This week saw the LTE World Summit taking place in Berlin. Two key themes emerged from the presentations of the European carriers – significant technical barriers still need to be crossed before most cellcos will commit to firm mass roll-out dates; and new approaches, notably femtocells, will be important to maximize return on investment.
T-Mobile and Orange were taking different standpoints on LTE. The former is determined to overcome a whole range of issues before deploying, because it wants to go straight to full services including voice (reminiscent of its approach to 3G in Europe). The latter sees LTE as a data-only platform in the early phase, so is less concerned, at least in the short term, with concerns like how to support voice and SMS.
T-Mobile is the most aggressive about moving voice to 4G, as seen in its leadership of the VoLGA project, which looks to use Kineto Wireless' GAN (Generic Access Network) technology, already included in 3GPP standards, to deliver voice (as opposed to relying entirely on 2G/3G fallback, or on a full move to IMS). "I don't think we should push LTE as a wireless DSL technology - it has much more than that. That's why we push heavily for early availability of all services, most importantly voice and SMS over LTE," said Klaus-Juergen Krath, senior VP of radio networks development at T-Mobile, as reported in an insightful conference write-up by Unstrung.
Apart from voice, the main concerns raised by the cellcos were the impact on backhaul capacity; patent burdens; the lack of standardization for self organizing networks (SONs); and the shortage of spectrum in many territories. Some of these are being addressed wholeheartedly by the vendor community, such as SONs (Motorola announced one at the show). Others, like spectrum and IPR, will be harder because they involve so many vested interests, though in the latter there has been recent activity in conjunction with patent pools like Via and MPEG LA.
Meanwhile, another European operator, Telenor, is to start its LTE field trial in capital Oslo this summer, testing RAN and Evolved Packet Core equipment from Huawei - another big breakthrough for the Chinese vendor in its bid to break into the big name carriers of the west.
And with rising operator interest in using femtocells to build LTE capacity rapidly, especially in data-intensive hotzone build-outs, the Femto Forum published an outline business case, and is promising a full white paper soon. The main reasons to invest in femtos during phase one of an LTE project are, according to the Forum, that they could "provide the best possible LTE experience for users, support new services, offer alternative roll-out models for operators and provide an improvement to the mobile broadband business case by lowering network costs while increasing network capacity."
The main performance benefit would come from enabling users to receive peak data rates for more of the time, especially within buildings or within congested urban zones, where outdoor femtos could create hotzones to complement the macrocells. The Forum also makes the point that, in many countries, much of the new spectrum that will be harnessed for LTE (or WiMAX) is in higher frequencies, around 2.5GHz and above, that are challenging for indoor penetration - but are ideal for high capacity in small cells.
Other advantages, the Forum says, will be a lower cost per bit of data delivery, because of low cell site costs and because the backhaul is generally provided by the user; reduced strain on macro network capacity because of offloading to femtos; and support for new types of services, such as downloading and streaming media from the internet or between devices in the home, without impacting the mobile network (and in the case of device-to-device transfer, without even needing backhaul).
Krath said: "We can prepare LTE in a way so that LTE is ready to support femtos in the best technological way, and the industry can work together on integrated chipsets so cost is at an economical level. The technical hurdles for femto adoption will be much lower with LTE than with 3G."