Importance of Testing for IoT Device Design

December 20, 2021 Anritsu Company

December 20, 2021

The Internet of Things (IoT) is a convergence of technologies being integrated into new use cases that go well beyond traditional wireless applications. From 5G and legacy cellular to Bluetooth® and Wi-Fi®, the spectrum is crowded with multiple technologies. Throw in mission-critical use cases ranging from telemedicine and industrial robotics to factory automation and autonomous vehicles and the RF world is akin to the “wild west.” Who (or what) can be the “sheriff” to keep everything operating peacefully? Test solutions.  Uptime is critical in these devices and they need to be thoroughly stress tested.

Because IoT use cases span virtually every industry, device type varies greatly, emphasizing the importance of proper testing. Device form factor and the materials used (i.e. plastic, metal, glass) can prevent key performance indicators (KPIs) from being met. For example, metal parts too close to the wireless module in an IoT device can block transmissions, leading to poor performance.  Even when a component such as a wireless module has been type approved, it’s performance can be degraded when used in end devices.

“Hidden” bottom-line benefits – such as lower cost-of-test and faster time-to-market of IoT products – can be uncovered using the proper test approach. Ultimately, having the proper test environment helps ensure that UE and networks operate at optimal efficiency. The challenge for engineers is to establish the correct processes using the best possible instrumentation.

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Multiple IoT Design Factors

Cost, as in most designs, is a major factor in IoT products and systems. There are other considerations for engineers, especially those developing mission-critical applications. Data reliability, security, and ease of use are essential. A failure to meet RF standards related to these variables can lead to unwanted attention from regulatory agencies. It can also lead to the loss of millions of dollars due to a shutdown of manufacturing facilities.

One common thread weaved through all IoT use cases is RF connectivity. Short-range Bluetooth, cellular, and Wi-Fi links are regularly integrated into systems that also utilize long-range low-power wide-area network (LPWAN) technologies such as LoRa, Sigfox, and NB-IoT. The end result is that ensuring connectivity between the network and UE is a complex dynamic that must be accounted for by engineers.

A case in point is interference between two different UEs using various technologies and within close proximity to each other. Corralling all these wireless signals into UE to ensure it operates according to specification and with high reliability across IoT networks is critical at every level of the ecosystem.

Standards Help Create IoT Roadmap

Standards developed by leading industry organizations and associations guide testing protocols. 3GPP is the leading body for establishing guidelines for cellular technology, with the exception of conformance and compliance testing. Narrowband IoT was adopted in 3GPP Release 13 (R13), which also included more nimble communications methods, more efficient battery consumption, low power, and low data rates.

Bluetooth, Wi-Fi, and similar short-range technologies have their own standards. The Bluetooth Special Interest Group (SIG) passed version 5.2 earlier this year. A continued focus on Bluetooth Low Energy (BLE) was part of the standard, as was high speed. Both performance attributes are integral for IoT use cases.

Wi-Fi 6e is the latest Wi-Fi generation developed. Based on the IEEE 802.11ax standard, it outlines performance specifications for the 6 GHz spectrum. IoT use cases will benefit from the faster speeds associated with Wi-Fi 6e.  

It is advantageous for engineers to stay current on these standards. A more efficient approach is to utilize test solutions with flexible platforms to support the most recent standard adoptions. It is particularly important for the aforementioned technologies. Anritsu conducted a poll that revealed cellular and Wi-Fi are used in 51% of IoT designs, followed closely by Bluetooth (48%), according to respondents. Zigbee (25%) was a distant fourth.

Need for Comprehensive Testing

Ensuring UE operation and security within an IoT network requires engineers to implement a comprehensive testing strategy. Part of the procedures need to include the critical tests outlined below.  

Adjacent Channel Power (ACP) – This test establishes the power in a designated frequency channel bandwidth relative to the total carrier power. It is important because it assures transmission quality and determines if power is leaking from the transmitter.

Effective Isotropic Radiated Power (EIRP) – An antenna’s radiated power in a specific direction is determined by EIRP measurements (figure 1). It is an important in antenna designs and beam forming used in 5G.

Wild west figure 1
Figure 1: EIRP measurements are integral for 5G antenna designs and beam forming.

Error Vector Magnitude (EVM) – EVM measures how accurate a wireless system transmits symbols within its constellation.

Transmit power – The average power for an RF signal burst is measured to determine the power delivered to the antenna system. It is particularly important for WLAN systems. When a UE connects to an access point or other device, a power surge occurs that is hard to measure since it is bursty. Transmit power measurements verify that the power levels are within specification.

Spectrum emissions – Out-of-channel emissions are compared to the in-channel power with this measurement. Engineers use the findings to calculate if interference will occur due to the surplus emissions.

Frequency error – This measurement ensures that the frequency hasn't leaked into another adjacent frequency.

5G’s Impact on IoT

The high-speed, large bandwidths, and low latency of 5G bring tremendous performance benefits to IoT use cases. New testing requirements must be implemented, especially at Frequency Range 2 (FR2), since millimeter (mmWave) bands are used. With mmWave UE, antennas are integrated with the base stand and the RF front end. As a result, antenna-oriented measurements, such as total radiated power and peak beam surge, must be added to the list of necessary tests. 

Ensuring Compatibility Between Technologies

Given the myriad of technologies integrated in an IoT network, measurements must be made on the UE to ensure these technologies do not interfere. Cellular and Wi-Fi desense/co-existence measurements are performed to verify that UE implementing the technologies are compliant. It is a particularly important test because cellular and Wi-Fi signals can easily overlap.

An Over-the-Air (OTA) configuration with dedicated test systems and software allows necessary tests to be made in the same environment. This set-up simulates a real-world scenario, so accurate and repeatable measurements can be made cost efficiently. Further, a test solution that can display antenna characteristics in a 2D/3D graph (figure 2) allows engineers to intuitively grasp the measurement results.

Wild west figure 2a
Wild west figure 2a
Figure 2: 2D (top) and 3D (bottom) graphs allow engineers to have better insight into antenna characteristics.

Another common co-existence scenario is Bluetooth and Wi-Fi, because both share the same band in the 2.4 GHz range. Therefore, a test solution must support both technologies. For Bluetooth verification, functionality such as Adaptive Frequency Hopping (AFH) is beneficial, as well.

Importance of Automated Testing

Because IoT utilizes a plethora of wireless technologies in so many environments, creating a time- and cost-efficient test environment is a challenge – and a necessity. There are thousands of potential frequency band combinations and network configurations in IoT. The only way to effectively support such a range of possibilities is through automated testing, such as the Anritsu SmartStudio Suite.

Anritsu SmartStudio offers quality-management functions to configure a real-world wireless environment to automatically evaluate cellular functions, find faults, and analyze causes of failed performance. Among the functional tests it can perform are data performance, mobility, battery, and traffic handling. It simplifies configuring a real world environment and lowers costs while ensuring product quality.

Figure 3 shows how the Anritsu SmartStudio automated test solution provides a Test Condition List whereby test cases are automatically listed. It allows engineers to easily and quickly select a target band combination to be tested.

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Figure 3: Anritsu SmartStudio display of a call connection measurement that includes a Test Condition List
for automatic testing of programmed test cases.

You can learn more about IoT trends and testing requirements by visiting Anritsu’s IoT Resource Hub. Educational materials, including videos, webinars, white papers, applications notes, and posters are available.

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