Sunday, November 21, 2010

Policies and Rules

With LTE ready for deployment, it is becoming increasingly important for operators to provide dedicated bearers. I had a chance to look at 3G demo, here in India, by one of the operators, and I was not pleased. There was an attempt to stream live TV over 3G supported mobile and stream was pretty bad. I was just wondering how far the base station was and if there was any secondary PDP context in place for enforcing a proper quality of service. Well that’s 3G.

In LTE PCRF is responsible for charging and triggering flow rules. PCRF is an intelligent device which based on the ongoing traffic or existing configuration triggers events towards PGW. There sits PCEF on PGW which is responsible for enforcing the rules triggered by PCRF. The interface between PCRF and PCEF is Gx.  Based on the triggers PCEF can go ahead and ask PGW to create a dedicated bearer or modify an existing bearer.  UE can request for a bearer creation or modification based on its need. But final decision is with PCEF. On other note I was wondering if LTE UE manufacturers would present any piece of code to mobile application developers for requesting a dedicated bearer for their app?

LTE is supposed to be a high speed network. Will creation of dedicated really matter at such high speeds? Will streaming video all of sudden get better once a dedicated bearer is created for it? Has any operator tested this? How does the result look?

8 comments:

Anonymous said...

Hmm, the Gx and PCRF/PCEF concept are used in many networks for the last two years. The difficult part is enforcing/controlling the QoS down to the RAN... There are some mechanisms, still it's not as it should be... Let's see if LTE will solve this or again the scarce radio resources will be not possible to manage, unless over-dimensioning is in place, which will be my expectation :-)

Anonymous said...

The only use case I've tested is VOLTE, like in the following document.
http://www.ericsson.com/res/thecompany/docs/journal_conference_papers/other_tech_papers/voice_over_ims_profile.pdf

Voice stream is going through a dedicated bearer, having QCI=1 and specific GBRs&MBRs.

Would be interesting to find some other implemented applications.

Santosh said...

VOLTE makes perfect case for dedicated bearer. Thanks for sharing the doc.

Santosh

Harish Kulkarni said...

does any current western operators supporting secondary pdp in there 3G deployment?.

is there any service which uses secondary pdp activation?.

-thanks
harish

Santosh said...

I dont know! Few said yes and few said no. I cannot confirm though.

Santosh

Dumitru said...

Usually for streaming services there's no need for a PCRF, you can use the static policies on GGSN that changes the QoS from INTERACTIVE to STREAMING(Update PDP context request to SGSN.... blah blah blah), then the MS decides either it will change the QoS on current PDP context or create a secondary PDP context(ME implementation issue).
This works perfectly but the throughput is limited to 384Kbit/s (see 3GPP for STREAMING on UTRAN).
PCRF is needed if you want PER SUBSCRIBER policies.

Anonymous said...

Hello Santosh

how is video streaming stablished in LTE? Do we have to use Multimedia Broadcast Multicast Service (MBMS)?


Thank you very much

Santosh said...

That is one solution to broadcast data. However you still have streaming servers setup and stream video over regular network without MBMS.