The LTE_NR_Simult_RxTx work item specifies the principles for simultaneous Rx/Tx UE capability for FDD-TDD or TDD-TDD band combinations s for which can support or not support simultaneous Rx/Tx for FR1, FR2 and FR1+FR2 and for each FDD-TDD and TDD-TDD band combinations for CA, SUL, MR-DC and simultaneous Rx/Tx capability NR-DC band combinations.

Simultaneous receive (Rx) / transmit (Tx) band combinations for New Radio (NR) C Carrier Aggregation (CA) / Dual Connectivity (DC), NR Supplementary uplink (SUL) and Long-Term Evolution (LTE) / NR DC band combinations were introduced in 3GPP from release 15.

Figure 1: Simplified simultaneous receive (Rx) / transmit (Tx) diagram

The brief procedure for handling of new band combination requests for analysis of support for mandatory capability of simultaneous Rx/Tx is provided in the steps below.

The brief procedure for handling of new band combination requests for analysis of support for mandatory capability of simultaneous Rx/Tx is provided in the steps below.

1.   The new request for additional band combinations for analysis of supporting simultaneous Rx/Tx capability would need to be submitted on the RAN4 reflector prior to the took submission deadline to the next RAN4 meeting.

2.   The basket work item (WI) would be updated with the new requests and submitted to the next RAN4 meeting for endorsement, before the submission to the RAN plenary meeting for approval.

NOTE: There were three applicable categories of basket WIs for Release 17. These included LTE/NR DC basket WIs, NR CA/NR DC basket WIs, and SUL basket Wiis’

3.   After the analysis for additional band combinations was completed, it was determined as to whether the band combination capability should be mandatory for UE supporting simultaneous Rx/Tx.

4.   If the band combination capability was determined to be mandatory for UE supporting simultaneous Rx/Tx, then all draft CRs related to one request would be submitted in the same RAN4 meeting to check for consistency.

5.   If all the draft CRs were endorsed, the basket WI Rapporteur would be responsible to merge all the draft CRs from all requests into big CRs (one per TS specification). After the RAN4 meeting preceding a RAN meeting, those big CRs would be sent on the RAN4 reflector for email approval and, if agreed, they will be submitted to the following RAN plenary meeting for approval.

The simultaneous Rx/Tx band combinations categories

The UE supporting band combinations that support the simultaneous Rx/Tx band are based on the capability class. If it is indicated that the band combination capability is mandatory, then for UE supporting simultaneous Rx/Tx, the capability should be reported. Reporting this capability is vital for network scheduling and should be reported accurately. If it is not reported accurately by the UE, then it could cause unexpected performance loss due to scheduling limitation. If the capability is absent or not reported, then the capability is optional.

For Release 17, the band combinations were analysed to determine which band combination should indicate capability as mandatory for UE supporting simultaneous Rx/Tx. The band combination categories analysed included:

• FR1+FR1 FDD-TDD band combination
• FR1+FR1 TDD-TDD band combination
• FR1+FR2 FDD-TDD band combination
• FR1+FR2 TDD-TDD band combination
• FR2+FR2 TDD-TDD band combination

The three RAN4 TS specifications that may be applicable to simultaneous Rx/Tx capability include: 3GPP TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone", 3GPP TS 38.101-2: "NR; User Equipment (UE) radio transmission and reception; Part 2: Range 2 Standalone". and 3GPP TS 38.101-3: "NR; User Equipment (UE) radio transmission and reception; Part 3: Range 1 and Range 2 Interworking operation with other radios". All the applicable specifications would be required to be in alignment. An example is provided for each TS specification in Tables 1.2-1, Table 1.2-2 and Table 1.2-3.

Table 1-2-1: An example of band combinations in TS 38.101-1

Table 1-2-2: An example of band combinations in TS 38.101-2

Table 1-2-3: An example of band combinations in TS 38.101-3

Configurations for NR CA/DC, NR SUL and LTE/NR DC

In the RAN4 TS specifications 3GPP TS 38.101-1: "NR; User Equipment (UE) radio transmission and reception; Part 1: Range 1 Standalone" and 3GPP TS 38.101-3: "NR; User Equipment (UE) radio transmission and reception; Part 3: Range 1 and Range 2 Interworking operation with other radios" the requirements are shown to be in alignment for simultaneous Rx/Tx band combinations for NR CA/DC, NR SUL and LTE/NR DC.

