Power Resilience at Hybrid LMR and Broadband Sites Under Longer Outage Conditions
Legacy radio frequency (RF) transmission towers are no longer simply about transmitting, receiving, combining, filtering, feeding and connecting signals via antennas. Many of today’s sites are equipped with internet protocol (IP) based communication devices, broadband routers, timing devices, remote monitoring equipment, network switches, climate control devices and connectivity points between traditional low/medium bandwidth (LMR) wireless networks and broadband networks. As such, these sites have much greater electrical loads than many of their predecessors were originally designed to handle.
CISA views power continuity and site hardening as two separate areas for ensuring public safety communications resiliency. CISA’s infrastructure dependency guidance also identifies an additional area of dependency that is easily overlooked – communications facilities rely on the energy sector for power and on the transportation sector for the delivery of diesel fuel to backup generators. Therefore, power continuity is not only an electrical design issue; it is also a fuel, access, maintenance and logistical issue.
Battery Autonomy Is a Defined Operating Window
Batteries offer a finite amount of stored energy. The amount of time your batteries will last varies depending upon what you are powering, how old your batteries are, how many you have installed in your system, how hot or cold it is inside your shelter, how well your batteries are charged and how high the demands are made upon them. When you add network devices, broadband equipment, monitoring hardware etc., to the already existing RF equipment you previously had in place, this further complicates the calculation of how long your batteries will last.
The operational lesson here is very simple. Do not assume the same level of battery capacity exists today as existed when your site was initially deployed. Instead evaluate your battery capacity based on the current level of load that you are currently carrying at your site. Additionally, do not assume that adding a few pieces of new equipment during a multi-phase upgrade process will not impact the amount of time your batteries will continue to function. Each piece of continuous load shortens the length of time you have until another power source needs to take over responsibility for the site.
Generator Capacity Does Not Equal Generator Resilience
Generators can provide extended periods of power for a given site only if the entire supporting operating chain remains intact. This chain consists of fuel, start-up systems, transfer equipment, cooling, exhaust systems, maintenance personnel with appropriate tools and training, access to the site and the ability to distribute electrical power throughout the site to the communications equipment. If one element of this chain is broken, even if the size of your generator matches the size needed to support your site, you will experience a lack of continuity.
An excellent example of correlated infrastructure failure occurred when FirstNet reported on the results of a survey conducted following the 2020 Nashville bombing. After commercial power went down due to damage caused by the explosion, communications equipment located at that site remained powered using backup batteries. However, backup generators were unable to begin operation due to water and fire damage sustained to those units and thus could not supply power to either the communications equipment or other essential site components. Subsequently, FirstNet employed satellite-connected deployable cellular sites to provide public safety broadband services once again. The resulting service outage occurred approximately six hours after the initial blast when the backup battery reserves were depleted. The incident clearly illustrated how factors including battery reserve life, generator capability to provide power when called upon, physical damage to the site and deployment-based recovery mechanisms can all become interdependent elements contributing to continuity issues at a single location.
Cooling and Environmental Control Belong in the Power Budget
Hybrid sites often contain equipment with different thermal profiles and operating limits. During an outage, maintaining RF equipment alone may not preserve the site if the shelter temperature moves outside the range required by batteries, network electronics, power supplies, or other active equipment. Whether cooling must be carried continuously, staged, or reduced is a site specific engineering decision, but its electrical demand belongs in the same resilience calculation as the communications load.
This is especially important when older shelters are modernized without a complete review of generator and battery capacity. Electrical load can increase while the available floor space, airflow, service entrance, generator, or cooling plant remains unchanged. The site may appear redundant on a block diagram while still having a common power or thermal constraint.
Hybrid Networks Add Diversity but Can Share Failure Points
Hybrid sites consist of equipment with various thermal characteristics and operational boundaries. During a power outage, preserving RF equipment itself may not prevent environmental conditions within the shelter from moving beyond acceptable ranges for operation by remaining active equipment including batteries, network equipment, power supplies and/or other types of equipment. The determination regarding whether cooling must be maintained continuously; temporarily staged; or significantly reduced during a power outage is dependent upon the specific needs of each site. Regardless of the method selected however; determining the electrical load created by cooling is necessary in order to properly determine overall resilience.
There are numerous examples illustrating why this is true; particularly when older shelters are retrofitted with new technology without performing a comprehensive evaluation of the potential impact on the total electrical load that must be supported by backup generators/battery banks. While it appears as though a facility may be fully duplicated on paper using block diagrams; there may exist a common power or thermal limit that restricts operational flexibility across both RF and broadband domains.
Remote Visibility Changes the First Minutes of an Outage
LMR and public safety broadband represent different technologies offering different functionality that together can create enhanced operational resiliency for public safety organizations as both technologies are utilized. The national institute of standards and technology (NIST) issued a report titled “mission-critical voice roundtable” in 2025 reflecting the ongoing necessity for LMR while public safety agencies increasingly adopt newer broadband technologies. Similarly, FirstNet continues to foster interoperability between LMR and broadband technologies as part of its mission while also maintaining deployable broadband resources available in situations where terrestrial broadband services are insufficient or damaged.
While hybrid LMR and broadband facilities may benefit from technological Diversity; neither LMR nor broadband technology inherently eliminates common dependencies. For example; although LMR and broadband equipment may reside in the same shelter; utilize the same commercial provider(s); be reliant on the same generator; share cooling requirements; or use the same access road/fuel delivery routes; it would be incorrect to conclude that LMR and broadband represent completely independent sources of communication. Consequently; resilience analysis must consider shared failure modes rather than solely relying on counts of independent radios/networks/communications paths. Field Service
Planning Has to Match the Outage Scenario
In cases where access to a site is difficult; remote monitoring provides significant value that extends far beyond replacing field service. Remote monitoring allows for narrowing down problems prior to a technician arriving at the site; provided auxiliary power and telemetry remain functional. Operators can differentiate between large-scale events causing disruption to all power at a site versus developing issues with RF signal propagation pathways; track rising temperatures affecting site operation; verify degradation in antenna performance and maintain historical records related to outages for subsequent forensic analysis.
TX RX Systems offers remote monitoring options for LMR antenna sites. Its TX Antenna Power Monitor monitors forward power, antenna return loss and temperature. It also tracks door alarm status. Its RX antenna monitor measures return loss at specified frequency intervals along with board and room temperature. TX RX also provides RF field services including spectrum analysis; noise measurements; signal strength surveys and site assessments. All of these functions are most effective when used as part of an overarching continuity strategy addressing backup power; generator operation; fuel; environmental control; backhaul connections and physical site accessibility.
Power Resilience Is a System Property
Service restoration during prolonged outage scenarios becomes complicated by factors such as physical access limitations; restricted movement due to flood/damage/fire/meteorological conditions; road closure/access restrictions; security protocols limiting entry; fuel shortages/delayed shipment deliveries; and simultaneous dispatches of technicians to multiple affected sites. Therefore; a continuity plan must account for remote diagnosis capability; immediate onsite response capability; locally stocked spares; and site-specific priority sequencing.
CISA’s continuity guidance emphasizes strategies for alternative backup power generation and continuity-of-operations planning. FirstNet’s deployable cellular resources apply similar principles at a network-level perspective by providing mobile coverage assets capable of functioning without commercial power. From a broader engineering viewpoint; pre-planning for recovery resources is equally as important as designing for primary infrastructure redundancy.