ThinkSmallCell introduction to Small Cells eBook · PDF fileAQuick!Introduction!to!Small!Cells!!!!!©ThinkSmallCell!2013! Page 7 of 7!! TheWi>Fiindustryhasdevelopedseveral!standardstoaddresstheseissues,!with

A Quick Introduction to Small Cells David Chambers ThinkSmallCell October 2013

A Quick Introduction to Small Cells ©ThinkSmallCell 2013 Page 2 of 7

What are Small Cells and what types are there? Small Cells are a class of low-‐powered wireless access points providing both cellular and Wi-‐Fi service. They deliver the same voice and data services available from larger cell towers today, and are fully compatible with existing smartphones and other wireless devices. They address four primary market segments:

§ Residential (for homes and homeworkers): These are often termed Femtocells, and were the first type of small cell brought to market

§ Enterprise (for business use): Slightly more powerful in terms of range and traffic capacity, these are connected by a single Ethernet cable that also provides power. A range of enterprise small cell products serves all sizes of office buildings from large to small.

§ Metrocells (for public access): More robust and rugged construction for use in unsupervised areas, these augment the cellular service by adding coverage and capacity where and when needed. Outdoor metrocells may be fitted to the sides of buildings, on lamp-‐posts and other street furniture. Indoor small cells may be used in public venues such as transport hubs, sports stadiums and hotels.

§ Rural (for remote areas): With a wider coverage area, rural small cells provide pockets of coverage in otherwise isolated hamlets and villages. Often connected via satellite links and with their own power source, these can be installed in remote areas of both developing and developed countries, bringing voice and data service to otherwise disconnected communities.

Small Cell Evolution The first small cells were arguably those developed by ip.access, which in 2002 launched an end-‐to-‐end GSM solution for indoor use called nanoGSM that used existing IP broadband to connect back into the cellular network. Around 2007, several companies started developing 3G indoor small cells targeted for residential use. Most vendors chose the popular 3G UMTS technology, but Samsung developed a 3G CDMA solution which was the first to market with Sprint in the USA. Several vendors and operators collaborated to promote this new concept, forming the Femto Forum in 2007. Several major operators launched residential femtocell services over the following years, including AT&T, Verizon and Vodafone (in more than 10 countries). Several have achieved large scale, with multiple US operators said to have each exceeded 1 million femtocells. Aggressive growth was forecast, but few operators actively marketed these products and instead limited them mostly


for use as a customer retention tool – giving them away only when customers complained of poor indoor coverage and threatened to leave. A few have been more proactive and actively give away free Femtocells to all their customers, such as Free France who incorporate them into every new wireline broadband set-‐top box shipped. In October 2012, the number of small cells exceeded the total of traditional macrocells – over 6 million – and the number continues to grow. Once the technology had matured, component vendors increased the capacity and capability to address additional use cases. System on a chip (SoCs) were developed which could handle 16, 32 and 64 concurrent active sessions. More recent designs support both 3G and LTE on the same platform. Products with higher RF power to expand the coverage footprint have been developed. High volume equipment manufacturers (ODMs) from Asia have participated, bringing down the unit cost significantly.

Residential Small Cells Often still called Femtocells, these residential small cells are similar in size and operation to a Wi-‐Fi access point. They transmit at low power, typically in the range 20mW to 100mW, and can handle up to 8 concurrent active calls with more users camped on in idle mode. Designed to be extremely simple to install and use, there is a very high level of built in self-‐configuration and adaptation. Typically there are no switches or end-‐user configuration parameters, with only a single Ethernet cable to the domestic router and a mains power source required. Vodafone’s Sure Signal product shown below integrates this into a unit the size little more than an electric mains power plug. A few lights indicate whether it is connected and operating.

Some operators limit access to these Femtocells, with the homeowner managing a white list of up to 30 telephone numbers that can be updated via a secure webpage. This is partly to avoid unexpected consequences and/or large landline broadband bills resulting from use by unknown subscribers nearby.


