Recently, in a comment to another post, Mike Demler asked about what benefit a femtocell would provide vs. VoIP via WiFi.   This is a long standing debate, and I thought I'd chime in.  Please comment! Generally, comparing WiFi and 3G is really comparing apples and oranges.  WiFi throughput is about 100x bigger with current technology.  3G is optimized for battery life and QoS.  Both are here to stay and Cisco is smart to sell both! Nothing should prevent people from using VoIP or VoIP-over-WiFi (VoWLAN) at home.  Skype is a good thing.  Services like this will be very hard for large SPs to compete with on cost.  Especially on international calls or PC-to-PC calls.  In fact, Mobile SPs started to allow VoWLAN even from their phones, e.g. Skype on iPhone in WiFi mode only.  But remember people with iPhones are not mass market!  Not yet, anyway. When talking about *mobile* communications though, cellular technologies and Mobile SPs rule and will likely continue to rule with 4G/LTE.  This has to do with ubiquitous coverage from a single provider, quality of service in licensed spectrum  and very sophisticated handover when you are on the move (e.g. soft-handover when handset talks to multiple base stations which combine the signals).  WiFi cannot compete on any of these today. Mobile SPs are uniquely positioned to provide you service both at home and on the go.   They can win you over with simple/integrated single-bill service.  Much harder to do with just WiFi.  Consider Amazon Kindle which uses 3G access.  It has always on internet without any configuration or extra cost.  This is huge!  There will be many more devices like this -- or so SPs hope.  As a customer with Kindle and similar devices, you would not want your home to be a blackhole.  Why does not Kindle offer a WiFi option?  Battery, extra cost, configuration complexity => not as suitable for mass market. Mobile SPs can cover you well on the go, but have a hard time within walls where data demands are even bigger.  They want to improve coverage while also offloading traffic from macro coverage onto your internet connection. Win win for them.   So, why should they deploy a femtocell instead of WiFi hotspots at your house? SPs have WiFi-based technology for this called UMA.  This securely tunnels signalling and voice/data traffic through WiFi hotspot all the way to the SP back-end.  T-Mobile USA, France Telecom and British Telecom offer such services. UMA was an easy choice initially because it required very basic/cheap WiFi hotspot, while femtocells were in their infancy.  But there are a few drawbacks usually quoted:     1. Limited number of dual-mode phones and cost. As an example, AT&T has around 80mln mobile customers and pundits estimate about 5 mln iPhone subscribers.  Most people still use a pretty dumb/cheap phone.  The selection of dual-mode phones is comparatively small and cost is higher due to less competition and more components/complexity.  It may change over time, but today, this is an obstacle when a customer calls SP and says they have bad coverage at home.  I do believe most phones will be dual-mode down the road because "data wants to be free".     2. Battery life. WiFi consumes more power.  Apparently, this is quickly improving, but may require new base stations and new phone models.  Also, if you wanted seemless hand-in/out from/to macro network, you'd need both WiFi and 3G radios operating at the same time.  Certainly, this would consume more power than 3G alone and some smart technology would be needed to minimize this to be negligible.     3. Quality of service.  First, WiFi is an unlicensed spectrum.  You can't completely control quality if you can't control what your neighbor does.  Second, it operates at higher frequencies which offers weaker penetration.  Third, if customer wants to use their own WiFi base station, it is a huge headache for SP to support configuration and quality issues with zillion different vendor devices (half of which don't work reliably based on my personal experience at home anyway). By contrast, the biggest benefits of femtocell are that (a) it works with existing phones, (b) improves battery life, (c) provides managed quality of service.  Albeit, many SPs may limit femtocells to 3G where they may have more spectrum, so it would only work with 3G phones (and not 2G).  But in time for mass femtocell roll outs, most customers should renew subscriptions and get new phones with 3G.  Since the phone requires no WiFi, you get better battery power and no extra headaches to manage quality of yet another radio network, unlicensed to boot.   It is also a no brainer that SPs would prefer to leverage their investment into spectrum and proliferate the coverage of 3G services with more base stations rather than prompte the "dump pipe" On the downside, the femtocells are still expensive devices because the market is still small and their deployment is a lot more complicated because of the licensed spectrum, handover, FCC rules, etc. So vendors are developing all sorts of automated means to provision, tune and periodically re-tune femtocell radio parameters such that each provides quality service and a population of femtocells interfere as little as possible.  It is not easy, but feasible. Finally, let's close the loop on the original question of consumer benefit of femtocell vs. WiFi.  If you have an advanced phone already + WiFi base station and are happy with Skype, you probably don't need a femtocell today.  Just charge your phone nightly.  Skype on iPhone even integrates with your phone book. However, if you are a typical customer, you don't want to pay for iPhone and have little technical savvy.  If you have bad coverage at home you either have to have a land line, switch mobile SP (churn) or call your SP for an option.  Some will go the DIY route with something like iPhone + hotspot.  If you are not so advanced or don't want big out of pocket expense, you will pay for SPs to offer you some bundle.  And many SPs will choose to offer femtocells (or a hybrid device) rather than just hotspots because this can address the broadest market with existing or cheaper phones. They can provide better managed quality of service and strategically expand coverage by getting 3G/4G into more places and proliferate devices with always-on 3G internet access like Kindle. At least on paper, there is a good bussiness case for Femtocells.  Exhibit 1: even the strong proponents of ubiqutous WiFi like Google, early adopters of UMA like T-Mobile and leading vendors in enterprise WiFi like Cisco, are also investors in the various Femtocell start-ups.  So my bet is that Femtocells will find a good market if SPs package them in appealing fashion, but WiFi is also going to proliferate and improve. How about that for hedging the bets? Well, I like both oranges and apples.   Thoughts? ... View more

