Options for increasing the number of LTE bearers 3GPP SA2 #12724 Reno, Nevada (US) 29 Nov 2017

What happened so far Telstra discussion paper ( S2-175383) handled in SA2#122bis on increasing the maximum number of LTE bearers presented the need / data usage examples hitting the barrier of 8 / 5+3 LTE data radio bearers LS (S2-176553) sent to RAN2, CT1, CT4 whether it is possible to extend the max no. of bearers to 15 or 16 in Rel-15 time frame. The feasibility has been confirmed by all these groups, with impacts on MAC + RRC layer (RAN2, S2-176553) UE capability indication, NAS signaling (CT1, C1-174658) GTPv2-C impacts for MME, SGW, PGW (CT4, C4-175278) WID (S2-178604) looking for 15 LTE bearers in Rel-15/for homogenous deployment (in a PLMN), with SID (S2-178605) for further study of other deployment options Discussions in Reno meeting 11 bearers could be added without core impact (even for mobility to UTRAN/GERAN) Focusing on 5G (NSA than can be reused for LTE coverage) only more acceptable (?)

Comparison of the impacts assuming homogenous deployment per PLMN VPLMN HPLMN 11 bearers: DRB/EBI harmonisation UE eNB MME SGW PGW SGSN Capability ind. MAC + RRC (reserved LCID /E-RAB ID) 12..15 bearers DRB/EBI extension UE eNB MME SGW PGW SGSN Capability ind. MME to limit no. of contexts GTPv2 (use reserved EBI values) GTP (use reserved EBI values) MAC + RRC (reserved LCID /E-RAB ID) 15+ bearers: NR / eLTE bearer harmonisation; “EDCE5+” UE eNB MME SGW PGW SGSN Capability ind. MME to limit no. of contexts GTP (extend EBI) MAC + RRC (reserved LCID /ext. E-RAB ID) S1AP (extend E-RAB ID) gNB

Pros/cons Pros Cons 11 LTE bearers Quick fix / pain relief for impacted operators in Rel-15 time frame Only RAN work (expected to be small) Will not be a final solution, further work expected (but less urgent) LTE bearers = NR bearers Final solution (for all operators intending to provide advanced QoS in future) Provides QoS equivalence within 5G RAN (eLTE – NR), seamless experience for mobility Support all bearers for 5GC to EPC IW / HO, seamless user experience However, also solves bearer issue for (e)LTE / with EPC, in Rel-15 time frame Requires exception in Rel-15 Challenging timeline for Rel-15 Requires SA2, RAN2, RAN3, CT1, CT4 work Not generic solution for the original problem (expect only 5G devices support) Any other (in Rel-16 time frame or later) Network operators will be able to provide advanced QoS offerings only ~2021

How could it happen – possible timeline Q4/17 Q1/18 Q2/18 Q3/18 11 bearers LTE bearers=NR bearers SA2 #124 LS: +3 bearers RAN2 ASN1 RAN2 #100 RAN2 #101/#10bis… RAN #78 SA2 #125-#126: study SA2 #12-#126: normative SA2 #124 WI with study phase LS: LTE/NR bearers RAN2 #101..#102 RAN2 ASN1 RAN2 #100 RAN3 #99..#100 RAN3 #198 RAN #78 CT1 #110..#111 CT4 #84..#85 CT #79