 |
||||||||||||||||||||||||||||||||||||||||||||||||
Femtocells - Path to Wireless Everywhere ?
Shashidhara Dongre, L&T Infotech Ltd, Bangalore, India Renu Jagadish, L&T Infotech Ltd, Bangalore, India Susmin Mathews, L&T Infotech Ltd, Bangalore, India
Introduction
The accelerated pace at which cellular technologies have taken off is leading to market saturation in most countries. Operators across the world are finding it difficult to cater to the ever-increasing customer demands. Femtocells assume significance in this context, by providing unique value propositions to the operator. In this paper, we have analyzed the business case as well as the technical architectures available for deployment of femtocells in the current network scenario. We have also tried to bring out the advantages of femtocells. At the same time, the challenges and limitations have also been identified.
It is very common for all of us to have experienced various issues with all kinds of communication - be it mobile, fixed, VoIP, etc. These issues like lack of coverage, poor voice/data quality, latency, etc occur mainly because of the shortcomings on the network side primarily controlled by the operator. It is a known fact that the whole world is geared to “mobility everywhere” syndrome. The trend of going mobile has been hindered by one major issue called “In-building coverage”. Operators across the world are trying to address this by various means. In an era where loyalty is a matter of the past, operators are finding it difficult to address customer churn arising out of this. Another challenge facing the operator is the emergence of converged services, be it data, voice and video or a combination of any of the above. The rapidly evolving nature of the market and the extremes of convergence coupled with saturated markets in developed countries make life difficult for operators.
We have analyzed some of the communication technologies currently available in the market, and tried to grade them on various parameters. For a particular parameter, grade A represents the “best” among the four communication technologies listed below. Table 1 illustrates this analysis, from both end-user as well as operator viewpoints.
 Table 1 : Comparison of Communication Technologies
From Table 1, it is very evident that, while cellular technologies are ahead of all others with respect to FMC, there is scope for operators to improve upon the aspects of “In-building coverage” and pricing.
One solution that seems to hold out some promise is the deployment of small base stations called femtocells in end customer premises, typically the home.
What are Femtocells ?
Simply put, a femtocell is a small, extremely low power, cellular base station designed to be located inside a home and using a DSL/Cable connection to backhaul traffic. In other words, femtocells are home base stations deployed in high volume for residential use, connected to the core network via broadband. They are connected to the general cellular network only through the IP core network, which they use as the main backhaul method. They can typically accommodate between four and six users, and they radiate very low power (< 10 mW). The high receive sensitivity of current 3G handsets lends itself to this.
From the end-user point of view, the same service and benefits as a converged offering would be delivered, but with the use of existing standard handsets, The elimination of the need to upgrade to expensive dual-mode handsets is an attractive proposition for customers. Also, the convenience of having a single mobile identity/phone number across devices removes inconveniences such as multiple address books and multiple billing.
There are two major approaches to femtocell architecture within a mobile service provider’s network. These are the “IP RAN” based approach and the “All-IP” approach.
IP RAN based approach
In the IP Radio Access Network (IP RAN) based approach, the femtocell is considered as an extension into the operator RAN network. Hence the protocol stack of “Iub” (the interface typically used between RNCs and BTSs) is encapsulated within the IP signaling, to transport messages into a Radio Network Controller (RNC) or a modified RNC/ concentrator. It is important to note that this scheme involves either introduction of new network elements or major modification to network elements at the RNC layer of the mobile core network.
There are two major alternatives within this approach being pursued by different service providers.
Figure 1: Tunneling Iub with Modified RNC
Modified RNC
This architecture is based on that of existing 3G networks, wherein the femtocells connect to modified RNCs via Iub over IP. In other words, the femtocell connects to an ADSL connection, and then uses the Iub as the transport protocol that will tunnel through the IP core network to the RNC. Thus there is a need to upgrade the RNC to allow it to support this type of communication protocol. Further, the RNC needs to be able to scale to support a large number of femtocells. Figure 1 shows a symbolic representation of this architecture.
Concentrator
Figure 2: Femtocells through a Concentrator
All-IP Approach
In this approach, the femtocell is integrated through a SIP or IMS based network. Here the femtocell converts cellular signals to SIP and uses Voice over IP (VoIP) over SIP. The RNC function is fully integrated into the femtocell. The support of this type of architecture depends on the rate at which IMS, which provides a standardized approach, catches on commercially. Figure 3 demonstrates this architecture.
