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TR 38.839
Principles and requirements for simultaneous Rx/Tx band combinations

V17.0.0 (Wzip)  2022/06  11 p.
Dr. Liu, Ye
Huawei Technologies France

Content for  TR 38.839  Word version:  17.0.0

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1  Scopep. 6

The present document is a technical report for simultaneous Rx/Tx band combinations. The TR includes principles to decide mandatory/optional capability for FDD-TDD, TDD-TDD band combinations in different cases, identify case by case issues and align the specification treatment for CA/DC/SUL band combinations.

2  Referencesp. 6

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.
  • References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
  • For a specific reference, subsequent revisions do not apply.
  • For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.
TR 21.905: "Vocabulary for 3GPP Specifications".
RP-210890: "New WID on New WID on simultaneous Rx/Tx band combinations for CA, SUL, MR-DC and NR-DC".
TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone".
TS 38.101-2: "NR; User Equipment (UE) radio transmission and reception; Part 2: Range 2 Standalone".
TS 38.101-3: "NR; User Equipment (UE) radio transmission and reception; Part 3: Range 1 and Range 2 Interworking operation with other radios".

3  Definitions of terms, symbols and abbreviationsp. 6

3.1  Termsp. 6

For the purposes of the present document, the terms given in TR 21.905 and the following apply. A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

3.2  Symbolsp. 6

For the purposes of the present document, the following symbols apply:

3.3  Abbreviationsp. 6

For the purposes of the present document, the abbreviations given in TR 21.905 and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905.
Adjacent Channel Leakage Ratio
Adjacent Channel Selectivity
Additional Maximum Power Reduction
Bandwidth Combination Set
Carrier Aggregation
Component Carrier
Dual Connectivity
Equivalent Isotropically Radiated Power
Error Vector Magnitude
Frequency Division Multiplexing
Frequency Range
The aggregated bandwidth of an E-UTRA sub-block and an adjacent NR sub-block
Intelligent Transportation System
Radiocommunication Sector of the International Telecommunication Union
Measurement bandwidth defined for the protected band
Allowed maximum power reduction
Maximum Sensitivity Degradation
Master Cell Group
New Radio
Network Signalling
Non-Standalone, a mode of operation where operation of an other radio is assisted with an other radio
Out-of-band emission
Over The Air
Physical Resource Block
Physical Sidelink Control Channel
Physical Sidelink Shared Channel
Resource Element
Reference Sensitivity
Radio Frequency
Secondary Cell Group
Subcarrier spacing
Spectrum Emission Mask
Supplementary uplink
Time Division Multiplex
User Equipment
Up Link Multiple Antenna transmission
Uplink sharing from UE perspective

4  Backgroundp. 7

4.1  Justificationp. 7

Simultaneous Rx/Tx capability for inter-band CA, SUL and EN-DC band combinations were introduced from Rel-15. Specifically, for inter-band CA and EN-DC combination, the capability is used for TDD-TDD and TDD-FDD band combinations. According to the description of the capability, it is conditional mandatory and the condition is described in the field, i.e. indicated in the RAN4 spec which combinations should mandatorily support simultaneous Rx/Tx. For the combinations which have no such indication, the capability is optional, i.e. for UE supporting simultaneous Rx/Tx, the capability should be reported, otherwise, the capability is absent or not reported. Since the capability is important for network scheduling, it should be reported accurately.
However, there are no clear principles to judge whether a band combination can mandatorily support simultaneous Rx/Tx capability, especially for FDD-TDD band combinations. It is noted that in Rel-15, whether a FDD-TDD band combination shall support simultaneous Rx/Tx is based on operators' request. But afterwards, most FDD-TDD band combinations are not indicated mandatorily in RAN4 specification. With increasing number of band combinations introduced after Rel-15, the applicability of simultaneous Rx/Tx capability for a band combination becomes more ambiguous in the specification, which is not helpful for both network scheduling and use of the capability for UE side. It is worth noting that if the capability is not indicated accurately by UE, unexpected performance loss may happen due to scheduling limitation.
Previously, the simultaneous Rx/Tx capability is focused on FR1 or FR1 and FR2, since now inter-band CA is also supported for FR2, the capability should also be considered for band combinations in FR2.
On the other hand, as the capability is defined for CA, SUL, MR-DC and NR-DC band combinations, and applicability of the corresponding requirements cover different specifications, e.g. TS 38.101-1 and TS 38.101-3, the way to treat simultaneous Rx/Tx capability as well as the requirements should be aligned among the specifications.

4.2  Objectivep. 8

4.2.1  Objective and scopep. 8

The objectives of the WI are as follows:
  1. Define clear principles for FDD-TDD or TDD-TDD band combinations for which can support or not support simultaneous Rx/Tx for FR1, FR2 and FR1+FR2.
    The principles should be studied firstly before detailed analysis carried out for specific band combinations
  2. Identify for each FDD-TDD and TDD-TDD band combinations for CA, SUL, MR-DC and simultaneous Rx/Tx capability NR-DC based on technical analysis in parallel with the basket WI intending to introduce the band combination.
  3. Align the specification treatment of simultaneous Rx/Tx capability for CA, SUL, MR-DC and NR-DC band combinations.

