This blog post is based on a webinar presentation given by Khushboo Kalyani. It outlines why it is important to test 5G product performance and how product designers can tailor a manufacturing test plan to a product’s performance. 5G is the newest technical standard for wireless networks, and it is expected to have a huge impact on consumers and businesses around the world. 5G is expected to support a variety of industry verticals with a massive number of new devices from IoT sensors to wearables. You will learn about 5G capabilities and market adoption, end-product test methodologies, why end-of-line signaling test is important and what are some essential test items in manufacturing. 

5G is unique among cellular technologies in that it offers a range of application benefits not seen in previous cellular generations. These include:

• Higher data rates than 4G – up to 10 gigabits per second. 
• Wider bandwidth – up to 1200 MHz when using carrier aggregation.
• Ultra-low latency of less than 1 ms.
• Network slicing allowing for specialized services for specific applications.

Because of these technical and performance advantages, 5G is driving the industry to pay attention to product quality and performance like never before. 

5G is off to a fast start with a market adoption rate that is almost four times faster than 4G/LTE. Statistics show that in 2020 there were more than 200 million 5G subscriptions globally; by the end of 2021, worldwide 5G subscriptions exceeded 500 million, and by the end of 2022 5G is expected to surpass one billion users. (See Figure 1.)

Source: Ericsson Mobility Report
Figure 1: Comparison of 5G (orange line) and 4G (green line) subscription uptake in the first years of deployment.

Considering the surging rate of adoption and diverse technical requirements, 5G end-user products need to be delivered in the fastest time to market at the same time maintaining superior quality and performance. This entails paying close attention to test methodologies involved in the product life cycle. From the standpoint of a wireless product during manufacturing there are two test methodologies that can be used:

1. Non-signaling Test
2. Signaling Test

Let’s understand the details of both these test techniques.

Cellular Non-Signaling Testing

Cellular non-signaling is a non-call processing test methodology with fundamental focus on calibration and verification of a device’s transmitter and receiver performance (see Figure 2). 

Figure 2. Conceptual block diagram of a RF transceiver.

In this test technique (see Figure 3), the tester and the test application make use of the chipset-specific test mode to take direct control of the device under test (DUT) over a serial connection to measure pre-defined transmission patterns. With this test method, no real-time network emulation or end-to-end call registration is required, thus eliminating the overhead associated with configuring both the DUT and the test equipment for network emulation. Which is why, cellular non-signaling test methodology is highly optimized for production environments and offers better economics and faster production test times.

Figure 3. Methodology for 5G non-signaling testing.

Signaling Testing

Unlike non-signaling test, signaling test is a call processing technique necessitating an end-to-end device registration and call establishment between the test equipment and the DUT. 

In a real-world scenario, any communication between a device and a base station involves the exchange of a sequence of control and user plane signaling messages. This includes (but is not limited to) decoding the broadcast channel, performing downlink and uplink synchronization, setting up the control channel, performing device authentication and security procedures, exchanging device capabilities, establishing protocol data unit sessions to facilitate user traffic exchange and much more. Below is an example of some significant control and user plane events:

Control Plane Events

• Attach and detach procedure
• Connection release and re-establishment
• Detection of radio link failure and recovery
• Dedicated bearer establishment and deletion
• Enhanced dual connectivity (EN-DC)
• Idle mode mobility
• Roaming and handover
• Connected and idle mode measurements

User Plane Traffic Events

• Voice call 
• Conversational video
• Data upload and download
• Email
• Instant messaging
• Voice mail

Figure 4. Seven-layer 5G protocol stack.

The exchange of this messaging is facilitated by the layers forming the 5G protocol stack (see Figure 4) performing distinct and crucial functions like signal modulation/demodulation, segmenting and assembly of data packets, numbering and orderly delivery of the packets, managing air resource control, retransmitting packets when needed and several other functions. 

In a standard lab environment, a signaling test methodology is employed to validate the device behavior and the sequence of control plane and user plane events underlying a typical user experience scenario and identifying defects at each protocol layer.

In signaling tests (see Figure 5), a network emulator is required to simulate the live network conditions and to generate a combination of control plane and user plane traffic to measure the true performance of devices under realistic channel conditions. In this procedure the test equipment has no direct control of the chipset and enables test and measurement across the entire protocol stack right from physical layer to application layer either over the air (OTA) or using a cabled connection between the DUT and the test equipment.

Figure 5. Signaling tests are needed for next generation 5G devices.

