When the pandemic shifted cellular demand from urban centers to suburbia, the Mobile Network Operators responded by changing their focus from densification to improving macrocell coverage and capacity in the suburbs. Now, as densification becomes a renewed priority, a pre-pandemic truth remains – achieving densification with outdoor small cells is not easy. The main culprits are time and the cost associated with powering small cell sites. Tapping into the electrical grid requires permits, work orders, truck rolls, and the physical connection to the grid. Power has been a major hurdle for small cell deployment, but that’s about to change.
In 2022, a new standard called Fault Managed Power (FMP) was introduced that simplified the small cell powering process. New powering solutions emerged to convert a single grid tap into power for up to 10 small cell nodes. Eliminating grid taps at every small cell site minimizes the dependency on the utility and gives the operator more control over its network build. The ultimate result: accelerate revenue generation by building and activating networks quicker.
How does it work?
A central power hub consists of power conversion electronics housed in an environmentally controlled cabinet. The power equipment converts the incoming AC electrical feed into direct current (DC) transported over copper cables. To achieve longer distances, the voltage is elevated to reduce line losses. The electricity is transported over special copper cables to small cell nodes up to a
6000 feet away from the hub. At the end of the cable a powering device called a downconverter lowers the elevated voltage to a level required by the small cell radios.
Is it safe?
The FMP standard development was initiated by the Association for Telecommunication Industry Solutions (ATIS), and later supported by UL, the National Electrical Code® (NEC®), and the National Electrical Safety Code® (NESC®). The standard enables a voltage up to 400VDC to be delivered over the cables. Unlike other standards the FMP standard does not limit the amount of power delivered, but requires real-time monitoring of the circuit, rapid fault detection, and power source shut down in the event of human contact. The result is the ability to safely deliver enough power to energize modern, higher power small cells. An explanation of the standard can be found here.
Is it practical?
While minimizing dependence on utilities is desirable, there are trade-offs. The operator or network builder has to design, install, and maintain the copper cables. The installation costs can be minimized by installing the copper cables at the same time the fiber cables are installed. Some operators use hybrid cables consisting of both fiber and copper in a single sheath to accomplish this task.
Cost comparisons between the FMP architecture and local powering will vary depending on application. In any case, grid taps can cost thousands of dollars with the cost increasing signficantly with distance. The need to add a transformer or overcome site issues like boring through rock or an intersection of a street can raise the cost dramatically. Once an operator is committed to a project and engaged with the utility, these unforeseen obstacles leave them little choice other than paying the incremental costs and delaying network activation.
Life cycle costs are also factors in the analysis. For example, FMP systems may offer a built-in communication path between the central power hub and downconverter. This path allows a radio to be rebooted remotely without the need to dispatch a technician, saving time and money.
If battery backup is needed, it is easily added at the FMP central power hub to provide back up for all the radios in the network. On the other hand, adding battery backup to locally powered sites is problematic due to the incremental cost of an additional cabinet for the batteries, the cost of installing the cabinet, and the potential public resistance from the perception of visual pollution.
The FMP power architecture offers sustainability benefits as well. The power cycle feature can be used to power down radios that are only required at certain times of the day (e.g., near a venue that is not in use). In addition to avoiding truck rolls to cycle power at a site, there are also sustainability benefits for the utility companies. Since the FMP architecture eliminates the need for grid taps at the small cell sites, the utility company no longer needs to roll trucks to the sites, potentially eliminating as many as nine out of ten truck rolls.
Conclusion
For densification, coverage holes, and fixed wireless access to ramp and meet network needs, simplifying the small cell installation process is a must. Changing the power paradigm is a great first step toward speeding the deployment process and accelerating revenue generation for the operators.