When does A2 critical parameter comes into the picture?

[gdtelecomm]

Dear Experts,

I would like to understand the role of the A2 critical parameter in 5G. Below is a sample parameter configuration for a cell in my network:

• A1: -95 dBm
• A2: -97 dBm
• A5T1: -98 dBm
• A5T2: -101 dBm
• B2T1: -102 dBm
• B2T2: -113 dBm
• A2critical: -103 dBm

Could you please clarify when the A2 critical parameter comes into play? Specifically, if there is an ongoing voice call session and the RSRP drops below the A2 critical value, will the handover process be triggered, or will it result in redirection?

[darshanmalde]

A2 Critical is a crucial parameter in 5G networks that defines a threshold for the Reference Signal Received Power (RSRP).

When the RSRP of the serving cell falls below this threshold, the network initiates a process to either hand over the user to a stronger cell or redirect the user to a lower radio access technology (RAT) like 4G, if available.

In your specific scenario:

A2 Critical = -103 dBm: This means that if the RSRP of the serving cell drops below -103 dBm, the network will consider taking action.

Ongoing Voice Call: If a voice call is in progress and the RSRP falls below A2 Critical, the network’s primary goal is to maintain the call quality.

Handover vs. Redirection: The network will prioritize a handover to a stronger cell if possible. However, if a suitable cell is not available or if the call quality cannot be maintained, the network may resort to redirection to a lower RAT.

[gdtelecomm]

Thanks for the detailed explanation!

I have one query regarding this:
Since A2 = -97 dBm, the UE must have already attempted inter-frequency handover but didn’t find a suitable cell before its RSRP dropped below the A2 critical threshold. In this case, would the UE preferably be redirected to a lower-priority cell or another cell instead of performing a handover?

[sadanandk2]

A2Critical - which vendor have this name?

[Sareenr]

@gdtelecomm

Since A2 = -97 dBm, the UE must have already attempted inter-frequency handover but didn’t find a suitable cell before its RSRP dropped below the A2 critical threshold. In this case, would the UE preferably be redirected to a lower-priority cell or another cell instead of performing a handover?

This value seems too high for critical thresholds.

[gdtelecomm]

@sadanandk2

A2Critical - which vendor have this name?

Ericsson.

@Sareenr

This value seems too high for critical thresholds.

It’s specific to voice calls. For data, the threshold is set to -118 dBm.

[LordGm]

@gdtelecomm

Since A2 = -97 dBm, the UE must have already attempted inter-frequency handover but didn’t find a suitable cell before its RSRP dropped below the A2 critical threshold. In this case, would the UE preferably be redirected to a lower-priority cell or another cell instead of performing a handover?

For QCI 1, the A2 critical parameter doesn’t hold much significance. Before the threshold is reached, inter-frequency handover or inter-PLMN 4G handover (if there’s an agreement) or SRVCC should already be performed.

[Sareenr]

@gdtelecomm

It’s specific to voice calls. For data, the threshold is set to -118 dBm.

Okay,

Can I ask the value of a1a2searchthreshold?

[Nganyo_JC]

@darshanmalde

In your specific scenario:

A2 Critical = -103 dBm: This means that if the RSRP of the serving cell drops below -103 dBm, the network will consider taking action.

Ongoing Voice Call: If a voice call is in progress and the RSRP falls below A2 Critical, the network’s primary goal is to maintain the call quality.

Handover vs. Redirection: The network will prioritize a handover to a stronger cell if possible. However, if a suitable cell is not available or if the call quality cannot be maintained, the network may resort to redirection to a lower RAT.

Clearly explained

@LordGm

For QCI 1, the A2 critical parameter doesn’t hold much significance. Before the threshold is reached, inter-frequency handover or inter-PLMN 4G handover (if there’s an agreement) or SRVCC should already be performed.

I think it depends, even though it might be rare, considering the context that we are in an NSA network.

[LordGm]

In an NSA setup, the same applies to 4G, using QCI 9/8/6.

[gdtelecomm]

@LordGm

For QCI 1, the A2 critical parameter doesn’t hold much significance. Before the threshold is reached, inter-frequency handover or inter-PLMN 4G handover (if there’s an agreement) or SRVCC should already be performed.

We have both 5G SA and 4G networks. So, during a VoNR call, if the UE doesn’t find any suitable cell to hand over to before the RSRP reaches the A2 critical threshold, it gets redirected to the 4G network.

[ankgitm]

@gdtelecomm

Could you please clarify when the A2 critical parameter comes into play? Specifically, if there is an ongoing voice call session and the RSRP drops below the A2 critical value, will the handover process be triggered, or will it result in redirection?

Is this a 3GPP-defined parameter? If yes, where can this parameter be configured?

[LordGm]

@gdtelecomm

We have both 5G SA and 4G networks. So, during a VoNR call, if the UE doesn’t find any suitable cell to hand over to before the RSRP reaches the A2 critical threshold, it gets redirected to the 4G network.

Yes same good point.

[sadanandk2]

@ankgitm

Is this a 3GPP-defined parameter? If yes, where can this parameter be configured?

No, it’s not a purpose-specific parameter defined by 3GPP.

3GPP only defines the A2 event. It’s up to the vendor to determine how to implement and utilize it.