LTE Femtocells: Opportunities and Challenges

Dr Sanket Nesargi, Senior Marketing Manager at Aricent discusses the opportunities and challenges for developing and deploying LTE Femtocells

The global Femtocell market is now seeing wide acceptance with nine commercial deployments by major operators worldwide, and many other trials in progress. With operators and vendors now trying to differentiate their solutions through pricing strategies, Super Femtocells and Femtozone applications, it is expected that the number of femtocells in 2014 will reach 40 million units. Vodafone's recent commercial launch of femtocells, with its SureSignal offering, has given the technology the much needed push the industry has been waiting for, and shown that operators are willing to go the extra mile ,driving prices down to attractive levels, to ensure the uptake of Femtocells.

At the same time, operators are in various stages of migrating their 3G and 3.5G networks to LTE to tap into the mobile data market, which has exploded in the last few years. LTE promises to change the mobile broadband landscape with theoretical data rates in the range of 86 -172 Mbps. Operators around the world understand that capacity and coverage are the two key ingredients to ensure a successful deployment. Femtocells provide the ideal solution to fulfill both requirements.

Aditya Kaul, senior analyst, mobile networks at ABI Research reinforces this view: "LTE network trials using traditional macro-base stations are already under way in the US, Japan and Europe. While LTE will most likely be deployed from the macro layer first, operators realize that simply providing LTE coverage will not be enough. They will need to soon complement the macro network with targeted metro, enterprise and residential femtocell deployments. We forecast that by 2014 shipments for LTE femtocells will reach 20 million annually, with most LTE femtocells supporting 3G in multimode."

LTE femtocells providing capacity

There is currently a capacity crunch forming as high-traffic zones - such as airports, business centres, hotels, enterprises, and city centres - have more and more users logging into their networks and overloading the infrastructure. LTE will address this challenge, but given the technology will use high-frequencies, it offers poor indoor coverage - creating a need for femtocells.

Deploying femtocells to enhance LTE coverage ensures that more users have access to the peak LTE throughput most of the time. With newer wireless technologies fast approaching theoretical limits on data transfer rates, the only way to improve wireless capacity is to reduce the size of the cell, which is exactly what is achieved by LTE femtocells. The value of femtocells extends much beyond the home environment to enterprise and hotspot deployments, which are addressed with Super femtocells being developed to cater to these niche requirements.

Femtocells needed for LTE

Coverage problems are the result of issues such as difficult urban terrain and the poor indoor penetration of high frequency LTE. Reports show that 70-80% of mobile traffic is generated at home or in the office. LTE Femtocells help deliver a rich data experience indoors and at the same time take the load of mobile data off the macro network. The spectrum optimisation offered by femtocells is a key factor in enhancing the business case for LTE femtocells.

Improved indoor coverage and capacity offload are not the only benefits the technology offers. LTE femtocells provide options for operators to 'test the water' for LTE deployments and incrementally build their networks. Additionally, as these do not have heavy dependencies for integration into existing networks, and because of this 'bottom-up' approach, operators can deploy their networks swiftly. LTE Femtocells play a key role in enabling a wide spread adoption of LTE, and they will also play a key role in the enterprise and metro deployment areas.

LTE femtocells for hotspots

According to ABI Research senior analyst Nadine Manjaro; "Some vendors are looking to deploy LTE in hot spot-like deployments, where the demand is highest first. So it makes sense that they would cover a building with a picocell and femtocells for the smaller buildings or personal usage." Manjaro suggests that some early LTE deployments will be entirely femtocell based.

An important point is that femtocells can considerably lower the delivery cost per bit through various means like self optimised configuration and backhaul costs - making it more cost effective for operators to invest in LTE networks. Self Optimising Networks (SONs) are an important concept in LTE designed to enable auto-configuration of networks as well as add self healing capabilities to them, which could result in significant OPEX reductions for operators. Extending this concept to LTE Femtocells ensures that operators do not incur excessive expenses in configuring, troubleshooting, and maintaining the femtocell-based LTE deployments.

LTE Femtocells will help in the extension and enhancement of the Femtocell value proposition with Voice, Data and Femtozone applications being integrated into the 'Cloud services' universe. As next generation networks become more pervasive, monetising new revenue streams via managed content, services and applications is crucial to operator strategy. LTE Femtocells are also poised to become an integral component of the smart home of tomorrow. As the number of devices in the household that use Wi-Fi (baby monitors, security cameras, VoIP telephones, car alarms, gaming systems, remote controls) continue to increase, the user experience will continue to recede. Integration of LTE Femtocells into the home environment will enable operators to enhance the quality of services like IPTV, gaming applications, customer service and billing to end user while at the same time reducing churn.

LTE femtocell challenges

However, several challenges need to be addressed before LTE femtocells can become a commercial reality. The first and foremost is the unavailability of complete standards at the time of writing. The Home eNodeB (HeNB) is expected to be standardised in Release 9 on 3GPP specifications planned for December 2009. While three architectural variants have been proposed in 3GPP 28.830, the architecture which was recently presented in the Femtoforum presentation at Supercomm 2009 is as shown below. Thus, multiple aspects of standardisation including details related to interference, interoperability with 3G Femtocell architectures, security aspects, role of the HeNB Gateway, etc., need to be finalised before true commercial solutions can be introduced. Also, manageability of Femtocell deployments has always been a concern despite TR-069 based femto-specific data model (TR-196). While SONs are expected to help alleviate these concerns, the enhancement of SON functionality to address all possible HeNB scenarios will take some time.

NOTE: Communication between the HeNB and the HeNB GW/S-GW is secured by a mandatory Security Gateway (SeGW) function, which is not shown in the figure.

Further, given that the 3G Femtocell market itself is in its nascent stages with the industry lacking a clear consensus on suitable business models and true mass adoption of femto services, operators are reluctant to commit to LTE femtocells. Also, given the data rates that LTE is expected to support, capacity on the backhaul from the customer premises will continue to remain a major concern. As with any network, the user experience is capped by the slowest link in the network, and in the case of femtocells, it is quite likely that this could end up being the backhaul. Additionally, operators need to ensure the integration of the backend systems to optimise the use of femtocells, in terms of QoS, billing, authorisation, security, etc. Only after a true end-to-end integration of the offering is completed - from the infrastructure to the network core to the back-end systems - will LTE femtocells be ready for prime time.

Summary

With LTE having a strong roadmap and industry backing, and operators cautiously approaching their LTE investments, a very strong business case for LTE femtocells does exist, even more so than for 3G femtocells. This necessity for a viable 'small cell' solution should help drive Femtocell standards to completion in a short timeframe, enabling femtocell vendors to leverage and accelerate R&D. The ecosystem, industry participation and standards-body partnerships built by the Femto Forum will continue to drive the long term success of LTE Femtocells.

Dr Sanket Nesargi is the Senior Marketing Manager at Aricent responsible for the OEM segment. Sanket has 12 plus years of experience in the telecom industry and has worked with Aricent since May 2009. Sanket holds Ph.D. in Computer Science from the University of Texas at Dallas, and an MBA from the McCombs Business School at the University of Texas at Austin.

Aricent has been pioneering Femtocell software development since 2006 and has worked with multiple manufacturers in R&D, Product development and deployment. Aricent works with manufacturers to address key issues in Femtocell software development including software interoperability with multiple platforms to reduce integration complexity and cost, R&D to design and develop differentiated solutions, help to accelerate feature introduction and development with proprietary software frameworks and conceptualising and design of smart-home Femtocell solutions.