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Can any one clearly explain about this bearers .. I have confusion in understanding these?

+2 votes
519 views
  1. Signalling Radio Bearer (SRB)

  2. Data Radio Bearer (DRB)

  3. Default Bearer

  4. Dedicated Bearer

How these are interlinked to each other?

posted Sep 13, 2016 by Suchakravarthi Sripathi

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1 Answer

+2 votes

SRB stands for signalling radio bearer and it is solely used for transmission of signalling messages such as RRC messages and NAS messages. Three signalling radio bearers have been defined in LTE . SRB0 which is used for transmission of RRC common channel messages. SRB1 which is established for UE and dedicated RRC messages are transmitted over this signaling radio bearer. SRB2, which is established to transmission of UE NAS signalling messages.

DRB stands for data radio bearer and a particular data radio bearer is established to meet a particular quality of service. For example: QCI "1" is established for data transmission of voice packets. Since Voice packets has its own delay budget and error rate.

As per my knowledge so far, an UE can establish maximum of 8 data radio bearers.

Out of these eight radio bearers, at least one bearer would be default and others will be dedicated. One default bearer represents one PDN connection and one PDN connection means one IP address.

Hope it will be helpful.

answer Sep 14, 2016 by Harshita
Hi Harshita,

Thanks for your detailed explanation. I have 2 queries here

1. Is default bearer should create by core network or it by default?
2. Apart from default bearer , can dedicated bearers also have separate PDN connection?
3. Max how many PDN connections can possible with single UE?

Regards,
Suchakravarthi
1.Default bearer will be created by network according to the UE PDN connectivity request  
2. Dedicated bearer doesn't have separate PDN address, It will map to the default bearer PDN address.
UE can request for the default EPS bearer but dedicated bearer allocation procedure will start by network based on the QoS.

3.  UE can have maximum 3 default bearer/ PDN connection.
As per my knowledge, one UE can support 11 bearer (3 default and 8 dedicated bearer)
Similar Questions
+3 votes
#include<stdio.h>
#include<string.h>

int main()
{
    char ptr[]= {'a','b','c','0','e'};
    char str[]= "abc0e";
    printf("\nptr = %s\t len = %d\n",ptr, strlen(ptr));
    printf("\nstr = %s\t len = %d\n",str, strlen(str));
    return 0;
}

Output : ptr = abc0e len = 6
str = abc0e len = 5

Why the length for ptr is 6 ? Can someone please explain it ?

+2 votes

Please explain these LTE terms in simple understanding way -
RRC CONNECTED
RRC IDLE
ECM CONNECTED
ECM IDLE

...