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Designing the Perfect Femtocell
Steve Shaw of Kineto Wireless looks at the requirements for the perfect femtocell and how to achieve the goal.
The mobile world is buzzing about femtocells. The concept of a small, low-cost, customer-deployable home cellular base station that leverages a subscriber’s existing broadband connection for backhaul is an incredibly compelling proposition for mobile operators. Femtocells hold the promise of reducing churn by improving indoor coverage, saving costs by offloading the macro radio network, and generating additional revenue by offering new ‘Home Zone’ services. However, as the initial femtocell trials are now concluding, and results are being feed back into the market, it’s clear there are a number of technical, standards, business case and regulatory challenges that still need to be addressed before femtocells can really take off in the consumer market. There is now an opportunity to step back and consider the question, “what are the requirements and capabilities that make the ‘perfect’ femtocell?”
The ‘Perfect’ Femtocell
There are several key points that need to be incorporated into any femtocell design.
- Very Low Cost: To justify the femtocell business case, most operators are demanding that vendors keep the cost of the device well below €100 and target the €40 to €50 range. In addition, in a perfect world, operators would not even need to provide all subscribers with a new access point for them to receive a Home Zone service. Ideally, existing home broadband routers would already incorporate femtocell capability, or subscribers would have already purchased and installed a femtocell for other reasons, like home network connectivity. Any installed base would dramatically reduce an operator’s financial and logistical burden of populating the network with new customer premise equipment (CPE), and would immediately improve the business case.
- No Macro Network Interference: The macro radio network is a finely tuned mesh of cell towers designed to maximize connectivity and minimize interference. The ‘perfect’ femtocell could be added into this mix and not have any detrimental effects on the performance of the macro network. In addition, it would not cause any detrimental effects to mobile customers who are not femtocell users but come within range of a femtocell. For example, if you and your neighbor receive service from the same operator and you have a femtocell, the femtocell should not interfere with your neighbor’s handset.
- Future-Proof Radio: The perfect femtocell would not have to be replaced as the macro network evolves to include the next radio network technology. Cellular radio technology is constantly evolving, and operators are continually upgrading their macro networks. In the last five to 10 years, many operators have evolved their macro networks from GSM to GSM+GPRS to GSM+EDGE to UMTS to UMTS+HSDPA to UMTS+HSD/UPA. Soon, they’ll evolve to HSPA+ and LTE. In addition, the perfect femtocell would be able to support handsets no matter what macro radio technology they used (e.g., GSM/EDGE, UMTS, HSDPA, or even HSPA+ and LTE in the future).
- Predictable Indoor Coverage: The perfect femtocell would enable operators to provide a predictable wireless coverage range within a home. That coverage range should not fluctuate based on how near or far a subscriber may happen to live from a macro cell tower. For marketing reasons, it is imperative that operators are able to accurately set subscribers’ expectations for the service.
- Access Point Mobility: People move, and the perfect femtocell would be able to move with them- no matter where in the world they may go.
- Enable Local Internet Offload: One of the biggest selling points for femtocells is their ability to offload rapidly growing mobile data traffic (think iPhone) from the macro network. However, the vast majority of that data is standard Internet traffic, not operator-specific mobile data services. As a result, the perfect femtocell would allow mobile operators to let Internet-related traffic route directly to the Internet and bypass their core data network.
- Facilitate Connected Home Services: In-home networking is an important trend for consumers. Traditionally, mobile phones have been completely excluded from the ‘connected home’ because they maintained a direct cellular connection to the mobile network. The perfect femtocell would overcome this limitation and enable mobile phones to communicate directly with other devices in the home.
- Add Value to Other Consumer Electronics in the Home: The perfect femtocell would add value to other devices in the home; not just mobile handsets. It would work with any and all devices in the home or office that require wireless connectivity.
What about Wi-Fi Access Points?