Figure 3: All IP Architecture
Benefits of Femtocells
Femtocells offer certain unique benefits, both to operators as well as end-users. These advantages are explicated below from both end-user and operator perspectives, and demonstrate the business case for femtocells.
End User Perspective
Operator Perspective
There are some other approaches that provide a few of these benefits. For instance, repeaters and distributed antennas can mitigate the problems of in-building coverage, but fail to addresses issues of call costs and FMC. Similarly, Wi-Fi and Bluetooth solutions can be enhanced to deal with FMC and call cost aspects, but put additional burden on the end-user in terms of the necessity for dual-mode handsets. Overall, femtocells come across as one of the significant technologies that provide a unique combination of the above benefits.
Market Trends
For any communication technology to be successful, serious commitment from players such as operators, infrastructure vendors and semiconductor vendors is a must.
UK based semiconductor vendor picoChip Designs has come out with a reference design for a standalone femtocell. Also, Korea Telecom (KT) has signed a partnership agreement with picoChip to develop WiBro / WiMAX femtocells. KT is the first to develop such a program for WiMAX.
Tatara Systems has recently been issued a patent entitled "Mobile Services Control Platform Providing Converged Voice Service.", for an invention that provides the technology basis for enabling any IP-connected device (like a femtocell or a PC) to make or receive voice calls tied to a user's mobile identity.
Market reports also seem to be pointing favorably, with ABI Research predicting 102 million worldwide users on 32 million femtocells by 2011.
Issues and Concerns
As with many other nascent markets the femtocell market is surrounded by confusion. The most significant contributing factor for this is the lack of standardization in the market. This leads to certain inertia in the semiconductor market because it is very difficult to produce reference designs to proprietary and fluid specifications.
The concept of femtocell may find its way to saturated markets like Europe, but may not find early adopters in BRIC countries where mobile market is in the growth stage.
Another fear is that the femtocell may be a quick fix solution, and hence may not sustain long enough for vendors to make enough money on their R&D investments.
The mass adoption of femtocell is still 3-4 years away.
Cost is an important gating factor that can make or break the mass adoption of femtocells, especially because it is viable for cellular operators to deploy them only if end-customers finance the femtocells at their sites. However recent developments in embedded technologies point to an encouraging possibility of an acceptable price point of $100 in the near future.
Conclusion
Femtocells offer operators an effective way of enhancing in-building coverage and providing seamless fixed to mobile convergence. There are multiple architectures that can be deployed to achieve integration of the femtocells with current mobile networks. While there are some concerns such as lack of standardization, there are encouraging indications from some leading players in the market for the favorable adoption of femtocells in the years to come.
About the Authors
Shashidhara Dongre has over 20 years experience in design and development of telecommunication products. Currently he is the WiMAX Practice Head in L&T Infotech, a premier Indian Software Services Company. His interests are in the areas of advanced air interface technologies and Network architecture consisting of multiple Radio interface technologies. He can be contacted at shashidhara.dongre@lntinfotech.com
Renu Jagadish has an overall industry experience of over 10 years. Prior to joining L&T Infotech, she worked for Siemens Communication Software in NMS and Corporate GSM projects. In L&T Infotech, she has been involved in various projects in the mobile base station infrastructure area. In her leisure time, she loves engaging in public speaking, reading, poetry, music and organizing cultural & literary activities. She can be contacted at renu.jagadish@lntinfotech.com
Susmin Mathews joined L&T Infotech in the year 2005. Currently he is functioning as a senior marketing analyst in the WiMAX practice. He constantly scans the technology space for latest trends and provides inputs to the technical team. He can be contacted at susmin.mathews@lntinfotech.com or wimax@lntinfotech.com
References
The Case for Home Base Stations, Technical White Paper, September 2006, www.picochip.com
Fixed Mobile Convergence Solutions, www.tatarasystems.com 802.16 News Forum, http://www.80216news.com/pubs/2007/02/16/page1299-461787.asp
TelecomRedux Press Release: http://www.telecomredux.com/index.php?option=com_content&task=view&id=3478&Itemid=35
Definitions, Acronyms and Abbreviations
|
||||||||||||||||||||||||||||||||||||||||||||||||
|