Public-Safety Broadband Applications and Benefits
By Brendon McHugh
Where timing and proper, clear communication is a matter of life or death, infrastructure and technology become the backbone of emergency response, especially in more remote and isolated areas. In our highly digital world with a massive amount of mobile phones, internet of things (IoT) devices, sensors through LTE/5G networks and satellites, these advances are thankfully also benefiting public safety.
Traditionally, communications infrastructure for first responders has been based on narrow bandwidth, voice only and using two-way LMR systems requiring push-to-talk (PTT) services and/or using commercial carriers specific to one geographical area. Limitations included cost for specific equipment, licensing requirements and limited coverage areas for communications. Many organizations and governments have acknowledged that an important step in improving the telecommunications issues in their countries is improving and extending digital connectivity to remote and rural communities, especially 9-1-1 emergency services.
Public-safety broadband networks (PSBN) are wireless broadband networks that provide prioritized and exclusive access to first responders and commercial critical infrastructure entities that ensure the smooth operations and functionality of our communities. Such systems are even being deployed as countrywide systems, often referred to as national public-safety broadband networks (NPSBN). These types of networks are wireless broadband networks that provide prioritized and exclusive access to wireless data for emergency first responders including police, fire services and EMS.
Vulnerabilities in communications infrastructure, inaccessibility to information required by emergency services and lack of interoperability are all issues being addressed with PSBNs. Considering the vast amounts of data that will be streamed in real time as networks continually increase backhaul capabilities, it’s becoming possible to obtain vast amounts of data containing critical information from emergency and/or catastrophic events nearly anywhere.
The difficulties of such an undertaking can be realized by just considering the amount of data securely streaming related to body-worn cameras and 9-1-1 dispatcher headquarters, and reliably relaying this transmission of voice, text, video and data information to first responders in the field. Canada and the U.S. are currently developing regional and NPSBN that comply with core concepts in public safety: interoperability, resiliency, priority communications, reliability and security. Numerous organizations such as the PSBN Innovation Alliance and First Responder Network Authority (FirstNet Authority), are advocating, as well as developing these networks.
Of particular importance to solving these issues and enabling PSBNs are software-defined radios (SDRs), which are found in nearly all modern radio communications devices, as well as mobile LTE/5G network infrastructure, especially the radio access network (RAN) and satellite ground stations. Providing the highest performance for bandwidth, channels, wide frequency ranges and processing, SDRs are the new way of communication and signal processing for mission-critical applications.
Current Challenges
Lack of interoperability between first responders is a fundamental disparity in modern public safety and largely a consequence of not having access to technology that enables interoperable broadband communications. A major capability gap during emergencies results from inadequate access to applications and sharable information due to a lack of a dedicated high-speed data network to distribute them. As well, most often today, first responders subscribe to mobile broadband services from different commercial carriers, with no easy way to share information among a common platform in near real time. Moreover, in many rural communities, or areas affected by natural disasters such as forest fires, mudslides or other catastrophic meteorological events, there is a lack of access to networks to allow for life-saving and emergency services.
LMR systems also present an issue for modern mission-critical communications. While these low frequency, narrow bandwidth and high-power radios enable covering long-distance and/or capabilities to penetrate through buildings or underground better, they tend to only support voice-only services. Such radios are not equipped to handle high data rate image, video and other large file transfers.
Moreover, vulnerabilities in communications infrastructure are also extremely common. Network outages leading to failed communications between the public and first responders are common. Numerous high-profile incidents, such as September 11, Hurricane Katrina, or even mass spectator events and celebrations like when the Toronto Raptors won the NBA Championship in Canada, lead to overcapacity of networks and failed communication between the public and first responders that could lead to dangerous outcomes. Thus, a prime focus of PSBNs is in ensuring that there are dedicated networks for first responders when the main network fails for overcapacity or other technological reasons.
