5G/NR - Configured Scheduling

Configured Scheduling

Configured Scheduling is a mechanism in which gNB can schedule PDSCH/PUSCH without using DCI for every transmission. I think this is equivalent to SPS in LTE. How gNB can schedule those physical channels without using DCI ? Simple, it configures all the detailed scheduling parameters in RRC and gNB / UE is supposed to transmit PDSCH and PUSCH according to the parameters specified in RRC. This would greatly help gNB reduce the load of PHY/MAC scheduling.

One possible drawback of this mechanism would be that gNB cannot change scheduling parameter for individual transmission, implying that there may be some issues for Radio Link Adaptation when the channel condition goes very bad.

Configured Scheduling mechanism for downlink is called SPS and Configured Scheduling mechanism for UL is called Configured Grant.

Configure CS for Downlink / SPS

The overall procedure for Configured Scheduling for downlink (SPS) can be illustrated as below.

It can be summarized

i) gNB send RRC (RRCSetup or RRCReconfiguration) configuring all the parameters necessary for PDSCH scheduling

ii) UE Monitor PDCCH

iii) When gNB want to start PDSCH transmission, it sends DCI with CS-RNTI and start PDSCH transmission.

Configure CS for Uplink

The overall procedure for Configured Scheduling for uplink (Configured Grant) can be illustrated as below. For UL there are two different types of mechanism called Type 1 and Type 2.

In Type 1,

i) gNB send RRC (RRCSetup or RRCReconfiguration) configuring all the parameters necessary for PUSCH scheduling

ii) As soon as UE processed the RRC, UE is expected to transmit PUSCH without any specific lower layer trigger (i.e, DCI Trigger).

NOTE : Even in this situation, UE is supposed to monitor PDCCH just in case gNB transmit other type of DCI.

In Type 2,

i) gNB send RRC (RRCSetup or RRCReconfiguration) configuring all the parameters necessary for PUSCH scheduling

ii) When gNB want to start granting(scheduling) PUSCH, it sends DCI masked with CS-RNTI.

iii) Once UE processed the DCI with CS-RNTI, it is supposed to transmit PUSCH as scheduled in RRC

NOTE : Even in this situation, UE is supposed to monitor PDCCH just in case gNB transmit other type of DCI.

RRC Parameters

ConfiguredGrantConfig ::= SEQUENCE {

frequencyHopping ENUMERATED {intraSlot, interSlot} OPTIONAL, -- Need S

cg-DMRS-Configuration DMRS-UplinkConfig,

mcs-Table ENUMERATED {qam256, qam64LowSE} OPTIONAL, -- Need S

mcs-TableTransformPrecoder ENUMERATED {qam256, qam64LowSE} OPTIONAL, -- Need S

uci-OnPUSCH SetupRelease { CG-UCI-OnPUSCH } OPTIONAL, -- Need M

resourceAllocation ENUMERATED { resourceAllocationType0,

resourceAllocationType1, dynamicSwitch },

rbg-Size ENUMERATED {config2} OPTIONAL, -- Need S

powerControlLoopToUse ENUMERATED {n0, n1},

p0-PUSCH-Alpha P0-PUSCH-AlphaSetId,

transformPrecoder ENUMERATED {enabled, disabled} OPTIONAL, -- Need S

nrofHARQ-Processes INTEGER(1..16),

repK ENUMERATED {n1, n2, n4, n8},

repK-RV ENUMERATED {s1-0231, s2-0303, s3-0000} OPTIONAL, -- Need R

periodicity ENUMERATED {

sym2, sym7, sym1x14, sym2x14, sym4x14, sym5x14, sym8x14, sym10x14, sym16x14,

sym20x14, sym32x14, sym40x14, sym64x14, sym80x14, sym128x14, sym160x14, sym256x14,

sym320x14, sym512x14, sym640x14, sym1024x14, sym1280x14, sym2560x14, sym5120x14,

sym6, sym1x12, sym2x12, sym4x12, sym5x12, sym8x12, sym10x12, sym16x12, sym20x12,

sym32x12, sym40x12, sym64x12, sym80x12, sym128x12, sym160x12, sym256x12, sym320x12,

sym512x12, sym640x12, sym1280x12, sym2560x12

configuredGrantTimer INTEGER (1..64) OPTIONAL, -- Need R

rrc-ConfiguredUplinkGrant SEQUENCE {

timeDomainOffset INTEGER (0..5119),

timeDomainAllocation INTEGER (0..15),

frequencyDomainAllocation BIT STRING (SIZE(18)),

antennaPort INTEGER (0..31),

dmrs-SeqInitialization INTEGER (0..1) OPTIONAL, -- Need R

precodingAndNumberOfLayers INTEGER (0..63),

srs-ResourceIndicator INTEGER (0..15) OPTIONAL, -- Need R

mcsAndTBS INTEGER (0..31),

frequencyHoppingOffset INTEGER (1.. maxNrofPhysicalResourceBlocks-1)OPTIONAL,--Need R

pathlossReferenceIndex INTEGER (0..maxNrofPUSCH-PathlossReferenceRSs-1),

...,

[[

pusch-RepTypeIndicator-r16 ENUMERATED {pusch-RepTypeA,pusch-RepTypeB} OPTIONAL,-- Need M

frequencyHoppingPUSCH-RepTypeB-r16 ENUMERATED {interRepetition, interSlot} OPTIONAL,

