Testing 5G User Equipment: Review, Challenges, and Gaps from the Medical Device Perspective

Abstract

5G technology can enable novel healthcare applications and augment existing medical device use of wireless technology to improve healthcare delivery. Having the dual role of medical device and cellular user equipment (UE), 5G-enabled devices navigate a plethora of rules and tests before they can operate on a 5G network to deliver their intended medical function. In this paper, we review the state-of-the-art of 5G UE certification programs and testing specifications. We then identify test challenges and discuss the relevance of existing test practices to support the 5G-enabled medical device safety and effectiveness. This information is useful to medical device developers planning to incorporate 5G technology in their products and wireless engineers working to expand mobile services into the healthcare vertical.

II. Introduction

The fifth generation (5G) cellular technology has been rapidly commercialized and increasingly popularized in major telecommunication markets including North America, Europe, and East Asia. 5G services support many use cases with diverse quality of service (QoS) requirements, such as enhanced mobile broadband access (eMBB), massive machine-types communications (mMTC), and ultra-reliable and low-latency communications (URLLC). With increasing wireless and mobility data needs, medical devices and healthcare applications form one of the vertical domain industries that expect a significant growth of 5G adoption. Notably, the market is predicted to provide a total of $76 billion revenue opportunity in 2026 for operators addressing healthcare transformation with 5G [1]. 5G provides pervasive cellular coverage and individualized Internet Protocol (IP)-native wireless solutions with QoS provisioning. 5G communication features can facilitate remote patient access to healthcare providers, improve diagnostic performance with enhanced data collection, transmission and sharing, and support novel medical device applications like remote robotic surgery and connected ambulance. 5G-enabled medical devices are now attracting attention from medical device vendors and regulators, telecommunication service providers, and digital health innovators, with pre-competitive forums emerging to share ideas and expertise. An example of such forums is the Medical Device Innovation Consortium (MDIC) 5G-enabled Medical Device Workgroup [2].

Having the dual role of a medical device and a cellular network node, a 5G-enabled medical device will navigate several regulatory paths—like those of the U.S. Food and Drug Administration (FDA) and the Federal Communication Commission (FCC)—in addition to certification from industry groups and network operators. In the U.S., the wireless technology use in medical devices is considered by the FDA as described in the guidance document “Radio Frequency Wireless Technology in Medical Devices - Guidance for Industry and FDA Staff ” [3]. The topics addressed in the guidance document include the selection and performance of the wireless technology, wireless QoS, wireless coexistence, and the electromagnetic compatibility (EMC) of the wireless technology. These topics are considered in device premarket submissions to help support the device safety and effectiveness. On the other hand, the 5G user equipment (UE) in the U.S. needs certification by the Personal Communications Service Type Certification Review Board (PTCRB) and the target mobile network operators (MNOs) in addition to market grants from the FCC. Similar to other existing wireless technologies, e.g., 4G and Wi-Fi, new entrants in the 5G medical device space also face the complex task of bringing their devices to market through certification tests and regulatory process while weighing the associated cost and delay when making design decisions. Furthermore, as the 5G technology evolves to introduce new technical features, use cases, and service requirements, certification programs are also evolving to include new test vectors and update existing practices in recognition of technology changes. Certification tests are normally of two types: conformance and acceptance. The former is either required by national/regional market regulators or recommended by industry certification bodies; the latter is organized by individual MNOs. Conformance tests are used to check whether the equipment under test (EUT) conforms to regulation criteria or supports interoperability with products of different vendors in compliance to industrial standard specifications. Acceptance tests are more focused on the part of the EUT’s performance associated with a specific MNO’s infrastructure and service capability. Once the device is accepted, its information, e.g., the International Mobile Equipment Identity (IMEI) that uniquely identifies each manufactured device, can be uploaded to the MNO’s database, and used in activating the device on the network.