The latest 3G Femtocells can handle data rates up to 21 Mbps, often far exceeding the wireline broadband internet service they are connected through. One limiting factor for multiple voice calls can be the uplink DSL broadband data rate, although typically at least four concurrent calls are feasible. The primary driver for residential small cells is indoor voice coverage. The close proximity to the handset to the small cell reduces the RF power required, extends battery life and improves voice quality, data speeds and latency resulting in excellent customer experience. A few companies have developed and launched LTE residential small cell products, and these are beginning to be adopted in a few countries such as Korea and Japan. It’s likely that 3G will remain the major focus for residential small cells for some time, because the advantages of LTE require a high speed broadband wireline connection still relatively uncommon in many parts of the world.

Enterprise Small Cells Business users can often be a higher spending market segment for network operators. Delivering adequate coverage and capacity inside offices can often be a challenge, with a choice of solutions such as penetrating inbuilding from outdoor macrocells, using repeaters which don’t add capacity or installing an expensive DAS (Distributed Antenna Systems) equipment. The materials used to construct new office buildings are often very resistant to RF signals, and the growing demand for cellular data is makes traditional solutions less effective. There is a wide range of different sizes of businesses and office buildings, from the smallest business of 1-‐2 employees whose needs could be satisfied by a single residential femtocell up to systems catering for large office buildings with thousands of staff. Different small cell products addressing these needs have been developed. Multi-‐tenant buildings shared by multiple smaller companies may be centrally provisioned or have their own individual small cell solution. Enterprise small cells are designed to be easily and quickly installed, using a single Ethernet cable to each unit which carries both power and data. Dedicated wiring can be used, but the standard Ethernet connection can also be routed over a segregated VPN or shared Ethernet network. Slightly higher RF power of 100mW to 250mW extends the range to handle warehouses and larger office spaces, with higher traffic handling capacity coping with more intense usage. Busy environments such as financial trading floors have been successfully equipped with enterprise small cells in what are some of the most demanding use cases. Some of the larger systems include a central controller which co-‐ordinates and collates the traffic from a group of small cells. Today’s small cells are connected to a single network operator and only serve their subscribers, but typically they are open access and can be used by visitors. Current solutions are almost entirely 3G with combined 3G/LTE products under


development. While national roaming agreements could be put in place to extend access to competing networks, this hasn’t overcome the commercial advantage of linking provision of indoor enterprise small cells with a bulk corporate subscription contract.

Metrocells and Public Access Small Cells Where Residential and Enterprise small cells have been primarily positioned as a (voice) coverage solution, metrocells have been mostly promoted for additional capacity. The capabilities of existing macrocell sites are being fully exploited by deploying all available 3G and LTE spectrum, refarming existing 2G spectrum for more efficient use by 3G and LTE, sector splitting and other techniques. With data demand continuing to grow rapidly, this traditional approach cannot meet future needs and it is widely accepted that small cells will be required at some point to deliver the additional capacity. Metrocells are similar to picocells (small macrocells), with an RF power range of some 1W to 5W or more, supporting a larger number of concurrent users spread over a wider footprint. These higher power units can penetrate into nearby buildings from the street outside, and are often positioned to cover street canyons in the densely populated urban areas. Since they operate in outdoor and unsupervised areas, they are ruggedized to protect from the environment – including wide temperature fluctuations, harsh weather and attempted vandalism. Accurate positioning of metrocells is extremely important to ensure they deliver worthwhile benefits. With a much smaller footprint than a larger macrocell, it is important to ensure they offload as much capacity from the existing network as possible to be viable. Since metrocells are often installed outdoors, a backhaul connection to a nearby macrocell or other transmission hub is needed. Many vendors have sought to address this need with short range, high capacity wireless links. There are a plethora of technology choices, from point-‐to-‐point to point-‐to-‐multipoint, Non-‐Line-‐of-‐Sight to Line of Sight, and in frequency bands from 3GHz to 80GHz from licensed to unlicensed. Wireline, both fibre and copper, would be used where available, but a large percentage of connections are expected to require this last short range wireless capability. Early 3G metrocells have been trialled extensively, but it is using LTE where these are expected to become most popular.

Rural Small Cells There are still many people living in areas of the world today without any terrestrial cellular coverage. Satellite phone services reach almost everywhere, but are costly and limited in bandwidth. Three technical developments have come together which make it feasible for rural small cells to be commercially viable:


• Small cell technology has been adapted for use in remote areas, extending the coverage footprint of a 3G small cell up to 2km, while retaining to low power consumption and equipment cost benefits.

