Telegraph
Terragraph is a 60 GHz, multi-node wireless system focused on bringing high-speed internet connectivity to dense urban areas. Utilizing commercial off-the-shelf components and leveraging the cloud for intensive data processing, the Terragraph system is optimized for high-volume, low-cost production.
Delivering gigabits of capacity requires multiple gigahertz of spectrum via frequency reuse. Although 60 GHz has traditionally been avoided due to its high absorption of oxygen and water, countries such as the United States, United Kingdom, Germany, China, South Korea, Japan, and others saw the benefit of making this part of the spectrum — also known as “V-band” — unlicensed, similar to the Wi-Fi 2.4 GHz and 5 GHz bands. Up to 7 GHz of bandwidth is available in the 60 GHz band, and forward-thinking countries like the United States are seeking input to expand this to a total of 14 GHz.
One of the beneficiaries of this decision is WiGig, an enhancement to the Wi-Fi standard, designed to provide in-room high-bandwidth communication. 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.
Given the limited range of the 60 GHz signal, these nodes are placed across a city at 200-250 meter intervals. The vast bandwidth and unique signal-absorbing nature of the band limits interference and simplifies network planning, while the unlicensed nature of the spectrum helps to further minimize costs. Designed to provide street level coverage, Terragraph implements a phase array antenna to retain the highly directional signal required for 60 GHz, but makes it steerable to communicate over a wide area. Given the architecture of the network, Terragraph is able to route and steer around interference typically found in dense urban environments, such as tall buildings or internet congestion due to high user traffic.
Urban deployment of Terragraph network.
Terragraph also leverages technology created to manage Facebook’s massive data center infrastructure. We implemented IPv6-only nodes, an SDN-like cloud compute controller, and a new modular routing protocol for fast route convergence and failure detection. We also re-architected the MAC layer to solve the shortcomings of TCP/IP over a wireless link. By implementing a high performance TDMA-TDD MAC, we saw up to 6x improvement in network efficiency and at the same time made TCP/IP predictable compared to the existing Wi-Fi/WiGig standard.
Finally, Terragraph incorporates attributes and industrial design required for fast, attractive, and affordable deployment across cityscapes. Its reduced interference and ability to operate in non-line-of-sight conditions increases customer reach. For customers or business in multi-dwelling units or high-rises, the Terragraph system can be externally attached to a building and connected to an in-building Ethernet data network. Combined with Wi-Fi access points, Terragraph is one of the lowest cost solutions to achieve 100 percent street-level coverage of gigabit Wi-Fi.