As part of the RCR Wireless Test & Measurement Forum, LitePoint’s Khushboo Kalyani shared some 5G product development challenges and testing strategies.

5G is an exciting market with new services, capabilities and applications driving big growth in data consumption. Ericsson’s Nov. 2021 Mobility Report estimates that at the end of 2021, between 70 – 80 exabytes of mobile data was consumed monthly – and that this will grow to 370 exabytes of data per month by 2027.

To develop successful 5G products for this market, product design teams must deal with increased RF complexity that comes with 5G including more RF bands, wider bandwidths and support for multiple antennas. 

Testing these systems thoroughly during R&D, at design verification and at manufacturing is critical to success. And while pre-engineered RF modules can help to simplify the addition of 5G to a product, these modules don’t alleviate the need for product testing.

The Importance of Spectrum

One of the challenges of 5G is a higher user density with more devices per cell sharing the 5G spectrum and network resources. This calls for a judicious use of the 5G spectrum. There are huge expectations for 5G – high data rates, low latency, private networks, Internet of things, low-cost broadband and more – and the key to delivering is spectrum.

The industry is adopting new spectrum efficiency tools including reframing existing spectrum from 2G/3G/4G for 5G use. Other techniques include carrier aggregation, multiple input-multiple output (MIMO) antennas, or higher signal modulation in order to improve data rate. Opening up new spectrum is another solution. Regulators have added more mid-band spectrum to support 5G; just last year in the US the FCC opened up spectrum in the 3.45 GHz, 3.7 GHz. and 3.98 GHz bands. 

5G devices must support newer spectrum as it becomes available, which increases device complexity and also has an impact on testing at each phase of development: R&D, device verification test (DVT) and manufacturing. This impacts time to market, testing time and cost of test. 

From a hardware design perspective, there are two extremely important and critical changes. The first is the increase in RF chains. Unique and discrete RF chains are required to support additional bands, bandwidths and carrier aggregation combinations. Second, is an increase in antenna count needed to support each of the RF chains as well as MIMO schemes. 

These changes drive significant test validation needs for devices:

• RF parametric for extensive calibration and verification of devices across different bands and bandwidths. This is needed to ensure the wider bandwidth requirements are not causing any adjacent channel leakage resulting in interference, and there is adequate RF filtering to avoid RF signal overlap, etc.
• Antenna pattern measurements across all antennas for both sub-6GHz and mmWave antenna modules. This testing requires an over the air (OTA) environment and can help identify any issues related to antenna tuning, assembly and impedance match, that could impact the antenna performance or cause impairment in call reception or registration. 
• Functional verification such as call registration, call handover and latency across all carrier aggregation combinations. Each one of the carrier aggregation combinations has some signaling overhead, so these tests ensure this latency doesn’t impact performance. 
• Application level throughput testing with MIMO to verify the performance of the primary and diversity antenna chains. 
• User experience testing to evaluate the impact of software changes on final packaged product performance or functional device behavior.

Test Challenges & Solutions

5G spectrum complexity makes it more important to test products, and creates test challenges that product developers or manufacturers must be aware of. These include:

Increased test case count: testing a new 5G device requires multiple – potentially thousands – of test cases to be designed, developed, and executed to test and verify myriad combinations of bands, MIMO, modulation schemes, etc. This increases test time, which contributes to a longer time to market.  

The answer to this challenge is to build test cases that are specific to the SKU thus optimizing test development and execution time. Furthermore, deploying a turnkey, high-speed automation test tool, which allows for easy customization and development of test flows and enables hardware and software regression of critical device metrics spanning RF parametric, functional, and throughput cases would significantly minimize debug and analysis thus improving time to market.

Finite tester port count and resources. The increased number of antennas due to more frequency bands and support for up to 8×8 MIMO requires higher tester port density for conducted testing. Again, this increases the cost of test because it requires additional investment in upgrading existing capacity or buying new test equipment. 

To overcome this physical limitation, the choice of an RF port expander to increase tester port density will facilitate reuse of existing capacity and enable testing of multiple antennas and DUTs. Moreover, the companion tester that is chosen must be able to enhance multi-DUT test efficiencies thus reducing test time and lowering operational and equipment costs.

Non-signaling test is not enough. Many of the products that use pre-calibrated, pre-certified 5G modules, leave OEMs to think they can perform only non-signaling testing on these devices. However, once packaged together with other wireless modules (Wi-Fi, Bluetooth, GPS, etc.) there’s a possibility of interference that can degrade wireless performance. Non-signaling testing of these products won’t catch these issues.  

The solution for this challenge is to conduct a signaling test that will aid in validation of the product performance through the establishment of an end-to-end user plane call. This signaling test will examine the vitals of the final packaged product to warrant basic user experience functionality and minimize returns from the field. 

Conclusion

The rising need for data capacity and lower latency in 5G devices is being provided by the growing use of 5G modules and the addition of newer spectrum bands – but these have led to increased device complexity. To meet rapid 5G adoption demands, a different approach to testing must be undertaken to continue to ensure quality device performance, and, at the same time, control cost and complexity. If you want to hear more from Khushboo’s 5G testing presentation at RCR Test & Measurement Forum go here: https://www.testandmeasurementforum.com/home