Terragraph is Facebook’s proposed new  60-GHz fixed wireless system focused on bringing high-speed internet connectivity to dense urban areas. Terragraph uses off-the-shelf components and leverages the cloud for intensive data processing, hopefully leading to creation of a high-volume, low-cost platform that uses traditionally-troublesome spectrum. It is yet one more example of “non-telco” access platforms already deployed, or gearing up for possible widespread deployment.

Terragraph uses a dense, small cell network putting nodes at 200 meter to 250 meter intervals, using license-exempt 60-GHz spectrum.

Terragraph uses phased array antennae to allow “steerable” if still “ line of sight” signal propagation, software defined network principles and cloud computing to support control functions, plus a new modular routing protocol. But Facebook also is using non-traditional approches to media access and transport protocols.

Facebook says it re-architected the MAC layer to solve the shortcomings of TCP/IP over a wireless link, for example.

“Terragraph’s wireless system consists of radios that are based on the WiGig standard and are designed for consumer electronics, which allowed us to create nodes that are inexpensive relative to traditional telecom infrastructure.”

“By implementing a high performance TDMA-TDD MAC, we saw up to six times improvement in network efficiency and at the same time made TCP/IP predictable compared to the existing Wi-Fi/WiGig standard,” Facebook says.

Interest in using fixed wireless for communications–for business or consumer customers–comes in waves. The last big upsurge came in the late-1990s and  focused on connecting business customers.  An earlier wave in the 1980s focused on connecting consumers for entertainment video.

The episodic interest is obvious. Wired networks are relatively expensive and take time to build. Wireless always has held attraction because it is relatively cheaper and can be installed faster.  Firms as disparate as AT&T, Facebook and Google now are testing–or planning to deploy–fixed wireless networks for Internet access, for example. The business model is the driver.

“While solutions such as GPON optical fiber can provide 100s of megabits up to several gigabits of capacity, the high costs associated with laying the fiber makes the goal of ubiquitous gigabit  citywide coverage unachievable and un-affordable for almost all countries, says Facebook.

The point is that we are in the midst of a periodic wave of interest in fixed wireless. Dynamic and shared spectrum efforts and experimentation with TV white spaces provide other examples of the trend.