NR SA PDSCH Aggregation
The purpose of this tutorial is to show you how to configure and test PDSCH Aggregation Factor / Repetition. Main user case of this mechanism is to provide chance of more reliable PDSCH reception. Conceptually you may consider this to be similar to PDSCH in LTE IoT application. Overall mechanism of PDSCH Aggrection Factor can be illustrated as below.
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Table of Contents
- NR SA PDSCH Aggregation
Test Setup
Test setup for this tutorial is as shown below.
Key Configuration Parameters
Followings are important configuration parameters for this tutorial. You may click on the items for the descriptions from Amarisoft documents.
- pdsch
Test 1 : PDSCH Aggregation -TDD
This test is to test PDSCH Aggregation Factor operation in NR SA TDD
Configuration
I used the gnb-sa-pdsch-agg.cfg on gNB which is copied and modified from gnb-sa.cfg
I used ims.default.cfg as ims configuration and mme-ims.cfg as mme configuration. These two are default configuration on Callbox.
In gnb-sa-pdsch-agg.cfg , the configuration is done as follows.
I added a log option phy.rep=1 for clear verification in the log. This is not mandatory, but recommended if you want to capture all of the repeated transmission.
In this test, I used TDD. You can select any specific tdd pattern with the parameter NR_TDD_CONFIG. To apply TDD configuration, you first need to configure the duplex mode (NR_TDD) to 1 (TDD). And then I set NR_TDD_CONFIG to 2 which is one of default sample configuration provided by Amarisoft sample
configuration. (
In this test, band n78, subcarrier spacing(subcarrier_spacing) 30 is used, but this is not the mandatory condition. You can specify any band and subcarrier spacing that 3GPP allows.
Enabling PDSCH aggregation is simple. Just add a parameter aggregation_factor in pdsch configuration.
I used the ue-nr-sa.cfg as it is.
Configure UE as TDD which matches to callbox configuration. Set the band, subcarrier spacing(subcarrier_spacing), channel frequency(dl_nr_arfcn) and SSB frequency(ssb_nr_arfcn) to match with Callbox configuration.
Set UE access release (as_release) to 15 and ue_category to "nr".
Perform the Test
Start LTE service (gNB) and run 'cell phy' and 'cell' command, then everything is configured as you intended.
Power on UE on UE sim using power_on command.
Confirm that the UE completes the attach and check the throughput with 't' command.
Log Analysis
Before you start logging (i.e, before you turn on UE) I would suggest to check 'Repetition' in eNB log property window for more detailed verification.
Once the initial attach is done, check UE capability information message and see if UE support PDSCH aggregation (pdsch-RepetitionMultiSlots).
If UE notifies that pdsch-RepetitionMultiSlots is supported, gNB enables the PDSCH Aggregation by setting pdsch-AggregationFactor in pdsch-Config IE (Information Element)
Once PDSCH aggregation is enabled, you can check in PHY log to confirm that it is really working as expected.
First find any PDCCH/DCI 1_1 that schedule a PDSCH and then check a few consecutive PDSCH. You see the first PDSCH log after the PDCCH is printed with n_rep and the following three PDSCH are transmitted with different rep values and rv_idx values without any separate PDCCH/DCI 1_1. The k1 value in this case is calculated from the last repetition of PDSCH.
You can confirm the transmission of the aggregated PDSCH in visual way on the WebGUI. As shown here, you see the 4 consecutive PDSCH. First transmission is marked in dark color and the following repetition is marked in ligher colors.
RRC / NAS Signaling
RrcReconfiguration (SA)
: This is the RrcReconfiguration sent by gNB to configure PDSCH Aggregation Factor. (
{
message c1: rrcReconfiguration: {
rrc-TransactionIdentifier 0,
criticalExtensions rrcReconfiguration: {
nonCriticalExtension {
masterCellGroup {
cellGroupId 0,
spCellConfig {
spCellConfigDedicated {
initialDownlinkBWP {
pdsch-Config setup: {
resourceAllocation resourceAllocationType1,
pdsch-AggregationFactor n4,
rbg-Size config1,
mcs-Table qam256,
prb-BundlingType staticBundling: {
bundleSize wideband
}
}
},
uplinkConfig {
initialUplinkBWP {
pusch-Config setup: {
txConfig codebook,
resourceAllocation resourceAllocationType1,
mcs-Table qam256,
mcs-TableTransformPrecoder qam256,
codebookSubset nonCoherent,
maxRank 1
}
}
},
pdsch-ServingCellConfig setup: {
nrofHARQ-ProcessesForPDSCH n16,
maxMIMO-Layers 1
},
tag-Id 0
}
}
},
dedicatedNAS-MessageList {
'7E020F53BDA1017E0042010977000BF200F110800101CAA35AD154070000F11000006415020101210203005E01BE3408031F19F1031F11F2'H
}
}
}
}
}