LTE Testing moves ‘Far afield’

Complexity of testing requires lab-based environment to reproduce real-life scenarios

Paul Beaver-Anite

Paul Beaver, Products Director, Anite

There is no denying that consumers are driving the massive expansion of mobile data consumption supported by enhanced HSPA+/ LTE networks and services. LTE presents operators with a complex new environment that requires a highly capable testing solution that can address a broad range of factors including MIMO, interoperability and data throughput.

In order to quantify and qualify the key performance considerations of throughput, interoperability and radio/antenna performance, it is necessary to establish a testing environment and methodology that produces precise, repeatable and reliable results. The testing environment and associated testing methodologies must be highly flexible and reconfigurable to accommodate the expanding number of test configurations. Not only that, it must be capable of managing a large number of variable parameters and permutations and isolation of variables. This include items such as frequencies, power levels, channel bandwidths, radio technologies, RF channel conditions and network loading conditions. A high level of automation is critical so that tests can cycle through numerous iterations of variables, channel/network conditions and configurations unattended.

Automation enables 24-hour testing and provides cost and time efficiencies when compared to manual testing. Ultimately, the test environment needs to replicate/recreate, as near as possible, the real-world environment, conditions and performance of the device that the user experiences.
A controllable, repeatable and flexible test environment can only be delivered through laboratory testing. Prior to final product release, whether it is chipset, device or network equipment, tests are typically performed in a conducted environment. This means that the equipment under test (EUT) is connected by a cable to the test and measurement equipment. Connection by a cable means that the antennas are removed and the cables is/are connected to the antenna ports of the EUT.

In order to quantify and qualify how a device performs against the key considerations of throughput, interoperability and radio/antenna performance, it is necessary to establish a testing environment and methodology that produces precise, repeatable and reliable results. These must also be flexible and reconfigurable to accommodate the variety of test configurations.

Another important factor is the need to provide a high level of automation, so that tests can cycle through numerous iterations of variables, channel/network conditions and configurations unattended. Automation enables 24-hour testing and provides cost and time efficiencies when compared to manual testing.

The controllable, repeatable and automated test environment described above can only be delivered through laboratory testing. Prior to final product release, whether it is chipset, device or network equipment, tests are typically performed in a conducted environment. This means that the EUT is connected by a cable to the test and measurement equipment, with device antennas removed and the cables connected to the antenna ports of the EUT.

While all the key performance items such as throughput, audio quality and radio performance can be quantified and qualified under conducted test conditions using signal generation/measurement and channel emulation equipment with the EUT, it is recognised industry practice to supplement this by testing the EUT in its final configuration, i.e. with the antenna(s) attached. With the antennas attached, performance testing is then performed with the signal being transmitted/received through the antennas, which is called radiated testing. For many years, radiated testing was performed in the field. However, field testing can be time-consuming and difficult to replicate.

Test equipment companies have continued to improve the techniques used to replicate the real-world environment in the lab. Two recent and important capabilities have been added to provide more realism to conducted and radiated laboratory testing.

The improvements for radiated testing involve testing the EUT in the lab (versus field) inside an RF anechoic or reverberation chamber with specially-modified channel models. This testing technique, known as MIMO OTA (over-the-air) testing, allows utilisation of “real-world” channel models, thus achieving the goal of closer-to-reality testing as well as being able to test in a configurable and controllable laboratory environment.
Ultimately, the test environment needs to closely replicate the real-world environment, conditions and performance of the device that the user experiences. For complex LTE devices, virtual drive testing and MIMO OTA testing supplement conducted and field testing to provide superior device testing environments, covering both physical layer performance aspects (e.g. throughput) and application-related performance aspects (e.g. battery performance).

 

Columnist: Paul Beaver, Products Director, Anite

(As Products Director within Anite’s Handset Testing business, Paul Beaver is responsible for product strategy and R&D. Paul joined Anite in 1997 and has held a number of positions in the company and has been instrumental in developing Anite’s strategy to enter new markets and expand the product portfolio.)

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