In this turbulent time, it seems few days pass without news of a major incident that calls for Herculean response efforts from emergency services. Be it a terror attack in a major commercial business district, widespread wildfires in remote regions, or devastating flood; the news brings reports of courage along with stories describing enormous challenges facing agencies coping with these destructive events.

An essential fabric that underpins emergency responses are the critical communications networks linking control centers to fire, police and emergency medical personnel. Primarily voice oriented, these networks deliver mission critical push-to-talk (MCPTT) capabilities essential to operational command and control.

Beyond the conservative world of public safety mission critical operations, enterprises have made tremendous progress migrating applications to the cloud. For enterprises with mobile field force workers, the shift relies upon high-performance LTE networks to ensure fast access to cloud-hosted data. The payoff for these enterprises is significant, from costs savings in server infrastructure to efficiency boosts that come from more time in the field. The benefits of a shift towards LTE-enabled cloud network has not escaped the attention of emergency services officials, but without confidence in network availability at times of crisis, these agencies must remain with tried and true functionality.

Breaking with the Past

Ideally, public safety agencies would simply leverage the trusted legacy push-to-talk services. While these systems provide a minimal level of data service support, they occupy narrow slivers of spectrum designed for support of voice communication paths that come and go as system users push microphone buttons to speak. Cloud-based applications and video rapidly exhaust the bandwidth available in these narrowband systems.

As a case in point, TErrestrial Trunked RAdio (TETRA) provides Professional Mobile Radio (PMR) functions over multiple 25 kHz channels. Another PMR technology, APCO Project 25, operates over 12.5 kHz channels. These systems are optimized for voice, not data, and these channel sizes make sense.

In contrast, supporting data-intensive applications calls for wide bandwidth and vastly different architectural approaches for radio access and core network design. Not surprisingly, agencies now turn to 3GPP Long Term Evolution (LTE) technology for an answer. LTE networks bring access to wide spectrum bands, with flexible sizes up to 20 MHz. For more demanding requirements, multiple LTE carriers can be combined with LTE aggregation to enable gigabit service delivery.

In major public safety agencies across the United States, day-to-day operations already tap the power of commercial LTE services to link computer aided dispatch (CAD) systems with terminals in police and fire vehicles. But no public agency counts on these LTE systems for mission critical operations and provisions exist to fall back to pure voice operation on a PMR system in event of LTE network congestion or failure.

3GPP Saves the Day

Before LTE can serve the needs of public safety agencies, 3GPP needed to expand the capabilities supporting quality of service. With Release 12, 3GPP added the essential elements needed for critical communications traffic support. The first feature, Access Class Barring, protects a cell sector when too many users attempt to access the radio resources of the sector. The standards body added a ranked set of five priority access classes to differentiate high priority non-public safety users, security services, utilities and emergency services. The Access Class is incorporated into the user's SIM, allowing rapid acceptance or barring of access attempts during periods of congestion.

After the base station admits the UE connection, the base station must allocate base station scheduling resources. The allocation and retention priority (ARP) feature of Release 12 handles the setup and prioritization of data bearer connections. With this feature, lower priority connections may be pre-empted by higher priority connections.

As traffic flows between the user equipment and application, the base station's scheduler software executes Quality of Service (QoS) procedures that ensure guaranteed bit rate and non-guaranteed bit rate traffic is handled properly. In the base station and across the Evolved Packet System (EPS), bearer connections are associated with an QoS Class Identifier (QCI) that reflect the needed traffic characteristics. Before Release 12, the original QCI mechanism helped distinguish between best-effort data and Voice over LTE traffic. With Release 12, 3GPP introduced new QCIs that allow a higher level of priority than Voice over LTE. These QCIs are needed to ensure low latency mission critical push-to-talk transmissions.

Taken together, the features of Release 12 provide the basis for mission critical data application support on public and private LTE networks. But full support for MCPTT remained incomplete due to a requirements for group calls and direct device-to-device communications when the network is not available. That condition arises frequently during emergency operations and PMR systems all provide a direct mode of connectivity for users to continue operation.

