Larger UpLink TBS size in LTE-M on nRF9161/51 ?

[fdup78]

Greetings,

One question on the nRF9161/51 capabilities: is the 3GPP Rel-14 LTE-M Cat-M1 larger UpLink transport block size (TBS) of 2984 bits supported (instead of 1000 bits in Rel-13 Cat-M1) ?

Cf. Rel-14-defined ce-PUSCH-NB-MaxTBS-r14 Information Element (IE) reported by the UE.

Best regards,

François.

[dejans]

Hi,

One question on the nRF9161/51 capabilities: is the 3GPP Rel-14 LTE-M Cat-M1 larger UpLink transport block size (TBS) of 2984 bits supported (instead of 1000 bits in Rel-13 Cat-M1) ?

Which 3GPP Rel 13 and Rel 14 Technical Specifications do you refer to? Can you provide links to relevant pages/tables in those documents?

Best regards,
Dejan

[fdup78]

Hello,

This evolution was introduced in Rel-14 for LTE-M, in the UpLink only.

Please refer to the following GSMA documentation :

Mobile IoT Deployment Guide

https://www.gsma.com/solutions-and-impact/industries/smart-mobility/wp-content/uploads/2022/10/Mobile-IOT-Deployment-Guide-October-2022-1-1.pdf

More precisely §5.2 LTE-M Specific features, section « Higher UL peak rate » :

Higher UL peak rate

This Release 14 feature introduces support for a larger transport block size (TBS) of 2984 bits instead of 1000 bits in order to increase the UL peak rate for Cat-M1. Increasing the UL TBS is not expected to increase the UE complexity significantly but will provide an UL peak rate boost which may be particularly useful in DL-heavy TDD configurations.

Recommendations

It is recommended Higher UL peak rate for LTE-M be supported by both the network and devices.

From what I understand this is specified by 3GPP TS36.213, §8.6.1 & §8.6.2 (the ce-pusch-nb-maxTbs IE element is mentioned there).

It points to Table 8.6.1-2A which was added in Rel-14

[…]

For a BL/CE UE

-    if the UE is configured with CEModeA, and higher layer parameter ce-pusch-nb-maxTbs-config configured with value 'On', and if the MPDCCH corresponding to the PUSCH transmission is located in UE-specific search space, the modulation order is determined according to table 8.6.1-2A.

[…]

-    elseif the UE is configured with higher layer parameter ce-pusch-nb-maxTbs-config with value 'On', and if the MPDCCH corresponding to the PUSCH transmission is located in UE-specific search space, the UE shall first determine the TBS index () usingand Table 8.6.1-2A;

Table 8.6.1-2A: Modulation and TBS index table for PUSCH

MCS Index	Modulation Order	TBS Index
0	2	0
1	2	2
2	2	4
3	2	5
4	2	6
5	2	8
6	2	10
7	4	10
8	4	12
9	4	14
10	4	16
11	4	17
12	4	18
13	4	19
14	4	20
15	4	21

 

Hope this helps.

Best regards,

François.