What PSBNs Provide
PSBNs bring numerous benefits to first responders in the form of one-to-many, direct and dispatch style communications in the form of voice, image, video and other high data-rate communications. Additionally, cross-jurisdiction/nationwide communication, connecting responders to people in need in rural areas, enhancing situational awareness during emergencies, increasing network capacity, and ensuring priority is given based on the severity of the situation, will all improve first responder service. Recent technologies are even beginning to allow for LMR systems commonly used today to be updated to work with various SDR technologies. For public-safety dispatchers, networks such as FirstNet are providing software tools that provide control and visibility into the network’s status and site conditions. Such features such as managing PTT groups/channels or creating groups for managing an emergency are now possible. Moreover, checking the location of PTT users, providing mapping tools and setting priority levels is possible. Moreover, all these communications are done securely using identity, credential and access management (ICAM) systems.
PSBN Technical Requirements
The technical requirements for PSBN rely on several factors, including the geographical size of the network, as well as the number of users on the network and how much data is going to be exchanged. For a NPSBN, the use of large commercial mobile network vendors is essential, as they have the infrastructure in place. Moreover, for connecting rural areas, satellite constellations are also of importance as their orbit can cover a larger space.
Critical to the performance of mobile network providers is the RAN. First responders interact with a PSBN using RAN eNodeBs for LTE networks and/or gNodeB for 5G networks and various other modem designs for satellite operator ground stations. The eNodeB/gNodeB contains the air interface, control functionality and network interface intelligence for allocating radio resources to the devices (i.e. user equipment or UE) on a PSBN. The amount of resources allocated, such as bandwidth, to each user equipment (UE) on a PSBN can then be based on the type of information that is to be exchanged between the eNodeB and UE.
Another aspect of the mobile communication functions of a PSBN is the backhaul network. This is also part of the RAN and interconnects eNodeBs/gNodeBs of a cell site base station to the core network, as well as to each other. It also provides connectivity for the elements of the core network (CN) and is designed with a high degree of availability and redundancy. The CN performs key functions such as authentication, call control/switching and provides gateways to other networks, such as other PSBNs or data centers.
Some other important emerging technologies include mission-critical standards in LTE/5G-based networks, which provide public safety with mission-critical PTT (MCPTT), mission-critical data (MCData), and mission-critical video (MCVideo) capabilities. By including MCData and MCVideo into an NPSBN, new powerful tools for the first responder community are becoming available.
Of course, the network layers must also guarantee the protection of the transmitted/stored data and regulated access to PSBN communication services. These networks must have a combination of availability and reliability to withstand failures. Upgradeability is also very important, as the deployment of dedicated PSBNs is a long-term investment requiring significant government funds, as it generally requires less resources to update than to fully replace.
SDR for PSBN
An SDR contains a radio front end (RFE) and digital backend. The RFE contains the receive (Rx) and transmit (Tx) functionality over a very wide tuning range. The highest performance SDRs contain 3 gigahertz of instantaneous bandwidth using multiple independent channels and DACs/ADCs. A field-programmable gate array (FPGA) with onboard digital signal processing (DSP) capabilities for modulation, demodulation, upconverting, downconverting and more is found on the digital boards. Furthermore, the FPGA is a configurable fabric containing logic blocks for customizations such as updating to the latest radio protocols or DSP algorithms, as well as providing packetization of data for sending over high bandwidth Ethernet links using 10 to 100GBASE-R qSFP+ optics transceivers.
SDRs can be integrated into PSBNs in ways related to the actual user devices, as well as the networks themselves. For instance, there are now ways to use an SDR to interface a traditional LMR system to talk to LTE/5G network users using the same PTT network is now possible. Moreover, in modern telecommunications networks, SDRs are commonly used in the RAN portion of cell base stations due to their very high digital backhaul capabilities and ability to be integrated into legacy system equipment. For satellite-type communications, various downlink/uplink and modem capabilities are found in SDRs utilized for ground monitoring stations.
Naturally, SDRs solve many of the issues and fulfill many of the requirements needed for a PSBN. Such systems provide interoperability due to multiband/multiwaveform capabilities, as well as support security, resiliency, upgradeability and reconfigurability required because of an on-board FPGA which provides means for everything from cryptographic messages to reconfiguring the system for an entire set of different communication protocols. Moreover, open-source platforms like GNU Radio, allow for the configuration of an SDR and the development of programs that use flow graphs for signal processing involved in communication (modulation/demodulation, tuning, gain, waveform generation, etc.). Multiple input multiple output (MIMO) SDRs also provide a solution to perform transport level gateways as multi-RAN base stations, such as for checking the validity of connections for data to be opened and/or exchanged. MIMO channels also supports phased antenna arrays often used in satellite ground stations.
