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The disruptive 5G technology

With ubiquitous, extremely-fast connectivity and seamless service delivery in all circumstances utilizing very high capacity infrastructure at tens of GHz frequencies, a 5G network will represent the most powerful, efficient and intelligent network the world has ever known. 5G technology enables a variety of techniques which will foster mobile communications to an unheard-off level. With expectations laying to support 1,000-times more devices than 4G with 100-times faster speeds and 10-times lower latencies, the challenge for test vendors is enormous. With a dramatic increase in user expectations on the network, the need to test devices and base stations solely on an OTA manner becomes essential. One of the most attractive use cases for 5G technology is the Internet of Things (IoT), which is expected to bring in billions of connected wireless sensors on the same communications network. Ubiquitous things communicating Massive MIMO (mMIMO) products generate agile beams for unparalleled accuracy in dynamic spectrum power placement. Beamsteering and beamforming techniques still have to prove its effectiveness on the field, and having the possibility of testing beamforming capacity or associated effects on latency are undoubtedly important prior to deployment. 5G networks have also brought extremely challenging requests to the test & measurement industry, ballooning testing complexity to a previously unseen level. The need for rapid, precise and simple OTA testing solutions is critical for identifying issues a priori and enabling fast prototyping cycle time during 5G product development.


5G OTA test methods

Three different 5G Device Under Test (DUT) antenna configurations and several 5G OTA test methods are being discussed within 3GPP TR 38.810, summarized in Table 1. The Reverberation Chamber (RC) method can be very useful for isotropic Key Performance Indicators (KPIs), particularly total radiated sensitivity (TIS) or spurious emissions, and recent progress has added the capability of directional measurements by means of either time-reversal or Doppler-discrimination effects. Non-conventional uses of RCs for 5G OTA measurements are also being explored, in particular for devices designed to function in directional-channel environments and for real-time OTA testing of throughput and latency. RC-based methods have some positive aspects for 5G Non-StandAlone (NSA) and Stand-Alone (SA) OTA testing, like considerably-reduced setup cost compared to other solutions for the complex multicarrier requirements of technologies. While spatial information may be partially lost in these rich multipath systems, an average 3D isotropic emulation of delay and final throughput performance, which is after all what the user perceives in a reasonable time slot, may very well serve the purpose. Yet, little progress has been made for 5G OTA using isotropic 5G channel model emulation using reverberation chambers and with RCs lack of strong support at 3GPP, it is not yet a 5G-standardized permitted test method.


Table I


Extending the multiprobe anechoic (MPAC) approach to 5G implies the use of 3D channel models and mm-wave operation, which makes it impractical due to the increase in complexity and the fact that too many probes would be needed, with their associated channel emulator ports, and the effect on the already-reduced quiet zone will be large. Although some simplified sectorized MPAC variations have been proposed, the additional need to operate in the far-field makes the use of MPAC for 5G OTA certainly very limited, at least at mmWave frequencies.

The incorporation of the Radiated Two-Stage (RTS) method into standardized 5G OTA testing is benefiting from an apparent harmonization to the MPAC method using seven 4G LTE FDD devices in single 2x2 single-carrier MIMO OTA mode, but the “Wireless Cable” is not transparent with respect to the DUT antenna characteristics, as these must be measured beforehand for the method to be applicable. In addition, the RTS method cannot yet support the User Equipment (UE) beamlock test function (UBF) for 5G UEs which is clearly a limiting factor for standardized OTA testing. On the other hand, the electrical size of DUT is only limited by the size of the test chamber.

The Indirect Far Field (IFF) Compact Antenna Test Range (CATR) method can create a plane-wave field in much less space than a Direct Far Field (DFF) method by means of a reflector, and it seems ideal for 5G mmWave OTA testing, but it has difficulties providing very different frequency ranges. With the options on the table CTIA operators have recently considered the IFF method as essential for consideration during development of the CTIA 5G NSA mmWave OTA Test Plan v1.0, due for release in 2Q 2019.

The Near Field to Far Field (NFTF) method relies on using a mathematical transformation to determine the KPIs in the far field from a near-field pattern scan. The NFTF method shows deficits with respect to testing during real-time operation of the device. Initially, Equivalent Isotropic Radiated Power (EIRP) and Total Radiated Power (TRP) have been reported to be measured by NFTF test systems.

The Direct Far Field (DFF) method requires Fraunhofer far-field distances and for mmWave frequencies it is not practicable due to the space and cost requirements and also the large link budget. Figure 1 illustrates how the far-field range for an N×N array of half-wavelength spaced elements increases dramatically as the size of the array increases. The hybridization of DFF for use at 5G Sub6GHz frequencies, however, may be quite useful since other methods present drawbacks at low frequencies.




It is clear that there is no single OTA method today capable of providing answers to all the questions. In consequence, several companies and institutions have called up for the development of new or hybridized test methods which can provide the required answers to the numerous 5G OTA challenges on the table. EMITE provides the only hybridized-methods 5G OTA test systems available in the market today.



