As we’ve said several times, the business case is particularly strong in North America, where the combination of poor mobile phone coverage and widely available domestic broadband service (plus the disposable income to pay) provide early market demand. We’d also expect strong early takeup in Japan which quickly adopts new technologies.

Where can I buy a femtocell? 

Femtocells are today only commercially available in Japan (where NTT DoCoMo are obliged to send a technician to install and maintain it) and from Sprint in the US (called Airave), but only in selected areas of Denver and Indianapolis. Many other operators are said to be trialling the system, with up to 500 users in a UK trial by Telefonica O2. Commercial launches are anticipated later in 2008, but this will depend on resolving technical issues and agreeing a clear business model to benefit both operator and consumer. It is more likely that 2009 will be the year of the femtocell, with more widespread availability.

Who can I buy a femtocell from?

The femtocell equipment has to be managed by a licenced mobile phone operator, using the frequency spectrum that it paid (usually huge sums to) its government for. This differs radically from WiFi access points, which use unlicenced spectrum and can be setup pretty much anywhere.

Therefore, in order to work with your mobile phone, you will have to buy the femtocell from your mobile operator or a reseller.

Where can I use my femtocell – can I take it to my country/holiday home at weekends?

• Provide an accurate clock timing frequency reference (GPS is calibrated from Caesium atomic clocks), thus ensuring calls handover to/from the external cellphone network easily and don’t disrupt users nearby.

• Determine which frequencies are licenced for use in the area, and use the correct ones.

• Block usage outside licenced operating areas.

Additionally, femtocells often have a 2G and 3G receiver which can scan for signals from external cellsites and determine the country and available networks. It can use this to identify if it has been moved since last used, because the local cellsite identities would have changed.

Therefore, taking the equipment to a different location in the same country could work, but would be known to the network operator. Some operators have considered charging for this “service”, although they don’t actually have to do anything other than bill for the privilege. Alternatively it could just be allowed.

However, taking the device with you on your travels abroad is much less likely to be successful. If you were in such a remote location that there was no outside mobile service but broadband was, then this would be possible. If its just a business trip to a mainstream hotel, then you would much less likely find this to be the case.

Can I have more than one femtocell at home?

Why not! (but not from the same mobile operator) Just as we see multiple cell towers from different operators in close proximity (there are three in the corners of my local football ground), it should be possible to do this in domestic premises. Femtocells provided by different mobile phone operators will transmit at different frequencies, so providing there is some spatial separation (ie the units are not stacked directly on top of each other), then this should be feasible.

The limit of 4 simultaneous calls applies to each femtocell. Additionally, the limited capacity of the broadband internet connection would be applied across all femtocells sharing it. Depending on the femtocell system architecture, this may limit simultaneous use to 4 voice calls (worst case: Tunnelled Iub over Secure IP on 256kbit/s uplink).

Obviously, the phone companies will want (expect) end users to consolidate on a single mobile phone supplier for all family members in a home, sharing the same femtocell. They may also be able to provide the broadband service as part of the package (we have seen “free broadband” offers from mobile operators in the UK for higher spending postpaid subscribers already). But there may be cases where users have different phone operators (eg a work phone), and might install a separate femtocell in their study area for that purpose.

Femtocell vendors also talk about using them in high traffic density office environments, effectively providing many independent cells each capable of handling 4 simultaneous calls. This competes with several other techniques widely deployed today, such as Distributed Antenna Systems (DAS), Remote Radio Heads and picocells. The business case to do this will be based around lower deployment costs, because the femtocells would be pretty much self-installing and self radio optimising.

I’d not expect domestic users to have more than one femtocell from a single mobile phone. In some exceptional cases, multiple femtocells may be installed from different operators.

Can I sell my femtocell on eBay when I’m done with it?

Probably not. Apart from the question of whether you own it (or are just renting it from the mobile phone operator), it really isn’t of any use unless its actually connected into a mobile network. Operators are likely to be quite wary of connecting equipment that they don’t know about into their systems. Some femtocells use the UMA standard, and take a SIM card (just like a mobile phone) to identify themselves. Perhaps these systems will be transferable, and operators will simply ship a SIM card to the new user.