As illustrated in Figure 1, certification testing has a key role in the cellular product lifecycle, which includes 5G-enabled medical devices. For vendors and importers, obtaining the necessary certification in the target market is a prerequisite to initiating the next production stage. As early as in the research and development (R&D) stage, the vendor validates the product design through a series of tests to verify the 5G module functions, interfaces, and the overall system design. Once the design is finalized, the prototype that is ready for production will be sent out to test its compliance with certification rules. Unlike the R&D tests that are typically performed in a vendor’s lab, certification tests are usually conducted by accredited 3rd party testing labs recognized by certification bodies following test plans that apply to the submitted EUT. The vendor needs to address any reported issue causing test failures, modify the design, and retest. As certification failures cause extra certification delay and increase test cost, the vendor might choose to test the product per the required test regime prior to submission, which is known as pre-conformance testing. The next section will detail the certification programs in the U.S. that are relevant to 5G products. Additional tests can be conducted when needed like quality checks in factories and diagnostic tests for maintaining deployed products.

Figure 1.

Certification tests in the cellular product path to deployment.

This paper provides an overview of the state-of-the-art processes—in the U.S. market—for certifying 5G equipment including 5G-enabled medical devices. Individual programs are highlighted, based on publicly available information, in Section III along with key elements in the conformance/acceptance tests. In Section IV, we highlight the challenges and knowledge gaps from the medical device evaluation perspective to consider the overall 5G-enabled medical device safety and effectiveness when using 5G. Furthermore, we note certification challenges that are generally applicable to 5G UEs. This information can be useful to medical device developers planning to incorporate 5G technology in their products and help the efficient design of a testing and certification regime. It can also be useful to wireless engineers working to expand mobile services into the healthcare vertical by highlighting the uniqueness of 5G use in medical devices and the risk considerations that can be associated with that use. Finally, Section V concludes the paper.

III. Existing Certification Programs in the US Market

5G UE certification programs help verify the UE conformance to spectrum regulatory rules and demonstrate the UE capabilities and compatibility with other cellular users and network elements. Accordingly, UEs are typically certified by three types of certification bodies: the radio frequency (RF) spectrum regulator, industry associations, and MNOs. As shown in Figure 2, UE certification can be illustrated as a sequence of steps that result in obtaining the necessary grants for market access. Notably, although these certification reviews are conducted by independent entities in parallel, the successful completion of a given step is often conditioned on completing the previous ones.¹ Each certification body considers the rules that are relevant to its mission. Specifically, certification by the spectrum regulator emphasizes RF safety as well as protection for legitimate RF users through limits on relevant UE characteristics like the maximum output power and out-of-band emissions. Industry conformance tests address interoperability between the UE and the network elements. For example, UE behavior when roaming to another carrier’s serving area. MNOs set diverse requirements for their acceptance tests, which can include the signaling procedure between the UE and a proprietary network infrastructure, the QoS level for on-premise services, or even specific requirements on the UE firmware version.

Figure 2.

Participants and procedures in UE certification programs. Clockwise, (a) a general certification model with major participants, (b) FCC wireless certification process, (c) PTCRB certification process, (d) an MNO’s acceptance process.

The UE certification process can be represented by a three-party model, as shown in Figure 2(a), that includes: 1) the UE manufacture or importer requesting the certification; 2) the certification body managing the certification and concluding a request by issuing a grant or a rejection; and 3) the testing body that tests the requester’s product and provides test results to support the certification decision. In the rest of this section, we will elaborate on the certification programs for launching a 5G UE product in the U.S. market.

FCC Certification

As shown in Figure 2(b), the certification is issued by an FCC-recognized telecommunication certification body (TCB) that evaluates all the supporting documentation and test data submitted by a “responsible party”, which can be a manufacturer, importer, or integrator. Testing is conducted by an FCC-recognized accredited testing laboratory. The technical parameters and a description of the certified UE are posted on an FCC-maintained public database (DB), known as the equipment authorization electronic system (EAS).

Developers of 5G-enabled equipment can use an off-the-shelf cellular module without further FCC testing if it has been certified by FCC and used in the host device the same the way as stated in EAS DB grant. However, FCC evaluates RF features and safety risks at the device level, which might result in requesting additional compliance tests. Details about this scenario are included in an FCC guidance document for host product manufacturers integrating modular transmitters into their device [4], which recommends testing of the host product with all the transmitters installed. This can be applicable to 5G-enabled medical device with multiple FCC-certified transceivers.