Configuration for Inter-band CA

If the mandatory simultaneous Rx/Tx capability applies for a lower order band combination, when the applicable lower order band combination is a band pair in a higher order band combination, the mandatory simultaneous Rx/Tx capability also applies for the band pair in the higher order band combination [TS 38.101-1].

Configuration for operating bands within FR1 for 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 [TS 38.101-1].

NOTE: This is for operation with NR dual connectivity configured, where all operating bands are within FR1.

Configuration for operating band combination for SUL

If the mandatory simultaneous Rx/Tx capability applies for a band combination, when the applicable lower order band combination is a band pair in a higher order band combination, the mandatory simultaneous Rx/Tx capability also applies for the band pair in the higher order band combination [TS 38.101-1].

Configuration for Inter-band CA between FR1 and FR2

If the mandatory simultaneous Rx/Tx capability applies for a lower order band combination, when the applicable lower order band combination is a band pair in a higher order band combination, the mandatory simultaneous Rx/Tx capability also applies for the band pairing the higher order band combination [TS 38.101-3].

Configuration for DC

If the mandatory simultaneous Rx/Tx capability applies for a lower order DC configuration, when the applicable lower order DC configuration is a band pair in a higher order DC configuration, the mandatory simultaneous Rx/Tx capability also applies for the band pair in the higher order DC configuration [TS 38.101-3].

NOTE: This is for operation with EN-DC, NGEN-DC, NE-DC or NR-DC configured. The EN-DC, NGEN-DC or NE-DC band combinations include at least one E-UTRA operating band.

Conclusion

The Release 18 work item was approved at 3GPP TSG RAN Meeting #97e in document RP-222648. Currently, four NR band combinations were identified for analysis for supporting simultaneous Rx/Tx. These four band combinations are provided in Table 1.4-1.

Table 1.4-1: Identified NR band combinations to be analysed for supporting simultaneous Rx/Tx

The following principles were introduced as part of the Work Item:

• Principles for FDD-TDD or TDD-TDD band combinations objectives: To define clear principles for which can support or not support simultaneous Rx/Tx for FR1, FR2 and FR1+FR2.
• Principles for CA, SUL, MR-DC and simultaneous Rx/Tx capability NR-DC band combination: Simultaneous Rx/Tx capability for LTE CA band combination can be applied for the corresponding inter-band NR CA band combination. The same simultaneous Rx/Tx capability can be applied for the corresponding band combination among NR CA, NR DC and NR EN-DC.

The latest Status report for the Work Item (RP-221520) reported on agreements approved at 3GPP TSG RAN meeting #96 (June 06-09, 2022), on detailed work from RAN4 Working Group.

• See a list of related CRs: select "TSG Status = Approved" in: https://portal.3gpp.org/ChangeRequests.aspx?q=1&workitem=911018,911118

Acronyms:

BCS         Bandwidth Combination Set

CA           Carrier Aggregation

CC           Component Carrier

DC           Dual Connectivity

EN-DC     E-UTRA/NR DC

FDM        Frequency Division Multiplexing

FR            Frequency Range

ENBW     The aggregated bandwidth of an E-UTRA sub-block and an adjacent NR sub-block

MBW      Measurement bandwidth defined for the protected band

MCG       Master Cell Group

NR           New Radio

NS           Network Signalling

NSA         Non-Standalone, a mode of operation where operation of an other radio is assisted with an other radio

RE            Resource Element

RF            Radio Frequency

Rx            Receiver

SCG         Secondary Cell Group

SCS          Subcarrier spacing

SUL         Supplementary uplink

TDM        Time Division Multiplex

Tx            Transmitter

UE           User Equipment

ULSUP    Uplink sharing from UE perspective

3GPP Work Plan:

See a listing of all work & study items here:  https://www.3gpp.org/ftp/Information/WORK_PLAN/ and search for ‘Simult_RxTx’ in the acronym field of the Excel sheet there.

The text above is largely taken from the Release 17 description document TR21.917 (clause 18), which is a summary based on RP-221054 (LTE_NR_Simult_RxTx).

Working Groups:

RAN4

3GPP Release:

Rel-19
Rel-18
Rel-17

See also:

IMPORTANT NOTE: Please be aware that these pages are a snapshot of the work going on in 3GPP. The full picture of all work is contained in the Work Plan (https://www.3gpp.org/ftp/Information/WORK_PLAN/)

Updated: 25/7/2022