First Vodafone Femtocell User Review

Vodafone UK has recently launched their first Femtocell product which they call the 'Vodafone Access Gateway'. Andrew Grill over at 'London Calling' is probably one of the first in the UK to get one to test and use at home.
An interesting report about clueless shop managers, setup procedure,
femto features and performance at home. Thanks Andrew, very insightful

3GPP Femto Specifications

The post on Femtospots a couple of days ago had some good feedback and one reader pointed me to TS 22.220 where 3GPP currently lays the ground for an end-to-end femtocell architecture, or Home NodeB architecture in 3GPP talk. Thanks for that, quite an insightful document! Here's a link to the document after the latest 3GPP meeting (December 2008) which hasn't yet made it to the official specification server. While still being a somewhat early draft today, it nevertheless gives some interesting insight into which directions operators want to go with femtos.

I've had a look at the contributors to the document and from the operator side, T-Mobile, Vodafone, Softbank, SK Telecom, and NTT-Docomo seem to be the most enthusiastic ones. On the vendor side, I've seen input from RIM, ETRI, Qualcomm, NEC, Alcatel, Huawei, Nortel and Marvel. The lists are not exhaustive but show that there is a lot of interest in the topic.

Here are the some of the highlights of the document:

Open and Closed Operation

3GPP TS 22.220 is a requirements specification so it will serve as a guideline for future stage 2 and stage 3 documents which will contain the implementation details for those requirements. So while trying to stay realistic, the document tries to explore the topic in as wide a range as possible and to keep as many options open as possible. Three operating modes are specified for femtos / Home NodeBs (UMTS) or Home eNodeBs (LTE) and I use the terms interchangeably below: The first one is called open, which means all UEs (user equipment in 3GPP talk or mobile devices) of an operator are allowed to use the cell. The second mode is called Closed Subscriber Group (CSG), which means only selected UEs, for example those belonging to a household, are allowed to use the cell. The third mode is called hybrid and combines the first two. I imagine that in hybrid mode, CSG users might potentially get higher priority and access to the local network.

Local IP Access

Speaking of local network access, the requirements specification also contains a chapter on allowing the UE access the the users home network. No specifics are mentioned yet as to how this should be implemented in practice or what kind of services could be used over such a connection. I expect that the 'how' will be clarified in stage 2 and stage 3 documents while the 'what' will be left for other standards bodies to clarify. The document says that both operator and users will have a say which users are part of the CSG and which users will be allowed to have access to local resources.

Local IP Access to the Internet

A so far empty chapter is present for how to connect to the Internet via the local network therefore bypassing the operators core network. I can hardly wait to see if this chapter will be filled with text or removed in later versions of the document.

MBMS and Mobile TV

Some parties also seem keen to use the Home NodeB for mobile TV and would like to see MBMS specified for femtos.


Further, there seem to be operators or vendors who would like to have some parts or all of an IMS implemented in the femto in a transparent way for the UE to potentially bypass the circuit switched network. I don't quite yet fully get the concept and purpose of this feature but I am sure some more text will be added to this chapter as the document evolves.

The Achilles Heel : Pre-Release 8 UEs

In my opinion the biggest overall issue for femtos used in closed subscriber group (CSG) mode is how to prevent mobiles not belonging to the CSG trying to reselect to the femto. For future 3GPP Release 8/9 compliant UEs, things can be standardized to avoid unnecessary cell reselections and signalling. TS 22.220 gives some general guidance on how that could be done by adding femto related information on the broadcast channel of the cell. For today's UEs, however, any solution has to work with what is already in place. 3GPP TR 25.280 gives a number of potential solutions in Chapter 6.2. Personally I think the Equivalent PLMN solution has a lot of merrit, but no definite recommendation of how to solve this is given yet.


These days I was wondering if in the mid-term, femtocells might replace public Wi-Fi hotspots!?

With the rise of 3G USB keys and notebooks with built in 3G connectivity, the popularity of Wi-Fi hotspots, especially paid ones, is likely to degrade over time. Once people have a 3G card anyway and have instantaneous connectivity anywhere, people just won't bother anymore to search for a public Wi-Fi hotspot and go through the manual login process. In addition, femtos remove another shortcoming of public Wi-Fi, the missing air interface encryption which today leaves the door wide open for all kinds of attacks.

