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Guaranteed Bit Rate. A minimum bit rate requested by an application. In LTE, minimum GBR bearers and non-GBR bearers may be provided. Minimum GBR bearers are typically used for applications like Voice over Internet Pro- tocol (VoIP), with an associated GBR value; higher bit rates can be allowed if resources are available. Non-GBR bearers do not guarantee any particular bit rate, and are typically used for applications as web-browsing.

Maximum Bit Rate. This is to restrict the traffic flow in a particular bearer. If the traffic exceeds this then it will be dropped. ( MBR does not apply to non-GBR bearers, only GBR bearers.)

The APN-AMBR defines the total bit rate that is allowed for all non-GBR bearers associated with a specific APN. The APN-AMBR limits the total non-GBR traffic for an APN, independent of the number of PDN connections and non-GBR bearers that are opened for that APN. For example, if an operator provides an APN for Internet, the operator may then limit the total bandwidth for that APN.

The UE-AMBR is defined per subscriber and defines the total bit rate allowed to be consumed for all non-GBR bearers of a UE. The subscription profile contains the UE-AMBR. The eNodeB enforces the UE-AMBR.

There are different AMBR values for uplink and downlink directions - UL APN-AMBR, DL APN-AMBR, and UL UE-AMBR, DL UE-AMBR.

posted Jan 28, 2014 by Meenal Mishra

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thanks for your reply, I would request you to  clear my following doubts -

As per you PBR is for both GBR and non-GBR bearers,

so PBR we can defined as minimum bit rate for the bearer.

but when we talk about GBR bearer then GBR is the minimum bit rate that a particular bearer can send.

so in case of GBR bearer my questions are -

1.) what is a difference between PBR and GBR as both defines the minimum bit rate for GBR bearer?

2.) what do we exact mean by guaranteed bit rate? suppose for a GBR bearer the GBR rate is = 8kbps, so does it mean that at particular ms scheduler should guarantee 8bits to send atleast for this bearer? and if this so then what is the need of PBR here?

3.) MBR also means to restrict the traffic flow in a particular bear and (PBR *BSD) also means same? then how i can differentiate these two values?

for NON-GBR bearer -

1.) how do the RRC or upper layers calculate the value of PBR for this bearer?
@Luv: I would suggest that you can ask a fresh question as Meenal may have not received the intimation or may have missed it. Let me know if I need to ask on your behalf.
Hi Meenal,

QoS concept is very well explained by you.

However I doubt about why MBR cannot be applied to a non-GBR bearer
According to spec 23.203, section A.    Policy and Charging Enforcement Function (PCEF)

It is mentioned that "The MBR (per PCC rule / per bearer) and the authorized APN-AMBR are used for rate policing."
So APN-AMBR along with the MBR per SDF should come into picture for non-GBR bearer.
Could you please provide any reference if possible where MBR is restricted for Non-GBR bearers?

Let's take in another way

Every SDF in Non-GBR bearers could have a MBR but if we consider a bearer as a whole there will be no MBR value like in case of GBR bearer.
MBR values will not be sent to SGW in Create/Update Bearer Request but internally PGW will manage a MBR value for every SDF/Rule

One reference i would like to share for easy understanding

Peeyush Sharma

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