Facebook has unveiled two new experimental technologies it’s developing as part of efforts to increase internet connectivity around the world.
The Terragraph system builds on the WiGig standard developed for wireless connections between consumer electronics, such as a computer and TV.
It uses the unlicensed 60 GHz band. Using the existing components developed for WiGig offers a low-cost solution compared to traditional telecom networks to deliver multi-gigabit internet for dense, urban areas, Facebook said. Given the limited range of the 60 GHz signal, the Terregraph network 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. 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 and around potential obstacles such as tall buildings.
The Facebook Connectivity Lab’s other new project is called ARIES and focuses on efficient usage of spectrum and energy.
Its proof-of-concept base station with 96 antennas can support 24 streams simultaneously over the same radio spectrum. It’s achieved 71 bps/Hz of spectral efficiency, and when completed ARIES is expected to offer 100+ bps/Hz of spectral efficiency.
Building on the concept of Massive MIMO under development in cellular networks, ARIES uses the notion of ‘spatial multiplexing’, meaning the antenna array at the base station can serve a multiplicity of autonomous user terminals on the same time-frequency resource.
This type of spectrum sharing reduces the need for additional frequencies or more base stations. Facebook is currently testing Terragraph at its headquarters in Menlo Park and preparing a broader trial with the city of San Jose in California.
More trials are planned around the world, with the aim of eventually adding the technology to the Telecom Infra Project. ARIES is under development in a testbed, with the hope of rolling it out to cities in order to support coverage for surrounding rural areas.
Facebook said it hopes to contribute the technology to the research community for further development.
Source: Telecom Papers