With rising demand for Internet access in hotspot areas such as hotels, airports, train stations, etc., HSPA or LTE femtocells might be the ideal replacement for aging Wi-Fi access points which at some point have to be replaced by new equipment anyway. So mobile operators such as T-Mobile, Orange and others, who have a dual 3G / Wi-Fi strategy today could at some point just make such a move if they see that use of their Wi-Fi systems is decreasing and use of their 3G/4G macro base stations in the neighborhoods of their Wi-Fi installations is significantly increasing.

Some 'dual-mode' operators might even have a database with the geographical location of their base stations and their Wi-Fi installations. Together with traffic statistics of both systems an automated system could document changes over time and could be used to help predict when and if a replacement of the Wi-Fi access points for femto cells might make financial sense. After all, femto cells are just as easily connected to a DSL line than a Wi-Fi installation.

Maybe some femto manufacturers even come up with integrated Wi-Fi/Femto boxes for public installations with the Wi-Fi being used to create a wireless mesh between several nodes in locations with only a single backhaul line and for access for those people not yet having 3G connectivity. Agreed, femto vendors today mainly position themselves around the femto base station for home networks but public femtos might be an interesting opportunity as well.

Femtocells and Connected Home Services

Last week I met Thierry Samama in Paris, who is looking after ip.access' pico- and femtocell business in France to discuss a bit about the wireless industry and, of course, about femto cells. I asked him what he thinks about accessing devices at home via a 3G device directly via the femtocell instead of going through an operators core network. It was good to hear that ip.access is actually already working on this and he pointed me to this video in which they demo their connected home services capabilities. The video doesn't give many technical details but the applications shown are just what I had in mind concerning interaction between 3G handsets and devices at home such as a media server, TV set, etc.

The Key To The User's Heart

To me, accessing the home network via the femtocell holds the key for users actually wanting a femtocell at home. An alternative are of course dual mode devices with a Wifi interface. However, without pre-configuration of those devices by the mobile operator, who could of course do that if they wanted to, most people will have difficulties configuring the device to make use of them in the home network. Definitely an advantage for femtocells since no configuration of the mobile is required.

The video doesn't say exactly how local access works and how the applications on the Windows Mobile driven devices access devices and in the home network. UPNP perhaps? Nokia has already made strides in this direction with UPNP, which is part of S60 and Nseries phones which come equipped with a Wifi interface.

Femto In A Bundle

So I think femtos packaged together in a single box with Wifi and DSL/cable access sold by a converged fixed/mobile operator will best sell in a bundle which also includes mobile devices, pre-configured applications on them that can access resources in the home network, a media server at home and some IPTV. So instead of getting a subscription for a DSL line which includes IPTV and fixed line telephony offered these days in many countries, I could very well imagine that the femto that allows local access forms the bridge to the wireless world and removes the need for that extra telephone line. Others like Nokia are likely to take the Wifi/UPNP approach and it will be interesting to see how the different approaches compete with each other.

For more info on Femtos, connected home services, handover, autoconfiguration etc. have a look at ip.access' home page, they've got some good ressources there.

Will Femtos Be More Successful than UMA?

Recently, Telecom Italia Mobile (TIM) and BT, two of the three tier one operators in Europe who’ve adopted Unlicensed Mobile Access (UMA) have decided to ditch the fixed/mobile convergence service. I wonder what that spells for the future uptake of 3G femtocells!?

While femtos are based on an entirely different technology, their value proposition seems to go in same direction: Replacement of the fixed line telephony service and better indoor coverage. Looks like users are not ready for it yet. So what’s your opinion, why should femtos be more successful than UMA?

Femtocell Thoughts – Part 3

In part one of this miniseries on femtocells I’ve been looking at
the benefits for mobile operators and part two covered the question why users would
put a femtocell into their home. This final part looks at the technical background and hurdles and gives a conclusion.

In practice it is extremely important to integrate femtocells with DSL or cable modems for several reasons. First, femtocells are installed by the user and such an approach therefore ensures that the installation is easy and is done properly.