Considering this test technique is focused on device functionality testing, it is commonly used in research and development, design validation and field testing for real world scenario testing.

Having briefly understood the two test methodologies- signaling and non-signaling test-it is evident that the two are designed to accomplish distinct test needs and are optimized for use across different product life cycles. Non-signaling is a more targeted approach – cost- and time-optimized for manufacturing. Whereas signaling is a comprehensive approach and may take longer based on the test plan. However, as 5G continues to be widely employed, the subsequent section highlights the relevance of signaling test for 5G devices even at manufacturing/ end of line (EOL).

Expanding World of 5G Devices

There is an ever-expanding need for hyperconnectivity, large data traffic, reliability, lower latency, monitoring, and tracking. And 5G cellular wireless will be embedded in a much broader set of devices beyond traditional smartphones, laptops and PCs ranging from industrial sensors to wireless watches and other personal devices. Here are some key reasons driving the need for user experience testing at EOL:

1. Newer Form Factors Being Equipped with Cellular Capabilities 

5G has unique technical capabilities that are being adopted by different industry verticals that often use innovative and new devices that have never been equipped with cellular capability and thus have not been tested for reliable connectivity (see Figure 6). This underlines the importance of performing extensive hardware testing as OEMs and manufacturers need to reevaluate their existing manufacturing test setups to accommodate the new form factors and testing needs with respect to OTA chambers, cables, or any other test fixture required to ensure the device performance is within the tolerance levels. Additionally, based on the products’ real world use model it is essential to tailor the test plan to meet each product’s performance to ensure repeatability.

Figure 6: Non-wireless products that are being equipped with cellular capabilities.

2. Growing Use of 5G Module-Based Devices

As the 5G use model diversifies with increasing number of small players, the use of pre-certified, RF modules continues to increase exponentially due to lower barrier to entry and associated development costs. Predominantly, each module is individually tested and comes pre-calibrated and hence the temptation might be to not conduct a separate quality test during assembly and manufacturing. But a typical final product might also have other modules such Wi-Fi, GPS, Bluetooth^®, a SIM card, battery, speaker microphone, millimeter wave antenna module, and others. When any subset of these is packaged together – especially in a non-traditional product – there could be interference and coexistence situations that reduce wireless performance even if each module is separately tested and in compliance. 

Antenna performance is a good example of this. When packaging the final product, hardware casing and tuning errors can cause signal loss and impact the antenna radiation pattern, leading to communication failures. Dropped calls, poor reception and downloads could result from improper antenna installation, or in-device coexistence issue between Wi-Fi/Bluetooth^®/cellular modules causing transmitter power from one antenna increasing noise power at another receiver causing interference and thus decreasing sensitivity. A few other common and basic issues are call registration failures or SIM connectivity issues which could be a result of software and/or firmware issues. Scenarios like these strongly suggest the importance of testing the final product in its entirety to ensure signal quality is within the acceptable levels of transmission and reception over the device’s range of operation and to ensure holistic device performance when deployed in the real-world. 

However, in practice, testing at manufacturing and assembly is fairly time constrained which is why regressing through exhaustive hardware and software capabilities is not possible. For that reason, the test plan must be tailored in a way that examines the vitals of the final product warranting the basic user experience functionality in a real-world scenario. With that in mind below is a checklist of top-level test areas that must be evaluated using signaling test to ensure quality device performance:

1. Basic device registration and call procedure

To ensure end-to-end product functionality. Hardware and software components could potentially impact DUT’s wireless performance.

2. Antenna performance

Final product casing, implementation and tuning errors could cause signal loss and impact the antenna radiation pattern leading to communication failures.

3. RF performance

To ensure signal quality is not heavily degraded under real-world conditions with acceptable levels of signal transmission and reception over the supported bands of operation (mobility).

4. Data Throughput 

With the surging data consumption trends its crucial to validate in user applications. This is to ensures that the device can sustain and handle a variety of levels of user plane traffic and quality of service requirements. 

5. Advanced functional features

In reality, cellular devices are meant to do much more than basic call and registration with the network. Typical device use models like voice over new radio (VoNR), SMS, internet browsing, file transfers, and others are some of the key functional features to verify the device’s real-world performance. 

In summary, signaling may be time consuming and complex but it is important to ensure holistic device performance. A comprehensive test plan that covers device registration and call procedure, antenna quality, RF performance, data throughput and advanced functional features is the minimum needed to ensure that the end-product quality… In the long run this will help recognize product flaws prior and minimize returns from the field.