In Top ten challenges to Femtocell deployment--Part I, published on March 24, 2008, we discussed five of the top ten challenges that need to be addressed for successful femtocell deployment--low-cost implementation; network architecture harmonization; remote device management and software upgrades; RF interference; and potential consumer concerns.

6. Quality of Service and Traffic Prioritization
Due to a stronger RF signal based on better indoor coverage, femtocells will provide faster handset data speeds than what mobile subscribers may be used to, which is expected to encourage greater use of data services and video streaming inside the home. This is probably the most important strategic reason for a mobile operator to deploy femtocells in its network, as femtocells could enable the mobile phone to compete not only with the fixed line phone, but also with the PC and TV for entertainment and information services in the home. Voice is real-time and latency-sensitive, which means that best-effort IP delivery is not good enough. Delivering high quality of service is a major challenge when there is a shared IP access link simultaneously carrying voice, video, peer-to-peer (P2P) traffic, and data. In this operating environment, traffic prioritization becomes essential--not only for effective handling of real-time voice packets, but also for prioritizing network time protocol (NTP) or IEEE 1588 timing packets. If timing packets are not prioritized, then femtocells can go out-of-sync and lead to dropped calls, which results in poor subscriber satisfaction. DSL uplink bandwidth, in certain deployments, adds additional constraints. In the U.S., for example, depending on the distance from the CO, many mid-tier plans have only 200K throughput on uplink. With other devices like PCs that have active VPN connections sharing the same uplink with the femtocell equipment, traffic prioritization becomes essential to ensure consumer experience does not deteriorate with events like VPN connection breaking when making a mobile voice call.

7. Timing and Network Synchronization
Attaining required timing and network synchronization levels is a major femtocell challenge. 3GPP specifies that base station transmit frequencies be very accurate and closely synchronized, requiring precise clock references which add to base station costs. The standard has been relaxed for picocells in Release 6, and it has been proposed that future versions of the standard relax it even further. Lower-cost synchronization solutions are still needed.

Femtocell Reference Design

To meet stringent network synchronization requirements, femtocells can use IEEE 1588 for an accurate clock synchronization protocol between networked equipment. As picoChip points out, "[B]y distributing a high precision time base around the network that is resilient to the typical levels of packet delay and jitter found on broadband Internet connections, a low-cost implementation is possible." Alternatively, a GPS timing reference could be used, or the base station could receive transmissions from the overlaying macro cellular network and adjust its timing accordingly. Finally, there are some innovative, low-cost / high-stability temperature-controlled crystal oscillators coming onto the market that may make it easier to attain the required synchronization levels. More study is needed for this critical facet of femtocell operation.

8. Provisioning
From a consumer point of view, femtocell technology must be "plug-n-play," and hence seamless installation and activation is critically important. If the equipment is not easy to install, and if the service is not simple to activate and use, on-site support from a service technician will be required. Since "truck rolls" add to an operator's operational expenditures and run contrary to the femto value proposition, carriers must be able to achieve "zero touch installation" for successful femtocell deployment.

In order to keep femtocell customer service and technical support costs down, operators will re-use large portions of their current core networks such as billing, authentication, authorization, and accounting. Registration and provisioning could be carried out in the same way as is done by many cable and ADSL network operators. For example, in most cases, the subscriber has a password to gain access to the broadband connection. DSL Forum's TR-069 standard that already exists for the remote provisioning and management of DSL gateways could be extended for the provisioning of femtocells. Alternatively, the femtocell could include a Subscriber Identity Module (SIM) that stores a key to identify the user. When the femtocell is connected and switched on, the SIM is used to authenticate with the network and provide a secure connection.

Either way, operators must closely manage the customer experience in order to ensure a smooth and swift installation process. The need for standardizing remote device provisioning and activation is a must to ensure that carriers can deploy femtocells from multiple vendors without having to change their BSS and OSS systems. It will be essential for carriers to have a strong control on the remote activation of femtocells. Carrier must be able to de-activate femtocells depending on the location or based on gray lists and black lists to prevent femtocell activation followed by reported theft.