It appears that US Mobile SPs are very eager to put GPS modules into their Femtocells (aka FAP). In Europe and elsewhere, however, this is not the case.  Why? Everybody knows that getting reliable GPS lock inside buildings is very hard.  The best GPS reception is at the window.  But for the best Femto coverage you want it in the middle of a typical McMansion.   When SPs embed Femto into other devices such as STB, they won't be by the window.  External antennas are pain. Trees interfere with line of sight.  And GPS modules are not free.  So, why do US providers want to inflict this pain on themselves and their customers? Let's review why folks *think* they need GPS in a FAP:   1. FAP location verification. This ensures:          (a) FAP does not radiate on the wrong frequency and does not violate FCC rules; this is relevant if an SP has different spectrum channels in different coverage areas;          (b) FAP can provide data to e911 services for UE (phone)   2. FAP oscillator disciplining.  Accurate and stable frequency requires expensive crystal hardware - too expensive for FAP.  One of the techniques used to sync clock of the cheaper crystals is to continuously obtain precise time from GPS.  But there are viable alternatives, such as sync'ing from neighbor macro broadcasts or via NTP from a quality source. These two mechanisms can provide sufficient accuracy for WCDMA and are much cheaper.  Certainly, European SPs targeting deployments without GPS think so. It is possible that 1.a can be more of a problem in the US with SPs there having grown by a lot by acquisitions and covering many different spectrum ranges varying not only by state but also by country and even sub-county level.  However,  there are likely easier solutions than introducing the GPS for this problem. For example, the FAP could periodically scan for transmitters on the target channel(s).  If it decodes a foreign neighbor (wrong MCC/MNC), we know it is not where it should be or someone else is violating the rules.  In the few cases where it finds no neighbors, the FAP may violate FCC rules and transmit on the wrong frequency, but this would require a customer who lied about the placement of their FAP. Therefore, such incidents should be minimal. The damage is limited because the FAP ensures there are no other transmitters around on the same channel (and PSC) and the FAP transmits at relatively small power.  But would FCC agree with such interpretation? Now, e911 gets even more interesting.  FCC wireless e911 rules mandated a two phase roadmap .  In Phase I, the SPs were required to provide the location of the base station to the emergency services.  In Phase II, they were required to provide the location of the UE itself within 50-300 meter accuracy. For Phase I, the location of FAP would need to be provided.  For macro, this is based on its registered address.  The idea of movable base station was probably not considered back in 1996 when the regulation was first issued.  A more recent precedent in FCC is the e911 rules for VoIP issued in 2005.  These rules require SPs to transmit customer's "Registered Location".  The customer must maintain his latest location in the SP database.  This recognized the fact that it may not always be technically feasible for SPs to automatically determine the location of their end users without users' active cooperation.  The same should hold for FAPs IMHO. For Phase II, we need UE location.  The solution has to work on macro as well as on Femto.  A number of approaches for UE location determination have been investigated including network-based (such as triangulation of signals), UE based (such as with GPS) and hybrid.  None of them are 100% reliable.  The current winner appears to be a hybrid approach with GPS and assistance data (AGPS) from the network.  Knowledge of the FAP location may help in providing assistance data to UE.  But again, it is not clear why registered location won't suffice. To sum up... the pain was inflicted by FCC & SPs' conservative interpretation of the current rules:   1.  The e911 requirements could be addressed with user registering their FAP address with the SP.  However, it is not clear if FCC's current rules allow this.   2.  The non-interference requirements could be met in the same fashion, plus enforced by having the FAP periodically scan for conflicts and shut itself down. Should SPs take action at FCC to clarify the rules?  I think so.   The current FCC rules are ambiguous as they relate to Femto.  This leaves SPs to incur extra costs, while providing a less ideal experience to users, some of which have to place Femto devices close to a window, use external antennas, etc. And some customers will never get a GPS lock anyway because of external barriers such as trees and fences. My take is that FCC rules will eventually be relaxed to be "best-effort only" GPS in Femto.  But in the meantime, it is up to each SP to interpret the rules as they see fit. What do you think? ... View more

Hi all! My first post here. I want to blog once in a while about Femto / Pico technology.  My expertise is in Femto provisioning and management, but I'd like to have a dialogue about all things Femto.  Most important, I want to hear what you think.  Please comment, share Femto news and contribute to discussions. Now, to the topic of the day in the next post... ... View more