Dealing with density: The big move to smaller cells

By Steven Glapa, Senior Director of Field Marketing, Ruckus Wireless | Nov 1, 2011

Cellular networks have a big problem: too many people want to use them for too many new things. Conceived and designed for voice traffic — not photos, videos, music downloads or other high-bandwidth fun — traditional wireless networks are struggling to keep up.

You can’t find a report that doesn’t show that global mobile data traffic has tripled each year for the past three years. And there’s more to come.  This traffic is expected to grow by more than 25x in the next four years.

Massive growth in data traffic has profound implications for network infrastructure. In response, carriers are looking at several techniques and technologies to catch up with rapid growth in bandwidth demand, but there is no silver bullet.

Operators will use a combination of tools to manage this data explosion: acquiring new spectrum, deploying more efficient wireless technologies like LTE, putting smarter Wi-Fi everywhere, adding femtocells, and getting more aggressive about cell splitting. Other techniques include more use of tiered mobile data pricing plans and traffic flow optimization. 


As a result radio access network (RAN) infrastructure will change dramatically. Operators will begin deploying large numbers of small form factor RAN devices to accommodate bandwidth growth, and combination Wi-Fi/Pico LTE nodes will also become an important part of the solution.

While operators continue to rely on their macro cellular networks to provide wide-area coverage for voice, they’re hurrying to find complementary alternatives that will ease the increasing pressure, especially in areas where 3G/4G subscriber density and usage is high, like urban centers, airports and transit stations, and stadiums and convention centers. And each operator wants to find the right technologies and deployment strategy before their competitors figure it out and take their subscribers with them.

To address all this, mobile operators are looking at anything and everything including:


•Upgrading the 3G HSPA network — this makes technical and financial sense but doesn’t provide the increase in capacity that is required in high-traffic areas


•Building a Wi-Fi underlay network — for mobile data offload to address the immediate need for additional capacity


•Purchasing more RF spectrum — as operators move to macro LTE to establish coverage, promote device adoption, and maintain access for high-mobility users


•Rolling out a small-cell LTE underlay network — to provide additional capacity where needed, once LTE device adoption takes off. The small-cell LTE network complements the Wi-Fi network (and to a large extent it is expected to cover the same high-traffic areas) and the LTE macro network (mostly deployed for coverage and high-mobility access) to provide an additional capacity boost.


•Using 5GHz Wi-Fi for NLOS backhaul — as the sheer number of smaller cells makes it nearly impossible to run expensive fiber or fixed broadband connections everywhere they're required.

Operators need a roadmap for a long-term and multi-step strategy to increase RAN capacity density (i.e., capacity per square kilometer) in high-traffic areas to meet the subscriber demand for data services. Wi-Fi for mobile data offload is one of the most efficient and economical means by which operators can immediately realize a steep increase in capacity — getting access to most desirable locations in high-traffic areas.

Wi-Fi, long regarded the ugly step-child in the RAN family because of its inherent unreliability and unpredictability, has grown up to be considered now one of the best solutions to traffic congestion in high-density locations — not only because of improvements to the technology like 802.11n with adaptive antenna arrays, but also because nearly all smartphones, tablets and laptops support Wi-Fi connectivity. Operators are also exploring additional options, such as small cell underlays, to provide high capacity density, while complementing and strengthening their Wi‑Fi and macro cell deployments.

Content caching, tiered pricing, and policy enforcement are other approaches available to mobile operators that can further improve their network utilization and allow them to actively manage the traffic beyond the RAN within the core. While these solutions do not increase capacity, they make data transmission more efficient and allow operators to pack more content within the same infrastructure.