,0,600,800,0,1000-1200
OK

The pin toggles to the configured state regardless of RX or TX, as long as the RF frequency (of the LTE band or GNSS) is within the frequency range(s) given in the AT command. But note that in full duplex LTE the RX and TX frequencies are different, so you can set the frequency ranges so that on a TX frequency of a band there is e.g. 0 state and RX frequency has state 1.

COEX1 functions only as 1PPS in GNSS mode. Nothing else is supported or planned to be supported (no timemark as described in PS).

2.a COEX2 is an indicator about the LTE modem RF activity. If modem is not using PSM there should still be gaps where RF is turned off and pin goes low, it depends on the network and how much and often data is sent/received.

2.b: Yes, the AT command manual is good, also for XCOEX0.

2.c: This is a good question and not clearly explained in the AT document. The timing of the <ctrl> = 4 and 5 corresponds to the "as late as possible" option, where the COEX2 toggles to the configured state about 50-100us before the transmission or reception begins in antenna. Pin goes down about 50us after the transmission or reception ends.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Wed, 28 Sep 2022 09:23:38 GMT

Thank you for confirming the versions. Some of the firmware updates includes changes to the COEX interface.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

optical — Wed, 28 Sep 2022 08:04:09 GMT

This is general question about the functionality and options.

We will be using modem firmware 1.3.1 and 1.3.2.

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Tue, 27 Sep 2022 13:06:06 GMT

Hi Tomas, is this modem firmware version v1.3.1 (as mentioned in one of your previous cases)?

RE: nRF9160 Bluetooth coexistence Insufficient Documentation

helsing — Tue, 27 Sep 2022 11:17:58 GMT

Hi Thomas,

Just letting you know I received your request. I will get back to you.

Regards,

Håkon