Similar to much of the United States, and indeed much of the world, the City of Tucson’s digital divide has been amplified by the quarantine brought on by the COVID-19 pandemic. With schools forced to quickly move all interactions online and parents working at home, it became painfully obvious; that roughly one third of Tucsonians did not have high-speed internet and could miss out on learning and, possibly even a regular paycheck.
Tucson CIO Collin Boyce quickly realized in early 2020 that the residents in his city did not have a viable way forward to move their daily routines online. Looking to expand affordable connectivity to more households, Boyce said he evaluated options like fiber to the home, but found it to be too costly and slow to deploy. Since time was limited, he shifted his focus to wireless options and considered WiFi, but learned it would require some 7,000 Access Points to cover the required communities and therefore would also be too expensive.
Upon further evaluations, Boyce learned about and eventually decided to deploy an LTE network using General Authorized Access (GAA) spectrum in the Citizens Broadband Radio Service (CBRS), which was launched by the FCC in 2015, when it adopted rules for shared commercial use of the 3550-3700 MHz band (3.5 GHz band or LTE Band 48). The FCC approved the start of the initial commercial CBRS deployments in the Fall of 2019. This new wireless spectrum model, both from a technical and financial standpoint offered to open up all kinds of new use cases and opportunity.
LTE offered clear advantages, like less network equipment since the wireless signal propagation was better than alternatives like WiFi, and the ability to offer true broadband speeds to households, backed by the security of using proven authentication methods. This became the foundation of his city-wide solution to connect all of his communities.
In Phase 1 of the project, the city identified 20 square miles that were underserved and required immediate coverage with these high speed services, in short, where the digital divide for school age children was largest. Integrator Insight Enterprises was hired to oversee the network rollout and Tilson handled site construction and deployment.
“The city picked a specific neighborhood within Tucson that was underserved in terms of broadband connectivity. Families weren’t able to access even the public network for data, so they were pretty disconnected and isolated during the COVID quarantine,” Tadhg Kenny, Druid Software Senior Vice President of Marketing and Public Relations, told Inside Towers.
The heart of the municipal broadband network is the Geocore Druid Raemis Evolved Packet Core (EPC), supplied by Geoverse, which provides the control element that manages all of the CBRS radio network infrastructure, including the radios from JMA Wireless, the Spectrum Access Service (SAS) from Google, and the large number of user devices to connect to the network by each household. All of these mobile devices and end points use a Geoverse SIM card so that they can securely connect to the Geocore Druid Raemis private network and use its capabilities such as roaming if they travel off-net.
The CBRS network currently consists of 40 JMA Wireless radio nodes connected to off-the-shelf servers that run JMA’s XRAN baseband software. A typical node has one JMA 5-watt CellHub radio, connected by jumpers to one or more antennas. The radios are connected by fiber to the baseband servers, which are connected via fiber to the Geocore Druid Raemis core network, which is connected to Google’s SAS. The SAS is responsible for negotiating the availability of the shared CBRS spectrum.
The success of the network can be seen in the network speeds. Boyce reports the network is already delivering 50 Mbps download and 3 Mbps upload at his own house, which isn’t even in the designated coverage area. Households in the target coverage areas are getting faster speeds. Even for those who had some connectivity prior, these new speeds are a major improvement.
In addition, the GeoCore Druid Raemis core allows for network slicing, or enterprise slicing, across the private cellular network, resulting in multiple virtual networks, each being dedicated to a specific audience or use case. This gives the City of Tucson the ability to prioritize the laptops over the gaming that children might engage in outside of remote learning.
“You can give those devices top priority and ensure a quality of service, further dedicating the network,” Kenny said. “We’ve given them the ability to deploy an end-to-end solution.”
Plus, Kenny added, “They can decide to establish priority at any time. One of our other customers, an energy provider in an equipment maintenance scenario, decided that the video and audio traffic should have priority.”
The ability to slice the network and prioritize functions provides the foundation for the deployment of smart city solutions across Tucson. Each network slice can be dedicated to a specific function to help better manage a different domain within the city’s infrastructure.This includes connecting the city’s network of traffic lights, monitoring and managing its critical water systems, serving city parks and recreational spaces with public WiFi, and connecting the city’s first responders. Additionally, it can even be the platform to offer its city staff low-cost, high-performance internet service.
“They’re looking at connecting up traffic lights and the fire services,” Kenny said. “In addition, utilities are looking at it now. We’ve been deployed in a number of utilities already in the fixed wireless access space in the City of Tucson. The water services in the City of Tucson are looking at it from an IoT perspective, because there’s a lot of momentum behind cellular IoT right now.”
Unlike a public cellular network, where public safety use can be throttled in case of a natural disaster, private cellular networks can be broken into separate networks through enterprise slicing, which builds in resiliency and autonomy, according to Kenny. Plus, there are no surprise data overages or data caps that sometimes come with a public network service. The network belongs to the city and the communities it serves.
“Private cellular is really important, when you want to deliver a quality of service, and you want to deliver guaranteed coverage in particular locations,” he said.
Private cellular with enterprise slicing allows customization of the network. For example, each fire truck, drone or body camera, could have its own autonomous network. “They’ve got their own ability to slice up the use cases for when the respond to a major event or emergency,” Kenny said.
Work continues on the private cellular network in Tucson. The city’s Geocore Druid Raemis network is already one of the largest municipal cellular deployments rolled out so far in the United States. In phase two, 40 more towers will be deployed, doubling the coverage of the network. The municipal network will continue to offer more households access to high-speed wireless internet and design multiple smart city applications to better serve the people of Tucson.
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