Facebook took the wraps off of two terrestrial connectivity technologies for fast wireless access.
Terragraph is a 60 GHz, multi-node wireless system for dense urban areas and that uses radios based on the WiGig standard. Facebook said Terragraph will deliver gigabits of data capacity. IPv6-only Terragraph nodes will be placed at 200m intervals. Terragraph will incorporate commercial off-the-shelf components and aim for high-volume, low-cost production. Facebook noted that up to 7 GHz of bandwidth is available in the unlicensed 60 GHz band in many countries. U.S. regulators are considering expanding this to a total of 14 GHz.
Facebook Terragraph will also leverage an SDN-like cloud compute controller and a new modular routing protocol that Facebook optimized for fast route convergence and failure detection. The architecture also tweaks the MAC layer to solve shortcomings of TCP/IP over a wireless link. The company says the TDMA-TDD MAC layers delivers up to 6x improvement in network efficiency while being more predictable than the existing Wi-Fi/WiGig standard.
Terragraph is already in operation at the Facebook campus in Menlo Park, California, where it delivers 1.05 Gbps bidirectional (2.1 Gbps total throughput per distribution node) in P2P mode, up to 250 meters away. A wider trial is planned for San Jose, California.
Facebook also released details on Project ARIES, a transmission technology that is a) spectrally efficient and allows for higher throughput in even the smallest bandwidths, and b) energy efficient, allowing for extended coverage range.
The proof-of-concept system features a base station with 96 antennas and can support 24 streams simultaneously over the same radio spectrum. Researchers have demonstrated 71 bps/Hz of spectral efficiency. The target is aiming for an unprecedented 100+ bps/Hz of spectral efficiency. Facebook said ARIES is an embodiment of Massive MIMO — by using “spatial multiplexing,” the antenna array at the base station can serve a multiplicity of autonomous user terminals on the same time-frequency resource. This opens up possibilities such as resource sharing as an alternative not only to the need for spectrum licensing.
Facebook already has an ARIES testbed delivering 10x spectral and energy efficiency gains in point to multi-point deployments.
