A new slant on VoIPo3G - Circuit voice over mobile HSPA IP tunnels

A few months ago, I published a quite controversial report about VoIPo3G. I said that I expected as many as 250m users of fully mobile VoIP by the end of 2012 - mostly driven by the operators themselves, rather than independent players like Skype and Truphone - although partnerships between the two groups would also be important.

I stated that this was particularly because operators will want to exploit greater spectral efficiencies for packet voice, that become possible in later versions of 3.5G. I also argued that because LTE, WiMAX and UMB are all-IP, it was inevitable that we would ultimately end up with full mobile VoIP, and that the question was then about the timelines and roadmap. Moreover, I said that I thought that VoIPo3G (or VoIPo4G if that’s how LTE etc become defined) would quickly overtake VoWLAN in prevalence.

It’s fair to say that I came in for some criticism. Some commentators thought that VoWLAN would grow much more rapidly than I expect pointing to growing availability of dual-mode phones. Others pointed out that using 3G networks for VoIP ran into barriers of power consumption, operators blocking 3rd-party VoIP traffic, or the potential need for IMS or other IP-based core networks.

My view has been that the 3GPP operator “fully standardised” version of mobile VoIP would be slow in arriving, partly because it was expected to be tied to IMS, and partly because of the lack of a defined “plain vanilla VoIP” services in 3GPP or OMA standards. Yes, there’s MMTel (IMS Multimedia Telephony), but that’s not “just VoIP” and in my view is part of the problem rather than the solution, because it bundles in useless and unwanted fripperies like video sharing, rather than just focusing on voice (or web services mashups).

Instead, I expected two things to happen instead – growing use of non-IMS operator VoIP (based on softswitches) extended to the mobile domain, using “naked SIP” handset clients, or possibly standalone VoIP app servers on top of "IMS lite" implementations. And secondly, I anticipated the growing use of fully “over the top” Internet or corporate VoIP applications using 3.5G data channels and flatrate tariffs.

Because I saw standardised “vanilla VoIP” as so slow in arriving, I’ve been exhorting operators who’ve bought the report, or spoken to me personally, to instead consider partnering with the Internet VoIP players – who will inevitably exploit flatrate data and smartphones/3G-connected PCs anyway. Basically, my view is that operators should either work with Skype, Truphone, fring et al – or compete head-to-head with them using their own pre-standard mobile VoIP implementations.

I still believe this is a good route to VoIPo3G, especially for operators that are already moving to VoIP in their fixed networks, or which are early deployers of IMS or other IP-NGN architectures. (This is also relevant for CDMA operators, which seem more IP/IMS friendly at present). Blocking VoIP it not a viable option in competitive markets - as evidenced by the increasing trend towards openness that's been seen in recent weeks.

But interestingly, another ‘flavour’ of mobile VoIPo3G is now emerging as an alternative for mobile operators – Circuit Switched Voice over HSPA, as an early specification within 3GPP’s Release 8 generation of standards. This was just starting to evolve seriously when I published the report in November, and is mentioned in the comments on this post of mine. And it now seems to be moving fast. In the last week, two of the largest ‘'movers and shakers' in mobile technology - from both handset and network sides - have talked up this approach to me unprompted. And I’m in agreement that it’s undoubtedly going to be important.

Basically, CS voice over HSPA takes the ordinary mobile circuit voice service, using ordinary diallers on the phone, and circuit core switches in the network... and tunnels it over an underlying IP bearer. So the application isn't VoIP, but ordinary circuit telephony, but the wireless transport (down in the guts of the phone) is IP.

In other words, it's "Mobile Circuit Telephony over IP"

In fact, we've all heard this concept before. It is an almost direct HSPA equivalent of UMA’s voice over WiFi. In both cases, there are benefits for operator voice calls, derived from the nature of the radio IP bearer: cost in WiFi’s case as it’s unlicenced spectrum, and the efficiencies of new packet transmission techniques in HSUPA and beyond. And in both cases, it’s not necessary for the operator to have already deployed IMS, VCC and so forth – they can reuse their existing core networks, and get away with less messing-around at the handset application layer. [I’m not sure yet whether the IP tunnel uses a similar IPsec approach to UMA, and could use a similar gateway, or if it’s entirely new]. The downside is that this isn’t a next-gen IP voice service in terms of application capability – it’s voice 1.0 transported over network 3.5.

There are also various reasons why I'm more positive on CS over HSPA than I am about WiFi-UMA.

It's a matter of semantics (and your company's point of view) whether you treat CS Voice over HSPA and UMA as 'true' wireless VoIP. Both are using classic circuit signalling, rather than SIP or proprietary protocols like Skype. Neither are as easy to use as "full VoIP" as the basis of innovative applications like voice mashups.

The interesting thing to me is that the industry is starting to polarise into different points of view on this issue. Ericsson remains a staunch MMTel advocate, driven by its desire to push IMS as the main future application layer. But other major players seem to be edging towards a CS over HS worldview, albeit with a hedge around naked-SIP VoIP.

So… taken together, the various types of VoIPo3G are going to be:

• Over-the-top independent VoIP (Skype, Truphone, IP-PBX etc) with a dedicated client on the handset or PC
• CS voice over HSPA, using the ordinary circuit voice app plus some lower-level IP ‘plumbing’.
• IMS MMTel – needing a full IMS client on the device
• Other IMS or standards-based voice apps like PoC or perhaps a standalone SIP VoIP server plugged into the IMS application layer
• Standalone operator softswitch-based VoIP connecting to a (probably) SIP client on the handset.
• Partnerships or mashups of the above.

Messy and diverse, in other words. And all of these have different use cases, different pro’s and con’s, different requirements in terms of user behaviour, cost and so on.

But the bottom line is that with the addition of CS Voice over HSPA, my top-level VoIPo3G predictions are still looking feasible, although some of the fancier web- or application-based VoIP capabilities will be trickier to exploit by the operators choosing that approach.

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