Challenges for 5G OTA testing

EMITE has published a Technical Feature on 5G OTA testing challenges at the February 2019 issue of Microwave Journal, which you can access here.


EMITE OTA Test Systems copy


A. Fully-integrated antenna arrays
In addition to a densely antenna-populated layout, illustrated in figure 4, and unlike previous generations, 5G UE antenna arrays do not provide access to their RF ports due to small form factor and higher frequencies for some bands. Testing connector-less antenna arrays is an obvious challenge, which forces RF tests and calibrations to be performed Over-The-Air in a well-controlled environment. Phase calibration between the chains is typically required in addition to signaling performance tests and power measurements. The fact that coupling may occur and the limitations of the testing enclosure makes the coherent calibration of each RF chain not necessarily leading to optimal beams. The presence of up or down conversion when operating at mm-Wave frequencies further complicates the testing equipment.

B. DUT form factors
Each DUT form factor type has specific requirements and restrictions. Chipset 5G OTA measurements can be defined as the test that provides the chipset RF performance evaluation in the real standalone environment. It is good that chipsets are small since the mm-Wave wavelengths of some 5G frequencies are also small, and therefore the issues with large far-field distances are minimized. The problem arises due to the fact that the chipsets usually do not have RF connectors and are also very fragile. Two other chipset-specific challenges for 5G OTA testing are the need to accurately control temperature and humidity cycling within the chamber due to the chipset being extremely sensitive to environmental conditions, something that is not at all a trivial task, and the fact that for mass production chipsets may need to be measured in the form of panels. With each panel containing a lot of similar type of chipsets, their accurate and individual 5G OTA testing becomes a very challenging task. Controlling the temperature and the humidity within any OTA test environment is also an extremely challenging task, and only two companies have announced such feature at their test systems, R&S and EMITE. 5G OTA UE testing is thought to be, at least initially, compatible with legacy 4G technologies. While it has been proposed that in consequence 4G OTA methods should be first attempted to for the new 5G devices, it is also clear that 5G OTA testing will further complicate if we also have to support 4G OTA testing in a simultaneous manner. gNodeB testing, in addition to their associated larger size, also requires phase coherency calibration, which is currently a concern due to the large number of channels. The specific OTA measurements challenges of high directivity beam performance, not only for the gNodeB end but also for the 5G UE end, deserve its own section in this technical feature.

C. Spatial agility
Spatial intelligence is yet another key performance aspect of 5G. 3GPP has defined centered and off-center KPIs for static beams, but the beam dynamics are an inherent part of 5G. Processes such as beam searching, beam matching, beam tracking, beam forming or beam scheduling, among others, become essential when the UE moves dynamically. When the gNodeB incorporates massive MIMO (mMIMO), the spatial non-stationary property, the angular spreads and the 3D spatial properties cannot be ignored, and since the number of probe antennas is large, the channel between different probe antennas has a strong correlation, and removing the impact of the channel correlation across gNodeB antennas and probes remain an issue of concern. Finally, the addition of multiuser bidirectional channels introduces yet additional challenges to the OTA test. Interestingly enough, the whole 5G gNodeB-UE end to end (E2E) set seems to be attracting most attention, as it is the pair that provides a specific user-performance. Extraordinarily complex cascaded chamber sets are being proposed for this type of testing, aiming at getting accurate and realistic KPI evaluation versus range when using power-fix connector-less gNodeBs in one end and a moving UE on the other end. In this type of OTA test setup, illustrated in figure 5, for NR beam steering, beamforming or baseband beam tracking algorithms performance testing, real-time throughput, latency and mobility tests are being proposed. One chamber captures the 5G signals coming from the gNodeB and redirects them to a channel emulator and an attenuator matrix, which in turn attenuates and re-route the signals to a second chamber, an RC or AC, in which the 5G UE is located. This clearly represents a breakthrough over previous single-chamber OTA test setups, with a lot more complexity, associated required expertise and cost. A real challenge, but already in operation.

D. Channel modelling
Realistic channel modelling represents yet another key aspect of 5G OTA testing. Several studies have found some extensibility of the existing 3GPP channel models to be somehow applicable at higher frequency bands up to 100 GHz. The measurements indicate that the smaller wavelengths introduce an increased sensitivity of the propagation models to the scale of the environment, which is to be expected, and show some frequency dependence of the path loss as well as increased occurrence of blockage. Furthermore, the penetration loss is highly dependent on the material and increases with increasing frequency of operation. The shadow fading and angular spread parameters are larger and the boundary between line of sight (LOS) and non-line of sight (NLOS) depends not only on antenna heights but also on the local environment. This has simplified some initial proposals, but the main drawback remains, that is, how to model a signal which is divided into several carriers and MIMO paths which can extend from very different frequency bands. It is expected that FR1 + FR2 bands will be successfully combined, providing total user throughputs in excess of tenths of gigabits per second and new channel modelling challenges.

