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Friday, 27 May 2011

Dual Radio Solution for Voice in LTE

I did mention in the Twitter conversations post from LTE World Summit 2011 that there are now certain analysts and players in the market who think that it should be possible to have two radios. Here is a slide from ZTE that shows that they are thinking in this direction as well.


Click on the pic to enlarge.

Tri-SIM phones have been available for quite a while but now there are Quad-Sim Shanzhai phones that are available in China. I am sure there is a market for these kind of phones.

With the battery life and the mobile technology improving, these are no longer the concerns when talking about dual radio possibility in the devices. Another common argument is that there may be additional interference due to multiple radios simultaneously receiving/transmitting. I am sure these can be managed without much problem.

Another problem mentioned is we may need multiple SIM cards but the SIM cards used is actually a UICC. There can be multiple SIM applications and IMSI's on it. The network may need some very minor modifications but they should be able to manage this with no problems. In the good old days, we used to have mobiles with built in Fax. The mobile number used to be different from the Fax number. It was a similar kind of problem but managed without problem.

So there may still be time to keep LTE simple by standardising the dual-radio solution rather than having CSFB, VoLTE, SRVCC, VoLGA, etc.

Any thoughts?

16 comments:

Ulf said...

Is it more than two phones glued together?

Zahid Ghadialy said...

In the simplest form, if the standards do not take any initiative then it may be just two phones glued together. If the standards do take an initiative and do something, it can be one phone with two simultaneous radio access technology support.

Anonymous said...

VoLTE and SR-VCC have been specified and only require single radio to be active at a time.

Therefore, this kind of dual-radio (with up to dual power consumption at least when voice and data are active simultaneously) sounds a bit exotic.

To me this likely seems to be aimed at delaying investments to network equipment (or steer investments to providers that have either no capability to provide IMS/interworking or are behind the competition).

Note also that LTE-only operators (and therefore device vendors) anyhow need to be able to provide voice service (this should also interest all operators e.g. when roaming is concerned).

Finally, in general fragmenting the topic to have several solutions is never good for interoperability, schedules, or costs.

Anonymous said...

LTE's major use case is broadband data overlay, and not voice - at least for the foreseeable future. therefore the more integrated CSFB/SRVCC approaches are not required - again, from a pure use case perspective.
One ofnthe major advantages of dual standby comes actually from the semiconductor angle - CSFB/SRVCC can only be implemented by QUALCOMM and their likes, which push a very cynical pitch in favor of this approach. Behind it is the desire to lock the ecosystem to using integarted multimode solutions supplied by such vendors instead of opening the ecosystem, hence reducing cost and enhancing terminal OEM supply base.
In addition, CSFB/SRVCC are years away fro commercial realization and therefore dual standby is likely the ONLY architecture available to carriers today an in the coming 2-3 years. Carriers suc has Softbank in Japan and China Mobile understood the dynamics of this some time ago and had spec'ed dual standby as a required feature support on their multimode terminals.

Anonymous said...

"therefore the more integrated CSFB/SRVCC approaches are not required - again, from a pure use case perspective."

I disagree. Any meaninful LTE operator has interest in voice - be it in short term via legacy CS or via IMS VoIP (VoLTE) in the medium term.

Unless, of course, it's a greenfield bitpipe operator that can live with Skype/Fring etc. 3rd party voice. In such case, though, incoming calls from landline/other cellular devices might be problematic (addressing).

"One ofnthe major advantages of dual standby comes actually from the semiconductor angle - CSFB/SRVCC can only be implemented by QUALCOMM and their likes, which push a very cynical pitch in favor of this approach. Behind it is the desire to lock the ecosystem to using integarted multimode solutions supplied by such vendors instead of opening the ecosystem, hence reducing cost and enhancing terminal OEM supply base."

I wouldn't say CSFB and SR-VCC are the most difficult parts of making a chipset solution. If an operator has multi-mode network, then it typically requires multi-mode devices there (for coverage and load balancing). Maybe an exception could be CDMA operators that probably want to be able to phase out the CDMA network, and therefore will require a voice solution over LTE anyhow. In short-term dual radio makes sense (e.g. Verizon), but they have a chipset vendor lock-in anyhow in place..

"In addition, CSFB/SRVCC are years away fro commercial realization and therefore dual standby is likely the ONLY architecture available to carriers today an in the coming 2-3 years. Carriers suc has Softbank in Japan and China Mobile understood the dynamics of this some time ago and had spec'ed dual standby as a required feature support on their multimode terminals."

I'm not so sure about this either. MY understanding is that CSFB will be deployed already this year or latest in 2012. SR-VCC requires VoLTE and this probably takes another year or so, and that's exactly why CSFB makes sense to fill the gap.

Besides, dual radio chipsets are more expensive than single radio ones, and consume more battery. But as said, they do have a use case, but a transitory one.

Dean Bubley said...

I think that dual-radio is by far the most obvious approach to voice on LTE.

As I've said at many events "A strip of velcro and a $20 GSM phone" will likely outperform all the other options for the forseeable future.

In particular, it removes the need for an IMS core network, which is a significant investment for a service which is likely to see declining revenues and profit margins in future.

Various LTE operators are likely to avoid using voice at all. In a future world of 50bn devices, it is not essential to design your network or business model around the 7bn primary mobile phones that are likely to exist.

Also, many LTE providers will be wholesale-centric - it will be up to their MVNO-style retailers to deploy voice if they wish.

Dean Bubley
Disruptive Analysis

Anonymous said...

If you really do need two KIs etc then I guess you could specify a dual SIM in a single physical SIM, but why do you need two SIMs? A single SIM is already used to authenticate onto switched and packet networks in the current architecture.

p.s. Multiple MSISDN (ie voice/fax/data) is a different issue and handled in the network.

