5G/NR - tdd UL/DL Common Configuration                             Home : www.sharetechnote.com

 

 

 

 

 

tdd UL/DL Common Configuration (tdd-UL-DL-configurationCommon)

 

When operating in TDD mode, we have to clearly define on exactly when to expect the transmission and when to expect the reception. In LTE TDD, we defined 7 predefined pattern for UL and DL allocation in a radio frame. In 5G/NR, we don't have any predefined pattern. Instead, we can define the pattern in much more flexible way using several parameters as shown below.

 

 

 

 

These parameters are defined in 38.331 v15.3.0 as follows :

 

TDD-UL-DL-ConfigCommon ::= SEQUENCE {

    referenceSubcarrierSpacing                 SubcarrierSpacing,

    pattern1                                   TDD-UL-DL-Pattern,

    pattern2                                   TDD-UL-DL-Pattern OPTIONAL,

    ...

}

 

TDD-UL-DL-Pattern ::= SEQUENCE {

    dl-UL-TransmissionPeriodicity              ENUMERATED {ms0p5, ms0p625, ms1,

                                                           ms1p25, ms2, ms2p5, ms5, ms10},

    nrofDownlinkSlots                          INTEGER (0..maxNrofSlots),

    nrofDownlinkSymbols                        INTEGER (0..maxNrofSymbols-1),

    nrofUplinkSlots                            INTEGER (0..maxNrofSlots),

    nrofUplinkSymbols                          INTEGER (0..maxNrofSymbols-1),

    ...,

    [[

       dl-UL-TransmissionPeriodicity-v1530 ENUMERATED {ms3, ms4} OPTIONAL -- Need R

    ]]

}

 

maxNrofSlots INTEGER ::= 320    // Maximum number of slots in a 10 ms period

maxNrofSymbols-1 INTEGER ::= 13 // Maximum index identifying a symbol within a slot

                                   (14 symbols, indexed from 0..13)

 

dl-UL-TransmissionPeriodicity: Periodicity of the DL-UL pattern. If dl-UL-TransmissionPeriodicity-v1530 is conifgured, dl-UL-TransmissionPeriodicity is ignored.

nrofDownlinkSlots : Number of consecutive full DL slots at the beginning of each DL-UL pattern  

nrofDownlinkSymbols : Number of consecutive DL symbols in the beginning of the slot following the last full DL slot

nrofUplinkSlots : Number of consecutive full UL slots at the end of each DL-UL pattern

nrofUplinkSymbols : Number of consecutive UL symbols in the end of the slot preceding the first full UL slot

 

 

 

Transmission Periodicity

 

The applicable periodicity(P) of the UL/DL configuration varies depending on the reference numerology (n_ref). This can be summarized as a table as shown below. I created this table based on the descriptions in 38.213-11.1

 

P(ms)

u_ref (scs Khz)

Applicable u

P/20

Number of Slots in a P

0

1

2

3

4

0.5

Not described

 

40

 

1

2

4

8

0.625

3(120)

3,4

32

 

 

 

5

10

1.25

2(60), 3(120)

2,3,4

16

 

 

5

10

20

2.5

1(15), 2(60), 3(120)

1,2,3,4

8

 

5

10

20

40

5.0

Not described

 

4

5

10

20

40

80

10.0

Not described

 

2

10

20

40

80

160

 

NOTE : I've calculated P/20 to clarify the statement in the specification saying 'The first symbol every periods is a first symbol in an even frame.'.

 

NOTE : The 'Applicable u' is specified based on the statement in the specification saying 'A UE expects that the reference subcarrier spacing configuration ref μ is smaller than or equal to a subcarrier spacing configuration μ for any configured DL BWP or UL BWP.'

 

NOTE : I calculated the section 'Number of Slots in a P' just to show how many slots for each numerology in a P(Period). It doesn't necessarily mean that all of the numerology is applicable to the specified period.

 

 

 

What if TDD-UL-DL-ConfigCommon is not configure ?

 

UE determines if each of the slot is uplink or downlink and the symbol allocation within each of the slot purely by DCIs as stated in 38.213-11.1 Slot configuration.

    If a UE is not configured to monitor PDCCH for DCI format 2-0, for a set of symbols of a slot that are indicated as flexible by higher layer parameters TDD-UL-DL-ConfigurationCommon or TDD-UL-DL-ConfigDedicated, when provided to a UE, or when TDD-UL-DL-ConfigurationCommon and TDD-UL-DL-ConfigDedicated are not provided to the UE

    • the UE receives PDSCH or CSI-RS in the set of symbols of the slot if the UE receives a corresponding indication by a DCI format 1_0, DCI format 1_1, or DCI format 0_1
    • the UE transmits PUSCH, PUCCH, PRACH, or SRS in the set of symbols of the slot if the UE receives a corresponding indication by a DCI format 0_0, DCI format 0_1, DCI format 1_0, DCI format 1_1, or DCI format 2_3

 

 

 

Reference

 

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