Principles of QoS Mechanisms in Mobile Network

16 Aug

Interestingly, when “QoS” is referred to the Mobile Network, you need to forget about the main referral of the notion, which is the “NETWORK” based. Because, as everything is related to the User Equipments, the QoS is always referred to the “SUBSCRIBER” side when congestion occur.

The congestion is maintained in a Packet Core network in two ways;

A) Congestion Aware Throttling (Static QoS)
B) E2E QoS (Dynamic QoS)

Congestion Aware Throttling requires the Radio Node to be checked in intervals to observe if there are any Congestion occurences. If there’s any, the report taken by OSS is reported to SAPC, and appropriate action si taken for the congestion by a rule defined in SAPC. The drawback of this approach is that you may not aware of the congestion in real-time, and may not exactly know when the congestion is over. You may still apply “Over Throttling” when there’s no congestion and use the system resources.

End-to-End QoS is the de-facto required approach for an LTE/4G network to maintain the successful EPS bearers for example VoLTE bearer. The QoS policy is enforced from the Radio Base station and to the exiting interface, and the equipments involved know how to behave when congestion occur. This application of QoS method requires extensive configuration, mapping and checks rather than Congestion Aware Throttling. Becasue, in Congestion Aware Throttling you deal with a congestion in a particular cell rather than the complete network in E2E QoS.

In result;

The E2E QoS has a decision mechanism in two ways;
– Either SAPC checks the cell report provided by Radio Network->OSS and adjust the QoS profiles for that particular cell based on the historical data. The network is controlled based on pre-defined reports and congestion is planned earlier.
– Or, SAPC adjusts the QoS profiles based on real-time data provided by Radio Network->OSS. The latter is not favorable because the time to know congestion + application of throttling, and releasing it is not real-time. UEs are affected in the first, resources are not used in feasible way in the second method.

So, how is the QoS is enforced in the network? ;

Differentiation Methods:

Basically, limiting the bw for the maximum usage + specifying guaranteed bw for the base, and speciying the priority during admission are the three most important cases for the differentiation.

DiffrentiationToolbox1

Usage of QCI QoS Class Identifier
– From SAPC to GGSN over Gx interface in 3G:

QCI Mapping to UMTS

Source: http://telcoworks.wordpress.com/2013/08/15/principles-of-qos-mechanisms-in-mobile-network/

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