My suspicion is that the cost of femtocells in the future will drop to a level where it’s not worthwhile, and operators will be keen to ensure the latest software is used to reduce disruption on the external mobile network and especially to avoid support calls for any installation problems.

If this is permitted, it’s more likely to be between users of the same mobile phone networks. The buyer will need to have checked they can register the femtocell on their own account before purchasing it.

Can I reuse or transfer my femtocell to another mobile operator?

Standards, standards, standards. One of the great things about mobile phone systems (and particularly the GSM family) is that all equipment must comply with previous agreed specifications. Pretty much any phone sold anywhere in the world can work on any other mobile phone network of the same type – either through roaming or by swapping out the SIM card. Yes, there are a few places where these standards vary (frequencies used in the US differ, Japan didn’t deploy GSM), but this approach has been incredibly successful (87% of the worlds phones are GSM based).

Femtocells also comply with these standards and so will work with pretty much any mobile phone using the same system. However, there are many different system architectures used to connect them back into the mobile phone operator’s systems. Specifically, the way in which the data connection is used over the broadband internet link varies widely and is often incompatible between different vendors.

Operators would much prefer if femtocells were completely transferable, because it allows them to trade-off purchase decisions between different suppliers and get the best deal. This was tried (and failed) for the GSM system, tried again (and failed) for the 3G UMTS system and is being tried again for LTE. Vendors supply both the femtocell and the femto-gateway at the operator’s central site, and this is likely to be the case in the medium term.

Lastly, it may be obvious to the reader, but femtocells are not designed and manufactured to work with CDMA and 3G UMTS in the same unit. Customers of Sprint or Verizon (which use CDMA) will not be able to use their femtocells on T-Mobile or ATT Cingular (which use 3G UMTS/HSPA technology). Different hardware parts are required on the RF side, so its unlikely to see a dual-mode CDMA/UMTS femtocell in the near future.

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Dimitris Mavrakis said:

Sprint has discontinued femtocell sales Apparently Sprint has discontinued sales of its femtocell product with a better product to be offered probably end of this year. Also, I am not sure whether operators will want to restrict the geographical distribution of femtocells (and place femto gateways/concentrators only for certain areas - I am not sure whether a femtocell access point will be able to connect regardless of its position in the country).

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Konstantin Shemyak said:

A correction and a question in order to work with your mobile phone, you will have to buy the femtocell from your mobile operator or a reseller. This is not true. Femtocells from most vendors, plus femtocell subscriptions from most operators, will allow mobile phones from any operator. The IMSI has to be added to the closed subscriber group, naturally. In the US, all femtocells are required to include a GPS receiver. Could you please point to the source of this information?

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Thinkfemtocell said:

Answers to recent comments Thanks for your comments: @Dimitris: Since the femtocell is connected by broadband IP, the location of the femtocell gateway is relatively unimportant. Technically it can be at any geographic location as long as it has a connection into the network operator's core network. There may be some benefit in co-locating femtocell gateways in the same region to reduce the cost of trunking for calls which actively handover between femtocell and external network (ie using the same MSC), but this is probably not a huge factor, and may not be the case during initial rollout. For example, calls used to be routed via an MSC in Newcastle (in the east coast of England) from Northern Ireland in the early days of GSM in the UK. This allows operators to buy femtocells from several vendors and distribute them across the country, each will connect to its own "home" gateway from the same vendor if required. @Konstantin: Although a femtocell product can be used by any operator, just as a phone can be connected to any network, these will be integral and directly connected to a single mobile operator's systems. It will use the licenced frequency, emit the identification of that network and handle calls to/from phones authorised to use that mobile network's services. In most countries, national roaming is not permitted (ie using Vodafone subscription on a T-Mobile network), and phones are configured to ignore non-Vodafone basestations. So whilst roaming subscribers and other phone users from the same network operator may also use your femtocell (subject to either the femtocell being open or their phone listed on the white-list), it isn't technically feasible for a single femtocell to simultaneously support multiple networks. Regarding the issue of GPS receiver being mandated in the US, I may have heard this at a conference rather than seen it online. It's related to the E911 emergency service requirement. I'm not aware of this being a requirement elsewhere. Samsung's CDMA femtocell (as used by Sprint for their Airave launch) includes one.

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