16 TELECOMMS POWER https://www.advancedenergy.com Issue 1 2024 Power Electronics Europe www.power-mag.com Power choices to minimise maintenance The choice of power source can reduce telecomms maintenance cost. By Andy Brown, Director, Technical Marketing DC/DC, Advanced Energy Industries The telecomms RAN (radio access network) is essential to almost every aspect of our daily lives and operators are being challenged to deliver ever greater capacities and coverage with high uptime and low costs. Unsurprisingly, energy is one of the largest operating costs for cells and towers that support the RAN infrastructure. Meanwhile, the power consumption of macro cell radios has increased steadily as access technologies have evolved. Typical power consumption for radio units was in the range of 100 to 300W in 2001 and is estimated to reach up to 1,800W by 20301. As a result, careful selection of the power supply, converter and power management technologies is a fundamental aspect to enabling modern RAN design. However, there is another significant cost associated with running a RAN that can also be impacted by the choice of power technologies, namely maintenance. Unplanned downtime and maintenance costs can mount very quickly, reaching many hundreds if not thousands of times the cost of any specific part or system that has failed. The cost of failure Consider a large network such that has 100,000 cell sites in a network. Each will have a variety of power supplies and modules, including AC/DC and DC/DC converters (Figure 1). There are two key areas for power supply technologies in a RAN infrastructure. One is the DC/DC converters that support the power amplifiers in the integrated radio antennas and the second are the high-power systems deployed in base station controllers. In terms of a DC/DC converter in a remote radio head (RRH), even the highest quality, well-engineered module may have a failure rate of about 10ppm (parts per million), so it would be expected to exhibit failure at some point. Once time is factored in to diagnose the fault, and an engineer is dispatched to ascend the antenna and fix the problem, costs can run to many thousands of dollars. Actual costs will vary depending on the individual scenario. However, an approximate cost of $20,000 to $30,000 to repair a fault of a failed DC/DC converter located in the RRH equipment is many times the value of the DC/DC converter itself. Figure 2 shows the key factors contributing to such a cost might break down. As the cost of the converter is likely to be in the range of $50, the cost of repair makes the cost of the original part negligible in comparison. If a batch of DC/DC converters has a latent fault, the ppm failure rate could be higher. Furthermore, if this were to reach 500ppm, then the same network could experience 50 failures at a significant cost. While clearly these figures are just for illustration purposes and could be debated, it is clear that component / module fallibility has the potential to drive Figure 1: Power modules for RAN applications.
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