Intelligent power solutions for radio networks

Radio system designers are adopting intelligent DC power infrastructure to improve the reliability of their networks.

Even the most robust, well-designed land mobile radio (LMR) networks can experience problems with network devices such as digital radios, base station repeaters, RF amplifiers and network switches. External events such as power surges or lightning strikes can cause network devices to lock up and, with the transition of radio network equipment from analog to digital within the last decade, onboard firmware in these devices can also occasionally freeze. While these instances are infrequent, they do occur.

A well-designed radio network will often allow for these events to occur without affecting the overall operation. However, such events often require a site visit to resolve the problem, which can be sometimes as simple as cycling power to the troublesome device. Sending a technician to do this can be both costly and time-consuming. And if the affected devices are non-operational, this can occasionally cause disruptions to the radio network.

Within the last decade there has been a technology shift in LMR network devices. The IT world has merged with the RF world. The ability to remotely monitor RF devices within a radio network is becoming the standard. GPS-enabled devices enable location tracking of portable and mobile radios, which can provide geo-fencing capabilities and help manage employee and vehicle fleet movement tracking, for example.

This change in technology is also occurring with DC power plant products, with some DC power conversion equipment manufacturers leading the way in providing, via Ethernet, remote power monitoring and remote power control capabilities for their DC products such as rectifiers, power supplies, distribution panels and inverters.

Virtually all radio network designs incorporate DC power plant infrastructure to power various network devices. This infrastructure is critical in maintaining reliable power. Being able to remotely monitor and control DC power plant devices, such as rectifiers, power supplies, distribution panels, batteries and inverters, provides substantial benefits.

Radio network operators can monitor power conditions for each RF device that is connected to the DC plant, enabling the monitoring of parameters such as power consumption of individual devices; fault conditions; system voltage levels; AC mains status; and backup battery conditions, including voltage, state of charge and run time remaining.

Although DC power plants vary based on each site, a typical site comprises a primary and secondary power source. The primary is typically 230 VAC, which is provided by the electric utility company. In very remote areas where AC mains is not available, solar power is sometimes used to supplement the battery bank.

The secondary source is typically a battery bank which is sized to provide the required amount of backup time should the AC mains fail. These banks are typically 12 VDC for LMR networks, although 48 VDC battery banks are becoming more prevalent as network device manufactures change the input power requirements for their equipment. Some sites will utilise multiple DC voltages; in these cases, a DC-DC converter is used to convert from 48 VDC to 12 VDC, for example.

Most devices within a radio network will operate from DC, so converting from AC mains power to DC is required. Depending on the number of devices (loads) that are at the site, the DC from the rectifier is distributed to the loads using a distribution panel. (While most devices are DC-powered, some require AC; in this case, an inverter is used to convert the DC to the AC.)

Many rectifiers developed specifically for LMR applications incorporate circuitry to power the load(s) and charge the battery bank simultaneously to keep the battery in optimal condition. In the event of an AC mains failure, the energy stored in the battery bank is diverted to the loads to provide continuous, uninterruptable power to these devices.

This functionality is important: a failure of the AC mains should not cause a network to shut down, and having a seamless transition to battery power in the event of a mains failure is crucial to maintaining network operation. A low-voltage disconnect device can also be installed, which will automatically disconnect the battery bank should the battery voltage become too low. Over-discharging a battery bank can permanently damage the batteries.

By using intelligent DC rectifiers and DC distribution panels with Ethernet monitoring and control, radio network operators can remotely cycle DC power to individual devices, often resolving issues without having to physically visit the site. The ability to remotely disconnect, or load shed, non-critical loads while maintaining critical loads online enables longer preservation and run time of the backup battery bank in the event of an AC mains failure. The ability to monitor battery voltage at a site and determine how much run time remains on a battery bank enables technicians to schedule their visits to the site for corrective action.

Innovative Circuit Technology (ICT) recognised early the advantages that remote monitoring and control of DC power infrastructure at a radio communications site could provide. ICT released its first intelligent DC distribution panel with remote monitoring in 2010, and has since added DC rectifier systems, DC power supplies and inverters, all with remote monitoring and control, to its product portfolio. No additional software is required — a PC, tablet or smartphone using a standard web browser is all that is needed to access the graphical user interface.

Radio communications network designers are adopting this technology at a rapid pace. It enables them to provide more robust network designs with more monitoring and control capabilities. It provides benefits not only to the network operators themselves, but also to the users of the network and ultimately the general public, particularly in the public safety arena. The ability to have comprehensive monitoring and control of the DC power plant at radio communication sites ultimately enhances the effectiveness of LMR networks.

Image credit: © Rob d/Shutterstock

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