Cell Reference Power

 

This tutorial shows how Amari Callbox specify Cell Reference Power for each radio technology (NR SA, LTE, NB IoT) and how you can verify it. CellReferencePower indicates the power of reference signal that is transmitted by eNB/gNB. UE compares this value broadcasted by SIB and the reference power it measures, and estimate the downlink pathloss based on the result.  Regardless of radio access technology, all radio technology broadcast this information (reference power) in one of SIBs. The IE (information element) name for each of the radio technology is as follows :

• NR : ss-PBCH-BlockPower
• LTE : referenceSignalPower
• NB IoT : nrs-Power-r13

NOTE : By default, Amarisoft eNB/gNB set these values in SIB automatically based on sdr card, frequency etc. But if you want, you can hardcode these values in SIB. Refer to this wiki for further details on hardcoding the reference power value.

NOTE : Unless specifically mentioned, all the measurement result shown in this tutorial is based on SDR50. You may get different result if you are using SDR100.

 

 

Table of Contents

• Cell Reference Power
• Test Setup
• Configuration
• NR SA Cell Reference Power
• LTE Cell Reference Power
• NB IoT Cell Reference Power
• Broadcast Reference Power Variation Among Software Release
• Release 2021-11-17 : NR SA Reference Power in SIB1
• Release 2022-04-01 : NR SA Reference Power in SIB1
• Broadcast Reference Power Variation with Channel Bandwidth
• Tips
• Differnce Between tx_gain and cell_gain

 

 

Test Setup

Test setup for this tutorial is as shown below.  

• 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

This tutorial is checking only on SIB transmission of each radio access technology. You may use any of the configurations that you want.

 

NR SA Cell Reference Power

Restart lte service and go to screen window. Get the basic phy information of the cell.

Enable SIB logging

Check ss-PBCH-BlockPower

 

Do some experiments to find the correlation between tx power of the call box and ss-PBCH-BlockPower set by the callbox

 

 

LTE Cell Reference Power

Restart lte service and go to screen window. Get the basic phy information of the cell.

Enable SIB logging

Check referenceSignalPowerr

 

Do some experiments to find the correlation between tx power of the call box and referenceSignalPower set by the callbox

 

 

NB IoT Cell Reference Power

Restart lte service and go to screen window. Get the basic phy information of the cell.

Enable SIB logging

Check nrs-Power

 

Do some experiments to find the correlation between tx power of the call box and nrs-Power set by the callbox

 

 

Broadcast Reference Power Variation Among Software Release

In most cases, the reference power broadcast in SIB does not change with Software Release, but in some rare case there might be some changes in the broadcast reference power due to various reasons (e.g, Calibration table adjustment).

 

Following is one example of Broadcast reference power of NR Cell between the two different software release.

 

Release 2021-11-17 : NR SA Reference Power in SIB1

 

Release 2022-04-01 : NR SA Reference Power in SIB1

 

Broadcast Reference Power Variation with Channel Bandwidth

Broadcast Reference Power varies with Channel Bandwidth As shown below. This is with SDR 50 and Callbox software release 2022-04-01

 

 

 

 

 

Tips

 

Differnce Between tx_gain and cell_gain

There are roughly two different ways to change cell power. One is to use tx_gain and the other is to use cell_gain. Whenever you change tx_gain, the reference power value in SIB gets changed but cell_gain does not change the reference power value in SIB message.