Femtocell

January 18, 2010

By Utkarsh

A femtocell is a small cellular base station designed for use in residential or small business environments. It connects to the service provider’s network via broadband (such as DSL or cable) and typically supports 2 to 5 mobile phones in a residential setting. A femtocell allows service providers to extend service coverage inside of your home – especially where access would otherwise be limited or unavailable – without the need for expensive cellular towers. It also decreases backhaul costs since it routes your mobile phone traffic through the IP network.
A femtocell is sometimes referred to as a “home base station”, “access point base station”, “3G access point”, “small cellular base station” and “personal 2G-3G base station”.

The Benefits of Femtocells

Due to the substantial benefits, femtocell technology is causing quite a “buzz” in the industry. ABI Research has forecasted that by 2011 there will be 102 million users of femtocell products on 32 million access points worldwide.

Femtocell Benefits to End Users

Reduced “in home” call charges
Improved indoor coverage
Continued use of current handset
Reduced battery drain
One consolidated bill
Multiple users/lines
Landline support

Femtocell Benefits to Mobile Operators

Improves coverage
Reduces backhaul traffic
Provides capacity enhancements
Reduces churn
Enables triple play
Addresses the VoIP threat
Stimulates 3G usage
Captures termination fees
Allows for multiple users/lines
Addresses the fixed mobile convergence market with a highly attractive and efficient solution

Femtocells: Why Now?

Indoor coverage has been an industry problem for year and vendors have unsuccessfully tried to develop relevant technology solutions for the home. Most services to date involved micro or pico base stations and did not really have the price points to support residential users. Alternative approaches tried most recently involve dual mode devices based on Wi-Fi. While technically compelling, these solutions depend on adoption of new (and expensive) handsets.

A number of factors are coming together to enable femtocell based solutions:
• The high adoption of broadband connections allows the service providers to leverage the IP backhaul to reduce the backhaul costs for additional usage.
• Advances in embedded technologies make it possible to offer a home base station at an acceptable price point approaching $100 over time
• Users are now accustomed to the idea of having a home gateway – thanks to prevalent products like TiVo, Vonage, Slingbox, Wi-Fi AP, as well as DSL/cable modems.
• As 3G adoption increases, indoor coverage becomes a challenge even in otherwise good 2G coverage regions such as Europe and Asia.
• Operators who have trialed cell-site based home zone type services have seen the potential to leverage home zones for improved customer retention.
• New low power GSM spectrum has enabled new players to participate in mobile offerings based on licensed band femtocells.

Femtocell Architectures

There are two broad femtocell architecture approaches within a mobile service provider’s network.

1. All-IP (SIP/IMS): The SIP/IMS based approach integrates the femtocell through a SIP or IMS based network. This approach leverages a SIP based VoIP network for cost-effective delivery, while interworking with a cellular core to extend legacy circuit switched services. In this approach, the CPE converts cellular signals to SIP and interfaces to a SIP-MSC inter-working function (IWF) which connects to the SIP (or IMS) network as well as the circuit switched network.

2. Radio Access Network (IP RAN): The IP RAN based approach effectively considers a femtocell an extension into the operator RAN network and ties the femtocell into the circuit switch core at the edge of the network. This typically involves transporting “Iub” messages over IP into a Radio Network Controller (RNC) or a modified RNC/concentrator. (The Iub is the interface used by an RNC to control multiple Node B’s in a UMTS network.)

There are three different variants of this approach being pursued by different vendors, however all three of these variants require either the introduction of or major modification to network elements at the RNC layer of the mobile core network:

Modified RNC: This approach uses existing or modified RNCs to connect to the circuit switched core network. The CPE connects to the RNC via Iub over IP.
Concentrator: This is similar to modified RAN in that it connects to the CS core, but it does it through a new ‘concentrator’ device that interfaces with the CPE. The interface is again based on Iub over IP.
UMA: This approach incorporates a UMA client into the CPE and connects to the core network via a UMA UNC.