NR UAI (UE-Assistance Information)
The purpose of this tutorial is to show you how to configure gNB so that it can handle UE assistance Information from UE. UE assistance information is a special set of RRC messages introduced since Release 16 mainly for several purpose summarized below. (This is short summary, for the details specified in 3gpp, refer to 38.331-5.7.4.1
- Power Saving : The messages related to the configuration for drx, aggregated bandwidth, MIMO layers, scross-slot scheduling
- Overheating Mitigation : Overheating Assistance Information
- Measurement : The messages related to relaxation for RLM, BFD, RRM measurement
- Others : Preference on RRC Status and etc
As of now, Amarisoft support the receptions of many of the UAI message, but in most case Amarisoft gNB just recieves the message and does not perform any specific activities for the message except 'Preference on RRC State' (Amarisoft gNB performs a specific activity as per the contents of the UAI for 'Preference on RRC State').
Table of Contents
- NR UAI (UE-Assistance Information)
Test Setup
Test setup for this tutorial is as shown below. This is just for low layer testing, you may not need any complicated IP layer setup.
- SIM Card used in this tutorial is the one delivered with the system as it is.
- If you want to change the configuration, The tutorial Configuration Guide would help
If you have a commercial UE that support UE assistance information with Release Preference, you can use the Setup A. If you don't have any commercial UE supporting this feature but have Amarisoft UEsim you can use Setup B. In this Test, Setup B is used.
Setup A
This setup is the case where you use a commerical UE as a DUT supporting UAI (UE-Assistance Information)
Setup B
This setup is the case where you use a commerical Amarisoft UEsim as a DUT supporting UAI (UE-Assistance Information)
Key Configuration Parameters
Followings are important configuration parameters for this tutorial. You may click on the items for the descriptions from Amarisoft documents.
- ue_assistance_information : In this link, you can find the descriptions for all the parameters below.
- overheating_assistance
- max_bw_preference
- max_cc_preference
- max_mimo_layer_preference
- release_preference
Following is Remote_API configuration on UEsim to trigger UE assistance information message.
- ue_assistance_information: In this link, you can find the descriptions for all the parameters below.
- ue_id
- power_pref_indication
- preferred_rrc_state
Test 1 : Release Preference - RRC Inactive
This test is to show how to configure and test a case of UAI for Release Preference with RRC Inactive. This is to let gNB to have preference of releasing with RRC Inactive instead of regular release.
Configuration
The configuration shown here is common configuration for all the subtests belonging to Test 1 and I will not show this configuration repeatedly for every subtest.
I have used gnb-sa-uai-rrc-state.cfg which is copied and modified from gnb-sa.cfg on Callbox (gNB)
I am using mme-ims-cn-assistance.cfg and ims config as shown below.
On UEsim, I used ue-nr-uai-rrc-inactive.cfg which has been copied and modified from ue-nr-sa.cfg (
gnb-sa-uai-rrc-state.cfg is configured as follows.
In gNB configuration, both rrc_inactive and ue_assistance_information configuration is set. With this configuration, ue_assistance_information configures release_preference in it. When release_preference is applied, RRC Inactive is performed according to the configuration set by rrc_inactive parameter.
mme-ims-cn-assistance.cfg is configured as shown below.
In mme configuration, enable cn_assistance_info_support to make core network capable of triggering RRC Inactive state.
ue-nr-uai-rrc-inactive.cfg is configured as shown below. (
The key parameter on UEsim is to enable rrc_incative_support parameter. This parameter let UEsim to inform the supportability of rrc-inactive in UE capability information.
Perform the Test
Start trace on gNB (Callbox)
Power on UE on UEsim (If your DUT is a commercial phone, turn on the phone)
Wait until the initial attach is complete.
Then, send the following remote API command at /root/ue/doc directory on UEsim to let UEsim send the specified ue-assistance-information message. (
./ws.js ue '{"message": "ue_assistance_information", "ue_id":1, "preferred_rrc_state": "inactive"}'
Confirm that RRC State switches to [inactive] as soon as you send the ue-assistance-information message as shown below.
Log Analysis
Following is the log snapshot that are involved in UE assistance information message and handling process.
First check if UE notifies its capability of supporting releasePreference UAI. You can confirm on it from nonCriticalExtension.powSav-Parameters IE in UE capability Information.
When you run the remote API ./ws.js ue '{"message": "ue_assistance_information", "ue_id":1, "preferred_rrc_state": "inactive"}', UEsim is supposed to send UE assistance information with releasePreference.preferredRRC-State inactive.
Once gNB (Callbox) recieves UE assistance information, it is expected to respond. In this case, it is expected to respond with rrcRelease with suspendConfig (i.e, RRC inactive).
RRC / NAS Signaling
ueAssistanceInformation - preferredRRC State : inactive (SA)
: This is ueAssistanceInformation message from UE with preferred RRC State = inacative.
{
message c1: ueAssistanceInformation: {
criticalExtensions ueAssistanceInformation: {
nonCriticalExtension {
nonCriticalExtension {
releasePreference-r16 {
preferredRRC-State-r16 inactive
}
}
}
}
}
}