5G base stations and the challenge of thermal management

5G issues and challenges revolve around what makes 5G so amazing. With 5G, we’ll have larger channels for faster data downloads and uploads. It drastically reduces latency for the response times needed by applications such as autonomous vehicles. More devices than ever can connect to the internet at the same time, supporting the demand for more smart devices. So how can there be any 5G problems?

These technologies consist of a higher density of components in tight, confined spaces. Coupled with that is the increased power required. 5G energy consumption generates heat, which can lead to component failure – and creates 5G network problems, namely dips or even complete outages and downtime. As more data is collected and processed in the cloud, processing off-loaded data consumes more and more power – and generates more heat.

With high temperatures come electromigration. The radiation of embedded antennas weakens at the frequencies required. For 5G to deploy on a large scale, thermal management is therefore a top priority for 5G base station designs.

These 5G issues must be addressed at the design stage with active thermal management solutions.

5G connectivity issues

The challenges with 5G not only encompass base stations, but also device form factors, such as smart phones. Heat dissipation impacts a device’s maximum receiving rate. If the device is unable to manage heat, its data handling performance is compromised. Any solution that addresses 5G heat dissipation in base stations will need to be compatible with the requirements of device form factors while working seamlessly with core functionality.

Base stations and massive MIMO

5G requires more antennas.

The 5G base station is a wireless receiver and short-range transceiver that connects wireless devices to a central hub. Its antenna and analog-to-digital converters (ADCs) convert the radio frequencies (RF) signals into digital, and then back again. Base stations rely on advanced antenna technology.

This technology is in the form of an array of beamforming massive multiple-input, multiple-output (MIMO) antennas. These antennas direct multiple beams to targets on the ground using the millimeter wave, or mmWave, while also reducing inter-user interference and increasing network capacity. Each channel carries independent information to the receiver.

Massive MIMO is actually MIMO, but more. That is, it goes beyond the 4G legacy systems by adding significantly more antennas on the base station. More antennas help focus energy. This is what improves throughput and efficiency. With massive MIMO, we see increases in:

• Number of RF chains in each installation
• Beamforming capabilities
• Amount of antenna elements employed by networks

While the number of antenna elements increases, the smaller wavelength means the antenna can be smaller. This helps alleviate the density of components, but also leads to more power amplifiers and beamforming components that must be integrated.

 

Digital beamforming means that each antenna should have its own RF transceiver. Signal integrity isn’t an issue when an antenna’s circuit elements are integrated into a single transceiver chip located close to the antenna. If you have a 4x4 array of antennas, then you have 16 transceiver chips on one board. With more process units in 5G baseband architecture, power demands are high, and with it the heat generated and the possibility of 5G overheating.

Thermal management of electronic devices and base stations

New, integrated thermal solutions are needed. Right now, one of the major challenges of 5G is the fact that form factors limit heat management systems for base stations. Remember, the solutions developed must work together. Powerful cooling fans that would work in a base station will obviously not fit in a cell phone. And then, unwanted EMI from fans can interfere with a base station’s ability to receive low-level signals, creating another 5G technology concern.

Let’s look at some of your options, which can work together in most cases – one method is rarely enough to work on its own.

Liquid cooling

Air cooling is an option, but a power-hungry one. That takes us to liquid cooling. As liquid, typically a coolant, moves through a waterblock, it absorbs heat from a baseplate. The liquid then moves through the system and through a tube to a radiator. It’s here where the radiator exposes the liquid to air, helping it to cool. Fans attached to the radiator then direct the heat away. The coolant then re-enters the waterblock for the process to start over.

Liquid-cooling equipment is compact, which makes this an excellent option where space is limited. It also lowers power consumption by up to 30%, depending on the brand, reducing CO2 emissions by up to 80%. All of these reasons are why liquid cooling is growing in popularity in data centers.

PCB materials

Use ceramic for your PCB components too, such as these non-threaded spacers.

Vapor-chamber cooling

Copper plates can help dissipate heat by dispersing it towards the bottom of PCBs. This isn’t 100% effective, as there are still hot spots to contend with. Very thin vapor chambers sandwiched between two copper plates between a liquid cavity can help. As the liquid heats up, it vaporizes, which dissipates the heat before condensing back into a liquid.

Heat-sink principles

Heat-transfer thermal management of electronics can be effective. This involves thermal interface materials (TIM), which come in different formulations and formats. These materials transfer heat energy away from components to a heat sink, but here again, EMI can become a problem, so the heat sinks should be made of copper or aluminum.

Advanced thermal management materials also include thermal gels which dissipate heat at high rates for large-scale infrastructures. Phase change 5G materials enhance the transfer of heat to heat sinks, which allows the component to run at a lower temperature, minimizing base-station power consumption.

GaN

Of all the components that make up RF transceivers, power amplifiers require the most energy. These are incredibly inefficient, responsible for as much as 75% of total dissipation during transmission. But without power amplifiers, there is no 5G. This makes Gallium Nitride, better known as GaN, indispensable to mmWave 5G networks. It’s relatively new to the scene but is showing great promise in improving thermal management of electronic devices and systems.

GaN is a direct bandgap semiconductor technology able to handle a wider range of frequencies. It’s ideal for massive MIMO base stations, delivering:

• Higher efficiency
• Excellent high-voltage sustainability
• Reduced power consumption
• Higher temperature attributes
• Power-handling characteristics

GaN is perfect for passively cooled base-station electronics and it won’t be long before it’s used in cell phones. Still, thermal management is still a challenge without an efficient thermal structure. The stress heat can have on GaN devices can affect reliability and limit their RF performance. You should consider also using natural cooling configurations. If the heat density is particularly high, look at air- or liquid-cooling systems.

RoF

RoF stands for radio-over-fiber and delivers broadband wireless services at mmWave frequencies. A radio wave is upconverted from a baseband signal. It’s then applied to modulate an infrared light source, specifically laser diode. The modulated signal transmits over a fiber link. This highly efficient communication method is entirely optical, driving multi-gigabit transmission to base stations over long distances with either SMF or MMF optical fibers with dense wavelength division multiplexing (DWDM).

The result is higher bandwidth. It can also replace multiple lossy coax cables. The drawback is that the conversion between digital and RF analog pulses can generate heat that will have to be removed. Every method for thermal management mentioned so far can be applied here.

You might also find it helpful to read Fiber optics and requirements for 5G infrastructure.

Designing for thermal management

Which thermal management solution, or combination of solutions, you use needs to be considered before you begin designing. Once you determine what you need, you can make better decisions for the components you need. You should also check out our Quick guide: components for 5G base stations and antenna.

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