What is small cell?

Peak mobile bandwidth is projected to grow 500 percent by 2018, so mobile networks are under pressure to add capacity and improve coverage.

One option is to add more standard macro cell towers, but they’re very expensive to build and operate, must clear regulatory hurdles, and often face community opposition because they’re so big and visible.

That’s where small cells come in. They’re unobtrusive and consumes less power. Forecasts show that more than 700,000 small cells will be deployed worldwide—on light or utility poles, strands of wire, buildings, or inside homes and businesses—within the next few years. It’s clear the potential exists to bring the radios physically closer to millions of end-users to improve coverage and capacity.

Small cell technology enables MNOs to deploy sites in strategic locations offering smaller coverage with higher capacities, using licensed and unlicensed wireless spectrum.

As the world increasingly goes mobile, operators and vendors are rapidly approaching the Shannon limit—the theoretical maximum information transfer rate of a channel. With the unbending laws of physics at play, operators are in a seemingly futile battle to extract more bits per hertz over available wireless spectrum.

Wireless speeds have increased, but the theoretical maximum upload and download speeds are rarely achieved. In most cases, speeds are much slower due to a number of factors, such as the distance from a mobile device to a macro cell tower, line-of-sight obstructions, indoor usage, transmission signal interference, mobile device performance limitations, and other contributing factors. Small cell overcomes most of these limitations by moving the mobile network transmission radio closer to the end-user—with more cells covering fewer users, but with higher per-user capacities.

There are two ways to deploy small cell within existing mobile network architectures:

• Piggybacked on macro cells: Small cells can be homed back to existing macro cells with combined small and macro cell traffic backhauled to the MTSO. This results in increased capacity requirements onto the backhaul links currently feeding the macro cell, especially as more and more small cells are deployed.
• Direct to the MTSO: Small cells can be homed directly back to the MTSO, which results in longer-distance backhaul links. This often leads to more difficult and costly right-of way negotiations, especially if they employ protected dual small cell backhaul links. But the main advantage of this approach is that it doesn’t affect the capacity requirements of the existing macro cell backhaul links.

Both small cell approaches increase capacity for end-users because the overall mobile network coverage and proximity to the Small Cells improves. In turn, more network traffic goes through MTSO sites and over metro networks toward the data centers in search of popular apps and content. These increased demands placed upon existing metro networks will continue to drive the adoption of 100G.

Whether small cell backhauls to a macro cell or directly to the MTSO, Ciena’s solutions optimize existing infrastructures to alleviate the demand and prepare the network for what’s next.