The state of the femtocell industry

Femtocell momentum marches on as the spotlight shifts from a showcase to field deployments. The last couple of years have focused on proving the technology and demonstrating the value proposition. Now as the femtocells begin to move from early adopter operator trials to rollouts the vendor ecosystem has been confidently addressing the needs of scalability, economies of scale and manageability. Nonetheless the femtocell market is still in need of a stimulus package to get it to the inflection point.

The Operators Dilemma - Choosing between standard interfaces or time to market

Femtocells, like most disruptive technologies are the result of innovation. This innovation resulted in proprietary methods of interconnects to deliver signaling, traffic and management information for interworking to the core network. Whether the principal femtocell vendors provided end-to-end solutions or in combination with partners, they adopted the network interfaces suitable to their architecture. The interfaces have worked well, but posed the following challenges to the operators:

• Operators are handicapped in putting a best-of-breed solution together, if the interfaces remain proprietary.
• The ability for low cost innovators to enter the foray is limited with closed interfaces. This keeps the price-points high which is detrimental to the sought after sub-$100 model for the femtocell.
• Operators are hesitant to invest in training costs while introducing multi-vendor solutions.

CDMA femtocells have less complex interfaces than UMTS

CDMA Femtocells saw early deployments such as Sprint's AirRave. The 3G CDMA network architecture has offered fully IP-based packet data connectivity so femtocells were able to connect effectively to the CDMA Core. The 3G-UMTS architecture is more complex with the Iu interface for support to the circuit-switched and packet-switched networks. Additionally, ATM is still the dominant transport for the Iu interfaces deployed in today's networks. It became imperative that aggregation and interworking was necessary in this model to provide a simpler interface to the femtocell access points. This led to different variants of transporting the Iu signaling and traffic to the Femto Access Point (FAP).

Operators strongly supported the Iu-h interface standard

Fortunately the Femto Forum and 3GPP members have been working on simplifying this interface to provide the common set of features. This interface - Iu-h - allows the Home Node-Bs or the FAPs, to communicate with the Gateway Element (HNB-GW/FGW - Home Node B Gateway/Femtocell Gateway) in a standards defined interface. This interface allows the FGW to register and control connectivity to the FAPs. This also enables the transfer of signaling and traffic packets to be easily aggregated and routed at the FGW. This value proposition appealed to the operators and a majority pushed keenly for FGW and FAP implementations that support this interface in a timely manner.

But implementations of Iu-h are trailing

However, while most vendors have underscored their commitment, implementations are trailing. The main reasons being:

• Vendors are under delivery pressures for their current femtocell commitments.
• While the main framework for the Iu-h was defined by April this year. There is still enough of devil in the details which continues to be addressed. Practical issues for IP addressing, NAT, handover, etc. still need articulation.
• An open vendor plugfest has been in the plan, but is still awaited.

Operator momentum for Iu-h has weakened a bit, which is what really needs a boost. Operators have been focusing more on the management interface to address the manageability of these boxes. This includes the TR-69 DSL forum recommendation and the TR-196 data model.

3GPP standards focus has moved on

Most of the 3GPP focus has also shifted to connectivity to the forward-looking network core, which includes IMS and LTE-EPC.This has had two ramifications on Iu-h:

• Progress on resolving some of the deployment issues has stalled in Iu-h. This spawns vendor specific workarounds to address challenging issues in what should be a standard interface, thus resulting in the déjà-vu of a vendor specific variant.
• The positive side for the defense of Iu-h is the requirement for the standards to push for the FGWs to support both Iu-h and Flat-IP schemes for network interconnect, Flat-IP being the goal for LTE and IMS. This is obviously causing heartburn in the standards discussions, but affords a long-term commitment to the operators.

So what is really needed now is a positive re-enforcement from the operators about their mandate for an open-interface. This is truly the stimulus which will drive further innovation in this ecosystem, help to meet price points and will hopefully get to a plug-and-play architecture.

About The Author

IntelliNet provides a broad portfolio of software solutions for the telecoms industry. This includes a Femtocell Gateway and related products which are compliant with the Iu-h interface.

Arun Handa is CTO of IntelliNet Technologies and leads the development of their next generation technology vision and roadmap, identifies new development opportunities, and expands the company's position as an industry leader and innovator. With over 15 years of experience in the wireless industry, he has been instrumental in delivering complex network elements for IMS, wireless, mobility, location, and messaging applications, including the Accelero and Convero product lines.

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