Salt Lake City’s Murray City School District wants to be the first district in the country to implement a private CBRS network for students in grades K-12. Private LTE in publicly available spectrum could be the key to bridging the digital divide for some students who lack internet access at home.
The Murray school district qualifies for federal E-Rate funding, but can’t use it to build or operate a CBRS network because federal regulations prohibit schools from competing with ISPs by delivering internet service off-campus.
Jason Eyre, Murray City School District’s technology coordinator, used district funds to buy Ruckus CBRS radios and state funds to buy the initial core network, and he plans to use charitable donations to finance the hotspots the students need to access the network from their homes. “We use charitable funds to buy the end user devices because we can stick somebody’s logo on that device and thank them for it,” Eyre explained.
When Eyre first started talking about CBRS, district officials were skeptical of the idea that a school could operate a private cellular network. Eyre staged a proof-of-concept demonstration with help from vendors Ruckus and Baicells, as well as the state-funded Utah Education and Telehealth Network and the University of Utah. The team secured a Special Temporary Authority (STA) from the FCC to set up CBRS at the Colorado Convention Center.
“Several vendors came and every vendor had an LTE receiving device on their table,” Eyre remembers. “So we prototyped a convention where instead of running miles of wires we used LTE devices to give a fully customizable Wi-Fi network so they could stream video and do whatever they’d do at a trade show.”
Following the successful demonstration, Eyre secured his funding and his school’s private CBRS network launched in April 2019 using Ruckus radios, an STA from the FCC, and General Authorized Access CBRS spectrum. The initial results were not what Eyre had expected.
“Our [existing] network is about a 2 millisecond network and yet everything was 100-plus milliseconds, and speeds were 60 Mpbs down,” Eyre remembers. He turned to his vendors for help.
Solving the core problem
The network was slower than expected because all the traffic was being routed back to the core. Juan Santiago, head of the Ruckus CBRS Business at CommScope, suggested that Eyre separate the user plane traffic from the control plane traffic. Athonet, which was providing the core network, supplied a gateway to accomplish this separation. Now user plane traffic stays on-premise and control plane traffic goes to the AWS cloud.
“We have fantastic bandwidth now,” said Eyre. He said users now get 134 Mbps on the downlink and about 16 Mbps on the uplink, and that those numbers are even higher when sitting close to a radio. Latencies are almost always below 38 milliseconds.
An even more robust core network is on Eyre’s roadmap. The Utah Education and Telehealth Network (UETN) has applied for a CARES grant to fund a new core network. UETN wants to host core network functions for any Utah school or college that wants to use CBRS. The goal is to use CBRS to connect students from their homes to their school curriculum and teachers. By extending school networks, UETN can give students connectivity that enables access to their curriculum but not to the broader internet.
During the COVID pandemic, the Murray district’s CBRS network did not reach far enough to serve most students, but Eyre said the next generation of Ruckus radios will transmit further. He thinks these will be powerful enough to serve dozens of students living in low-income housing less than a mile away from the high school. The school district plans to install Ruckus 710 CBRS access points in a 10-building complex near the school, and Eyre is asking donors to help cover the cost of MiFi-style hotspots and home gateway devices. The students already have Chromebooks, and Eyre wants them to work as well in the home environment as they do at school.
Other use cases
Connecting students from home is the primary use case for Murray’s CBRS network, but it isn’t the only one. Eyre wants to use LTE to replace Wi-Fi in many classroom settings, and he is already using it for connected cameras at the far end of the campus parking lot. He said the network is handling “hundreds of megabits a day of camera traffic with zero problems.”
Ruckus’s Santiago said a group of school districts in California’s Central Valley is also looking at private CBRS networks, but hasn’t moved forward yet. “There are some limitations on how far you can go, but this is the kind of thing that we’re starting to see,” he said. “CBRS sort of falls between Wi-Fi and cellular … you can do a lot of things you can do with CBRS on a cellular network but you don’t have the control or the reliability. You can do a lot of the things you can do with CBRS on Wi-Fi, but you don’t have the quality of service or the reliability. So it really kind of fits a sweet spot in between Wi-Fi and cellular.”