nRF9160 - mfw 1.3.5 - EARFCN - uplink/downlink

[Achim Kraus]

Using %XMONITOR I get one EARFCN value.

According 3GPP TS 36.101 (V14.3, page 107) there are two EARFCN values, one for the uplink, one for the downlink. The value I get reported with XMONITOR seems to be the one for the downlink. Is there a possibility to get also the uplink value?

The background for that question is band 20, where the uplink range is critical close to an unlicensed range in Germany (862 upper border of band 20 to 863-870 unlicensed in Germany). If it's possible to get that value, it's easier to exclude or consider interference as source of errors.

[Simonr]

Hi Achim

I'm only aware of the EARFCN value reading back one value, this being the channel number for identification of the LTE band. I think this corresponds to both downlink and uplink for each E-UTRA operating band in the specification. You say that band 20 is close to an unlicensed range, but from what I can tell operating band 20 has an uplink bandwidth at 832 MHz, isn't that sufficiently far away from 863MHz?

If you want me to find the specifics on the EARFCN value and if it's possible to get the uplink bandwidth specifically let me know, and I'll ask the developers.

Best regards,

Simon

[Achim Kraus]

> I'm only aware of the EARFCN value reading back one value

Did you read the related and cited 3GPP 36.101 specification?

"5.7.3 Carrier frequency and EARFCN
The carrier frequency in the uplink and downlink is designated by the E-UTRA Absolute Radio Frequency Channel Number (EARFCN) in the range 0 – 262143. The relation between EARFCN and the carrier frequency in MHz for the downlink is given by the following equation, where F DL_low and N Offs-DL are given in Table 5.7.3-1 and N DL is the downlink EARFCN.

F DL = F DL_low + 0.1(N DL – N Offs-DL )

The relation between EARFCN and the carrier frequency in MHz for the uplink is given by the following equation where F UL_low and N Offs-UL are given in Table 5.7.3-1 and N UL is the uplink EARFCN.

F UL = F UL_low + 0.1(N UL – N Offs-UL )"

The table with the frequencies shows also different value ranges for down- and uplinks.

(Band 20 DL, 791-821 MHz, EARFCN 6150 – 6449, UL,  832-862 MHz, EARFCN 24150 – 24449)

> I can tell operating band 20 has an uplink bandwidth at 832 MHz, isn't that sufficiently far away from 863MHz?

According 3GPP 36.101 it start at 832 MHz, but the range is 832-862 MHz

> If you want me to find the specifics on the EARFCN value and if it's possible to get the uplink bandwidth specifically let me know, and I'll ask the developers.

That was my intention. It may be even missing for now. Then I would appreciate, if that could be added in one of the next versions. I consider, this cause in the future quite a lot of trouble and to be clear at that, will help to reduce complains.

[Simonr]

Hi again Achim

Thank you for clarifying. I skimmed through the specification on EARFCN and apparently didn't get the full picture. I've created an internal ticket to the cellular team in Finland and will let you know as soon as I hear from them if we have a way to read the uplink value. Thank you for your patience.

Best regards,
Simon

[Achim Kraus]

Thanks!

[Simonr]

Hi Achim

I got an update from the devs on this today. We're in the middle of summer vacation and low on staff, so that's why it's taken some time to get back to you. 

It seems like UL EARFCN is not provided in the AT interface. The UL channel is defined by default TX-RX separation (36.101 / Table 5.7.3-1 and Table 5.7.4-1) or it may be explicitly signaled with SIB2 (SIB2 content can be seen from traces).

36.331 / Ch. 6.3.1:

SystemInformationBlockType2 field descriptions

ul-CarrierFreq
For FDD: If absent, the (default) value determined from the default TX-RX frequency separation defined in TS 36.101 [42, table 5.7.3-1] applies.
For TDD: This parameter is absent and it is equal to the downlink frequency.

Additionally there is restriction for EUTRA on how channel numbers may be configured near band edges.

The channel numbers that designate carrier frequencies so close to the operating band edges that the carrier extends beyond the operating band edge shall not be used. This implies that the first 7, 15, 25,
50, 75 and 100 channel numbers at the lower operating band edge and the last 6, 14, 24, 49, 74 and 99 channel numbers at the upper operating band edge shall not be used for channel bandwidths of 1.4, 3, 5, 10, 15 and 20 MHz respectively.

Best regards,

Simon