Now, reviewing the list above, there seems to be a glaring omission to this discussion. What about Wi-Fi access points? Wi-Fi access points alone may not meet the requirements for the perfect femtocell, but when used in conjunction with 3GPP UMA/GAN technology, the situation would seem to change By enabling all mobile services to be extended over Wi-Fi to dual-mode handsets, the 3GPP UMA/GAN standard can effectively turn any Wi-Fi access point into a femtocell. In fact, with UMA/GAN, Wi-Fi access points can become the “new, perfect” femtocells. Let’s think about how that works:
| Requirement | UMTS Femtocell | Wi-Fi/ UMA “Femtocell” |
| Very Low Cost | Current UMTS access point cost estimates are in the €150 to €200 range. In addition, there is no installed based of UMTS access points for an operator to leverage. | Wi-Fi access points under €50 are readily available from many large consumer electronics vendors. In addition, almost 50 percent of broadband households in many countries already have a Wi-Fi access point installed. |
| No Macro Interference | By definition, UMTS access points will have some level of interference with the macro network, as well as with the handsets of non-femtocell users. However, much hard work is underway to try to minimize the detrimental effects. | By definition, Wi-Fi access points do NOT interfere with the macro network or with the handsets of non-”femtocell” users. |
| Future-Proof Radio | As the macro network evolves to support HSPA+ and LTE, UMTS femtocells will need upgrades. But by definition, UMTS femtocells will only be able to support UMTS handsets. | It is not necessary to upgrade a Wi-Fi “femtocell” access point as the macro network evolves to HSPA+ and even LTE. In addition, the access point can support handsets based on any macro radio technology: GSM, UTMS, HSPA or even LTE. |
| Predictable Indoor Coverage | To mitigate interference with the macro network, the wireless coverage range for a UMTS femtocell will vary based on how close a subscriber lives to a macro radio tower. The closer to the tower, the smaller the effective access point range. | As Wi-Fi “femtocells” operate in a different spectrum range from the macro network, they provide predicable wireless coverage and do not vary based on the proximity of a subscriber’s house to the nearest cell tower. |
| Access Point Mobility | UMTS femtocells allow for some level of mobility. But since they use licensed spectrum, they can only operate in a territory where the operator has a license to use that spectrum. | Wi-Fi “femtocells” operate in unlicensed spectrum, so they can be moved and used anywhere in the world. |
| Internet Offload | A UMTS femtocell can identify and route relevant traffic directly to the Internet, without going through an operator’s core network. However, in some countries, there may be regulations that require all traffic traveling over licensed spectrum to first be routed through a mobile operator’s core network prior to the Internet. | With Wi-Fi “femtocells”, handsets can route Internet-related traffic directly to the Internet, not back through an operator’s core network. |
| Enable Connected Home Services | A UMTS femtocell can function as a proxy to enable handsets to access resources on the home network. | A Wi-Fi “femtocell” enables handsets to directly access resources on the home network. |
| Provide Value to Other Devices in the Home | UMTS femtocells operate in a specific operator-licensed spectrum, so they can only support UMTS devices that also have a subscription with that mobile operator. | Wi-Fi “femtocells” are standard Wi-Fi access points and can be used by any Wi-Fi-equipped devices in the home for network connectivity. |
What’s Perfect?
So, will the ‘perfect’ femtocell at the right price with the right features appear anytime soon? Are Wi-Fi access points with UMA/GAN technology actually a ‘perfect’ femtocell already available and widely used around the world? There is certainly a lot of debate from vendors and operators alike. Regardless of the technology choice, it’s clear that delivering a home zone service is a priority for mobile operators. The ‘perfect’ solution is poised to capitalize on this pent-up demand.
Steve Shaw is VP of market development and chief evangelist for UMA/GAN technology at Kineto and is a thought-leader on FMC strategy and market development for femtocells and dual-mode/Wi-Fi services. He has over 16 years of experience in product and business development roles with telecommunications companies. Steve holds a bachelor of science in computer science from the University of Southern California.