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How many DRB's in LTE? can some one explain their Functions?

+3 votes
How many DRB's in LTE? can some one explain their Functions?
posted Sep 16, 2013 by Giri Prasad

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1 Answer

+4 votes

Answer is 8. As per Table B.1-1 of 36.331 following DRB combinations are supported, based on featureGroupIndicators, received in UE capability information message .

Case 1 ( Bit 7 and bit 20 are set 1 ) :

SRB1 and SRB2 for DCCH + 8x AM DRB    OR   SRB1 and SRB2 for DCCH + 5x AM DRB + 3x UM DRB

Case 2 ( BIT 7 is set 0 and BIT 20 is set to 1) :

SRB1 and SRB2 for DCCH + 8x AM DRB

Case 3 ( BIT 7 and BIT 20 are set to any value ie 0/1) :

SRB1 and SRB2 for DCCH + 4x AM DRB

Case 4 ( BIT 7 is set to 1 and BIT 20 is set to any value 0/1) :

SRB1 and SRB2 for DCCH + 4x AM DRB + 1 UM DRB

I hope this should clarify ur doubt.

answer Sep 16, 2013 by Luv Kumar
Thank You for your earliest Response.
can u please explain little more about the BIT 7 and BIT 20? why depends on this value only RLC mode is changing?
Not sure what u are trying to ask, let me explain bit 20 and Bit 7 -
Regardless of what bit number 20 is set to, if bit number 7 is set to ‘1’, UE shall support at least SRB1 and SRB2 for DCCH + 4x AM DRB + 1x UM DRB
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+1 vote

Hi All,

It is mentioned in different websites that in LTE max. of 8 DRB can be established per UE. But as per page 652 of 36.331 V13.2.0, the max no. of DRB is 11.
"maxDRB INTEGER ::= 11 -- Maximum number of Data Radio Bearers"

Based on what source are we saying that max. DRB in LTE is 8 and not 11.

It was mentioned in one of the old threads the following:

If EPS bearer ID is = x +4 ;
DRB ID = x;
Logical Channel ID = x + 2

I found the above relationship of DRB ID & EPS Bearer ID to be true for one of the eNB vendors but not for another one.

EPS ID is 5 and DRB ID is 4 instead of 1. Can somebody comment in this?
NOTE : All these ranges is with respect to DRB establishment

EPS Bearer ID Range is INTEGER (0..15) (But 0-4 is reserved so we use starting from 5 )
DRB ID Range is INTEGER (1..32) (As in LTE max 8 DRB can be established per UE so we use from 1-8)
Logical Channel ID range for DRBs is INTEGER (3..10) ( For for DRB1 we use 3 as logical channed ID)


+1 vote

Why the numbers of SRB’s and DRB’s are fixed as 3 and 8 in LTE?

0 votes

Is EPS bearer ID and RAB ID common for all UE ? or RAB ID will be unique for default bearer ?
Please, explain

+1 vote

As we know Per Resource Blocks (RB) SINR from UE report. I know that an UE reports all the RBs SINR as quick as possible (maybe each subframe period, that is 1 ms). I’m thinking of the Higher Layer-configured subband CQI report since it’s the most capable of inspecting the RBs status as I saw in 3GPP 36.213 Table 7.2.1-1. I’m interested in FDD; unfortunately the least “RB contiguous number” is 4 as in Table 7.2.1-3. Do we have a better method capable to inspect each RB?

+1 vote

I have very limited insight in mutlimedia multicast/broadcast services. An article says one LTE cell can have maximum of 8 MCCH channels and each MCCH configuration corresponds to configuration of one MBSFN area.
If this is correct then it concludes that one LTE cell can be part of max 8 MBSFN areas.

Each MBSFN area can be used to broadcast multiple multicast/broadcast services.
Now I want to how many TV channels (a kind of broadcast/multicast service) can be broadcasted ?
One related query is how an UE come know about the channels such as DD news, ESPN etc are being broadcasted in cell ?