First responders can experience numerous communications problems when on-site at an emergency. As these breakdowns in communications can result in loss of property and life, technology innovation is vital when it comes to public safety equipment that resolves these communication problems.
Legacy public safety equipment typically uses wideband bi-directional antennas to send and receive signals that are broadcast from the high site, which is the remote Land-Mobile Radio (LMR) network tower, so emergency responders can talk with the command post and each other. However, wideband antennas are designed to pick up any radio spectrum, including bands that do not carry emergency communications, which often results in distorted, muffled, or interrupted communication on the radios used by emergency responders.
Another frequent problem is incorrect calculations of the transmit power for LMR signals to the high site. If the transmit power is set too low, the signal won’t reach the high site and communication won’t be established. If the transmit power is set too high and the signal reaches the high site with too much power, the high site will protect itself even to the point of bringing it down. Calculating transmit power is complicated – it could take an experienced engineer or technician as long as four to eight hours to calculate – and often human errors enter the equations. It is also not uncommon for environmental conditions to change after the system is installed, like a repositioned high site antenna or new construction between the high site and the building, which would require recalculation.
As several antennas are needed at a building to receive and redistribute the radio signal throughout the building, the signals from the donor and server antennas can interfere with each other causing problems like echoing and feedback. To prevent this, the minimum isolation separation required between the signals is 20dB per code. Calculations need to be done to correctly set the system for this isolation manually. Then, any time there is a change in the environment – like somebody opens a door or window and a bit of signal leaks out that hits the donor antenna, or there are renovations made inside the building – that isolation number can change and will need to be reset manually. This takes constant diligence and can require repeated truck rolls to ensure the system is ready for any emergency.
Also, due to the normal fluctuations of any environment, signal power inside the building can fluctuate and impact communications. Not all emergency responder systems are created equal, and some take longer to adjust to the changes, so are slower to restore clear communication.
As Authorities Having Jurisdiction (AHJs) or Fire Marshalls often require the installation of an ERCES (Emergency Responder Communication Enhancement System) before they will issue a Certificate of Occupancy (CO), building owners understandably want the systems installed up to code as rapidly as possible. Unfortunately, slow installs – with some taking months – is a common problem due to the type of technology deployed or even worse, test readings on coverage levels not meeting code after the system has been deployed.
All of these issues have been addressed in recent innovations in public safety equipment.
Innovations that make a difference include:
Intelligent, automated setting of the uplink transmit power, and calculation and setting of isolation and downlink gain are now available in ERCES public safety solutions such as Cel-Fi QUATRA RED, eliminating the time it takes for manual calculations and potential for human errors.
Faster microprocessors have been installed in these innovative systems, so processing is done in a fraction of a second – less than the 1.2 microseconds between frames that LMR radios use to transmit. This makes response instantaneous – one radio keys up and sends a signal while the second radio also keys up and sends a signal almost at the same time with the correct amount of attenuation or gain automatically reaching the high site with the correct transmit power. This guarantees that the communication channel will be available regardless of when or where the communication needs to be stablished.
Built-in grid test functionality that generates a full signal report is a recent innovation that can make a significant difference in how rapidly a Certificate of Occupancy (CO) is issued. This data has traditionally only been available for integrators with access to expensive equipment (with costs as high as $35,000), or when the AHJ does a walk-through test. If the system fails the AHJ walk-through test, repeat tests need to be scheduled until it passes, delaying the CO and adding additional cost. With built-in grid test functionality, system integrators can ensure the system is performing up to code and make any adjustments needed before the AHJ is scheduled to do the walk-through test.
Built-in end-to-end remote monitoring and management is another essential innovation that allows for customized real-time monitoring of the high site-to-server antenna , as well as notifications that help ensure the system is operating up to code – without needing a truck roll.
It is important that system integrators are aware of these innovations so comprehensive due diligence can be performed when advising a building owner on the best public safety solution for their facilities. After all, this is about saving lives.
Victor Mejia is a Product Manager at Nextivity, specializing in deployments of indoor commercial cellular and public safety networks. Over the past 20 years, he has led DAS and RF network engineering projects for Comba Telecom, Huawei, Ericsson, Motorola, Nextel, Telcel, AT&T, Verizon, and American Tower. Victor holds an MBA from the University of Oviedo in Spain. For more information, contact [email protected] or visit www.cel-fi-com.