3GPP Release-16: Further LTE and 5G NR Enhancements

This year we have seen the rapid standardization of 3GPP Rel-15, 5G-NR, laying the foundation for the first 5G networks. This blogpost, discusses the ideas and enhancements that are currently being worked on for 3GPP Release-16. These enhancements cover not only 5G-NR, but also LTE which is being advanced in parallel. We had already covered the features and study items introduced in Release 15 in our blog posts here and here.

Note: In this post focuses on the Rel-16 features/work items [1].

Further Enhancements to LTE

Some of the interesting enhancements for the LTE within 3GPP Rel-16 include the following:

eNB(s) Architecture Evolution for E-UTRAN and Next Gen (NG)-RAN – This work item focuses and builds upon the Technical Report [2] in Rel-15 on the same topic, which studies the higher layer functional split architecture of eNB. A new architecture with central unit (LTE-CU) and distributed unit (LTE-DU) has been designed to achieve better integration between the LTE eNB and NR gNB (Next Generation Node B).

LTE-NR & NR-NR Dual Connectivity and NR Carrier Aggregation enhancements – is dedicated to exploring enhancements for Dual Connectivity (DC) and Carrier Aggregation (CA). The focus will be on the following four topics:

• Support of asynchronous and synchronous NR-NR Dual Connectivity;
• Early Measurement reporting – to ensure quick and efficient setup of MR-DC and/or CA;
• Efficient and low latency serving cell configuration/activation/setup;
• Fast recovery – in case of MCG (master cell group) Failure by utilizing SCG (secondary cell group) link and the split SRBs during recovery.

Rel-16 enhancements for NB-IoT – After successful commercialization of NB-IoT introduced in Rel-13 and further improvements made in subsequent releases (read more here), the following improvements are in discussion for 3GPP Release-16:

• Improved DL transmission efficiency and/or UE power consumption – by supporting mobile-terminated (MT) early data transmission along with support for UE-group wake-up signal;
• Improved UL transmission efficiency and/or UE power consumption – by supporting transmission in preconfigured resources (common or dedicated) in idle and/or connected mode based on SC-FDMA waveform for UEs with a valid timing advance;
• Scheduling enhancement – in the form of scheduling multiple DL/UL transport blocks with or without DCI for SC-PTM (Single-Cell Point-To- Multipoint) and unicast along with discussion for SPS (Semi-persistent scheduling);
• Network management tool enhancement – improvement of SON (Self-Organizing network) support;
• Improved multi-carrier operation – For non-anchor carrier cases support of Msg3 quality reporting and support for signaling to indicate on a non-anchor carrier for paging a set of subframes which will contain NRS (NarrowBand Reference Signal) even when no paging NPDCCH is transmitted;
• Mobility enhancement – allowing for NB-IoT mechanism which would assist idle mode inter-RAT cell selection for NB-IoT to and from LTE, LTE-MTC and GERAN [RAN2];
• Coexistence with NR.

5G NR Enhancements

After the introduction of 5G in Release 15, “5G phase 1”, there are already aspects that are being worked on for further improvements, as not all features could be in completed in time for Rel-15. The following are a list of work items that are being taken up for consideration for making it to 3GPP Release-16 i.e. “5G phase 2”:

Security Assurance Specification for 5G – With this work item the aim is to develop Security Assurance Specification(s) (SCAS) for the 5G network products to identify threats to critical assets of the 5G system architecture along with developing security/vulnerabilities related functional requirements and testcases.

LAN support in 5G – focuses on developing the initial requirements for the 5G system to support LAN-type services on 5G. The results of this work item will contribute to the update of TS 22.261 addressing various aspects such as 5GLAN creation and management, 5G Private Virtual Network, 5GLAN service authorization, Mobility and service continuity for 5G LAN-type service etc.

Integration of Satellite Access in 5G – focuses on developing the initial requirements for the 5G system to enable integration of satellite access when considering the different use cases mentioned in TR 22.822. The following use cases are to be addressed as per TR 22.822 :

• Roaming between terrestrial and satellite networks;
• Broadcast and multicast with a satellite overlay;
• Internet of Things with a satellite network;
• Temporary use of a satellite component;
• Optimal routing or steering over a satellite;
• Satellite trans-border service continuity;
• Global satellite overlay;
• Indirect connection through a 5G satellite access network;
• 5G Fixed Backhaul between NR and the 5G Core;
• 5G Moving Platform Backhaul;
• 5G to Premises;
• Off-shore Wind Farms.

