Release 16 enhancements for NB-IoT
This Feature builds on the base NB-IoT feature in Rel-13, and enhancements in Rel-14 and Rel-15, and adds features such as DL/UL transmission efficiency improvement, UE power consumption improvement, scheduling enhancement, network management tool enhancement, latency improvement, enhancement on coexistence with NR and connection to 5GC.
Improved DL transmission efficiency and UE power consumption
Reduced UE power consumption and improved transmission efficiency are
achieved through reduced downlink monitoring and reduced signalling, building
on features introduced in earlier releases.
UE-group wake-up signals (GWUS) (FDD):
With the introduction of Rel-15 wake-up signalling (WUS), UE can skip
the paging procedures if the wake-up signal is not detected to save power. This
feature (UE-group WUS) allows eNB to transmit a UE-group WUS to instruct the
UEs in the group that they must monitor NPDCCH for paging. This allows the UE
to skip the paging procedures to save more power if eNB sends UE-group WUS to
UEs in other groups. The UEs are grouped according to their paging probability
and/or their UE ID based on system information configuration.
Mobile-terminated early data transmission (MT-EDT) (FDD):
Rel-15 Mobile Originating Early Data Transmission (MO-EDT) allows one
uplink data transmission optionally followed by one downlink data transmission
during the random access procedure, avoiding transition to RRC_CONNECTED mode.
Rel-16 Mobile Terminating Early Data Transmission (MT-EDT) allows one downlink
data transmission during the random access procedure triggered in response to a
paging message. This feature allows the eNB to decide whether to initiate
Mobile Terminated EDT procedures towards the UE based on the data size received
from the core network. Mobile Terminating Early Data Transmission (MT-EDT) is
only supported in EPC.
Support for Preconfigured uplink resources (PUR) in idle mode (FDD)
In Rel-15, signalling overhead and power consumption reductions were
introduced by the (mobile-originated) early data transmission (EDT) feature,
where data can be transmitted already in Msg3 during the random-access
procedure.
In Rel-16, the earlier transmission of UL data payload has been further
enhanced by introducing UL transmission using preconfigured uplink resources
(PUR). This feature allows eNB to configure uplink resources, in which a UE in
IDLE mode can send UL transmission without performing random access procedures.
The UE can be potentially configured with a cyclic shift of DMRS, which allows
sharing of the preconfigured resources under which up to two users can transmit
NPUSCH simultaneously when the NPUSCH transmission is larger than or equal to
64ms for 12-tone allocation. By skipping the random access procedures, the
uplink transmission efficiency can be improved and UE power consumption is
reduced. Before performing a PUR transmission, the UE must evaluate the
validity of the timing advance (TA) based on either individual or combined
usage of any of the following attributes: a) serving cell change, b) TA timer,
c) RSRP change. Additionally, it is possible to configure the TA as always
valid within a given cell.
Scheduling of multiple DL/UL transport blocks with single DCI (FDD)
This feature allows the scheduling of up to two transport blocks (TB)
with a single DCI for uplink or downlink unicast transmission, where the number
of TBs is indicated by DCI. The transmission of multiple TBs can be configured
to be contiguous or interleaved. And HARQ bundling can be potentially
configured when transmission is configured as interleaved. It also allows the
scheduling of up to eight transport blocks with a single DCI for SC-MTCH, where
the number of TBs is indicated by DCI. The DCI overhead can be reduced for
contiguous UL/DL transmissions.
Network management tool enhancements - SON (FDD and TDD)
Rel-16 introduces SON features: RACH report, RLF report and ANR for
network resource optimisation. The ANR measurements are performed when the UE
is in RRC_IDLE and reported next time the UE enters RRC_CONNECTED. The NPRACH configuration of the NB-IoT Cells
are exchanged between neighbour eNBs for RACH optimization. And the RLF report
from UE is forwarded to the old eNB to determine the nature of the failure.
SON features are only supported in EPC.
Improved multicarrier operations - Quality report in Msg3 and connected
mode (FDD)
In cells with interference, the coverage level corresponding to the
estimate RSRP may be mismatched with the channel quality. This feature allows
the eNB to configure a UE in IDLE mode to report the downlink channel quality
in Msg3 for non-anchor access. It also allows the UE to report the downlink
channel quality in connected mode other than Msg3 for anchor and non-anchor
carriers. This allows the eNB to schedule NPDCCH and NPDSCH more accurately,
especially in cases with mismatch between coverage level and channel quality.
Presence of NRS on a non-anchor carrier for paging (FDD)
This feature allows eNB to transmit NRS in subframes on a non-anchor
carrier for paging even when no paging NPDCCH is transmitted. The NRS are
present in the first M subframes out of the 10 NB-IoT DL subframes before the
Paging Occasion (PO), where the PO can be a subset of POs or a whole set of
POs, and the values of M depend on the value of nB as defined in TS 36.304.
When NRS is present on a non-anchor paging carrier and the conditions
for NRSRP measurement on non-anchor carrier are met as defined in TS 36.133,
the UE may perform serving cell measurements on the non-anchor paging carrier.
Mobility enhancements - Idle mode inter-RAT cell selection to/from
NB-IoT (FDD and TDD)
With this feature, NB-IoT can provide assistance information for
inter-RAT cell selection to E-UTRAN/GERAN and E-UTRAN can provide assistance
information for inter-RAT cell selection to NB-IoT. A UE may use the assistance
information provided by the network for cell selection to/from NB-IoT.
Improved latency - UE Specific DRX (FDD and TDD)
Rel-16 introduces support for UE specific DRX to reduce paging
latency. The eNB may broadcast a minimum
UE specific DRX value shorter than the cell default DRX value. When UE specific DRX is configured by the
upper layers and the minimum UE specific DRX value is broadcast, the UE
monitors paging according to the longer of the two values.
Coexistence of NB-IoT with NR (FDD and TDD)
This feature allows the configuration of the DL/UL resource reservation
in subframe/slot/symbol-levels on non-anchor carriers for unicast transmission
to avoid resource overlapping with NR channels/signals. The configuration can
be for 10ms or 40ms duration, with a periodicity from {10ms, 20ms, 40ms, 80ms,
160ms} and a start position in a granularity of 10ms, which is independent from
legacy configurations. It also allows dynamic indication whether the resource
reservation is applied or not.
Three system scenarios have been studied and captured in TR 37.824:
• For NB-IoT operation
in NR in-band, RB alignment, power boosting and numerologies have been addressed.
• For NB-IoT operation
in NR guard band, RF requirements will not be specified.
• For NB-IoT standalone
operation, based on coexistence study, it is concluded that there is no issue
for NB-IoT standalone coexistence with NR.
Connection to 5GC (FDD and TDD)
Rel-16 introduces support for connection to 5GC reusing eLTE as a
baseline, including Unified Access Control (UAC). RRC_INACTIVE, NR SDAP and NR
PDCP are not supported and a maximum of two PDU sessions mapped to two default
DRBs is supported.
Rel-16 also introduces support for the CIoT 5GS optimisation, in
particular extended DRX (eDRX) in RRC_IDLE, control plane and user plane CIoT
optimisation, MO-EDT for the control plane and user plane CIoT optimisation,
RRC Connection Reestablishment for the control plane and restriction of use of
Enhanced Coverage.
Similar backhaul signalling to support control plane and user plane CIoT
optimisation are introduced over NG interface (between ng-eNB and AMF) and over
Xn interface (between ng-eNBs), including e.g. early UE radio capability
retrieval from core network after msg3, NB-IoT CP relocation procedures to
support connection reestablishment, Paging assistance information exchanging,
UE differentiation information exchanging, etc.
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