4.2.2  Way of workingp. 8

The new request adding CA, SUL, MR-DC and NR-DC band combinations for evaluation of supporting simultaneous Rx/Tx capability should be submitted on RAN4 reflector before tdoc submission deadline to the next RAN4 meeting (1 week before the meeting). The basket WI will then be updated with the new requests and submitted to next RAN4 meeting for endorsement, before submission to RAN meeting for approval.
When the work is completed, all draft CRs related to one request will be submitted in the same RAN4 meeting to check consistency. If they are endorsed, the basket WI Rapporteur will merge all draft CRs from all requests in big CRs (one per TS specification). After the RAN4 meeting preceding a RAN meeting, those big CRs will be sent on RAN4 reflector for email approval (1 week) and, if agreed, they will be submitted to following RAN meeting.

5  Principles for simultaneous Rx/Tx UE capabilityp. 8

5.1  Applicability of simultaneous Rx/Tx capabilityp. 8

The following consensus was reached in RAN4 on applicability of simultaneous Rx/Tx capability.
  • Simultaneous Rx/Tx capability for LTE CA band combination can be applied for the corresponding inter-band NR CA band combination.
  • Same simultaneous Rx/Tx capability can be applied for the corresponding band combination among NR CA, NR DC and NR EN-DC
  • If the mandatory simultaneous Rx/Tx capability applies for a band combination, the mandatory simultaneous Rx/Tx capability also applies for the band combination when the applicable band combination is a subset of a higher order band combination.

5.2  Rules to decide simultaneous Rx/Tx capability for a band combinationp. 9

5.2.1  FR1+FR1 FDD-TDD band combinationp. 9

For FR1+FR1 FDD-TDD band combination,
  • Simultaneous Rx/Tx is the default capability in FDD-TDD FR1 band combinations
  • For TDD-FDD combinations, the capability is mandatory without checking if there are no MSD issues and frequency range is not adjacent to each other for the band combinations
  • For TDD-FDD combinations with REFSENS degradation due to self-interference, MSD caused by harmonics/IMD, etc. should be defined. For some band combinations that are close in frequency, e.g. bands n7 and n38, other methods to mitigate interference can be considered as well. Simultaneous Rx/Tx capability for this kind of special cases could be handled separately from those having MSD issues.
  • Case by case analysis is considered for FR1 FDD-TDD band combination which may have difficulty to support simultaneous Rx/Tx operation, e.g. with large MSD. If a FR1 FDD-TDD band combination is identified which cannot support simultaneous Rx/Tx operation, a note similar to FR1 TDD-TDD band combination shall be indicated in the specification, and for such operation the minimum requirements are not applicable for this band combination. Otherwise, the FR1 FDD-TDD band combination with MSD can support simultaneous Rx/Tx operation.

5.2.2  FR1+FR1 TDD-TDD band combinationp. 9

For FR1+FR1 TDD-TDD band combination, the simultaneous Rx/Tx capability should be studied case by case.

5.2.3  FR1+FR2 FDD-TDD band combinationp. 9

For FR1+FR2 FDD-TDD band combination, the simultaneous Rx/Tx capability shall be mandatory if FR1 FDD band (<4GHz) is aggregated with FR2 TDD bands.

5.2.4  FR1+FR2 TDD-TDD band combinationp. 9

For FR1+FR2 TDD-TDD band combination, the simultaneous Rx/Tx capability is mandatory for band combination with FR1 bands up to 5GHz and FR2 bands above 24GHz. Whether the FR1 bands can be extended to 7.125GHz is FFS until there are such FR1+FR2 band combinations available in RAN4.

5.2.5  FR2+FR2 TDD-TDD band combinationp. 9

For FR2+FR2 TDD-TDD band combination, the simultaneous Rx/Tx capability should be studied case by case.

5.3  Release independent for simultaneous Rx/Txp. 10

The following consensus was reached in RAN4 on release independent for simultaneous Rx/Tx capability.
  • At least in the Rel-15 RAN4 specifications, the indication of mandatory/optional simultaneous Rx/Tx capability support for each combination should remain unchanged.
  • For the FDD-TDD and TDD-TDD band combination introduced in Rel-17 38.101-1, 38.101-2, 38.101-3, the simultaneous Rx/Tx capability affiliated to the band combination is considered as release independent from Rel-15 if the band combination is mandatory to support simultaneous Rx/Tx in Rel-17.
    For example: A band combination is specified as mandatory support of simultaneous Rx/Tx in Rel-17. If Rel-15 or Rel-16 UE wants to support this band combination with release independent manner, it shall support simultaneous Rx/Tx.

6  Specific cases for TDD-TDD band combinationsp. 10

6.1  FR2+FR2 TDD-TDD band combinationp. 10

For FR2+FR2 TDD-TDD band combinations introduced in Rel-17, it is clarified that the minimum requirements apply only when there is non-simultaneous Rx/Tx operation between inter-band NR carriers.
NR CA Band NR Band
CA_n257-n259 1n257, n259
CA_n258-n260 1n258, n260
CA_n258-n261 1n258, n261
CA_n260-n261 1,2n260, n261
The minimum requirements apply only when there is non-simultaneous Rx/Tx operation between inter-band NR carriers in the current version of this specification.
The band combination was introduced in Rel-16.

7  Specific cases for FDD-TDD band combinationsp. 10

<To be added>

$  Change historyp. 11

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