NR SA SearchSpace0

The purpose of this tutorial is to see how SearchSpace0 is configured and verified. In terms of test configuration and test procedure, it is very simple. Just configure a few configuration settings in enb.cfg and run the test. you don't even need to connect any UE. All you need to do for verification is to enable lower layer logging and MIB/BCCH.

It is assumed that you already have basic understandings on what is the SearchSpace 0 (If you are not familiar with the concept of the coreset itself, I would suggest to check out this note). SearchSpace0 is the search space where DCI for SIB1 PDSCH is allocated.

i) define various predefined set of configuration in 3GPP specification (both gNB and UE should have these predefined table in it)
ii) Inform the UE on which table and which index of the table to use via MIB (PBCH)

The summary of this mechanism would be illustrated as below (as per my understanding).

NR SA CORESET0 01

Image Source : SIB1 decoding Procedure in Sharetechnote

In 3GPP, SSB SCS,PDCCH SCS, Min BW determines which table to apply and the MIB parameter determines the index of the selected table. In Amarisoft gNB, SSB SCS,PDCCH SCS, Min BW determines which table to apply and the index of the table is specified in enb.cfg. (The index specified in the configuration file is populated in MIB).

NR SA SearchSpace0

Key Configuration Parameter
Test 1 : SSB index 0 or 1, SearchSpace 0 = {0,..,15}

Sub Test 1 : SSB index 0, SearchSpace0 = 0

Configuration
Perform the Test
Log Analysis

Sub Test 2 : SSB index 0, SearchSpace0 = 1

Configuration
Perform the Test
Log Analysis

Sub Test 3 : SSB index 0, SearchSpace0 = 2

Configuration
Perform the Test
Log Analysis

Sub Test 4 : SSB index 0, SearchSpace0 = 3

Configuration
Perform the Test
Log Analysis

Sub Test 5 : SSB index 0, SearchSpace0 = 4

Configuration
Perform the Test
Log Analysis

Sub Test 6 : SSB index 0, SearchSpace0 = 5

Configuration
Perform the Test
Log Analysis

Sub Test 7 : SSB index 0, SearchSpace0 = 6

Configuration
Perform the Test
Log Analysis

Sub Test 8 : SSB index 0, SearchSpace0 = 7

Configuration
Perform the Test
Log Analysis

Sub Test 9 : SSB index 0, SearchSpace0 = 8

Configuration
Perform the Test
Log Analysis

Sub Test 10 : SSB index 0, SearchSpace0 = 9

Configuration
Perform the Test
Log Analysis

Sub Test 11 : SSB index 0, SearchSpace0 = 10

Configuration
Perform the Test
Log Analysis

Sub Test 12 : SSB index 1, SearchSpace0 = 11

Configuration
Perform the Test
Log Analysis

Sub Test 13 : SSB index 0, SearchSpace0 = 12

Configuration
Perform the Test
Log Analysis

Sub Test 14 : SSB index 1, SearchSpace0 = 13

Configuration
Perform the Test
Log Analysis

Sub Test 15 : SSB index 0, SearchSpace0 = 14

Configuration
Perform the Test
Log Analysis

Sub Test 16 : SSB index 1, SearchSpace0 = 15

Configuration
Perform the Test
Log Analysis

RRC / NAS Signaling

MIB (SA)

Key Configuration Parameter

The list of configuration parameters for SearchSpace0 is very short as follows. In many cases, you may need to set search_space0_index only but you may need to set start_symb depending on situations.

start_symb

Test 1 : SSB index 0 or 1, SearchSpace 0 = {0,..,15}

Sub Test 1 : SSB index 0, SearchSpace0 = 0

In this sub test, it will be shown where (in which slot) Search Space 0 is allocated for FR1 and Coreset0 Multiplexing Pattern 1. In this case, the search space 0 is allocated based on TS 38.213 - Table 13-11

Configuration

gnb-sa-searchspace0index-0.cfg is used for gNB configuration.

In gnb-sa-searchspace0index-0.cfg , gNB setting is configured as follows.

In this case, the cell is set to TDD (NR_TDD = 1) and the channel bandwidth (NR_BANDWIDTH) is set to 40 Mhz. You can set it to any bandwidth as long as it is valid for the specified band (You may refer to 38.101-1 regarding the valid channel bandwidth for a specific band)

I set "10000000" for SSB bitmap which indicates that the configured SSB index (i) is 0. Remember this index since it is one of the parameter to determine the time domain position of searchspace 0 according to TS 38.213

The search space0 is set to the index 0 of 38.213 Table 13-11 (search_space0_index = 0). In this case, the first symbol index (start_symb) is not configured since it is 0 (the default value of start_symb). You can explicitely set start_symb : 0 in css if you like.

Perform the Test

Start the lte service and check out the result of cell phy and see if the configuration is properly set as intended.

This is all you need to do for the test. You don't need to connect any UE for the test.

Log Analysis

For this test, it is important to collect MIB and BCCH and PHY layer log. A simple way to do it is to check MIB, BCCH and click [+] button in ENB configuration on WebGUI.

First check out the confents of MIB message and make it sure searchSpaceZero is configured as intended.

Now check out the location of search space 0 slot in RB map on WebGUI. The RB map does not explicitely plot the resource allocation for CORESET0 and SearchSpace0, but you can indirectly figure out the slot based on SIB1 PDSCH since CORESET0, SearchSpace0 and SIB1 PDSCH are all in the same slot.