FCC certification tests include diverse items like radiated transmitter measurements in licensed radio services, RF exposure, and general EMC and radio equipment tests. 5G spectrum bands are defined in two groups of discrete radio frequencies, i.e., FR1 (known as sub-6 GHz bands) and FR2 (known as mmWave bands). With carrier aggregation (CA) being used in the 5G channel allocation, three types of channels are available in 5G operations: FR1 only, FR2 only, and the hybrid channel (supported by CA over selected bands from FR1 and FR2). An example of 5G licensed spectrum band is the 5G new radio (NR) band n2 at 1900 MHz.²

The radiated transmitter tests measure the EUT’s RF power level in and out of licensed spectrum bands at continuous transmission operation. The in-band test items include the occupied bandwidth of the active EUT, in-band RF power level, and frequency stability within the working temperature range. Another subset of tests is related to unwanted emissions caused by the EUT’s power output on a frequency or frequencies immediately outside the necessary bandwidth of the working band, which consist of out-of-band (OOB) emissions and radiated spurious emissions (RSE). OOB emissions are those measured in the bands immediately outside and adjacent to the EUT’s band, also known as OOB emissions at the band edge; RSE are measured in other bands excluding the OOB’s frequency range. Emission limits are specified per individual band, e.g., FR1 n2 follows the Personal Communications Service (PCS) emission limits [5] while FR2 n260’s emission limits follow the rules of the upper microwave flexible use service [6].

Limits for safe exposure to RF energy are used in RF exposure tests for products used in close proximity to the human body (i.e., the distance to the antenna in use is within 20 cm). These limits are specified in terms of the Specific Absorption Rate (SAR), which is a measure of the amount of radio frequency energy absorbed by the body when using RF devices including mobile phones. The FCC adopted limit for public exposure from cellular telephones is a SAR level of 1.6 watts per kilogram (1.6 W/kg) [7].

Unintentional radiators are devices without RF transmitters. However, the unintentional radiator’s RSE, also known as idle mode emissions, measure the RF noise made by electronic devices with digital circuitry. RSE test is required by FCC Part 15 Subpart B for products using time pulses at a rate in excess of 9000 pulses (cycles) per second, which applies to most modern digital devices with embedded processing units. For 5G UE, this test is performed when the EUT is in the idle mode, i.e., when it is synced to the network but with no active transmission [4].

PTCRB Certification

Founded in 1997, PTCRB is an industry certification program in North America³, which ensures compliance with a set of cellular network standards and is open to both cellular module and end-product manufacturers. PTCRB certification was originally designed to certify cellphone products for GSM networks. Now it has been widely expanded to cover more cellular technologies including UMTS (3G), LTE (4G), and data-native UE types such as CAT M1 and NB-IoT for the Internet-of-Things (IoT) applications. In its latest specifications, 5G NR is also included. PTCRB certification is recognized by many MNOs like AT&T and Rogers. However, some MNOs like Verizon have developed their own testing programs.

PTCRB certification is currently managed by the Cellular Telecommunications Industry Association (CTIA). CTIA wireless device certification ensures conformance of wireless devices using cellular, converged Wi-Fi, and IEEE 802.11 air-interface technologies, to specific requirements on behalf of the wireless industry. Besides PTCRB, CTIA also manages five other wireless device certification programs including battery compliance, battery life, hardware reliability, over-the-air (OTA) performance testing, and IoT cybersecurity. As shown in Figure 2(c), CTIA acts as the certification body for PTCRB certification and communicates with the two other entities, i.e., the requester and testing lab, through the PTCRB certification database.

PTCRB does not offer a public database similar to the FCC’s EAS database that allows checking specific testing documents that accompany a certified device. In this article, we searched for publicly available information about PTCRB certification and used as a source PTCRB’s permanent reference document NAPRD03, which provides a technical overview of the program.

RSE tests are a part of the PTCRB certification and characterize the 5G UE in both active and idle emissions. A 5G UE product often supports multiple cellular modes, such as 3G, 4G, and 5G. In each test, RSE is measured on all frequencies other than the one the UE is actively on. Such tests are repeated on every frequency of the spectrum bands supported by the UE. In addition to active RSE tests, RSE data is also collected in tests when UE is in the idle mode. In idle RSE tests, PTCRB adopts the limits set by the European Telecommunications Standards Institute (ETSI), which are stricter than the FCC’s limits.

