By Kelly Hill
Over the past several years, Facebook’s connectivity group has been focusing on research and development in communications network infrastructure, with an eye to how innovative approaches can reshape network economics and ultimately, benefit the company by connecting new users to the internet.
One of those efforts has been Facebook Terragraph, aimed at using the unlicensed 60 GHz band to deliver fiber-like speeds in urban and suburban areas at a lower cost than running fiber-to-the premises. Can Terragraph deliver on its performance premise? Signals Research Group spent some time assessing a 15-node Terragraph mesh test network at Facebook’s Menlo Park, California campus, and it found that the system “didn’t disappoint”, delivering high speeds and tidily accounting for the challenges of operating at 60 GHz.
While the test network was put up specifically for SRG to play with (the study was commissioned by Facebook and can be accessed here), Terragraph’s tech is already out in the wild, so to speak, in commercial products and deployments. Some of the companies that license and integrate Terragraph into their equipment include Cambium Networks, Siklu, Radwin, Edgecore Networks and MikroTik
SRG tested the network in California during mid-May of this year. The network was deployed based on SRG’s design requirements and the use cases it wanted to test, such as the impact of partial obstruction on the network’s performance, its resiliency if a link went down, and how well the system operated with a dense network of mesh nodes that could interfere with each other.
Ultimately, SRG’s testing found that Terragraph did indeed deliver, with fast bi-directional speeds (sustained in the range of 1.7-1.8 Gbps between two nodes and just a bit slower, 1.6-1.7 Gbps in a three-hop link), impressively low latency (0.33 ms over one hop and 1.6 ms over three) and jitter, and traffic routing that addressed the engineering challenges of operating at such a high frequency. Even when SRG deliberately blocked a transmission path, the mesh system was able to successfully handle the issue, and as a whole, the nodes played nicely with each other in terms of not interfering.
“There may be unlicensed systems which are not well-behaved, and which don’t perform well with multiple radio nodes in the network. Facebook’s Terragraph Reference Platform Test Network is not one of them,” SRG concluded. “The mesh network topology and Terragraph Mesh can also adjust to unforeseen sources of interferences by dynamically routing data traffic along alternative routes where the link quality is better.”
The company’s report continues, “Terragraph doesn’t change the laws of physics, meaning that providing extended coverage with 60 GHz spectrum will always be challenging. However, we also found the perceived interference issues associated with using an unlicensed radio platform do not exist since the Terragraph scheduling algorithms intelligently adjust for densely placed nodes. … The Terragraph network can intelligently adjust the routing of packets if external sources of interference are detected or if obstructions along the transmission path develop.”
SRG said that it believes that its testing was the first third-party benchmark study of the Terragraph platform.
