Emergency service communication can now cut through congested phone lines during a crisis thanks to two Cooperative Research and Development Agreements (CRADA) between the National Institute of Standards and Technology (NIST), the First Responder Network Authority (FirstNet), and more than 75 industry partners.
FirstNet is an independent authority under the Department of Commerce that develops and operates nationwide broadband network used by first responders.
The two five-year CRADAs allowed NIST, FirstNet, and its collaborators to identify gaps within today's long-term evolution (LTE) standards for wireless broadband communication based on public safety requirements.
"Everyone's heard of the situations like the Boston bombing where everyone gets on their cellphones at the same time to call home, and the network crashes," said Dereck Orr, Chief of NIST's Public Safety Communications Division in Boulder, Colorado. "Well, public safety was operating on that same network and didn't have service either. They couldn't depend on the cellular network in a mission-critical situation where lives depended on it, which is unacceptable."
Having an agreement among so many organizations provided more insight, so that NIST, FirstNet, and collaborators could come up with the best ways to implement LTE standards. The iterative testing process eventually led to the application of these LTE standards:
- priority access to service during network congestion
- preemption of bandwidth, which clears the cell-site of non-priority users when necessary
- quality of service that ensures the required amount of bandwidth for high-priority applications and services
Once these LTE standards were identified, the collaborators developed five key parameters for configuring priority and quality of service:
- Access Class: allows the device to identify itself as a normal, high-priority or Emergency user. It also allows the device to understand when it has been barred.
- Allocation and Retention Priority (ARP): allows the network to understand the priority of the user, which is provisioned in the user's profile.
- Preemption Capability/Vulnerability Indicators: Flags that allow the system to determine whether a user's resources can be taken by higher priority users or whether a user can take resources from lower priority users.
- Quality of Service Class Indicator: allows the system to put applications into specific categories. Each category has variables like priority, latency and throughput that it can use to finetune or optimize an application's performance.
- Bit- Rate parameters: allows the eNodeB, hardware that is connected to the mobile phone network and mobile handsets, to schedule and grant bandwidth appropriately, either on the downlink or the uplink.
These parameters were created with the bandwidth of a cell in mind. Each network tower typically has three cells that can support about 600 users each and up to eight active connections per user. When a device connects to the network, it establishes a default bearer, which is like a data pipe used to transmit information signals between network interfaces.
"We were able to prove that the service worked by simulating a stressed-out network to see if priority personnel would have the access they needed," explained Orr. "This allowed the government to go out and feel confident that it could actually do a contract for nationwide service for public safety on the same network used commercially and know that the first responders would still be able to perform their jobs."
After successful testing, FirstNet included these features in its procurement for a nationwide carrier to provide the cutting-edge capability to first responder units on a subscriber basis. Eventually, these standards will also apply to 5G.
