top button
Flag Notify
    Connect to us
      Facebook Login
      Site Registration Why to Join

Facebook Login
Site Registration
Print Preview

In LTE does UE performs contension based RACH or contension free RACH for UE uplink sync?

+4 votes
62 views
posted Feb 17 by Prabha
Share this question
Facebook Share Button Twitter Share Button Google+ Share Button LinkedIn Share Button Multiple Social Share Button

3 Answers

+3 votes

Both contention based and free rach are possible in case of UL unsynchronized.
If ue have UL unsynchronized and want to send data in UL then ue will perform contention based rach.

If ue is in UL unsynchronized and eNodeB want to schedule data in DL then eNodeB first send the pdcch order to ue. After getting pdcch order, ue will perform rach. This rach can be contention based or free. If eNodeB sends rach preamble in pdcch order then ue performs contention free rach otherwise ue performs contention based rach.

answer Feb 17 by Veer Pal Singh Yadav
+2 votes

It is contention based RACH, In msg3 UE will send MAC-CRNTI control element to make contention resolve.

answer Feb 17 by Jaganathan
+2 votes

UE performs both types of RACH but one at a time depending on the scenario. In handover case it performs contention free RACH if target enodeb instructs else it go ahead with contention based RACH.

answer Feb 17 by Vimal Kumar Mishra

Your answer

Preview

Privacy: Your email address will only be used for sending these notifications.
Anti-spam verification:
To avoid this verification in future, please log in or register.
Similar Questions
+1 vote

I don't know the complete use of CQI at eNodeB. Does it impact only downlink scheduling parameters or also considered while granting uplink resources ?

+2 votes

This is not a usual case. Assume an eNodeB has multiple bearers (GBR and non-GBR) with the UE, eNodeB enforces subscribed downlink data rate by using the different scheduling algorithm. Can eNodeB reject the uplink grant assuming UE is crossing its subscribed limit ?

+1 vote

Why do we need only contention free RACH in LAA cells?

+1 vote

MAC notifies RLC of a transmission opportunity asking for data each TTI. So does RLC respond with multiple PDUs one for each UE (with different RLC SNs for each of the PDU). Or just sends down one PDU (with one RLC SN) having data of all the scheduled UEs?
This same question could be put this way too: Are the RLC SNs assigned independently for each UE or are they assigned by incrementing by 1 every TTI?

+1 vote

How many times UE can ask SR for uplink grant is there any limit for SR for uplink grant? When SR will not be available , because i heard UE will do rach if it don't have SR configuration so when this scenario will occur.


Useful Links with Similar Problem
Contact Us
+91 9880187415
sales@queryhome.net
support@queryhome.net
#470/147, 3rd Floor, 5th Main,
HSR Layout Sector 7,
Bangalore - 560102,
Karnataka INDIA.
QUERY HOME
...