Also, I do not think that femto cells compete with dual terminal solutions (cellular/WiFi, UMA etc) since the end user simply uses the same mobile phone and could be unaware of the transition. This gives femto cells tremendous pull in the common end user market, while dual terminals are more suitable for business users.

I have written an article on what I think on femto cells on:
www.visionmobile.com/blog/

A more appropriate comparison is to an 802.11x box.
It either works or doesn’t. If signal reception is poor
in the premises, move the box to a better position.
you don’t get an operator doing a terrain simulation of
your house, nor a field engineer visiting to adjust
antenna tilt etc.

Regarding QoS/QoE aspects, the services invoked by a
user are required at worst to be comparable to that
experienced in the macro network. The (literal) weak
link is not the radio aspects (although coverage etc
by the CPE is not a totally solved problem) , but the
IP connection between the core network and the CPE.
For residential subscribers, this is likely to be an
xDSL link (with all the issues therein) .

And a link not dedicated to the femto env either.
Web browsing, IPTV, gaming etc all will be potentially
making demands of that link. So mobile operators will
be expecting QoS interfaces of access network operators
that are much more than “best efforts” . Which is supposed to be a key feature of the “converged” network is it not.

This begs the question of whether mobile operators
who are not part of a company with its own access
network division (networks and/or LLU experience) will
have their femto dreams smashed by an access provider
not up to the job. Think of the UK, with a Vodafone
having to guarantee QoS in an LLU env that inter-
works with a (pre-21CN) BT Openreach outfit.

The service patterns (bit rates, concurrent users etc)
are actually not that big a problem, being more
constrained by the capabilities of the CPE, and the
bit rates supported by the subscriber Internet
connection (which may be competing for resources needed
by surfing, IPTV etc) .

However, the big issues are on the systems engineering
side. The cell management issue (topology, neighbour
cell lists on a per-terminal as opposed to per-cell
basis, downlink scrambling code reuse etc) is a real
killer for networks of potentially 100,000s of cells
that may come and go as easily as a customer switching
on/off the CPE.

Quite a bit of work will be needed to define/
standardise the C-plane/OAM interfaces to control
things such as handover from macro to femto etc.
But from I have seen, worked on, and know, the missing
bits are not too far away.

If the networks are different (i.e. the WiFi dual mode scenario), then you need extra technology to make sure users can access the same services on the two networks using the same applications on the phone with the same settings. Mass market consumers are unlikely to want to change their browser settings when switching over from the cellular to the WiFi network.

UMA solves this issue, but the handset choice is poor. And all UMA handsets today are 2G, which means that they don’t have the horsepower to handle high-speed data. This explains why dual-mode offerings are all about cheap voice calls in WiFi hotspots, rather than about “WiFi-speed” data on your phone.

3G UMA is coming, but by the time we see the handsets 3G femtocells will be a viable alternative.

There will some architecture challenges though, as to how fixed and mobile subscribers will be handled in the IP network in relation with authentication, QoS and policy management. One possible business model with Femtos will be to eliminate the need for fixed connection altogether from the customer home. Such approach would simplify or even in some cases initiate the withdrawal of fixed subscriber management function from the Broadband service edge. This is a cost effective infrastructure strategy to deliver a “best fit” DSL or cable backhaul for Femtos based WCDMA mobile voice and data.

Femtos open up a real possibility for an integrated digital home solution, but would require some far reaching changes at the Broadband Edge to adapt to the new business model. If this happens, Femtos could deliver a competitive edge to the mobile operators over their fixed network rivals.

1. In-house/in-office wireless coverage is still unstable or inconsistent. Femtos mitigate this problem and provide a “under-the-tower” quality.

2. Though Wi-Fi is a good and already available alternative, its predominantly associated with Laptops (ofcourse there are WiFe cellphones as well). With evolved CDMA or GSM/UMTS technologies, corresponding Femtos provide you the luxury of using the “cell-phone” for “voice” as well as “data”.

The architecture point is also valid, using an IuB over IP to a standard RNC for femto will never allow true volume deployment due to the limited throughput of the RNC, those femto cell vendors offering a collapsed architecture, in effect and early version of the LTE Node E and those with the UMA based architecture are able to address both throughput and volume deployment.

These devices are the mobile approach to convergence, deploying 3G capacity where it is needed - in-building, with a model where much of the cost of providing that capacity has been covered by the mobile customer who can still use the standard 3G device.