9. Regulatory Hurdles
A number of regulatory hurdles must be overcome or removed for successful femtocell deployment. Since femtocells carry voice calls, they will be required to support a 911 emergency service. Alternative power sources or a fall-back to existing telephone infrastructure may be viable ways to achieve E911 availability. To meet E911 requirements, the operator must be able to provide the location of the equipment to the Public Safety Answering Point (PSAP), which poses a challenge because consumers might try to carry their femtocells to new locations. Some manufacturers are using GPS to lock the equipment when it is moved to a different location. In some countries, existing licenses require operators to maintain written records of base station locations. The need to create and maintain records of every femtocell is unnecessary and would create an excessive burden on operators. Such records are not required for existing systems such as cordless phones and wireless LAN access points, so many operators argue that femtocells should also be exempt from this registration requirement.

In some countries such as Japan, a licensed technician is required to install a "base station." If femtocells are classified as base stations by regulatory bodies and are not exempted from the licensed technician installation requirement, this regulation will defeat the femtocell value proposition because network rollout cost will significantly increase. To anticipate and proactively respond to these and other potential regulatory hurdles, the Femto Forum--the independent industry association that supports femtocell deployment worldwide--is already working with its members and international regulators to encourage a benign regulatory environment for femtocell deployments.

10. Marketing
Initially, operators have focused on the technical challenge of integrating femtocells into their mobile networks, but they must not overlook the importance of successfully positioning femtocells within the industry and amongst the wider public. In addition to developing a common terminology and branding the service effectively, it is critical to build robust usage cases and marketing plans to drive femtocell adoption. To be successful, operators will need to develop compelling value propositions aimed at the most appropriate segments. Enhanced indoor coverage and reduced call charges for voice calls made in the home may not be enough to persuade mobile users to adopt femtocell technology, especially in light of alternatives based on UMA / WiFi.

3G femtocells could clearly boost revenues by allowing mobile operators to offer relatively inexpensive, high-quality voice calls for mobile users when they are at home while charging a premium for mobile calls when users are elsewhere. Operators could also enjoy certain "soft" benefits such as increased uptake and reduced churn, by offering various group subscriptions and family plans linked to femtocells in order to attract all the members of a household to their networks. Furthermore, femtocells will enable mobile operators to compete against converged cellular/WLAN services by offering very similar plans without the need for special handsets. Regardless of the tactics, for femtocells to be successful, the industry will need to have a smart, targeted, and differentiated way to market the technology.

Final Note
The trends are clear: voice traffic will continue to migrate from fixed to mobile networks until 3G carries the majority of voice telephony. Likewise, consumer demand for mobile data in the home is growing and has significant future growth ahead. In the battle for the home, first-mover advantage is key, and femtocell technology has great potential but the race with WiFi is definitely on. In this "make-or-break" competitive environment, fast time-to-market could make the difference between wildly successful deployment of femtocell--leading to broad societal transformation " and another promising technology relegated to the dust-bin of history. With the help of many dedicated and talented telecom ecosystem professionals in meeting these challenges, femtocells will live up to the promise.

About the Author
Manish Singh is vice president, product line management at Continuous Computing. Previously he served as vice president of field engineering and vice president of engineering. Mr. Singh is an experienced engineering leader who brings 14 years of experience in telecommunications product design and development. Prior to Continuous Computing, Mr. Singh held various engineering management and architect positions at Intel Corporation, Trillium Digital Systems, and C-DOT (Center for Development of Telematics). Mr. Singh holds the patent as a sole inventor of "Configurable Cache" memory system. Apart from broad telecom domain knowledge, Mr. Singh brings specialized expertise in the wireless and VoIP telecom technology areas. In 1998, he successfully led the development of 2G MSC at C-DOT and since has led various VoIP and 3G/IMS wireless product development. Mr. Singh received a B.S. degree in electronics and telecommunication from Shri GSInstitute of Technology & Science, Indore and a M.S. degree in computer science from India Institute of Science, Bangalore. He can be reached at:manish.singh@ccpu.com