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LTE: When an UE is configured for event A1 ?

+1 vote

Can someone please explain, why UE is configured for the event A1?
I am want to know the purpose of behind it.

posted Apr 19, 2014 by Harshita

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1 Answer

+2 votes

Entering condition for Event A1 Serving becomes better than threshold:

Inequality A1-1 (Entering condition)

Ms - Hys > Thresh
Inequality A1-2 (Leaving condition)
Ms + Hys < Thresh

The variables in the formula are defined as follows:

  • Ms is the measurement result of the serving cell, not taking into account any offsets.
  • Hys is the hysteresis parameter for this event (i.e. hysteresis as defined within reportConfigEUTRA for this event).
  • Thresh is the threshold parameter for this event (i.e. a1-Threshold as defined within reportConfigEUTRA for this event)

The reason is very clear. You might have observed it when you go just down the Ground based tower and will make the call. Your voice quality will get disturbed and there will be lots of noise distortion. Threshold means it has some quality level say example -95dbm and if it getting -96dbm it means it is getting unwanted resources which is not required so it can reduce the frequency tuning to decrease it.

answer May 2, 2014 by Hiteshwar Thakur
what are the steps taken once A1 event occurs? (To reduce or tuning to decrease it). Does this affect other UEs?
No it does not affect the other UE's. As we know that for each UE eNodeB has to decide a power for which it has to transmit packets.

I remember in UMTS, Pilot Channel Provides the phase reference for coherent demodulation and help the mobile station to estimate the transmission power.

As the Entry condition of E1 is saying that when the Ms-Hys will be grater than threshold. So to maintain the equality we will tune in to decrease.
@Hiteshwar As u know that in case of LTE the channel is shared so each frame consist of info for all UEs at a time.

Based on C-RNTI and scheduling info available in PDCCH each UE will be taking thier own data.

So how can eNB will configure power for each specific UE ?
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+3 votes

I came to know when an UE attach to network, it is configured for events A1 and A2 by default as part of normal attach. Is it correct ? if yes then why ?

+2 votes

I was going through the measurement configuration sends from eNodeB to UE in RRC Connection Reconfiguration message.
I saw that multiple events have been defined and are used. Couple of parameters are considered to detect entering and leaving condition of an event for example event A1. Now I have a question "Threshold and Hys values are same for all the cell or it may different". Does the standard define the value of all these parameters or network operator defines ? If network operator does then what are points to derive these values ?

+1 vote

Since both the events B1 and B2 are used for Inter RAT measurement reporting. Which one is chosen by eNodeB and on what basis ? Is there any dependency on UE capability for that ?