5G and IoT applications can involve high densities of devices operating on similar frequencies. Designers of electronic devices regularly pay close attention to minimizing the generation of electromagnetic interference (EMI) and ensuring electromagnetic compatibility (EMC).
For 5G and IoT devices, it can also be important to minimize electromagnetic susceptibility (EMS), to protect from any potential cumulative effects from EMI or EMC underperformance.
Compared with fourth-generation 5G, called IMT Advanced, fifth generation devices, IMT 2020, include an order of magnitude increase in connection density of up to 106 devices per square kilometer and order of magnitude reduction in latency from 10 to 1 ms. Those changes are most pronounced in two of the three primary 5G application areas (Figure 1):
- Massive Machine-type Communications (mMTC) for the IoT, requiring low power consumption and low data rates for very large numbers of connected devices, and
- Ultra-reliable and Low Latency Communications (URLLC) to cater for safety-critical and mission critical applications.
Figure 1. The performance demands of mMTC and URLLC applications can make controlling EMS especially important. (Image: ETSI)
What could go wrong?
EMI can degrade the operation of low-latency communication in several ways:
- Adding noise to the signal can increase the need for retransmission, slowing communications.
- Corrupt data packets require even more extensive retransmission of data and greater increase in latency.
- Misalignment of timing and synchronization signals can also increase latency.
Conducted vs radiated
Noise and interference can be experienced through conducted and radiated mechanisms, or both (Figure 2). In general, conducted emissions are more often associated with low frequency interference while at higher frequencies, radiated emissions can be more challenging. Another challenge is that while fifth generation 5G supports a connection density of up to 106 devices per square kilometer, there’s no assurance that the devices will be evenly dispersed. They can exist in “clumps” that can exacerbate the potential for interference.
Figure 2. Radiated emissions can be especially challenging with 5G and IoT devices. (Image: Sierra Circuits)
Higher frequencies
Increasing device frequencies can pose a daunting challenge. In many cases, EMC and EMS testing standards are limited to a maximum frequency of 18 GHz. Newer device designs operate at up to 90 GHz, increasing the potential for interference. Designers face several new challenges, including:
- Shielding materials with high absorption capabilities are needed to manage radiated EMI.
- Circuit boards become more complex and trace routing, proper placement of ground planes and impedance matching present more challenging design issues.
Once those challenges are addressed, testing and confirming EMC and EMS performance at these frequencies requires specialized equipment and new testing approaches.
Unlicensed frequencies
The use of unlicensed frequencies for IoT devices further exacerbates EMC challenges. For example, the electromagnetic environment related to unlicensed frequencies varies between geographic regions. And since they are unlicensed, the number of active wireless connections can be especially challenging. The result is degraded signal quality that leads to unreliable transmissions and dropped connections.
In unlicensed spectrum there’s typically no coordination between devices to manage the power levels or transmission patterns of nearby devices, increasing the potential for interference. For example, complex modulation schemes in 5G devices can result in broader frequency spectrums increasing the potential for interference with devices operating in unlicensed spectrum.
Potential solutions
Potential solutions for the EMC challenges with IoT and 5G devices must contend with small form factors that can make is challenging to includes adequate EMI shielding and filtering. These devices tend to be low power making them more susceptible to power supply noise. Some potential strategies for dealing with EMC include:
- Optimized PCB design. The small sizes and geometries of the circuit boards in these devices can magnify even small errors or problems making it critical to optimize every aspect of the design and layout.
- Co designing of filtering and shielding to maximize the combined effectiveness.
- Optimization of antenna placement and design to manage unwanted radiation patterns and enhance reception sensitivity.
- Power management. These devices can experience large spikes in power during transmission and care must be taken to ensure that power supply noise is controlled.
- Testing for EMC, EMS and EMI performance should be implemented as an integral part of the design process, not relegated to only testing the final device.
Summary
There are several challenges associated with designing and deploying 5G and IoT devices, especially for applications like mMTC and URLLC. They include higher device densities and lower latencies. Add in the growing use of unlicensed spectrum and the challenges multiply. Fortunately, designers have several tools at their disposal for optimizing the performance of 5G and IoT devices.
References
Electromagnetic Compatibility (EMC), Vectornav
How to Prevent Electromagnetic Interference From Ruining Your Devices, TT Electronics
How Will 5G Development Impact EMC Susceptibility Testing?, Ametek
IoT Devices and EMC: Ensuring Connectivity Without Interference, FasterCapital
Review of the EMC Aspects of Internet of Things, IEEE Transactions on Electromagnetic Compatibility
The Challenges of Achieving EMC in IoT Applications, Cadence
Upcoming Issues and Solutions in EMC, Technical Textiles
Utilization of 5G Technologies in IoT Applications, MDPI sensors
Why do we need 5G?, ETSI
WTWH related links
The basics: What is EMC?
EMI control for power and signal lines
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