Hi Experts,
Below one for FDD, can anyone explain why PRB terminology.
I think it should be RB…
Isn’t it the same in terms of allocation?
How do you differentiate both?
Its my question as well.
RB and PRB used interchangeable.
But we discussed RB in frequency domain only.
I need confirmation in NR can we say RB = PRB.
In LTE:
1 RB = 12 subcarrier × 7 symbol
1 PRB =12 subcarrier × 14 symbol
In 5G can we say this?
1 RB = 1 PRB = 12 subcarrier
It is the same, except in LTE RB bandwidth is fixed to 180 KHz but in NR it is not fixed and depend on sub-carrier spacing.
I understand it this way:
RBs are virtual. When MAC allocates it allocates RBs. They are not mapped to PRBs as it as. PRBs are the actual allocation, they have their actual physical subcarriers. RBs can be mapped to PRBs in different ways. The word RB is just used to define different allocation for physical channels. The dimension of an RB and a PRB is the same.
(36.211, section 6.2.3) Now in LTE PRB means 12 SCs in frequency and 0.5 ms (Number of symbols can be 7, 6, or 3) in time (basically one slot),
In LTE PRB definition depends on subcarrier spacing (15kHz and 7.5kHz) and also on cyclic prefix.
Wherein NR there is no time definition involved to define PRB. In NR PRB means just 12 sub-carriers in frequency, irrespective of the subcarrier spacing.
Correct me if I am wrong…
1 Like
This is perfect.
In NR, dimension wise RB = PRB.
However there are 3 different things.
- VRB - Virtual RB. This just indicate resources. They may be numbered like 1,2,3 but physically theybme distrubuted or interleaved in BW.
- PRB- Actual RB allocation in time freq grid resources. They may be numbered like 2,8,13 in UE assigned BWP for VRB 1,2,3
- CRB - Carrier RB. They are actual number of RBs used in carrier BW.
Please correct me if wrong too.
You mean RB are VRB term seen many times in 5G books then we have VRB to PRB mapping.
I also agree with this one.
Is it somewhat related this that… in LTE 2 Physical ( each 0.5 ms ) Resource Blocks = 1 Scheduling Resource Block whereas in NR 1 PRB (1 ms) = 1 SRB and it is SRB which is scheduled and not PRB both in case of LTE and NR or is this a different concept as per specifications.
SRB is a different concept.
PRBs, VRBs and RBs are defines in physical layer prespective.
And time and frequency gives complete definition of these terms.
A RB can have many PRBs right and a PRB is the smallest grid defined in physical layer perspective and MAC schedules combination of PRBs and in that term in LTE smallest unit scheduled is SRB which is combination of 2 PRBs in case of LTE.
Please correct me in my understanding…
SRB generally refers to Signaling Radio Bearer for carrying RRC/NAS messages.
What do you mean by SRB here?
Scheduling Resource Blocks.
Yes, correct.
Never heard such definition…
This is a new one.
Not sure if this is something proprietary, never read it in the specs.
SRB is terminology used in Ericsson.
It’s not standard term.
I checked in Ericsson LTE air interface guide not able to find such terminology.
Is it related to some feature or parameter?
Try searching Scheduling Block.