Additionally, an integrated device is the only way to ensure quality of service for the femtocell since data traffic generated by 3G voice calls must be prioritized on the fixed line link over any other traffic. If a femtocell was attached to an already existing DSL or cable router which already serves other users, uplink data traffic of these users could severely impact 3G voice calls since ordinary DSL or cable routers do not have quality of service (QoS) features to ensure that traffic from the femtocell is prioritized. This behavior can already be observed in practice today in other situations. If an ordinary DSL or cable router is used for a VoIP call in addition to a simultaneous file upload, voice quality is usually very bad due to the packet delay and insufficient bandwidth availability caused by the file transfer.

Thus, a mobile operator deploying femtocells ideally owns DSL or cable access as well or is at least partnering with a company owning such assets. This way a single fixed line gateway could be deployed with Wifi for PCs and other devices and a femto radio module for 3G mobile devices. The single phone per user idea also benefits from such an approach since owning or partnering for DSL or cable access removes the competition between fixed and wireless voice. This also ensures that a femtocell is only used in locations where the mobile operator has licenses to operate femtocells since they use licensed 3G frequency bands.

In practice it can be observed today that a number of mobile operators are taking this route already by either buying DSL access provider companies or at least partnering with them (e.g. Vodafone/Arcor or O2/Telefonica in Germany). It’s unlikely that this is done specifically to roll out 3G femtocells at a later stage but it seems that such companies have understood that it is vital for the future of a telecommunication company to have both wireless and fixed assets in order to stand a chance to be more than a mere bit-pipe for services running over the network. On a side note it is interesting to see the trend of splitting up fixed and mobile access into separate companies several years ago seems to revert now and pains of separation are now followed by pains of re-unification.

Another technical aspect concerning femtocells is interference. In 3G networks, cells usually all transmit on the same frequency and interference is managed by having enough space between them and by adjusting output power and antenna angles. Most 3G operators have at least two frequencies they can use so femtos could for example use the mostly unused second frequency. However, there is still an issue with interference between femtocells of users which live in the same apartment building and have thus installed their equipment close to each other. Left on its own this will result in lower capacity of each cell and might impact quality of service.


When looking at the arguments presented above, femtocells are not likely to be an immediate and outright success. A number of hardware evolutions will probably be needed before form factor, usability and quality of service are adequate. This is likely to take a couple of years. Also, mobile operators need to continue their path of buying or partnering with companies owning fixed line DSL or cable access. This will surely also not happen overnight. However, there is currently still enough capacity available in the macro layer of the network so femtocells are not immediately needed to reduce the load on the network. Therefore, the major immediate benefit of femtocells is improving in-house coverage especially in rural regions, which thus remains a niche market for now, since 2G and 3G coverage and capacity for urban users is usually sufficient for in-house coverage. As such the story of femtocells might parallel the evolution of UMA (Universal Mobile Access) which has similar goals but a completely different concept. That’s a story for another day however…

As always, comments are welcome.

Femtocell Thoughts – Part 2

In part one of this miniseries on femtocells I’ve been looking at the benefits for mobile operators. This part deals with why users would put a femtocell into their home.

From the user’s point of view the advantages of femtocells are less clear to me. While the user shares all of the operator advantages discussed in a previous blog entry, increasing customer retention and thus churn is not necessarily in the interest of users since it could reduce competition. Also, it is unlikely that all family members use the same mobile operator and thus could benefit from a single femto cell.

In addition, mobile multimedia users are usually still early adopters which tend to use sophisticated phones, of which many include Wifi. With such phones a femto cell for multimedia content is not required since Wifi offers a similar or better experience for Internet content. Multimedia services offered by mobile network operators, however, are usually not available over Wifi which, from the end user perspective, is not a huge loss since early adopters tend to use Internet services rather than multimedia services of operators that are usually more expensive or come with limitations not acceptable to such users.

An advantage not mentioned before is that better 3G in-house penetration would increase call establishment success rate for 3G video calls since mobiles reselecting to the 2G network because reception quality is better can not be used for incoming or outgoing video calls. Thus, femtocells could become an important element in the future to make video calls more popular as the service still fights with the famous hen/egg problem of 3G network availability and number of users with compatible handsets.

Monetary incentives could persuade users to install femto cells. Operators could for example offer cheaper prices for voice calls that are handled via the femto cell. Also, the operator could propose to share revenue with femto ‘owners’ if other subscribers use the cell for voice and data communication instead of a macro cell.

