NR SA Radio Link Quality Test

This tutorial is a kind of Qualitative test rather than exact quantitavie test. So don't pay attention to the exact numbers... just try to get general understandings on radio link quality over the air link between UE and Callbox. It will also shows how handy the WebGUI would be for this kind of quick check. You would notice that the range of distance between UE and Callbox is pretty wide. Personally to me, the coverage for simple connection with low throughput is the widest with Amarisoft callbox comparing to other lab test equipment.

NOTE :  Strictly speaking, this test is more of coverage test for the equipment rather than radio link quality test. The main focus in this test is to check far I can move the DUT away from the equipment without call drop. The conclusion is that the DUT remain connected within 6 m distance without noticeable signal degredation.

NOTE :  The wide coverange as shown in this tutorial is suitable only for testing simple attach with lower data rate and for most of protocol function test, but it would not be good for high throughput test. If you want to achieve max (or near max) data throughput the distance between UE and Callbox Antenna should be very near or in some cases require RF connection (Conductive) between UE and Callbox.

Table of Contents

• NR SA Radio Link Quality Test
• Test Setup
• Configuration
• Perform the Test
• Radio Link Quality Change with Distance
• Initial Attach Success Check with Distances
• UL SNR Change with UL Rx Power

Test Setup

Test setup for this tutorial is as shown below.  This is just for low layer testing, you may not need any complicated IP layer setup.

• SIM Card used in this tutorial is the one delivered with the system as it is.
• If you want to change the configuration, The tutorial Configuration Guide would help

Configuration

I have used gnb-sa.cfg which is installed by default without any modification.

I am using the default mme, ims config as shown below.

Perform the Test

The way I perform the test in this tutorial is pretty much different from the case of other tutorials. In this test, you don't need to do much in terms of the operation of the equipment. Just establishing the connection is all that is required and the remaining part is just to move around with the UE (DUT). In this test, I moved the device farther away and closer to the callbox and observed various signal qualities in WebGUI.

Radio Link Quality Change with Distance

In this test, I checked  UL SNR, Data Rate, CQI value as I move DUT farther away from the Callbox and move closer to the Callbox. I noticed that overall signal quality (UL SNR) remain in relatively good condition across the entire range of the test.

NOTE : I checked only on Uplink Radio Link Quality because I analyzed the data on WebGUI on Callbox. If you want to check on the downlink radio link quality, you need to analyze the signal on UE sim (or other signal analyzer).

The throughput in this test looks very spiky. It is because the throughput generated in this test is ping. It is just to maintain the call connection with the minimum throughput demand.

Since I am analyzing the signal quality from callbox, I can do analysis of the signal quality with direct measurement only for uplink and no direct measurement for downlink. But we can at least get some indirect indicator for downlink signal quality by checking CQI report from UE. The observed result is that there is no significant drops for dowlink signal quality to cause call drop but fluctuation seems wider when the DUT is moving.

Initial Attach Success Check with Distances

In this test, I tried initial attach (Power Off and Power On UE) at various distances.

NOTE :  The purpose this test is just to show how to do quick check on signal quality. It is not to provide strictly verified test result. I just tried each of the test only once and didn't do repetative test for statistical analysis. So some test result would show a little bit counter intuitive result.

At the distance 6 m away from the callbox, SNR is observed relatively lower. However DL retx and UL rxko rate is not much different from other cases. (NOTE : if you push high throughput, you would see obvious differences in terms of retx and rxko)

At the distance 4 m away from the callbox, SNR is much higher comparing to the case of 6 m distance. However DL retx and UL rxko rate is not much different from other cases.

At the distance 2 m away from the callbox, SNR is much higher comparing to the case of 6 m distance. but it is lower than 4m case (this is a counter intuitive but it may just be test variation). DL retx and UL rxko rate is not much different from other cases.

At the distance 1 m away from the callbox, SNR is higher comparing to any other cases which is as expected.

UL SNR Change with UL Rx Power

In this test, I changed UL EPRE by changing rx_gain on callbox and check how UL SNR changes at different UL EPRE. EPRE drops strictly according to rx_gain drops, but SNR does stay same (no drop) within relatively wide range of EPRE drop.