Why MIMO OTA Testing is Needed

Traditionally SISO and MIMO capable devices have been tested with both conducted and radiated testing methods. DUT (device under test) has been cabled to the test equipment by antenna connectors which bypasses the device’s antennas and parameters to measure for example the throughput of the device. In addition to this, the device has been tested by carrying out OTA testing in an anechoic chamber to characterize the antenna performance by measuring Total Radiated (TRP) and Total Receiver Sensitivity (TRS/TIS). In traditional OTA testing, each antenna is usually measured individually.

When testing the MIMO systems’ performance, the methods described above are usually insufficient. This is because MIMO device performance testing is highly sensitive to different factors such as propagation environment, antenna design, antenna orientation, and base band algorithms. Traditionally MIMO systems have been tested by cabling and bypassing the antenna. But the downside of that is that cabling and bypassing the antennas can greatly impact the MIMO system’s performance results. This is why MIMO OTA testing is needed. Cabling and antenna bypassing are not required in this test method.

TRP and TRS/TIS are good factors to consider when evaluating the performance of SISO devices. Nevertheless, since MIMO systems’ performance is easily affected by various factors it needs to be evaluated in a different way. Most of the time, well-performing and poorly performing MIMO systems are differentiated by examining the differences in data throughput measured under realistic radio environment conditions (such as city centers), created by channel emulators.

MIMO OTA Testing in Verkotan’s Anechoic Chamber

Verkotan performs MIMO testing in an anechoic multi-antenna test system, which enables performance testing under realistic radio environment in a controlled laboratory setup. The principal components of the test system include the communication tester, channel emulator, test antennas and the anechoic chamber.

The downlink signal generated by the communication tester is fed through the channel emulator, which applies a spatial channel model to the signal. The spatial channel model contains the signal propagation information of the radio channel. Radio channel features, such as time varying amplitude, phase, delay and doppler shift due to multiple reflections and device movement in a dynamic environment are simulated. The spatially faded signal is then fed through 8 dual polarized antennas situated in a ring formation in the anechoic chamber, and a realistic MIMO channel is created at the test zone. The spatial channel emulated at the test zone makes it possible to test the performance of a wireless device in a repeatable test environment, with the device in normal operating mode.

The current industry standards for OTA MIMO testing describe methods for testing MIMO in 2×2 mode. Wireless devices on the currently on the market already support higher order MIMO modes. The anechoic multi-antenna method extends naturally to testing of higher order MIMO modes, for example 4×2 and 4×4 MIMO. When testing higher order MIMO modes, the spatial channel model is extended to include additional signal paths, and a higher order MIMO capable communication tester is used. Verkotan has implemented 4×2 and 4×4 MIMO OTA testing capability in its MIMO OTA test system.

Verkotan’s MIMO OTA Testing Services

• CTIA MIMO OTA Pre-Conformance Testing

We offer CTIA MIMO OTA pre-conformance measurements according to the newest CTIA specification.

• Fast MIMO OTA Testing

Fast MIMO OTA is a replacement for CTIA MIMO OTA and is extremely efficient for R&D purposes. The test cases provide similar results to the CTIA MIMO OTA testing but testing itself is 2 to 10 times faster.

• Advanced MIMO OTA Testing for R&D

We are able to provide MIMO OTA measurements for devices that supporting 4×2 MIMO and 4×4 MIMO.

Verkotan is always happy to provide more detailed information and make a proposal how we can verify the performance of your wireless device in the global environment.

If you have any questions or need assistance, contact us. We are happy to help you!