5G infrastructure power supply design considerations (Part I)

2021-05-05

With the advent of 5G, network power supply requirements are changing. 5G equipment is sensitive to the quality of the electricity supply and must operate in a broad variety of environments, both indoors and out.

 

5G changes this dynamic by allowing mobile cores and core routers to flip rapidly between active and idle states. Higher bandwidths and compression techniques will let 5G networks shuttle more data through systems in a given period, leaving more power-saving idle time.

 

In light of this, the move to 5G infrastructure is necessitating new power supply design considerations. FPS has a range of products designed to fit specific niches and improve power management for devices across the 5G ecosystem, from user equipment via masts, cell site gateways, aggregation routers, mobile core, and the cloud. The equipment ensures that devices across the infrastructure stack receive reliable power from the mains network, wherever they happen to reside. With it, individuals and organizations can continue to render services to both themselves and their customers.

 

5G Infrastructure Architecture And Power Supplies

 

The 5G network architecture uses multiple types of power supplies. Requirements include units that work indoors and outdoors, offer surge protection, provide step changes in voltage, and come in form factors that are compatible with heterogeneous systems.

 

The access side of the 5G stack includes user equipment such as smartphones, tablets, laptops, and desktop devices. Devices in this part of the stack require power supply equipment that can operate at room temperatures indoors and protect sensitive electronics - already a well-developed area.

 

The next area concerns power supplies suitable for masts and eNodeB units. This equipment must be suitable for outdoor use, dustproof and waterproof, and must be available in small form factors.

 

Mobile backhaul - the part of the mobile network that connects the radio access network with the core network - also requires specific power supply solutions to enable it to operate at high efficiencies. Power supply units feeding the cell site gateway, aggregation routers, and core routers need to be able to operate outdoors or semi-outdoors, withstand wide temperature variation, and offer surge protection.

 

There are also requirements for the mobile core itself - usually indoors or inside a container. Network operators need small and modular units to fit their applications.

 

Lastly, cloud operators require CRPS standard power supplies to homogenize across building clusters. Many also need redundant power supplies that can continue to provide power to critical units even if another power supply ceases to function.

 

Power Supply Design Considerations

 

If organizations hope to fully realize the potential benefits of 5G they will need to incorporate more millimeter-wave transceivers, faster data conversions, low noise power amplifiers for smaller cells, and more field-programmable gate arrays (FPGAs). The ultimate hope is that these new approaches will reduce the overall power consumption of 5G systems while also dramatically boosting the reliability for users. Given that waves will be on the millimeter-scale, dishes could be as small as a centimeter, allowing engineers to pack more of them into masts with minimal visual impact.

 

This new equipment is leading to new power supply requirements. While the overall power draw is often lower, 5G equipment has narrower tolerances. It often needs multiple, precise voltages to operate correctly, with scarce leeway on either side.

 

In the following section, we discuss 5G infrastructure power supply considerations in more detail.

 

Access Equipment

 

5G delivers coverage to an area in a different way from 4G. Instead of using large masts that cover up to thirty kilometers in any direction, it relies on “small cells” to provide local coverage over extremely limited areas, usually between 10m and 2,500m. Some of these will operate directionally.

 

For 3G and 4G, network operators used the eNodeB system for the distribution of the network. But now most operators working under LTE prefer thinking in terms of cells, usually arranged as a hexagonal grid, showing geographic signal coverage.
For 5G, estimates suggest that network operators will need to install millions of individual antennas to provide full coverage. That’s because 5G signals work differently from previous-gen signals in that they can only travel short distances. Building materials, landscaping, and even rain may interrupt signals. And that has substantial implications for power supply choice, as we discuss below.

 

Compactness

 

The eNodeB setup is innovative because it brings RNC functionality inside the mast itself. Masts in 5G systems have more control over their own operation instead of being controlled by a central tower.

 

However, these changes mean that power supplies need to evolve. Small cells will need to be able to fit in compact environments, such as traffic lights, utility poles, and rooftops. So power supply units will need to be compact, able to fit comfortably alongside the equipment they power.

 

Heat Dissipation

 

There are also considerable heat dissipation issues that 5G equipment power supply units will need to accommodate. Internal power supplies housed inside equipment won’t always be able to use fans to dissipate heat. So power supplies will need to cool components passively using advanced heat exchange mechanisms.

 

Blackout And Anomaly Protection

 

Inevitably, small cells will experience power outages from time to time. For this reason,  power supplies need to be able to accommodate backup power. As smart cities develop around 5G infrastructure, backups may become a critical component in keeping citizens safe.

 

Experts widely believe that 5G small cells need to be able to continue running in the event of electrical anomalies. Pairing them with integrated power supply devices costs more, but it also protects small cells if there are dramatic changes in voltage.

 

For instance, FETs can dissipate power and stabilize the differences between input and output voltages. They also use thermal control features to keep the internal power MOSFETs with a safe operating range.

 

Power supply units will also need to be able to protect against voltage and current spikes. Changes in the nature of the electrical circuit could result in loss of performance or even the destruction of sensitive 5G components.

 

Semiconductor Requirements

 

Next-generation small cells contain highly-sensitive millimeter-wave assemblies and field-programmable gate arrays. These integrated circuits need matching power supplies that can deliver precise voltages according to their design tolerances. Voltage spikes or other interferences could damage them, leading to outages and higher overall costs of ownership.