Telebloke said...

Mobile network operators and their handset-manufacturing buddies have been delaying investments in IMS forever. The traditional claim has been that 3G Packet-Switched (HSPA) would be unsuitable to carry VoIP. Yes sir even at 3 Mbps and 60ms round-trip delay. Hellooo!!! They could have deployed 3G differentiated QoS (Conversational, Streaming, Interactive, Background) forever, but these days it's more fashionable to do standalone LTE RfPs and trials. Conclusion : VoIP on packet is the way to go, with seamless handover between 3G PS, LTE and WiFi. Forget about dual radios, CSFB and SRVCC. Forget about 2G/3G Circuit-Switched.

Anonymous said...

"Conclusion : VoIP on packet is the way to go, with seamless handover between 3G PS, LTE and WiFi. Forget about dual radios, CSFB and SRVCC. Forget about 2G/3G Circuit-Switched."

In the long run, CSFB and SR-VCC are not needed, I agree with that. Meanwhile, for operators having established (and very cost-effective) GSM coverage, will probably need SR-VCC (and also reverse SR-VCC) for years to come. That's because VoIP over GSM doesn't fly (with established feature set).

Once VoLTE takes off, I see no reason why it couldn't be run also over 3G (eliminating need for SR-VCC and rSR-VCC between LTE and 3G). Note that in order to be even close to the radio efficiency of CS voice, RoHC (Robust Header Compression) plus maybe some other features are needed also in the 3G side.

Sivaram Kurapati said...

Reposted from Linkedin discussion:

I gues this is already existed with 1xRTT for voice and LTE for PS....UE(LTE+CDMA(1xRTT/EV-DO/eHRPD) will be registering to CDMA 1xRTT for CS services and can register to LTE for PS services

Michael Salmon said...

Reposted from Linkedin Discussion:

Battery life improving, maybe, but adding dual radios is surely going to negate any improvement to the detriment of the user experience.

Kit Kilgour said...

Reposted from Linkedin discussion:

One of the requirements for LTE was that it shouldn't require a dual radio solution. Motorola used Dual Radio 2G+3G phones at the start of 3G, expecting 2G to disappear eventually. I am also unclear why ZTE think that CSFB can't support CS+PS - if you are reselecting or handing over from LTE to 3G for a CS call, why not relocate a PS bearer as well - or just drop it and the application will re-establish. There are 3G networks at the moment that do not do combined CS+PS handover and drop PS before handover - operators do not seem too concerned.

Anonymous said...

Were dual-radio solution ultimately better, then why bother to specify single radio solutions (or interworking between technologies) to begin with in 3GPP?

I might even go as far as stating that the real deal behind dual radio solutions (with the exception of LTE+CDMA, for several reasons) is to shove the cost and inconviniece to the chipset/device vendors and the customers (higher price and power consumption) instead of the operators to upgrade their network (software).

Anonymous said...

"I might even go as far as stating that the real deal behind dual radio solutions (with the exception of LTE+CDMA, for several reasons) is to shove the cost and inconviniece to the chipset/device vendors and the customers (higher price and power consumption) instead of the operators to upgrade their network (software). "

Regarding inconvenience to chipset vendors, it depends who you... Dual stand-by open the market to 4G only players, and make the chipset market more competitive. Whereas single stand-by requires a deeply integrated 2G/3G/LTE system, which is natural for established big players but can lock out new entrants. I think that if WiMAX showed something to 3GPP operators, it's the benefit of having smaller competitive chip makers in a market. Look at the prices in WiMAX compared to 3GPP.

For the extra power consumption, it's not a practical issue. On a smartphone the biggest part of your power budget will typically be the screen, and you will recharge the smartphone mostly every day (2 at most). In such a context the extra stand-by power will not make a practical difference. You can do the math, it's Amdahl's law at work (stand-by power so low compare to active power and screen first).

So dual stand-by makes costs lower thanks to increased competition, to the benefit of new 4G chip makers, and the lower cost can also help handset makers and operators increase market penetration faster. The only ones who loose here are the incumbent chip vendors with expensive integrated 2G/3G/LTE solutions.

On the power consumption, it's not a practical issue for high end smartphones (do you see LTE in anything else for the coming few years?).

For network vendors, it makes life much simpler.

Really, it's no so surprising that more and more people talk about dual stand-by.

Anonymous said...

"So dual stand-by makes costs lower thanks to increased competition, to the benefit of new 4G chip makers, and the lower cost can also help handset makers and operators increase market penetration faster."

I thought we were not talking about dual standby (which can typically done with _single radio_), but dual radio with simultaneous voice (over 2G/3G/CDMA) and data (over LTE)...

"The only ones who loose here are the incumbent chip vendors with expensive integrated 2G/3G/LTE solutions."

if 2G/3G/LTE integrated solution is expensive, then is it always so that separate 2G/3G modem + RFIC + antenna(s) plus separate LTE modem + RFIC + antennas is always more expensive?

I understand the point that 2G/3G chipsets (due to competition) are quite cheap and LTE only chipsets (from new players especially) could be cheap, but still at least thinking in the medium term I don't see a dual radio solution cheaper, actually on the contrary - and with all the problems.

There is, after all, quite a lot of chipset vendors with integrated single radio 2G/3G/LTE chipset available or coming in the near future.

Anonymous said...

"..is it always so that separate 2G/3G modem + RFIC + antenna(s) plus separate LTE modem + RFIC + antennas is always more expensive? "

Sorry for the typo, here I meant that

"..is it always so that separate 2G/3G modem + RFIC + antenna(s) plus separate LTE modem + RFIC + antennas is always _cheaper_ ? "