The PTCRB certification requires measuring the EUT’s OTA performance using the test procedures in CTIA’s OTA test plans [10].

Separate OTA test plans are specified by CTIA for single-input single-output (SISO) radios, multiple-input multiple-output (MIMO) radios, 5G mmWave radios, and for cellular EUT equipped with a Wi-Fi modem. In OTA tests the EUT is placed in an anechoic chamber where the EUT’s RF characteristics are measured in terms of total radiated power (TRP), total isotropic sensitivity (TIS), and relative sensitivity on intermediate channels. TRP is a swept measurement of RF power output integrated over a sphere surrounding the EUT’s antenna, which depends on the antenna radiation efficiency, impedance match, and radio output power. TIS uses the same sweep but integrates the measurements into a single number representing the receiver sensitivity, which is affected by similar factors like the TRP as well as the noise originating from the host device’s non-RF electronics. The last one tests the EUT’s receiver sensitivity across a large subset of intermediate channels between a limited number of reference channels in the supported bands so that the total evaluated cases are significantly reduced [12]. The tests in 5G NR FR1 bands use the same procedures as in LTE; new test items are being developed to address the OTA performance in 5G NR FR2 (mmWave) bands [10]. The PTCRB certification doesn’t specify the pass/fail criteria for TRP or TIS results, which are left for individual MNOs to determine in their own acceptance tests.

MNO Certification

In addition to prerequisites like FCC grant and PTCRB certification, MNOs might require the UE to meet additional performance criteria before accepting the device to be used in their networks. Notably, carrier acceptance tests can vary with the device type and supported service, which are defined by each MNO whose testing methods, test cases, and performance criteria are proprietary. Publicly available information about those tests is scarce and UE vendors should directly contact the target MNO or the MNO’s authorized testing labs for details. An example of MNO certification program is that of Verizon as illustrated in Figure 2(d) based on the available information on Verizon’s website [8].

Standard Conformance and Interoperability

The 3rd Generation Partnership Project (3GPP) is an umbrella of regional/national telecommunications standard development organizations (SDOs), which defines, develops, and maintains the specifications of cellular communication technologies including 5G NR, 4G LTE, and legacy 2G/3G systems. Since most of commercial 5G networks are utilizing the system architecture and evolution paths defined by 3GPP, industry certification bodies, e.g., PTCRB and carriers, also heavily rely on testing methods and test cases developed by 3GPP to create their own test plans with respective focuses. Within the 3GPP Technical Specification Group Radio Access Network (TSG RAN), the 3GPP TSG RAN WG5 (RAN5) is the conformance testing group for UE, which comprises the RF and the signaling subgroups and encompasses both RF and radio resource management (RRM) conformance tests. This section covers a brief overview of the 3GPP UE conformance specifications.

The 3GPP UE conformance specifications can be found in 3GPP specifications TS 38.508 to TS 38.533 [9]. As shown in Figure 3, core conformance tests include TS 38.508–1 for common test environments, TS 38.508–2 for applicability of tests to different 5G UE categories, known as the Implementation Conformance Statement (ICS) proforma, and TS 38.509 for special functions, e.g., loopback. Conformance tests are organized into three main parts to measure the UE performance: RF performance, RRM, and protocol signaling.

Figure 3.

3GPP specifications for UE conformance tests.

As the first part, RF performance tests measure performance on the air interface (e.g., TRP, Effective Isotropic Sensitivity (EIS), and RSE.) The first three parts of the TS 38.521 specification (i.e., 38.521–1/2/3) address RF performance tests (test methods, test cases, and calculation of measurement uncertainty) for respective channel types, i.e., FR1, FR2, and FR1&2 CA. RF performance tests in the Evolved Terrestrial Radio Access Network (E-UTRAN) and NR - dual connectivity (EN-DC) mode, known as the non-standalone (NSA) mode where the RAN incorporates LTE and 5G base stations, are also included in TS 38.521–3. Tests for the demodulation and reporting of different channel state information (CSI) in all three channel types are specified in TS 38.521–4. These RF conformance specifications echo the design requirements specified in TS 38.101–1/2/3/4 in a one-to-one mapping with respect to minimum requirements for the tested items. The RF conformance tests also address 5G UE EMC in TS 38.124.

