Kyle Harper, Texas Instruments
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The mobile-accessible Internet age is here and quickly shifting mobile operators’ business and infrastructure requirements in a whole new demanding direction. 4G (LTE) is needed to keep up with the voracious appetite for wireless payloads to avoid dropped calls, download failure, and interrupted videos. |
So, how does an operator reliably serve up all these new and diverse wireless packets of data to users and gain profit? Transition, of course. It’s time for wireless to make the wireless broadband transition. When the transition is completed over the next few years, every mobile operator’s homogeneous topology of macro and compact basestations will be heavily fortified with a heterogeneous mix of smaller cell basestations.
The basestations will include outdoor remote radio head cells, pico cells, and metro cells, as well as in-building enterprise cells and residential cells. In addition, operators’ backhaul topology will be equally heterogeneous, with some places continuing to use and extend their own private connections back to the Internet and other places, piggybacking on top of another wireline operator’s existing connections back to the Internet.
This new mix of basestation and backhaul topology will be required to enable mobile operators to use and monetize their scarcest resource, spectrum, while providing voice, data, and entertainment reliably and cost effectively anytime and everywhere. Adding small cells into the mix outfits an operator’s arsenal with better solutions to fill in the inevitable coverage gaps, fill in new cell areas, and cooperate better with wireline Internet service provider (ISP) operators to backhaul an increasing percentage of its 4G network’s packet payloads to the Internet.
Ever-Increasing Data Rates
In 2010, voice gave way to video and multimedia as the killer app for mobile handset users. While smart-phone users represented about 13% of the operators’ customer base, they used up more than 33% of the operators’ bandwidth. Now with iPads and other mobile tablets hitting networks, operators must accelerate the wireless data bandwidth each user now expects.
The killer apps for these devices are entertainment, video, and media streaming as they gobble up even more wireless bandwidth. In the final analysis, there are only so many bits of data transfer available in any given mobile cell’s coverage area. All active users in a cell must share that cell’s transfer bandwidth.
So what can operators do to provide increased data bandwidth to each user? First, operators can provide larger chunks of data bandwidth for each user to reduce the number of users being served by each cell. This gives each user a bigger slice of the cell’s data packet pie.
In their overlay of 4G/LTE alongside 3G in each macro cell, many operators plan to deliver more data per user by cutting their macro cell radius in half from today’s nominal 10 to 30 miles to a nominal 5 to 15 miles. This change alone will significantly increase the gaps, or dead zones, in between existing macro cells. Since that won’t make for happy users, operators must plan out how best to fill in these gaps. Smaller cells may work nicely here and are more cost effective than macro and compact basestations.
Small Cells To The Rescue
Small cell installations come in a variety of form factors, including small outdoor cell installations such as remote radio head clusters, pico cells, and metro cells and indoor small cell installations such as enterprise and residential femto cells. Commonalities among the small cell installation types include:
- Radius cell coverage areas substantially smaller than macro or compact basestations (making them better suited to fill in small gaps)
- Substantially smaller form factors that are more easily hidden or masked from view
- Substantially fewer costs per installation to install and operate than macros and compact basestations
However, they do introduce the potential for more adjacent cell interference exposure, so operators are trying to understand the performance characteristics for users on the edges of these smaller cells as well as how to minimize such interference.
The remote radio head clusters, pico, and metro outdoor cell installations have larger cell ranges. Thus, they’re designed to handle more users than the smaller-range enterprise and residential indoor cell installations. Also, operators will pay the utility costs for operating outdoor installations, albeit as a lesser expense than for macro and compact basestations, whereas the utility costs for operating indoor femto cells will be paid not by the operator, but by the business owner or homeowner.
Ensuring Quality Of Service
Not all data packets can be treated equally anymore. Macro and small cells alike will need to be in the business of packet inspection. Cell basestations need to be able to distinguish between voice packets, data packets, multimedia packets, and video streaming packets so they are all prioritized and routed appropriately.
Backhauling this mixed payload of packets from small cells to the Internet will take a different path from backhauling from macro and compact basestations to the Internet. Whereas macro and compact basestations traditionally use an operator’s own proprietary connection to backhaul to the Internet, most small cell installations will “piggyback” their backhaul traffic on top of a pre-existing third party’s wireline broadband connection.
This “third party” will be the ISP used by the property owner in residential femto, enterprise femto, metro, and pico cells. The data transfer bandwidth made available by the ISP for the operator’s backhaul load will vary widely from installation to installation. To ensure a minimum quality of service in such installations, the operator will need to arrange for a minimum amount of bandwidth with the ISP, most likely in exchange for a share of some of the mobile operator’s revenue. That might become tricky, as mobile operators and wireline ISPs have rarely cooperated in the past.
This Really Isn’t Your Father’s Infrastructure
By moving from 3G to 4G, operators will transform their infrastructure from a voice and data-class delivery topology to a multimedia and entertainment-class delivery topology optimized for a diverse set of users and use-cases. By utilizing small cells to fill in the existing macro cell topology, operators and users will enjoy higher data bandwidth via better radio spectral efficiency and spectral reuse. Wouldn’t our dads be proud now?