 

Envelope Tracking

 

Envelope tracking is also expected to play a significant role in the development of power supplies for 5G-compatible devices. Many organizations are already using on-premises radio access equipment and 5G devices that are compatible with the latest 5G networks. However, the successful adoption of 5G will require plugging hardware gaps in a way that ensures that equipment is fast enough to support the new technology.

 

With envelope tracking, systems continuously adjust the voltage used by the RF power amplifier to help keep the supply running at peak efficiency. Boosting both power and frequency at the same time usually results in excess heat. However, with envelope tracking, continuously adjusting the voltage applied to the RF helps to cut down on waste heat generated by the system.

 

Powering systems in non-linear modes may help to cut power usage of 5G devices by around 50 to 60 percent. That’s because this approach reduces heat dissipation by only providing the energy that the system actually needs.

 

Dust-Proofing

 

Some 5G network applications require dustproof power supplies because masts, cells, and other controllers can’t always go inside buildings. In fact, designers may actively try to avoid this, given the fact that 5G signals can struggle to penetrate walls.

 

Dust-proofed power supplies have solid metal cases, sometimes coated in heat-conducting silicone gel. To keep dust out, they do not use fans. Instead, they rely on passive cooling technologies that help to dissipate any excess heat out of the chassis and into the wider environment. Systems will occasionally use closed-loop water-cooling using external fan-assisted radiators.

 

Waterproofing

 

Power supplies used outdoors on top of buildings, traffic lights and other external urban small cell locations also need to be able to withstand the rain and dampness.

 

Mostly, this will involve placing power supply units inside waterproof cabinets creating a “semi-outdoor” environment. The power supply will deliver power to small cells and other nodes in the 5G network via waterproofed wires.


The size of the cabinet will depend heavily on the needs of the power supply and whether it needs to house battery backup. In some cases, the manufacturer will waterproof the power supply simply using rubber seals and impermeable plastic.

 

The result of these approaches is safer overall power functionality and better system operation. Cells remain within their safe operating area, without guesswork or the need to continually monitor the system. And that’s good news for 5G, since finding, fixing, and replacing millions of small cells would be prohibitively expensive for network operators.

 

Backhaul Equipment

 

The backhaul part of the 5G network connects the access interface - including masts, eNodeB, and cell site gateway - to the mobile core and internet beyond. And just like the access equipment, it too has specific power supply requirements.

 

Backhaul power supplies must cater to aggregation routers and core routers. These units typically require supplies with 12V / 48V output.

 

Many backhaul systems operate at high altitudes. Thus, finding a power supply that has a high-altitude design is essential. Transmitters, repeaters, and broadcast towers occupy elevated locations to provide maximum coverage over a given geographic area.

 

Altitude is a factor when designing electronics because of the thinning of the atmosphere. As you go higher, the air becomes less dense, and so heat removal via passive or active air cooling becomes less efficient. Therefore, electronics will experience greater component temperature per unit of power supplied.

 

Furthermore, at altitude, the air becomes a less good insulator of electric currents (until you reach a vacuum) and so backhaul power supplies at higher elevations are at a higher risk of short-circuiting. Creepage - defined as the shortest distance between two conductive components along insulating material shared by those components - goes down the higher you get. So power supply specifications that were suitable for telecoms equipment at ground level, may not apply as elevations rise.

 

Power supplies also need to be able to convert from mains AC to DC. Many backhaul systems rely on semiconductors to perform their operations. And those, in turn, only work on DC.

 

Even though modern power supplies used in backhaul operations are exceptionally reliable, they can sometimes fail. For instance, issues with transistors or FETs can lead to a short circuit that creates an overvoltage. Such events can lead to the destruction of components inside core and aggregation routers, putting them at risk.

 

Adaptors and power supplies with overvoltage protection, however, can mitigate these risks. Several types of overvoltage technologies are available. One of the most common is the SCR crowbar. Here circuits use thyristors to link back to a fuse that blows, isolating the circuit and protecting the equipment.

 

Another method is called voltage clamping. This involved placing a Zener diode across the power supply’s regulated output, set to a voltage slightly higher than the maximum rail voltage. If the system is operating normally, the Zener diode will not conduct. However, if the voltage is higher than it should be, then the diet will “clamp” the voltage at a value slightly higher than that of the voltage rail.

 

FSP offers several core capabilities for backhaul power solutions. This includes:

 

  1. R&D capability to provide a standardized and intelligent power supply. For instance, products with digital and communication functions, high power density, high efficiencies, designs that can withstand harsh conditions, and highly scalable systems for wider roll-outs.
  2. Digitized product design. This allows the quick supply of modified standards.
  3. Modular product design. This makes it easy to construct power supplies from the bottom up, meeting specific customer power demand requirements.
  4. The ability to choose from a broad portfolio of power supply devices, suitable for a vast range of applications
  5. Quick response to customer demands. FSP makes it a priority to meet 5G infrastructure needs as they evolve in real-time.
  6. High quality. FSP’s power supply products meet the quality demands of agents in the telecoms industry.

 

We continue this discussion of 5G power supply design considerations in part II. In this next part, we will cover power supply considerations for the core of the 5G network, plus for internet- and cloud-connected devices (such as servers).

 
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