Is CS over PS and exit strategy from IMS?

A couple of days ago, Dean Bubbley over at Disruptive Wireless ran an interesting article on an effort by some 3GPP members to specify a way to use the current wireless circuit switched voice telephony infrastructure and telephony protocol stack on handset over wireless packet switched networks. In essence their approach replaces the circuit switched bearer with a packet switched connection on lower layers while leaving the protocol stack for call establishment in place. A gateway in the network and some modifications in the lower protocol layers on the mobile phone and ready is a potential competitor for voice over IMS. 

I’ve had this work item under my nose for some time but was not sure if 3GPP members were really serious about it. It seems they are and it looks like the Technical Recommendation (TR 23.8799) seems to be pretty much complete although the conclusion is still missing. Also interesting to see that in the Work Item description (SP-070401) Ericsson is listed as a supporting company and that handset vendors are not part of the initiators.

When I look at the timelines for this work item I would say that a practical implementation in the field is at least 3 years away at best. Adoption and ratification of the Technical Report (note, it is NOT a technical standard document yet) is due in June 08. Afterwards they would have to crank out the details. If they are quick then that takes 12 to 15 months in 3PP Release 9 and at least the same amount of time for standards conform ant implementation and the testing afterwards. That would make it 2010 – 2011 for deployment.

To me this whole thing looks a little bit like an IMS exit strategy. If after 10 years of standardization, IMS hasn’t made it out of the lab and into the pockets of people and the CS over PS solution makes it into the field before then it could very well spell the death for IMS. Once this is in the field why would an operator seriously consider IMS afterwards? By 2012 even the most backwards oriented mobile operator will have understood that except for voice telephony they have no chance on the application layer against the global Internet competition in a converging beyond 3G and Wifi network environment.

It’s like opening an additional front on the IMS battleground and would remove it’s ultimate insurance policy, i.e. being the only technology for operators for voice technology in their B3G networks.

But competition is a good thing and it might speed things up one way or the other.

4 thoughts on “Is CS over PS and exit strategy from IMS?”

  1. “..they have no chance on the application layer against the global Internet competition in a converging beyond 3G and Wifi network environment.”
    I don’t really agree on that, the fact that an operator controls the network is a terrific asset which allow an operator to provide a much fine grained, tailored service to its users. Besides, an operator has a special relationship to its customer. So I feel the statement is a bit definitive about the operator’s capabilities while competing with Internet actors on the service battleground.

  2. Hello Antoine,

    Yes, I am always a bit on the provocative side 🙂 You mention a number of good points that speak for the operator. Let’s see if they can find a strategy in the future that makes good use of these advantages.


  3. It has basically been decided to work only on the fallback-to-CS solution (also in the TR) for Rel-8 in 3GPP. This way forward was decided on because most of the active members in 3GPP are on the IMS track and do not want a yet another alternative for the same things.

  4. Just to clarify for all specification-hungry readers out there….the CS fallback solution I referred to is alternative 3 in the TR mentioned in the main text (the correct number is TR23.879)

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