• Satellite backhaul has become much cheaper, with deployment of new satellites using much higher frequencies (Ka Band) that allow reuse of spectrum through multiple antennas and spot beams.

• The reduced cost of solar panels and wind generators which can power this equipment continuously when used with suitable batteries.

These solutions address two quite different segments:

• Developing countries, where many villages remain completely “off grid” and can be provided with cost-‐effective viable solution that connects the community

• Developed countries, where there remain “notspots” with no coverage or service. Rural small cells expand the coverage footprint, and can also offload targetted traffic from existing wide area cells where there are known hotspots.

Evolution to 4G/LTE Unlike 3G, the 4th Generation radio standard called Long Term Evolution (LTE) was designed from the outset to encompass small cells. Not only did it clearly specify how small cells operate, but it also defines how layers of macrocells and small cells can be tightly integrated and share the same spectrum. In those countries where LTE has seen mass take-‐up, such as Korea and Japan, large numbers of LTE only small cells have been deployed. LTE small cell products for each of residential, enterprise and metrocell market segments are available from multiple vendors. Most installed to date are indoor, serving office and public areas. Network operators requirements vary across different regions, but there is a common theme of a combined small cell which simultaneously provides 3G, LTE and Wi-‐Fi. Several major silicon vendors are actively developing platforms to support this, with a power budget for the entire product that fits within Power over Ethernet limits.

Integration with Wi-‐Fi Network operators have changed their view of Wi-‐Fi and there is now widespread acceptance of its value both for private and public use. There are many operator partnerships which encourage Wi-‐Fi offload to relieve traffic load on cellular networks. A major concern is the variable quality of service which end-‐users might receive after being switched across to a partner Wi-‐Fi hotspot, in what is sometimes termed “blind handoff”. End users remain frustrated with the need to login to visited hotspots and have concerns about potential security risks and battery life impact.


The Wi-‐Fi industry has developed several standards to address these issues, with HotSpot 2.0 combining a number of features that should make access to public hotspots more seamless and beneficial. Using the cellular SIM card to authenticate and adopting back-‐office processes from existing cellular roaming schemes, it could quickly become very straightforward to be transferred across to a Wi-‐Fi hotspot when appropriate. Many small cell vendors have integrated Wi-‐Fi access into their products. In some deployment scenarios, this can double the backhaul traffic capacity required and may not be worthwhile. There also remains further work to be done to ensure that adequate Quality of Service is delivered to subscriber when using Wi-‐Fi, with several proprietary solutions already on the market.

Summary Many small cells have been deployed today to provide good voice coverage. Large investments in silicon platforms and other components has reduced the hardware cost to minimal levels. Software development has matured through large scale deployment to create robust, scalable solutions which are self-‐configuring and self-‐optimising. For indoor applications, 3G residential and enterprise solutions are mature and widely proven. As data traffic levels continue to grow, the macro network won’t be able to expand further to meet demand. Initial LTE rollout with its new spectrum provides some respite, but in the medium to long term there is little doubt that large numbers of small cells will be needed to satisfy demand. While both 3G and LTE small cells are actively deployed today, the long term goal of a combined 3G/LTE/Wi-‐Fi small cell product is within sight. The small cell itself is not a complete solution, and an associated set of wireless backhaul products and planning/optimisation tools and services are needed to complete the picture. As the number of small cells continues to grow and they become more integrated into the existing cellular network, in what is termed a HetNet, we can expect the additional complexity to require greater automation of tools and processes which today are handled manually. For more detailed insights into all aspects of small cells, visit ThinkSmallCell.com where you’ll find sections on Residential, Enterprise, Metrocell and Rural plus a range of interviews with leading industry players, pre-‐recorded webinars, slideshares and many other resources.

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ThinkSmallCell introduction to Small Cells eBook · PDF fileAQuick!Introduction!to!Small!Cells!!!!!©ThinkSmallCell!2013! Page 7 of 7!! TheWi>Fiindustryhasdevelopedseveral!standardstoaddresstheseissues,!with