PSBN Prototypes and Demonstrations
One interesting use of SDRs in PSBN is making analog LMR systems communicate with an LTE/5G-based MCPTT server. Researchers from the National Institute of Standards and Technology (NIST) developed a prototype for interoperability between an LMR signal and the LTE standard by using GNU Radio software. By using the widely used LTE standard, which essentially provides wireless broadband communications between mobile devices and terminals/base stations, a low-cost and reliable system was developed. The prototype allows two-way communications between LMR system device users and LTE mobile device users.
To develop the analog LMR system (LMRS) to LTE interoperability solution, GNU Radio was widely used for creating a flow graph that took an LMR system analog signal and performed signal processing on it to allow for communications with an LTE server. For this, a custom GNU Radio OutOfTreeModule (OOTM) was created. This is a module that is not within the GNU Radio source tree. The researchers called this the gr-LMR2LTE module and it contains only one block, called jsock, which provides control signaling to the MCPTT client. The flowgraph used in the prototype required both downlink and uplink communications to/from the server. The downlink GNU Radio flowgraph handles over-the-air (OTA) communications from the LMR system endpoint toward the MCPTT LTE system (top of Figure 1). The uplink essentially does the opposite (bottom of figure 1). Such systems could make a low-cost solution to enable widely used LMRS devices to be connected to PSBNs.
In Canada, one recent example of demonstrating a satellite-based PSBN is the Halton-Peel Public Safety Broadband Network Innovation Alliance. The alliance worked alongside Telesat and Motorola Solutions engineers to establish mission-critical PSBN LTE data services over a low Earth orbit (LEO) satellite link to Telesat’s operations center in Hanover, Ontario. The system solves issues for rural and remote first responders and the public who require data communications access and first responder connectivity. It is expected that as Telesat’s large constellation of 298 LEO satellites are put into orbit, providing ultra-low latency and ultra-fast Internet around the globe, more large-scale PSBNs will develop.
The FirstNet Authority
The FirstNet Authority’s mission, as mandated by U.S. Congress, was to oversee the buildout, deployment and operation of a NPSBN called FirstNet. In 2017, all 50 U.S. states and the district of Columbia agreed to the implementation plan developed for them by commercial partner AT&T as part of a 25-year, $47-billion contract signed by FirstNet to design, build and maintain a nationally interoperable PSBN. This included directing the FCC and AT&T to use the band 14 spectrum. This band has 20 megahertz of spectrum in the 700 MHz band.
AT&T has been deploying the implementation plan using RANs developed for each state that includes full data encryption and end-to-end cybersecurity. Many useful devices for first responders connected to this network include IoT sensors (smart intersections for detecting car crashes, etc.), wearables (police body cameras, etc.), drones (for gaining situational awareness of natural disasters, for instance), and various vehicles (from cruiser cameras to helicopters to deployable satellites), that can relay near real-time information to those on the PSBN. Such services will help first responders stay safe during both day-to-day operations, and during crisis and disaster response and recovery. An example of capabilities for a police officer is shown in the figure at the top of the story.
PSBNs are becoming a valuable tool for first responders to attend to emergency crises and natural disasters for a multitude of reasons, such as accessibility, ability to communicate in methods other than voice, ability to connect various networks and resources together at a moments notice, and more. Commercial mobile networks and satellite communications relying on SDR are both integral components to the overall function of these life-saving networks. There are more and more jurisdictions and organizations successfully implementing PSBNs that serve as case studies and guides for others. With the advancements in technology come advancements in public safety and the ability to utilize all resources at the right time effectively to saves lives, mitigate disaster and aid in recovery.
Brendon McHugh is a field application engineer and technical writer at Per Vices. He possesses a honors bachelor’s degree in theoretical and mathematical physics from the University of Toronto.