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

2. What happened so far
Telstra discussion paper ( S ) 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 (S ) 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, S )
UE capability indication, NAS signaling (CT1, C )
GTPv2-C impacts for MME, SGW, PGW (CT4, C )
WID (S ) looking for 15 LTE bearers in Rel-15/for homogenous deployment (in a PLMN), with SID (S ) 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 (?)

3. 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)
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

4. 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

5. 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