Essential information to know about 4G & 5G UE Capability Message
This article will cover some vital information regarding 4G & 5G UE Capability messages. It is important to highlight that UE Capability message is essential in Network troubleshooting, feature testing, and new devices benchmarking and testing; that is why it is necessary to get yourself familiar with UE Capability information and to learn how to read some info such as 4G Carrier Aggregation combination and ENDC Capability.
The following will be covered in this article:
- What is the UE Capabilities message?
- 3GPP Explanation for different band combination
- User Guide: How to read 4G CA & NR-ENDC Band combination?
- UE Capability signaling limitation and 3GPP Proposed Solution
What is the UE Capabilities message?
Definition:
UE capability is an RRC signaling mechanism in which the UE provides its capabilities to the network.
Why is it needed?
BTS will be able to make accurate scheduling decisions after receiving UE Capabilities info
Information Covered?
1- Network Capability: Included in Attach Request; Such as the following
- SRVCC to GERAN & UTRAN Capability
- Voice Domain Preference
- n1Mode capability for E-UTRAN
- dCNR Capability
2- Radio Capability: Included in UE Capability info; Such as the following
- ue-Category
- PDCP, RLC, MAC, PHY Parameters
- RF Parameters (Includes band combination)
- FGI- feature Group Indicators
- fr1-Add-UE-NR-Capabilities
3GPP Explanation for different band combination
The following 3GPP Tables summarize CA different bandwidth Classes, which will be used as a guide to read and understand Carrier Aggregation and ENDC Combination.
3GPP Tables of different band combinations for 4G&5G
User Guide: How to read 4G CA & NR-ENDC Band combination?
4G CA Band Combination guide:
CA Combination = B1A_B1A_B3C = 4 Carriers
- 1A: 1 = LTE Band 1, A = a single CC of up to 100 PRBs(Non Contiguous)
- 3C: 3 = LTE Band 3, C = two contiguous CCs of up to 200 PRBs total
ENDC Band Combination guide
DC Combination = B1A_B3A_B41C = 4 LTE CA + 1 NR
- 1A = LTE Band 1, A = a single CC of up to 100 PRBs(Non Contiguous)
- 3A = LTE Band 3, A = a single CC of up to 100 PRBs(Non Contiguous)
- 41C = LTE Band 41, C = two contiguous CCs of up to 200 PRBs total
- 77A = NR Band 77 , A = a single CC
UE Capability signaling limitation and 3GPP Proposed Solution
Background:
In the early phase of Carrier Aggregation, only 2CC CA was supported, and the supported band combination was simple. However, as higher carrier aggregation (i.e., 3CC CA, 4CC CA, 5CC CA) is supported and more band combinations are introduced, the size of the UE Capability Information message explodes.
Limitation:
The maximum supported size of a PDCP SDU/PDU is 8188 octets; accordingly, some of the UE Capability information will be missed if the UE Capability information message exceeds 8188 octets.
Solution:
The network can request the UE to send additional UE capability information or can force UE to send the only capability information necessary to the current Network.
