SON and MDT support for NR
SON and MDT features support in NR, includes MRO (Mobility Robustness Optimisation), MLB (Mobility Load Balancing), RACH optimization, MDT (Minimization of Drive Test) and L2 measurements. Specification of these features will help mobile operators reduce the CAPEX/OPEX and improve the use experience.
Also a new TS 38.314: L2 measurements for NR is introduced.
The key
functionalities are:
Mobility
Robustness Optimisation (MRO) aims at detecting and enabling correction of mobility related problems
including Connection failure due to intra-system or inter-system mobility,
Inter-system Unnecessary HO and Inter-system HO ping-pong. MRO also provides
means to distinguish the above problems from NR coverage related problems and
other problems, not related to mobility.
- Connection failure due to intra-system
mobility
- Intra-system Too Late Handover
- Intra-system Too Early Handover
- Intra-system Handover to Wrong Cell
- Connection failure due to inter-system
mobility
- Inter-system/ Too Late Handover
- Inter-system/ Too Early Handover
- Inter-system Unnecessary HO
- Inter-system Ping-pong
Mobility
load balancing (MLB) is to distribute load evenly among cells and among areas of cells, or
to transfer part of the traffic from congested cell or from congested areas of
cells, or to offload users from one cell, cell area, carrier or RAT to achieve
network energy saving.
Intra-RAT
and intra-system inter-RAT load balancing scenarios are specified and includes
the functions of Load reporting, Load
balancing action based on handovers and Adapting handover and/or reselection
configuration.
The load
reporting function is executed by exchanging load information over the
Xn/X2/F1/E1 interfaces via Resource Status Reporting Initiation & Resource
Status Reporting procedures.
The load
metrics that have been specified consist of
- Radio resource usage (per-cell and per SSB
area PRB usage: DL/UL GBR PRB usage, DL/UL non-GBR PRB usage, DL/UL total PRB
usage, and DL/UL scheduling PDCCH CCE usage);
- TNL capacity indicator (UL/DL TNL offered
capacity and available capacity);
- Cell Capacity Class value (UL/DL relative
capacity indicator);
- Capacity value (per cell, per SSB area and
per slice: UL/DL available capacity);
- HW capacity indicator (offered throughput
and available throughput over E1, percentage utilisation over F1);
- RRC connections (number of RRC connections,
and available RRC Connection Capacity);
- Number of active UEs.
RACH
optimization is
supported by UE reported information made available at the NG RAN node and by
PRACH parameters exchange between NG RAN nodes.
The
functionalities supported over the interfaces consist of
- PRACH configuration per served cell is
signalled from DU to CU and over Xn
- PRACH configuration of Served Cells over X2
- RACH report from UE over Uu
- RACH report from CU to DU over F1
NR
MDT takes LTE as
baseline and takes NR new features into account, including beam, RRC_INACTIVE
and EN-DC.
The
following functionalities are specified:
- MDT network signaling support over S1, X2,
NG, Xn, F1 and E1
- Logged MDT for RRC_IDLE and RRC_INACTIVE
UEs, support event-trigged or periodic logged MDT
- Immediate MDT
- CEF (Connection Establishment Failure)
report
- Resume failure report
- Immediate MDT for EN-DC
L2
measurements. In
this work item, a new spec TS 38.314 was produced to capture the measurements
performed by network or the UE that are transferred over the standardised
interfaces in order to support NR radio link operations, radio resource
management (RRM), network operations and maintenance (OAM), minimization of
drive tests (MDT) and self-organising networks (SON).
The
specified measurements includes
- Received Random Access Preambles
- Packet delay
- Number of active UEs
- Number of stored inactive UE contexts
- UL PDCP Packet Average Delay by the UE