4G/LTE - Measurement Report |
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NOTE : At high level view, it would not be difficult to understand overall concept of CSI. However, getting deeper into the details.. it would become much complicated .. and tooooooooooooo confusing (at least very confusing to me). That is one of the reason why I wrote multiple pages for the same topic (CSI). Multiple pages for the same topic can be additional confusion to some readers (even to me). However, I thought the page would get too big for download if I put everything in single page and I also thought it would not be bad to provide a little bit different aspect for the same topic with multiple post. But as I add more pages (post), I thought it would be good to write a page to provide high level view and help readers combine all those multiple pages that I wrote. Refer to CSI Overview page if you are not familiar with big picture of the CSI report.
CQI, PMI, RI Reporting Configuration - Details for Aperiodic Report
In most case, you would need more information for anything 'Aperiodic' implying 'irregular'. If something is periodic or regular, you may set a certain rule (like a mathematical formula) and pass a couple of parameters to the formula. But in case of Aperiodic, usually it would take more information to configure the behavior since it cannot be easily defined by a fixed rule (e.g, mathematical formula). Especially with the introduction of Carrier Aggregation and the number of Carrier gets larger, the amount of necessary information (e.g, when to send CSI, for which carrier it send CSI) gets larger.
In short, Aperiodic report is configured by two factors : one portion is configured in RRC message and the other portion is configured by DCI. The portion configured by RRC message is described in CQI/RI Feedback type page and the portion configured by DCI is described below in this page.
I assume that you have read through RRC portions of Aperiodic CQI configuration. Now let's look into DCI part of the configuration. The DCI can carry very short contents and it does not have enough space to carry all of those information.
Then, what would be the solution for this ? The answer is a common old trick. They configure a complicated part in RRC message and lower layer (i.e, DCI in this case) just select a specific configuration defined in RRC message.
Now let's look into the details. The Aperidic CQI/CSI gets configured in RRC message as shown below. At the first glance, you would immediately have questions as below.
If you can answer these two questions, you already have overall mechanism of Aperiodic CSI report. The answers are as shown below.
Formal definition of aperiodicCSI-Trigger is defined in 36.331 as below.
36.331- aperiodicCSI-Trigger
Indicates for which serving cell(s) the aperiodic CSI report is triggered when one or more SCells are configured. trigger1 corresponds to the CSI request field 10 and trigger2 corresponds to the CSI request field 11, see TS 36.213 table 7.2.1-1A. The leftmost bit, bit 0 in the bit string corresponds to the cell with ServCellIndex=0 and bit 1 in the bit string corresponds to the cell with ServCellIndex=1 etc. Each bit has either value 0 (means no aperiodic CSI report is triggered) or value 1 (means the aperiodic CSI report is triggered). At most 5 bits can be set to value 1 in the bit string. E-UTRAN configures value 1 only for cells configured with transmissionMode set in range tm1 to tm9. One value applies for all serving cells configured with transmissionMode set in range tm1 to tm9 (the associated functionality is common i.e. not performed independently for each cell).
NOTE : Regarding how each of these format are utilized and configured in signaling, check out this tutorial of Amarisoft TechAcademy.
< Example 1 >
Assumption : Carrier Aggregation is configured
< Example 2 >
Assumption : Carrier Aggregation is configured
< Example 3 >
Assumption : Carrier Aggregation is configured
< Example 4 >
Assumption : Carrier Aggregation is configured
Followings are tables from 36.213 v17.5 - 7.2.1
< Table 7.2.1-1A: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1B: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1C: CSI Request field for PDCCH/EPDCCH/MPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1D: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1E: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1F: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1G: CSI Request field for PDCCH/EPDCCH/SPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1H: CSI Request field for PDCCH/EPDCCH with uplink DCI format in UE specific search space>
< Table 7.2.1-1I: CSI Request field for PDCCH/EPDCCH with uplink DCI format in UE specific search space>
< Table 7.2.1-1J: CSI Request field for PDCCH/EPDCCH with uplink DCI format in UE specific search space >
< Table 7.2.1-1K: CSI Request field for PDCCH/EPDCCH with uplink DCI format in UE specific search space >
< Influence of other MAC activities on CSI report >
Since there are some other periodic activities, those activities can influence Periodic/Aperidic CSI Report as described in CQI Report and DRX section. CSI report is triggered by DCI, so a certain DCI format can influence CSI Report as described in CQI Report and SR section.
Procedure of Aperiodic CSI Report
rrc-TransactionIdentifier: 0 criticalExtensions: c1 (0) c1: rrcConnectionReconfiguration-r8 (0) rrcConnectionReconfiguration-r8 radioResourceConfigDedicated physicalConfigDedicated cqi-ReportConfig-r10 cqi-ReportAperiodic-r10: setup (1) setup cqi-ReportModeAperiodic-r10: rm30 (3) aperiodicCSI-Trigger-r10 trigger1-r10: 80 [bit length 8, 1000 0000 ] trigger2-r10: c0 [bit length 8, 1100 0000 ] nomPDSCH-RS-EPRE-Offset: 0dB (0) pucch-ConfigDedicated-v1020 pucch-Format-r10: channelSelection-r10 (1) channelSelection-r10 n1PUCCH-AN-CS-r10: setup (1) setup n1PUCCH-AN-CS-List-r10: 2 items Item 0 N1PUCCH-AN-CS-r10: 4 items Item 0 N1PUCCH-AN-CS-r10 item: 361 Item 1 N1PUCCH-AN-CS-r10 item: 362 Item 2 N1PUCCH-AN-CS-r10 item: 363 Item 3 N1PUCCH-AN-CS-r10 item: 364 Item 1 N1PUCCH-AN-CS-r10: 4 items Item 0 N1PUCCH-AN-CS-r10 item: 365 Item 1 N1PUCCH-AN-CS-r10 item: 366 Item 2 N1PUCCH-AN-CS-r10 item: 367 Item 3 N1PUCCH-AN-CS-r10 item: 368 nonCriticalExtension nonCriticalExtension nonCriticalExtension sCellToAddModList-r10: 1 item Item 0 SCellToAddMod-r10 sCellIndex-r10: 1 radioResourceConfigDedicatedSCell-r10 physicalConfigDedicatedSCell-r10 nonUL-Configuration-r10 antennaInfo-r10 transmissionMode-r10: tm1 (0) ue-TransmitAntennaSelection: release (0) release: NULL pdsch-ConfigDedicated-r10 p-a: dB0 (4) ul-Configuration-r10 cqi-ReportConfigSCell-r10 cqi-ReportModeAperiodic-r10: rm30 (3) nomPDSCH-RS-EPRE-Offset-r10: 0dB (0) cqi-ReportPeriodicSCell-r10: release (0) release: NULL
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