1. Draft WF on single Tx switched UL
3GPP TSG-RAN WG4#84bis Meeting
Dubrovnik, CR, Oct. 9-13, 2017
R4-17XXXXX
Draft WF on single Tx switched UL
Apple,…

2. Background 1: RAN#77 Agreement
RP : LS on single Tx switched UL (from RAN to RAN2 & RAN4)
RAN has discussed the issue of simultaneous dual Tx vs. single Tx for LTE-NR dual connectivity and endorsed the attached documents RP , RP RAN agreed that all the RAN WGs should complete their tasks by December 2017 to allow the feature to be introduced to the specifications.
RAN asks RAN WG2 and RAN WG4 groups to take the above into account and complete the work. The approval of single UL support in LTE – NR DC and related specification text in text proposals, draft TS proposals (presented for approval) and CRs (e.g. LTE specifications) will be done as a package in RAN#78.

3. Background 2: RAN#77 Endorsement in RP-172064
The categorization of band combinations is up to RAN4
RAN4 is to define a rule for categorization (of band combinations including channel assignments) in order to apply them
A possible rule could be based on presence of resulting IMD[2]…[7] (including harmonics as long as the cause includes simultaneous Tx) falling in Rx with the given channel assignment
Applies to a triplet of CCs
1 LTE PCell UL + 1 NR PSCell UL + 1 NR PSCell DL, or
1 LTE PCell UL + 1 NR PSCell UL + 1 LTE PCell DL

4. Background 3: RAN#77 Endorsement in RP-172085
Define in RAN4 specs for which band combinations and channel allocations (to the extent specified by RAN4) within that band combination the UE is allowed to indicate that it does not support 2 simultaneous UL tx (this is not implying the granularity of the signalling)
Signalling to be defined to support the 'red text' from RAN4 part of the single tx discussion (i.e. as in RP ):
UE capability indicates that the UE does not allow 2 simultaneous UL transmission for the RAN4 specified channel allocations in a given band combination. If the network chooses to operate the UE in a way that is not consistent with this capability indication then the UE behavior is not specified and the UE might not meet the performance criteria.

5. Proposed WF on single Tx switched UL
RAN4 is to define a rule for categorization (of band combinations including channel assignments), based on presence of resulting IMD2,3 (including harmonics as long as the cause includes simultaneous Tx) falling in Rx with the given channel assignment [RP ]
Note: IMD2,3 are valid for inter-band combinations
RAN4 should complete their tasks by December 2017 to allow the feature to be introduced to the specifications [RP ]

6. Proposed WF on single Tx switched UL
UE is allowed to indicate that it does not support concurrent 2 UL transmission for LTE-NR for inter-band combinations that have MSD due to IM2 and/or IM3. UE shall meet REFSENS requirements and BS is assumed to configure concurrent 2 UL transmission for all channel allocations (to be provided by operators) within that difficult band combination that do not have IM2 and/or IM3

7. Proposed WF on single Tx switched UL
For intra-band contiguous DC_71_n71 with 20 MHz maximum aggregated bandwidth, simultaneous 2 UL transmission is mandatory
Note: IMD5 does not hit on top of RX channel

8. Appendix 1: Example “Difficult Band Combinations”
LTE Band
NR Band
IMD Order Falling in Rx Band
Optional Dual Uplinks 1
n77 2
Yes 3
n78 39 18 28
n50 20
n28

9. Appendix 2: LTE 2UL CA MSD vs. IM order
Table 7.3.1A-0f: 2DL/2UL interband Reference sensitivity QPSK PREFSENS and uplink/downlink configurations
IM2 24 26
29.8
32.5 30
28.05
IM3 23
25.7 5
7.7 12
14.7
12.1
14.03
IM4 6
8.7 4 13
15.7 8
6.7 9
11.7
8.2
10.7 15
17.7
8.98
IM5
6.4
2.5
5.5
4.85
Table 7.3.1A-0g: 3DL/2UL interband Reference sensitivity QPSK PREFSENS and uplink/downlink configurations
IM2 30 29
10.5
13.2 26
28.7 20
23.81
IM3 15 11 19 18
15.75
IM4 13 9 12 16
12.43
IM5 4 8 1 3
4.00

10. Appendix 3
Expected UE behavior when operating in difficult band combination, but within easy channel combination.
UE has indicated that it does not support concurrent 2 UL for this inter-band combination
However, according to slide 6 concurrent 2UL is mandatory for this easy channel combination within that difficult band combination
NW configures concurrent 2UL when UE operates within this easy channel combination