-- Cond RepTypeB

timeReferenceSFN-r16 ENUMERATED {sfn512} OPTIONAL -- Need S

]],

[[

pathlossReferenceIndex2-r17 INTEGER (0..maxNrofPUSCH-PathlossReferenceRSs-1) OPTIONAL,

-- Need R

srs-ResourceIndicator2-r17 INTEGER (0..15) OPTIONAL, -- Need R

precodingAndNumberOfLayers2-r17 INTEGER (0..63) OPTIONAL, -- Need R

timeDomainAllocation-v1710 INTEGER (16..63) OPTIONAL, -- Need M

timeDomainOffset-r17 INTEGER (0..40959) OPTIONAL, -- Need R

cg-SDT-Configuration-r17 CG-SDT-Configuration-r17 OPTIONAL -- Need M

]]

}

[[

cg-RetransmissionTimer-r16 INTEGER (1..64) OPTIONAL, -- Need R

cg-minDFI-Delay-r16 ENUMERATED

{sym7, sym1x14, sym2x14, sym3x14, sym4x14, sym5x14, sym6x14, sym7x14, sym8x14,

sym9x14, sym10x14, sym11x14, sym12x14, sym13x14, sym14x14,sym15x14, sym16x14

} OPTIONAL, -- Need R

cg-nrofPUSCH-InSlot-r16 INTEGER (1..7) OPTIONAL, -- Need R

cg-nrofSlots-r16 INTEGER (1..40) OPTIONAL, -- Need R

cg-StartingOffsets-r16 CG-StartingOffsets-r16 OPTIONAL, -- Need R

cg-UCI-Multiplexing-r16 ENUMERATED {enabled} OPTIONAL, -- Need R

cg-COT-SharingOffset-r16 INTEGER (1..39) OPTIONAL, -- Need R

betaOffsetCG-UCI-r16 INTEGER (0..31) OPTIONAL, -- Need R

cg-COT-SharingList-r16 SEQUENCE (SIZE (1..1709))

OF CG-COT-Sharing-r16 OPTIONAL, -- Need R

harq-ProcID-Offset-r16 INTEGER (0..15) OPTIONAL, -- Need M

harq-ProcID-Offset2-r16 INTEGER (0..15) OPTIONAL, -- Need M

configuredGrantConfigIndex-r16 ConfiguredGrantConfigIndex-r16 OPTIONAL,--Cond CG-List

configuredGrantConfigIndexMAC-r16 ConfiguredGrantConfigIndexMAC-r16 OPTIONAL,

-- Cond CG-IndexMAC

periodicityExt-r16 INTEGER (1..5120) OPTIONAL, -- Need R

startingFromRV0-r16 ENUMERATED {on, off} OPTIONAL, -- Need R

phy-PriorityIndex-r16 ENUMERATED {p0, p1} OPTIONAL, -- Need R

autonomousTx-r16 ENUMERATED {enabled} OPTIONAL

-- Cond LCH-BasedPrioritization

]],

[[

cg-betaOffsetsCrossPri0-r17 SetupRelease { BetaOffsetsCrossPriSelCG-r17 } OPTIONAL,

-- Need M

cg-betaOffsetsCrossPri1-r17 SetupRelease { BetaOffsetsCrossPriSelCG-r17 } OPTIONAL,

-- Need M

mappingPattern-r17 ENUMERATED {cyclicMapping, sequentialMapping} OPTIONAL,

-- Cond SRSsets

sequenceOffsetForRV-r17 INTEGER (0..3) OPTIONAL, -- Need R

p0-PUSCH-Alpha2-r17 P0-PUSCH-AlphaSetId OPTIONAL, -- Need R

powerControlLoopToUse2-r17 ENUMERATED {n0, n1} OPTIONAL, -- Need R

cg-COT-SharingList-r17 SEQUENCE (SIZE (1..50722)) OF CG-COT-Sharing-r17 OPTIONAL,

-- Need R

periodicityExt-r17 INTEGER (1..40960) OPTIONAL, -- Need R

repK-v1710 ENUMERATED {n12, n16, n24, n32} OPTIONAL, -- Need R

nrofHARQ-Processes-v1700 INTEGER(17..32) OPTIONAL, -- Need M

harq-ProcID-Offset2-v1700 INTEGER (16..31) OPTIONAL, -- Need R

configuredGrantTimer-v1700 INTEGER(33..288) OPTIONAL, -- Need R

cg-minDFI-Delay-v1710 INTEGER (238..3584) OPTIONAL -- Need R

]]

}

CG-UCI-OnPUSCH ::= CHOICE {

dynamic SEQUENCE (SIZE (1..4)) OF BetaOffsets,

semiStatic BetaOffsets

}

SPS-Config ::= SEQUENCE {

periodicity ENUMERATED {ms10, ms20, ms32, ms40, ms64, ms80, ms128,

ms160, ms320, ms640,spare6, spare5, spare4,

spare3, spare2, spare1},

nrofHARQ-Processes INTEGER (1..8),

n1PUCCH-AN PUCCH-ResourceId OPTIONAL, -- Need M

mcs-Table ENUMERATED {qam64LowSE} OPTIONAL, -- Need S

...

}

Reference

[1] How 5G reduces data transmission latency

[2] R1-1900609 - 3GPP TSG RAN WG1 Ad-Hoc Meeting 1901 January, 2019