TS 38.533 specifies tests for RRM support including support for UE handover and mobility scenarios. TS 38.522 details the applicability of test cases and serves as a dictionary to pair an EUT with specific UE features with the subset of test cases from the above RF and RRM tests. This can be done in tandem with TS 38.508–2 where ICS proforma are used to identify the EUT’s 5G UE category with a set of features.

TS 38.523–1 includes tests for the UE signaling procedures in the full RAN protocol stack under different operation configurations, such as SA/NSA. Similar to the role of TS 38.522 in determining RF and RRM test cases for the EUT, TS 38.523–2 helps select the relevant signaling tests according to possible use cases. The signaling test utilizes a standardized testing suite named TTCN-3, which is introduced in the third part, TS 38.523–3.

Finally, 3GPP also developed two technical reports, TR 38.810 and TR 38.827, addressing OTA test methods for the general and MIMO cases, respectively.

Figure 4 provides a couple of examples showing how 3GPP conformance tests are referenced by certification programs. As introduced earlier, NAPRD03 identifies UE test items in PTCRB certification. Generally, PTCRB defines test cases from three types of reference sources: 1) the tests developed by the PTCRB validation group (PVG) in proprietary guidelines, 2) CTIA’s test plans for RF performance tests, and 3) test cases directly excerpted from 3GPP standards. In many cases, the tests of the latter two can be traced back to specific clauses in 3GPP UE conformance specifications. For example, the setup and TRP/TIS tests in the NR FR1 bands specified by 3GPP TS 38.521–1 are incorporated into CTIA’s SISO OTA test plan, which are further adopted by PTCRB in the RF performance tests.

Figure 4.

An illustration of PTCRB test references.

IV. Challenges and Gaps

In this section, we first address the knowledge gaps in the information generated during UE certification to support the safe use of 5G by a 5G-enabled medical device. Afterwards, we proceed to discuss the overall challenges of 5G UE certification.

The plethora of certification tests summarized in the previous sections focus on two themes: the UE RF characteristics and its interoperability with the 5G network elements. The former leverages measurements of SAR, OOB, RSE, etc. to demonstrate the UE’s adherence to regulatory spectrum rules and over-the-air behavior. The latter uses protocol conformance to demonstrate that the UE can operate with other network elements on a given carrier’s network to communicate at QoS levels of typical wireless services, e.g., voice or video calls. However, this information does not address how a medical device would safely use 5G connectivity to deliver its intended functions thus presenting a gap in the evaluation of 5G-enabled medical devices. The medical device functions that can be enabled by 5G connectivity are diverse (e.g., connected ambulance, remote robotic-assisted surgery) and can use various communication QoS profiles. While 5G UE certification supports that a 5G-enabled medical device can use the network, it does not consider the risks of lost, delayed, or disrupted transmissions, which might impact the 5G-enabled device safety and effectiveness [3]. Accordingly, there is a lack of evaluation methods to help assess the 5G-enabeld medical device’s unique needs for 5G communication capabilities. Developing these methods can benefit from characterizing the 5G network key performance indicators (KPIs) that support the 5G-enabled device performance and identifying test vectors to stress-test this support. Also relevant is the tradeoff between the test thoroughness (i.e., in exploring test vectors and parameter combinations) and cost, which can increase the financial burden to test the UE and delay the device availability on the market. This is also true for 5G UEs in general since 5G networks can be deployed with abundant degrees of flexibility in selecting the air interface, networking strategy, and data services. There is a large set of test parameters that can be used to exhaust all the UE supported frequencies, bandwidths, modulation and coding schemes (MCS), etc. Hence, an area of open research is the methodology of selecting test parameters to maximize effectiveness and efficiency of test plans while meeting test objectives.

