Femtocells and 4G: Sorting Out The Different Views

Femto Hub Blog (May 28 2009)

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  1. By Josh Adelson and David Nowicki

    The mobile communications industry is getting its arms around the role of femtocells and 4G for one another.  Last week at the LTE World Summit, Simon Saunders of the Femto Forum spoke on the benefit femtocells can bring to the rollout of 4G networks.  The key point here is that the benefits of small cells and heterogeneous networks are as important to 4G as they are to 3G. Other industry players including several network operators have subsequently echoed this sentiment.  On the other hand, people point out that 4G is still years away from widespread deployment, that current backhaul infrastructure could be a bottleneck, and therefore the need for 4G femtocells is still likewise some ways off.

    Femtocells and 4G intersect in a number of different ways, so it’s not a simple issue, and the right answer will vary by circumstance.  One useful organizing principle is to ask the simple question: what problem are you trying to solve?

    Consider first the problem of cost-effectively meeting the network capacity requirements for growth in mobile broadband traffic.  Dean Bubley recently pointed out that moving heavy users from HSPA to 4G will not by itself solve this problem.  Better to give these users a 3G femtocell—which will be available much sooner in any case—to shift their traffic off of the macro radio access network.  That same 3G Femto will continue to provide that same multi-Mbps user experience even when 4G networks are rolled out since dual-mode devices are likely to be the norm. A consumer with a dual-mode 4G/3G handset will easily connect to their 3G Femto at home. And 4G femtocells will eventually have a similar benefit, but most indications are that this problem won’t be able to wait for 4G.

    A very different problem is how to lay claim to offering the latest and greatest network technology with the highest peak rates.  Here, 4G by definition makes sense, and 4G femtocells are rightly seen as a tool with which to provide coverage more broadly and cost-effectively than via macro cells alone.

    Yet a third problem is how to launch the latest and greatest services.  Here there is probably a more complex interplay of 3G and 4G, femtocells and macro cells.  There are aren’t too many examples of services that can be done on 4G than cannot be done on 3.75G services like HSPA or CDMA EVDO Rev. B. Having said that, 4G will enable more cost effective delivery of simultaneous multimedia application and perhaps true HD streaming video.  For high-bandwidth services that are not as intense as these, 3G femtocells could provide a suitable in-building access complement to 4G in the macro network, since 3G femto and 4G macro will likely have similar throughput.  For applications that take advantage of presence status and connection to the home network, femtocells will be valuable independent of air interface generation.

    We will no doubt continue to see these kinds of discussions, and this is a healthy development for the industry.  The more focused the question, the better chance of arriving at a sound answer.

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