With the rapid growth of the IoT, the world around us now has billions of devices connected to the Internet, and more are online every second. The IoT consists of devices for the consumer market, agriculture, or mission-critical industries such as healthcare and automotive electronics. Device designers are adding wireless capabilities to their devices. However, you may not be aware of the regulatory compliance tests and certifications required in the country where you plan to sell your product. This article describes the regulatory compliance testing framework and its evolution to accommodate the rapid growth of wireless devices in the industrial, scientific, and medical (ISM) bands.
Regulatory compliance test
The ISM band can be used without a license, which is convenient for consumer applications without the hassle of licensing each installation. These bands are located at frequencies of hundreds of kilohertz to hundreds of gigahertz, with approximately 20 frequency allocations. Early ISM specifications were intended for non-communication purposes, such as metal furnaces, microwave industrial heating, and induction heating of home appliances. Over the past few years, with the increase in services such as IoT applications and short-range wireless communication Wi-Fi, Zigbee standard, Bluetooth Radiotelephones dominated these ISM bands with various types of modulations and protocols.
Interference has become a serious problem since the proliferation of devices in the ISM band. Regulators such as the Federal Communications Commission (FCC) in the United States and the European Union’s European Telecommunications Standards Institute (ETSI) have set out to promote the effective and efficient use of radio spectra. These institutions have established standards for coordinating between devices within the same frequency spectrum to avoid mutual interference and inefficiencies due to interference.
Tests such as receiver blocking and spurious emission focus on receiver performance and ensure that the device can operate in a busy radio spectrum without emitting unwanted signals.Protocols such as 802.11 family Wi-Fi signal You can demodulate signals from similar nearby networks. This process allows the spectra to be used cooperatively to avoid collisions and interference. However, there are many types of modulation in the ISM band. The device cannot intelligently share channels because it cannot decode external modulations and protocols. This causes a collision. Wireless regulatory compliance tests now include checks to reduce interference between radio frequency (RF) signals, regardless of modulation or protocol.
One example is the ETSI adaptability test of the channel access mechanism of the wireless subsystem. New wireless communication chips and subsystems must include a channel access engine mechanism to detect and avoid other signals and share the spectrum over time. This mechanism detects the RF energy of the active channel before the start of transmission. If the detected RF energy exceeds a certain level, delay the transmission of the device until the detected energy is no longer present. The delay or idle period should also be extended semi-randomly beyond the end of the detected signal. This random delay is especially necessary if multiple devices are waiting to send. Only one device initiates the next “conversation” during the broadcast, and the other device detects the signal and pauses.
This step is important to avoid conflicts that occur when all devices send at the same time after a delay period. The channel access engine includes calculations based on priority classes and pause periods to allow fair sharing of the spectrum over time.
Diagram of adaptability test.
The ETSI EN 301 893 Adaptability Test measures the behavior of the channel access mechanism. You need to reduce the chance of collisions between different signal types and increase the tolerance of extrinsic signals. The adaptability test simulates three different signal types using the following standard RF test waveforms. Orthogonal frequency division multiplexing, Additive White Gaussian Noise and LTE.
Complex challenges with new bands
As the WiFi band expands to include nearby frequencies, existing services in the band will need protection from new, unlicensed users. For example, radar services operating in the 5 GHz range can cause interference as the ISM band expands to operate at these radar frequencies. Regulators have defined dynamic frequency selection (DFS) tests to detect common radar signals. The channel associated with the radar signal is either emptied or flagged as unusable by the transmitter when it detects the signal.
Radar usage varies by region. In some places, there may be only a few radars that interfere with your wifi. Based on the operating frequency, the device must show a certain probability to detect the radar signal. The device must either stop working or move the network quickly to another channel to keep the radar frequency off for 30 minutes.
Regulatory testing of DFS is difficult because it requires important sequence of operations and timing for wireless LAN devices. Many types of radar signals are used, and each signal type must be tested. In addition, radar signals can be on different channels. An automated test system can significantly reduce the overall time an engineer needs to complete a tedious and repetitive DFS test task.
New regulatory test requirements for Wi-Fi 6E
Wi-Fi 6E This is another extension of the 5 GHz ISM band, up to 7.2 GHz in the United States and less in other countries. This is an additional spectrum 1.2GHz above the current allocation with active services in the additional spectrum. The FCC has defined a new set of tests for devices used in the Wi-Fi 6E band. The main purpose of these tests is to protect existing services such as terrestrial microwave links and satellite services. The new test requirements support antenna patterns to avoid emitting signals above 30 degrees from the horizon. Another new operational requirement uses a database to identify available channels based on the geographic location of Wi-Fi 6E devices. Unoccupied frequencies will be available at known existing user locations, but occupied frequencies will not be available.
Wi-Fi 6E testing requirements also include a feature named Conflict-based Protocol. This protocol is very similar to the ETSI adaptability test, which detects device activity on the active channel and delays transmission until no signal is detected. Semi-random delays help time transmissions, avoid conflicts, and increase the chances of a successful first transmission.
Preparing for complex regulatory compliance tests
These new regulatory compliance tests have significantly increased the complexity of the testing process. The days when all that was needed to achieve regulatory compliance was a simple test of power, bandwidth, and frequency are over. New tests such as DFS, adaptability, and conflict-based protocols require high-speed collection of large amounts of data at the exact timing of the device under test (DUT) behavior. To prepare for the future of regulatory compliance testing, the following are important:
Invest in automated test systems that can perform these complex tests quickly and accurately.
Verify that the test system can collect test data and process and analyze the dataset.
Maximize test system utilization by reconfiguring subsystems for parallel testing.And
Protect your investment through frequent software upgrades as wireless standards and regulatory testing requirements continue to evolve.
Early preparation helps reduce overall test time and achieve time-to-market goals, even for complex new tests required for regulatory compliance certification.
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About the author
Janet Ooi Keysight IoT industry and solution marketing. She graduated from Multimedia University in 2003, majoring in telecommunications and earning a degree in Business Engineering Electronics. After working for Intel for five years as a process and equipment engineer, she joined Agilent Technologies (now known as Keysight Technologies) as a product marketing engineer in 2008. Since then, Janet has also been a product management, business development and market analyst.
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