What is the difference between Resource Block (RB) and Physical Resource Block (PRB)?

Hello Experts,

In LTE, a Physical Resource Block (PRB) is defined as consisting of 12 consecutive subcarriers for one slot (0.5 ms), and is the smallest element of resource allocation assigned by the eNodeB scheduler.

But i also read it as Resource Block (RB), so I’m getting confused… What’s the tricky in here?

My query is: is RB and PRB exactly the same? (One RB = One PRB?). When to use RB and when to use PRB?


If below image is correct, then MPIRICAL definiton is wrong (https://www.mpirical.com/glossary/prb-physical-resource-block). :frowning:


RB (Resource Block) and PRB (Physical Resource Block) are exactly the same. 12 subcarriers x 7 symbols. The green rectangular in your image is correct.
PRB is usually used to differentiate Resource Block from RB (Radio Bearer).


Thank you very much @Masoleimani.

But if the red rectangle is correct, then green rectangle is wrong (It’s not RB too).

So, what is the name of the resources delimited by green rectangle? :frowning:

I modified it. The green is correct. The Red is wrong. Red which is 2 consecutive PRB is one TTI

Exactly, the green one is correct.

My take on this is: RB and VRB are logical definitions while PRB is the effective physical allocation into the time and frequency domain grid.

There is a 1:1 map between RB/VRB and PRB size, and it is important to remember that theorethically, a PRB lasts 0.5ms not 1ms.

3GPP TS 36.211 version 15.8.1 Release 15 6.2.3 Resource blocks
Resource blocks are used to describe the mapping of certain physical channels to resource elements. Physical and virtual resource blocks are defined.


A physical resource-block pair is defined as the two physical resource blocks in one subframe having the same physical resource-block number nPRB.


12 SC, 7 ofdma symbol = 1 RB or 1 PRB
12 SC, 14 ofdma symbol = 1 SB(Scheduling Block, smallest block to give to a user)
The above are Ericsson Terminalogy. I am not very sure if SB is 3gpp terminalogy as well or not

Hello Experts,

I’ve added this information here Radio Physical Resources :wink:


Hence from the quoted information its clear that the dimensions of RB & PRB are the same in LTE. although both are different logically. RB is a virtual concept assigned by MAC while PRB is the actual physical resource allocated to the user.

I guess smallest unit to allocate to user is RB not SB

@marcengo So, why do we need both of the logical and physical definitions, since the size of PRB and RB/VRB is mapped 1:1. Or what is the difference?