Allion Labs

In this article, we’ll discuss the 6.4.3 Downlink MU-MIMO Performance Test. In the context of the TR-298 Issue 2 Corrigendum 1 Test Plan, if the AP supports 4SS or more and also downlink MU-MIMO, this item is required for testing.

Test Summary

The main concept of 6.4.3 Downlink MU-MIMO Performance Test is to connect the AP through one 2SS antenna and two 1SS wireless devices (STA) to measure the throughput. The throughput is measured under different conditions to determine whether performance can be improved when the downlink MU-MIMO function is enabled. During the test, the OFDMA function of the AP will be disabled first. This step is only meant for the APUT that supports 11ax. Afterward, three downlink throughput tests will be conducted.

  1. Conduct a separate throughput test with the downlink MU-MIMO function enabled for each wireless device, including STA and APUT.
  2. Conduct a throughput test simultaneously for each wireless device with the downlink MU-MIMO function enabled
  3. Conduct a throughput test simultaneously after disabling the downlink MU-MIMO function of each device. This test is optional since some APs do not support the function of disabling the downlink MU-MIMO.

Picture: The different stages of the 6.4.3 test

Test Standards

The test will be divided into two parts, and both standards have to be met to pass the test. The first standard states that the total throughput of the second test must be greater than the first test. The second standard states that the total throughput of the second test has to be greater than that of the third test, the premise being that the AP supports disabling the downlink MU-MIMO function. The meaning behind these two standards is to determine if the performance is better when the downlink MU-MIMO is enabled.

Common Problems

In the 6.4.3 Downlink MU-MIMO Performance Test, most of the APs that fail the test just fail to meet the first standard. For example in the table below, the sum of the second throughput tests is 849.65 Mbps, which is 45% lower than the sum of the first throughput tests.

Table: Test results of the 6.4.3 Downlink MU-MIMO Performance Test.

Test Suggestions

According to our experience, we found that when the AP fails to pass the test, there are two common reasons. First, we can check if the OFDMA is disabled before the test. Generally, this function is enabled by default, so we’ll ask our clients to disable it before testing. Second, the antenna may have problems. Since the downlink MU-MIMO function can be affected by the way the antennas are set, we usually ask our clients to properly align the antennas so it is easier to pass the test. These are the two common suggestions we give our clients when they want to pass the 6.4.3 Downlink MU-MIMO Performance Test.

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Technical Highlights