A practical challenge to performing 5G UE testing is apparent in 5G OTA tests, especially those performed in the FR2 bands, come with new challenges to existing OTA methods and the test facility. The scope of current OTA tests is limited for MIMO radios that are prevalent in 5G UEs. For example, CTIA’s MIMO OTA test plan only supports the verification of 2×2 MIMO systems in its setup, i.e., the EUT can have up to two transmitter antennas and two receiver antennas. As 5G aggressively utilizes MIMO techniques to compensate the ultra-high path loss experienced in the mmWave bands, new test methods are needed to accommodate the use of massive MIMO, multi-user MIMO (MU-MIMO), and beamforming. Additionally, additional functionality in the 5G UE is needed to facilitate OTA tests (e.g., the UE permitting control of the device transmission characteristics to determine the worst-case beam pattern in RF measurements). Furthermore, test facilities might need to consider upgrading existing test fixtures (e.g., anechoic chambers, positioners) or acquiring new fixtures to support OTA tests in FR2 bands.

There are several non-technical challenges to the certification of 5G UEs, including 5G-enabled medical devices. For example, publicly available educational resources on the certification process are limited. In practice, testing labs often act as a source of information for the tests and processes that technology developers should consider. Therefore, it is common to find articles and blog posts on the websites of test labs offering summary descriptions of the certification programs they support. However, these resources lack in depth and can be outdated with the rapid pace of 5G technology development. The opposite is true for the publicly available 3GPP specifications that include up-to-date information about conformance tests. However, they require a steep learning curve for non-wireless professionals and are not designed to address the test focus of all relevant certification bodies. Furthermore, as 5G technical features evolve, certification programs need timely updates to facilitate technology implementation in relevant use cases. However, this can be challenging especially when 3GPP-based conformance tests are not yet available for incorporation into certification programs (e.g., PTCRB) leaving early technology adopters with an unclear path to certification. Finally, a coordination effort among the various certification bodies (i.e., regulators, industry groups, MNOs) might result in streamlining the certification process and eliminating potential redundancies in the certification tests, which in turn can facilitate user access to novel 5G devices.

V. Conclusion

The integration of 5G connectivity into medical devices can bring innovative healthcare applications to patients. In this paper, we provide an overview of the existing certification programs for 5G UE devices, which encompass 5G-enabled medical devices. The summary covers 5G UE certification programs by FCC, PTCRB, and standard conformance and interoperability tests commonly requested by MNOs. Finally, we discuss challenges and knowledge gaps that are generally applicable to 5G UEs in addition to those specific to 5G-enabeld medical devices including the lack of evaluation methods to help assess the 5G-enabeld medical device unique needs for 5G communication capabilities and the challenge of reducing the set of test vectors given the large number of tunable test parameters.

Biographies

Yongkang Liu is a Staff Fellow with the Center for Devices and Radiological Health (CDRH), U.S. Food and Drug Administration (FDA). He received the Ph.D. degree from the Department of Electrical and Computer Engineering, the University of Waterloo, Waterloo, ON, Canada in 2013. Before joining FDA, he worked at the National Institute of Standards and Technology (NIST), Gaithersburg, MD on wireless research in vertical sector applications, e.g., process/automation control and industrial robotics. His current research is focused on investigating novel uses of wireless technology (5G/Wi-Fi/Bluetooth) in healthcare applications and test methods to promote safe and effective use of wireless technology in medical devices.

Mohamad Omar Al Kalaa is a Staff Fellow Electrical Engineer with the Center for Devices and Radiological Health (CDRH), U.S. Food and Drug Administration (FDA). He received the Bachelor’s degree in electronics and telecommunication from Damascus University, Damascus, Syria, in 2008, the M.E. degree in advanced telecommunication from the Ecole Nationale Superieure des Telecommunications de Bretagne, Brest, France, in 2012, and the M.Sc. and Ph.D. degrees in electrical and computer engineering from the University of Oklahoma, Norman, OK, USA, in 2014 and 2016, respectively. His research interests include the healthcare applications enabled by wireless technology, wireless coexistence of technologies in unlicensed bands, and wireless medical device testing methodologies. Dr. Al Kalaa currently serves as the co-chair of the medical device innovation consortium (MDIC) 5G-enabled medical device working group and is the secretary of the ANSI C63.27 standard for evaluation of wireless coexistence working group.