Often the argument is brought forward that femtocells allow to market single phone solutions in which the user no longer has a fixed line phone and uses his mobile phone both at home and on the go. However, such solutions which use the macro layer instead of femtocells have already been available for several years in countries such as Germany (O2’s famous home zone for example) and are already very popular. Also, it is unlikely that mobile network operators would have competitive prices for all types of calls so many users would still use a SIP phone or software client on a PC for such calls at home. Calling a mobile number is still more expensive in most parts of the world excluding the U.S.A. than calling fixed line phones so single phone offers have to include a fixed line number for the mobile phone in order. Again, this is already done in practice for example by O2 in Germany for a number of years but femtocells might enable the mobile network operator to deliver such services cheaper than how it is currently done over the macro layer.

It should alsobe mentioned that using a femtocell would have a configuration and usability advantage over SIP Wifi phones. However, it is likely that the configuration process for SIP and Wifi on handsets will improve over the next few years thus decreasing this advantage.

To be continued

So much for now on the user’s point of view on femtocells. In the third part, to come soon, I will take a look at the technical background and hurdles.

As always, comments are welcome!

Femtocell Thoughts – Part 1

There is currently a lot of hype around Femtocells, tiny user installable 3G cells for homes and offices. Surely an interesting technical concept but still with many question marks attached such as why would users want a 3G cell at home or at the office and what the benefits are for the operator. Here’s what I think:

Operator Benefits

3G networks are operated on the 2100 MHz frequency band in Europe and Asia and in the 1900 MHz band in the U.S. which is far from ideal for in-house coverage. Even in cities it can be observed that dual mode 2G/3G mobiles frequently attach to the 2G network because many GSM operators use the 900 MHz band in Europe which is much better suited for in-house coverage as lower frequencies penetrate walls much better. Some proponents of Femtocells claim that in-house coverage for voice calls are greatly improved by Femtocells. In cities however, this benefit is rather small since GSM in-house coverage is usually not an issue. The user on the other hand does not really care if his voice call is handled by the 2G or 3G network.

An improvement could be seen however in cases where the mobile can’t decide to stick with either the 2G or the 3G network due to changing 3G signal levels. This creates small availability outages while the mobile selects the other network type. During these times, incoming voice calls are either rejected or forwarded to voicemail.

Also, it can often be observed in practice that a mobile device with weak 3G in-house coverage changes to the 2G network once a connection to the Internet is established (e.g. to retrieve eMails or to browse the web on the mobile phone) and sometimes changes back to the 3G network during the connection. The reason for these ping pong network selections are the changing reception levels due to the mobility of the user and changing environmental conditions. Such network changes result in outage times which the user notices since an eMail takes longer to be delivered or because it takes a long time for a web page to be loaded.

Another solution to the issues described above is the use of the 900 MHz frequency band for 3G in Europe and Asia and the 850 MHz band in the U.S. It is likely that this will happen over the next few years since regulators more and more tend to open the 900 MHz band for 3G networks in Europe. It will take a number of years however before network operators will have deployed their 3G networks in those lower frequency ranges and until devices for these bands are available. It’s also likely that 900 MHz cells would first be used to cover rural areas instead of enhancing coverage in areas already covered by 3G in the 2100 MHz band. In the meantime, Femtocells definitely have the advantage.

As the above weaknesses of 3G in higher frequency bands show, femtocells can increase customer satisfaction. Putting a femtocell in the user’s home would have the additional advantage for network operators of reducing churn, i.e. customers changing contracts and changing the network operator in the process. Customer retention is all the more reinforced if the Femto comes in a bundle with DSL access as further described below since changing wireless contracts also has consequences for the fixed line Internet access at home.

Another advantage of femtocells is to reduce the gradual load increase on the 3G macro network as more people start using 3G terminals for voice and data connections. This could result in a cost benefit since if the right balance of macro and femtocells are reached, fewer expensive macro cells would be necessary to handle overall network traffic.

The question is how much these advantages are worth to a network operator since Femtocells do not come for free!?

More to come

So much for now. Part 2 to come soon deals with why users would put a 3G femotcells into their home and part 3 will look at the technical background and hurdles for femtocells.

As always, comments are welcome!