It’s been THE news of the week for the wireless industry that Verizon has selected to go for LTE as their next generation network rather than UMB, the successor technology of their current CDMA1x EvDO network. I put down my initial thoughts on the deal here. In the meantime there are two additional important points which came to my mind: Multimode terminals and backwards compatibility!
UMTS operators that are upgrading to LTE will have a smooth migration path especially since mobile devices are likely to be GSM/UMTS/HSDPA/LTE compatible. LTE makes this especially easy since the air interface has been designed to be able reuse oscillators etc. from HSDPA. Also the software stack on higher layers will probably be partly reusable as I expect that high level (NAS) signaling will be similar.
CDMA operators such as Verizon will have a much more difficult story to tell their subscribers. I kind of doubt that there will be CDMA/LTE mobile devices since there won’t be many operators taking this path. Also from the core network point of view LTE won’t be able to interconnect with a CDMA network as easily as with a UMTS network. For UMTS, the LTE specification already contains all information of how to do handovers back and forth between the two worlds.
A small comfort for Verizon: Sprint will have a similar experience moving from CDMA to WiMAX…
That’s certainly a good point. Maybe the economy of scale of UMTS/LTE phones is SO advantegous that it makes sense anyhow.
Besides, the market introduction scenario is likely to be an LTE overlay network for data only that is initially targeted to PC card users.
Hi Martin,
I’m not convinced this is such a large/CDMA-specific issue; perhaps we disagree about how much GSM will still be there when LTE rolls around (worthy of a discussion)
1. I’d posit that many UMTS/GSM operators are likely to have wider GSM coverage than UMTS for some time. Full UMTS coverage at 2100 is rather expensive for countries that are not densely populated due to the increased number of sites. UMTS 900/850 would be the answer, but takes time and commitment esp. when you can see LTE just around the corner. Perhaps UMTS 900/850 is the new GSM for this rural coverage though?
If we accept that there is still GSM out there while deploying LTE: Are we saying that we’ll need to handoff to UMTS then to LTE? Implying all three technologies with overlapping coverage footprints and tri-technology handsets (won’t somebody think of the child^H^H^H^H^H batteries?)
2. I think jens is right and that this will be data only until they have sufficient coverage and handsets.
3. I’d also imagine that this press release focuses on LTE to save face and that (as above in point 1) they’ll deploy UMTS 850 as well for rural coverage.
(aside: is LTE spec’d at anything other than 1800? I’ve never looked)
I hope I’ve provoked a discussion 🙂
Hi Bruce,
it is absolutley correct to state that many operators have wider GSM than UMTS coverage. I think what Martin wanted to point out is that it is _especially_ tricky for Verizon to go from CDMA to LTE whereas it is much easier for a UMTS operator to go to LTE. For exactly the reason you have pointed out: A GSM/UMTS operator still has coverage for data and voice even though LTE is not deployed countrywide. And the user can use the same device.
Because of the economy of scale and the push from the 3G lobby as well as the LTE lobby (such as LTE/SAE Trial Initiative) I believe we will see GSM/UMTS/LTE handset in a midterm time frame. LTE PC cards will be first though.
The CDMA operator faces the problem that he most likely lacks a device that supports CDMA _and_ LTE because no phone vendor is likely to build such device as it will not be sold in sufficient numbers.
From a coverage point of view: LTE is foreseen for the UMTS and UMTS Extension bands, that is it can be deployed in all frequencies ranging from 900MHz to 2.6GHz provided that
a) vendors build the respective RF modules and
b) regulators allow the deployment in a specific country
Obviously an operator has to own the respective spectrum as well in sufficient bandwidth chunks.
Hello Jens and Bruce,
I couldn’t have replied better.
Cheers,
Martin
Jens, Martin,
Thanks for your comments, I’ll concede that LTE/CDMA is harder.
I’m fascinated by the transition for GSM/UMTS operators though. I must write about it.
If we assume that LTE will be run alongside UMTS then I don’t think LTE can really take off until GSM is gone; spectrum is expensive in all developed markets and supporting 3 networks (or more depending how you count) seems excessive. Esp. if you want MIMO antennas; it’d be a Christmas Tree.
If you turn off GSM you risk lose in-roaming revenue and you’re turfing out equipment that works and is probably at 0 cost on your books (it is old and/or cheap). The benefits are better spectrum utilisation (right?) and of course fast data.
So the next step for GSM/UMTS operators is a balancing act — GSM/LTE doesn’t sound nice (is handover possible?) but buying more UMTS equipment seems a bit wasteful if you’re deploying LTE.
So how about this, for the 2009-2011 timeframe?
1. Operators rollout UMTS900/850 nationwide, displacing their GSM networks. Voice and HSPA.
2. Operators roll in urban LTE1800 (for example) displacing UMTS2100 (and perhaps redeploying this equipment for the national network).
3. Operators hope that GSM is not extensively/exclusively used or they’ve just handed their competitor all the in-roamers and stopped their customers from outroaming (assuming non-GSM handsets).
Point 3 could be an issue; in-roamers from non-EU countries are going to be a nice earner compared with EU countries, and Latin America (for one) is rolling out new GSM networks even today. 3GPP “World Phones” [new name required] that are quint-band and tri-technology will be an impressive engineering feat, but they will come to solve the out-roaming problem.
Why not take the obvious choice ? Stop or at least slow down UMTS/HSPA rollout, keep the 3G coverage at the current state, invest into GSM/EDGE and free up existing UMTS spectrum for LTE (including the extension bands). You need only GSM/LTE terminal support which helps battery life.
Very interesting discussion. Yes, Verizon does have some tough choices relative to the 3GPP community.
Sprint’s case is slightly different. They are not looking at WiMAX to quickly replace their EVDO network. It will be a gradual 3-5 year transition. WiMAX is being initially targeted more for embedded devices in 10-30 metro areas and CDMA/EVDO will be the wider nationwide network.