To address this gap, Release 13 efforts addressing MCPTT requirements introduced functionality for group calls, call prioritization and operation in off-network mode. Multimedia Broadcast Multicast Services (MBMS), the underlying architecture for push-to-talk group calling, gained a new interface to support applications such as MCPTT console systems.

But efforts to leverage LTE device-to-device proximity services to solve the problem of supporting users that are out of network coverage remain incomplete. Beyond signaling challenges, the limited power transmission possible with LTE UEs raises concerns about the suitability of LTE for direct mode operation. That said, device makers can replicate direct mode functionality with simpler non-LTE mechanisms such as an emulation of TETRA direct mode or even simplex analog capabilities.

Combined, the features of Release 12 and 13 set the stage for LTE network support of public safety communications and other mission critical applications. These networks can be either public commercial networks or private networks.

Mission Critical LTE Networks Produce Results

Early network deployments with Release 12 features demonstrate that mission critical LTE networks work as promised. In Australia, Telstra's LTE Advanced Network for Emergency Services (LANES) supported critical communications operations during trials conducted at the 2014 Brisbane G20 event, the 2015 Woodford Folk Festival and the 2015 Australian Football League (AFL) Grand Final. Emergency services workers used devices with Lanes-equipped SIM cards to gain priority access to Telstra's 160 MHz of spectrum.

In the US, AT&T created a high priority wireless service using Release 12 features. The system faced an extraordinary test during protests in Washington DC, following the 2017 presidential inauguration. In his presentation at the IWCE Conference in March, Michael Newburn, Wireless and Radio Solutions Manager, Fairfax County, Virginia, described how the county's push-to-talk terminals operating on AT&T's Priority Wireless Service continued to operate in the face of intense data congestion.

Fairfax County had implemented a unique land mobile radio (LMR) interoperability solution that linked Sonim devices running on AT&T's Enhanced Push-to-Talk (ePTT) service with Fairfax County's Project 25 system. For the inauguration, Fairfax County loaned the Washington DC government 50 devices provisioned with AT&T's Public Safety Priority Service. Even though citizens struggled to use commercial AT&T data services at the height of the Women's March on the National Mall, DC city officials reliably used AT&T's ePTT service to make 1,430 group calls.

Operator Opportunity Emerges

Operators deploying 3GPP Release 12 and Release 13 networks have an important opportunity to craft service offers that go beyond "best effort" IP services. With priority access services, operators gain a differentiated offer that solves significant problems for government agencies striving to put expanded data resources in the hands of law enforcement, firefighters and emergency medical personnel.

Moreover, these priority access offers do not need to be restricted to government users. Operators can structure priority service in tiers that enable targeting lower-priority -- but high value -- users in the commercial sector such as utilities and transport companies. While lower-priority than emergency services workers, these customers gain preferential network access over consumer best effort service users.

In nations where the government has a strong commitment to migrate public safety users to mission critical LTE networks, financial incentives or spectrum resources may be available. Operators that engage and win these opportunities stand to gain a competitive advantage over rivals that may not gain the expanded coverage footprint that follows. As a case in point, in the UK EE is required to address coverage limitations in rural areas and tunnels. The resulting EE footprint can put them ahead of the operator pack.

Time for Action

Operators can ill-afford to sit back and wait for public safety users to arrive. Now is the time for operators to engage with government stakeholders planning the next generation of critical communications capabilities supporting the emergency services mission. Now is the time to work with national regulators to influence the direction of spectrum allocations addressing public protection and disaster relief.

At a time of commoditized mobile best effort data services, now is the right moment to bring to market differentiated mobile data services for businesses that stand to gain from offers that are more than best effort. Operators should look at the prospect for tiered data service offerings promising availability and QoS that assures delivery even when network performance collapses under the crush of demand following major civil emergencies.

Recent incidents around the globe point to the value of getting the right data to the right emergency services worker at the right time. It is, ultimately, a matter of life and death. With the network advancements brought by 3GPP Release 12 and 13, the network operators can be on the proper side of the equation.