Lately, one of the buzz words heard in the market is Femtocell, which is said to be a very promising technology in the wireless space. This article will detail this technology, its alternatives and the use of media gateways in these solutions.
FemtoCells are small CPE devices containing a 3G antenna (known as “Node B”) that are aimed at households and provide indoor 3G coverage. FemtoCells deliver superior voice and data connectivity, and a variety of 3G services. The handsets used for this service are regular 3G handsets. This breakthrough enables operators to offer cheap fares for in-house calling.
FemtoCells belong to a group of solutions that provide the Fixed-Mobile-Convergence (FMC) service for the cellular user. FMC service for the user means using a single handset for calls made externally (mobile) and internally (fixed) from home. The calls made from home make use of the user’s wireline internet connection for transporting the call (hence the name “fixed”). For making calls from home, the user expects to receive the same cheap flat rate as received from a wireline provider and to use the same handset.
The motivation for operators to launch FMC services or, also known as “home zone services,” arises from increasing the ARPU and gaining new subscribers (potentially from customers abandoning their wireline service providers). The FemtoCell and UMA (to be described below) technologies, provide an additional benefit to the operator, by saving valuable macro cell bandwidth on the operator networks.
There are several technological and non-technological alternatives in providing the FMC service. The first alternative is to simply apply special low rates for calling from your home zone without making any network change. The customer registers his home address and the cellular provider charges special low rates for any call made from the coverage area of the cellular base station, in the vicinity of the details given by the customer. This home zone area usually covers a 2KM radius which is sufficient enough to include the user’s home and neighborhood. Vodafone Germany is an example of a carrier that provides this service.
The additional two types of FMC solutions rely on introducing new components into the operator’s network.
Dual-Mode Handset (DMH) which is also known as UMA/GAN, is one of these two solution types. DMH uses special handsets that can activate a call on both the cellular network (such as a regular cellular phone) as well as on a WiFi network using Voice over IP. The DMH service requires the user to have a WiFi hotspot in his home enabling the use of the WiFi connection for all calls. Calls are delivered over the user’s broadband connection and the internet - to the operator’s core network. This solution provides an important advantage for the wireless operator, as it saves valuable macro cell bandwidth by using the user’s home WiFi network. Two examples for DMH services are France Telecom/Orange Unik service and T-Mobile’s HotSpot@Home service.
As in the DMH case, the FemtoCell makes use of the customer’s home broadband connection to deliver calls over the internet to the operator’s core network. Like DMH, FemtoCells also save up valuable operator macro cell bandwidth. FemtoCells initial deployments are expected in the second half of 2008.
The use of media gateways on DMH and FemtoCell:
The DMH/UMA solution connects to the operator’s core network via the standard core network interfaces (I Interface on the 2G case and Iu-CS interface on the 3G case). This connectivity was standardized by the 3GPP standardization group and named GAN (Generic Access Network). This method provides transparency in the sense that the core network remains unchanged.
The FemtoCell also connects to the core network via the internet. Several methods exist for accessing the cellular core network. One of them is utilizing the standard core network interfaces (as seen in the figure above), by relying on the existing UMA/GAN standards.
In order to use the standard core network interfaces, a media gateway is required to interwork the VoIP streams coming from the IP network, on the access side, into either TDM or ATM circuits on the cellular core network.
As calls are traversing the non-secured internet, special consideration is required in order to maintain the security and privacy of calls. The element in charge of this task is the security gateway which uses the IPSec tunneling standards to cipher and authenticate the VoIP streams and call signaling coming from handsets.
At the core network side, AudioCodes provides all the media layer components that are needed for both the FemtoCell and DMH/UMA solutions. This offering entails carrier-grade media gateways and security gateways which are already widely deployed on commercial UMA networks.
The Mediant™ family of media gateways are an ideal fit for the above FMC solutions as they offer a wide set of vocoders which may match any solution, be it FemtoCell or DMH. The Mediant family of media gateways includes vocoders such as: AMR, WB AMR, EVRC, EVRCB, G.711, G.723, G.729 and many others. This allows an operator who began with a DMH/UMA service and now wants to add a FemtoCell service to the network, to use the same Mediant media gateway, thereby saving on expenses and time to market.
The nCite™ Security Gateway (nCite™ SG) is a hardened security device that utilizes state-of-the-art network processors. The nCite SG performs deep packet inspection and advanced cryptography in order to securely connect the mobile subscribers.
In conclusion, FemtoCell is indeed a very promising technology which offers benefits to both cellular providers and users. The Mediant family of media gateways and the nCite™ SG security gateway are a perfect match for this application.