Please consolidate nRF9160 documentation about CP-RAI and AS-RAI

[Achim Kraus]

Knowing, that the AS-RAI implementation is experimental, I would still prefer to have more documentation about the details.

I already asked for these details in an other issue (see Details of AS-RAI and CP-RAI fallback ) but for me there are still some gaps.

The above referred thread discussed, that requesting to use Rel. 14 AS-RAI, the modem falls back to Rel. 13 CP_RAI, if AS-RAI isn't supported by the network provider. So far, so good. The nasty point seems to be, that you can't use this fallback without knowing that, because the supported options seems to differ for AS-RAI and CP-RAI and a function to see, that the modem decided to fall back, is missing.

My results (the trace are provided in the referred thread):

With Rel. 14 AS-RAI only the SO_RAI_NO_DATA seems to work, with SO_RAI_ONE_RESP I had no success.

With requesting Rel. 14 AS-RAI, but fallback to Rel. 13 CP-RAI, SO_RAI_NO_DATA doesn't work, but SO_RAI_ONE_RESP is now working.

My questions:

1. Please document, which options are working in which mode (SO_RAI_NO_DATA, SO_RAI_LAST, SO_RAI_ONE_RESP combined with Rel. 14 AS-RAI, AS-RAI fallback to CP-RAI).

2. Is it possible the check, if the modem falls back to Rel. 13 CP-RAI? Especially, if the first question shows, that there are no common supported options, such a function helps to implement a working application.

Thanks in advance. 

[dejans]

Hi,

I have asked internally. I will get back to you by Monday next week at the latest.

Best regards,
Dejan

[Achim Kraus]

Thanks!

Also for the answers in the other discussion.

[Achim Kraus]

OK, I give up.

This is mixed up and the sayings are moving ("fallback" is now "implicitly used").

The resulting table, as I understand it:

RAi option	AS-RAI	AS-RAI using CP-RAI implicit (fallback)
RAI_SO_LAST	works	works
RAI_SO_ONE_RESP	doesn't work	works
RAI_SO_NO_DATA	works	doesn't work

I would guess, for offering a easy to use and understand API, it will be very easy to map RAI_SO_ONE_RESP for AS-RAI also "implicit" to RAI_SO_NO_DATA after receiving the next datagram. Not sure, but maybe RAI_SO_LAST is already the result of using implicit RAI_SO_NO_DATA after sending the last  datagram.

An extension of LTE_LC_EVT_PSM_UPDATE with AS-RAI active in network would be very useful. As well as error codes for setsockopt (e.g. "-ENOTSUP" for RAI_SO_NO_DATA, if the network doesn't support it) will help a lot.

[Michal Mühlpachr]

dejans said:

- If AS-RAI is not enabled on the network side, then CP-RAI is implicitly used and both SO_RAI_LAST or SO_RAI_ONE_RESP are used accordingly.

What about SO_RAI_NO_DATA in this case?

The rest seams clear to me, even though it's a little convoluted ;-)

Thanks for the explanation.

[Achim Kraus]

Michal Mühlpachr said:

What about SO_RAI_NO_DATA in this case?

Isn't it your experience, that this doesn't work?

It also doesn't work in my tests.

[Michal Mühlpachr]

Achim Kraus said:

Isn't it your experience, that this doesn't work?

Yes, it is, I'm just making sure I understand this correctly.

[Michal Mühlpachr]

Achim Kraus said:

This is mixed up and the sayings are moving ("fallback" is now "implicitly used").

if I understand, the description is consistent with the previous ticket. AS-RAI and CP-RAI are used simultaneously if the operator supports them (priority undefined by standards, EPC implementation dependent, but usually AS-RAI has precedence). When AS-RAI is enabled on the modem but the operator does not support it, the modem attempts to use CP-RAI.

BTW is there API way to detect whether network is R13 or R14, weather AS-RAI or R14 features are supported?

[dejans]

Hi,

Michal Mühlpachr said:

is there API way to detect whether network is R13 or R14, weather AS-RAI or R14 features are supported?

Our customers do not need to know which RAI is supported or which is enabled (if any). It is enough to configure last_packet/one_resp/no_data socket option based on the situation in application and modem will use it in the best possible way depending on network's RAI support. Simply set the socket options to the best of application knowledge. There is no need for knowing other possible sockets in use when setting socket options for one socket because modem has common understanding of all sockets. In addition, it is not necessary to know which protocol (TCP or UDP) is used because the protocols are handled below the socket interface.

Best regards,
Dejan

[Achim Kraus]

> It is enough to configure last_packet/one_resp/no_data socket option

That is exactly not the case! Someone need to know, that using one_resp or no_data doesn't work reliable, these options must be used together.

[Michal Mühlpachr]

dejans said:

Our customers do not need to know which RAI is supported or which is enabled (if any).

We are your customer and we need to know that for troubleshooting purposes.

Knowing that and reporting that to our backend occasionally brings insight about operator/transport in use and allows battery lifetime estimation (based on communication power usage estimation). The modem do not provide information about "power consumed" unfortunately, so we do not have any other possibility how to estimate battery lifetime in case power consumption key drivers are unknown.

How would you suggest estimating energy consumed by the modem without knowing those details?