E. The future is here
5G is expected to bring unheard-off benefits for the wireless communications industry, but it also carries the need for drastic changes in the way OTA is tested today. Performance metrics and cost-efficient ways to measure them in a lab close as possible to what the operation will be in real networks is urgently required. This will necessarily include testing in the main beam, testing in the presence of other radios in same channel and testing the communication performance against interference from different directions, evaluating also the dynamic adaptation performance of both ends, the UE and the gNodeB sides.
While quite some progress has been made, consensus-based 3GPP standardization is far from reaching the goal, and is currently limiting the scope of what could be achieved in terms of solving the existing real challenges. Failure to meet the expectations is unthinkable at this stage of the process, and developing accurate and realistic OTA test methods is also the responsibility of the scientific community, who should provide the wireless communications industry with non-profit-oriented technically-based optimal solutions, those which can really provide what is being looked for. We are still in time, but it is rapidly running out, and using EMITE unique portfolio of 5G OTA test Systems can undoubtedly shorten the path to success.




Inaugurated in December 2017, EMITE 5G Lab is located at the ELDI Cátedra de Empresa building of Universidad Politécnica de Cartagena. EMITE 5G Lab was open with the support of several important founding members and collaborators including several carriers (Vodafone and the leading Australian operator), test vendors (National Instruments), the Centre Tecnològic de Telecomunicacions de Catalunya (CTTC) and OEMs (Sony Mobile Communications), which have signed a Memorandum of Understanding with EMITE to develop advanced and useful OTA test solutions for 5G using the partners’ knowledge and individual equipment developments.

5G Lab

EMITE’s 5G Lab will undoubtedly contribute to a faster development of fully-operative 5G OTA test systems targeting carriers’ requirements for realistic OEM’s capabilities.

EMITE 5G Lab has already produced some customers including carriers, original equipment manufacturers (OEMs) and network infrastructure vendors (NIV)







EMITE Test System solutions for 5G OTA testing

Thanks to a very solid OTA testing background, EMITE has released the perfect modular and upgradable set of chambers for 5G OTA testing, starting with the most advanced Reverberation Chamber (RC) in the market, the E600 but also with a unique patented hybrid Reverberation/Anechoic chamber for massive MIMO OTA testing, the F200, and with the release of a new 3GPP-permitted Anechoic Chamber (AC) for both Sub-6 GHz and mm-Wave 5G OTA testing, the H-Series, which incorporates in a single test system all three 3GPP-permited 5G OTA test methods, the Direct Far Field (DFF), the Indirect Far Field (IFF) with a Compact Antenna Test Range (CATR) and the Near To Far Field Transformation (NTFT) through an Spherical Near Field (SNF) range. The EMITE motto of making things simple remains applicable to the new 5G OTA Test Systems, with upgrade paths from existing 4G test chambers, always providing the best value-for-money for our customers.

5G OTA production testing for mm-Wave chipsets and devices can also be performed with our PT-Series. Techniques that traditionally relied on direct wired connector access to the radio are no longer possible, and from simple GO/NOGO tests to more complex non-signaling OTA tests, the PT50 Reverberation Chamber can fulfil your 5G OTA Production testing needs. With up to 8 DUTs being simultaneously OTA-tested in parallel, production testing for 5G has never been so easy. PT-Series

For 5G small devices and base stations OTA testing, the E-Series Reverberation set of Chambers can provide for 5G OTA testing of TCP, UDP and FTP Throughput versus range, providing overall sum Throughput figures at different OSI layers using a RRU + BBU setup, a parameter of the outmost importance for real 5G networks. 5G upgrade paths to 30 and 40 GHz from E500 and E600 RCs are available. E-Series

For standardized 5G OTA testing of wireless devices, the H300 anechoic chamber provides complete 3D performance assessment for 5G OTA devices and antennas including gain, efficiency, directivity, polarization and beam characteristics for frequencies from 600 MHz up to 110 GHz, capable of testing 3GPP 38.101 key performance indicators and in accordance to 3GPP TR38.810 and TR37.842. Being the only 5G OTA test system in the market capable of testing FR1 Sub-6 GHz and FR2 mmWave frequencies in a simultaneous manner and with a unique climatic enclosure for both control and set of temperature and humidity at the DUT, the H300 is undoubtedly the best-in-its-type worldwide for standardized 5G OTA testing. H-Series

The largest 5G OTA test platform by EMITE, the F-Series Hybrid Anechoic/Reverberation set of Chambers, allows mobile operators to test their gNodeBs prior to massive deployment, flexibly customize RF patterns in real time to foresee techniques to dynamically manage network capacity and coverage, including scenarios with diverse fading conditions and the introduction of diverse types of interference. Real mMIMO RRUs can be tested and benchmarked, with some novel figures of merit like beamforming capacity. F-Series

Combinations of the above systems is also possible to overcome some of the testing limitations imposed by connector-less 5G elements and subsystems, or to add realistic fading and an extremely large number of virtual devices. The pictures below illustrate complex single-chamber and cascaded-chamber setups for 5G OTA testing by EMITE, made in partnership with different top test equipment vendors.


f200b2 e600



For a 5G OTA tailored presentation or life demonstration, please contact our sales department in your region or email us at This email address is being protected from spambots. You need JavaScript enabled to view it.



EMITE, your 5G OTA Test Partner