RFID Tracks Antenna Health for Radio Networks

JR Wakabayashi

Written by 27 March 2019

Featured on RFID Journal.

Wireless solutions provider Comba Telecom, Inc. has released a system for monitoring the health of a network of antennas that are used to ensure first responder radio communication during emergencies. The CriticalPoint™ Antenna Monitoring System (AMS), designed for real-time monitoring of public safety service antennas, employs UHF RFID to ensure that those life-safety systems remain in good working order. The solution consists of a Master Control Unit (MCU), passive RFID tag, built into the service antenna, that can only respond to interrogation if the device is operating properly.

Public-safety radio systems provide radio coverage for emergency responders in places where two-way radios cannot be relied on—typically, in public buildings. Increasingly, local police and fire jurisdictions are requiring that public safety communications systems, including the service antennas be monitored where they will oversee safety.

Comba's FCC-licensed public-safety solution consists of a donor antenna that is typically installed on a building rooftop and then feeds a bi-directional amplifier (BDA) or Fiber DAS, which amplifies and redistributes the RF signal to service antennas. Those service antennas transmit voice communications back through the donor antenna out to the public safety base station, thereby creating a working radio network.

When emergency personnel enter a building and attempt to use their radios, the public safety communications system, including the service and donor antennas, ensure a signal. But the service antennas distributed around buildings are, like any device, prone to failure. In the event that an emergency responder—such as a firefighter at an active fire, or a police officer involved in an active shooter call—needs to use his or her radio, the good working condition of those service antennas can be a matter of life or death.

Comba Telecom, Inc. located in Milpitas, Calif., is a subsidiary of Hong Kong-based Comba Telecom Systems Holdings. The company makes cellular base station antennas, as well as commercial and public-safety BDAs and Fiber DAS systems, including the donor and service antennas used during emergencies. "We provide an internal public safety communications network inside buildings to get that outside signal indoors." says J.R. Wakabayashi, Comba’s marketing manager.

The company developed the CriticalPoint AMS to help those that monitor the operability of their public safety communications network. Without such systems, explains Wakabayashi, personnel may need to walk through a building testing the antennas one at a time, which is time-consuming and costly to find the problem. But initially, he states, "Although the code can be interpreted ‘requires monitoring’, there hasn't been a solution to do that until now."

Some similar systems designed to detect the antennas' working function require additional cabling or a high-cost voltage-measuring system. Comba's solution, Wakabayashi explains, is aimed at being affordable to retrofit into existing systems, as well as being applied to new public-safety communication installations. The RFID alternative requires a passive RFID tag inside the antenna, as well as a Master Control Unit (MCU) to detect transmission problems with the RFID tag.

Each tag has a unique ID number encoded on it. The Comba AMS solution stores the link between the tag ID and the specific antenna to which it is attached. 

The MCU combines a 910MHz pilot signal with the public safety UHF/700/800 MHz radio signal which is sent to the service antennas. It can be located many meters away from those antennas, so a standard passive  RF transmission would not be possible at that distance. That's when the service antenna itself is necessary for an RFID transmission, to capture the interrogation signal from the  antenna and send the RFID tag ID back to it. The MCU then identifies the tag ID, linked to that service antenna, and confirms that the antenna is in proper working order.

If the service antenna experiences a failure, the RFID tag will not receive the interrogation signal or send a response transmission. When the MCU detects that a tag is not responding, it knows which service antenna is not operating properly and can thus issue an alert to an annunciator panel that there is a problem. Comba has tested the system at 910 MHz, though the technology can utilize any channel between 902 and 928 MHz.

To retrofit an older system, users would need to install the MCU at the building site, as well as add a service antenna with a built-in RFID tag, or manually add an RFID tag to an existing antenna to receive the signal. A single MCU can manage up to 50 service antennas. The users could also acquire the RFID tags. Typically, a systems integrator would install the tags inside the service antenna and commission them in the system. 

In addition, Comba is building the RFID tags into new service antennas for those customers that require them. Buildings in California's Bay Area are now mandated to monitor the entire building's public safety network including service antennas and components.

"You're going to see more and more of these systems being mandated across the country," Wakabayashi states, and an increasing number of public-safety antennas are being deployed throughout the United States. Washington State, for example, has mandated that all public buildings 5,000 square feet in size or larger must have an public safety network. A typical building would require approximately 20 service antennas.

During internal testing, Wakabayashi says, the company has found the technology effective in capturing RFID transmissions, as well as losing those transmissions if the service antenna is disabled, such as when the transmission line is uncoupled. Within the next month, the firm expects the AMS solution to be deployed by customers. "They wanted to be able to monitor their systems, and there wasn't a solution until now," Wakabayashi states. "We're really excited to see this go country-wide."

Cost averages about $2,250 for the MCU and $144 for a package of six tags.