5G positioning services – focuses on developing the initial requirements for the 5G system to support positioning services. There are various use cases, such as regulatory requirements for emergency services along with new services, that might require positioning support. The work carried out on this work item will be used for updating the requirements related to positioning in 3GPP TS 22.261 apart from using the results and potential requirements identified in TR 22.872.

NR intra band Carrier Aggregation – In order to achieve higher level of carrier aggregation in NR with limited operating bands, it becomes important for the 5G system to support intra band carrier aggregation. This work item focuses on specifying the CA configurations and their specific RF requirements for contiguous as well as non-contiguous cases along with analyzing that the combinations introduced are not affected by RF limitations. Related conformance test cases also need to be investigated under the purview of this work item.

Dual Connectivity (EN-DC) – This work item will help in defining all the new 2 DL and 2 UL EN-DC configurations with different bands i.e. 1 LTE band and 1 NR band. In order for a combination to be introduced in EN-DC configuration it would be mandatory that the involved LTE or NR bands along with their intra band CA combinations also have been already included in the specification.

Enhancements on MIMO for NR – This work item is dedicated to the improvement of MIMO performance in 5G NR. A lot of new improvements have been introduced in Rel-15 building on top of the Rel-14 enhancements in LTE along with the change in the RF antenna array and introduction of Type II CSI (Channel state information). These changes help in achieving better MIMO performance. The following areas have been identified where further improvements could be made:

• MU-MIMO enhancements: by specifying the overhead reduction based on the Type II CSI feedback considering the tradeoff between performance and overhead. Also, possible extension of Type II CSI feedback to rank > 2;
• Enhancements on multi-TRP (Tx/Rx Point)/panel transmission including improved reliability and robustness with both ideal and non-ideal backhaul;
• Enhancements on multi-beam operation, primarily targeting FR2 operation;
• CSI-RS and DMRS (both downlink and uplink) enhancement for PAPR (peak to average power ratio) reduction for one or multiple layers
• full power transmission in case of uplink transmission with multiple power amplifiers (assume no change on UE power class).

NR mobility enhancements – As the introduction of Rel-15 5G NR was moved up and was carried out under very tight timeline, the current mobility aspects in NR were simply adopted from LTE. The handover mechanism similar to LTE isn’t ideal for 5G NR FR2 with beamforming as there might be higher interruption faced by the user due to beam sweeping delay. Also, the UE might experience high degradation of signal very quickly upon slight change in direction of the user due to the nature of beamforming. The challenges that come with operating in FR2 to the mobility aspects and KPIs are quite high which need novel solutions to deliver the 0ms interruption promised in 5G along with reducing the frequency of such interruptions. The following improvements will be worked upon:

• Solution(s) to reduce interruption time during HO/SCG change by:
  • Handover/SCG change with simultaneous connectivity with source cell and target cell;
  • Make-before-break;
  • RACH-less handover;
• Solution(s) to improve the HO reliability and robustness by:
  • Conditional handover;
  • Fast handover failure recovery.

Energy efficiency of 5G – The focus of 3GPP on energy efficiency continues in 5G as well and this work item will focus on building the concepts, use cases and requirements for achieving energy efficiency in the 5G system. Different parameters along with requirements would be introduced to assess the energy efficiency performance and compare it with other RATs.

Summary note

As we can see from the above, there are a lot of items currently being discussed in 3GPP for making into Release 16 that would enhance the existing LTE and 5G RATs towards achieving the goals of IMT-2020. 3GPP Release-16 or “5G phase 2” is slated to be completed by December 2019 and shall be fully compliant with IMT-2020 requirements. It would be interesting to see the final outcome of these work items and how they influence their respective RATs. We will keep you posted regarding the latest developments. In the next blog post we will focus on the study items being discussed for Release 16.

References

[1] http://www.3gpp.org/DynaReport/FeatureListFrameSet.htm

[2] https://portal.3gpp.org/ngppapp/CreateTdoc.aspx?mode=view&contributionUid=RP-180339

[3] http://www.3gpp.org/release-16

[4] M. Rahnema, M. Dryjanski, “From LTE to LTE-Advanced Pro and 5G”, Artech House, 2017.

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