Mechanism of Fast Data Retransmission in CU-DU Split Architecture of 5G NRG

The 5G radio access network （RAN） architectm＇e is supposed to be split into the central unit （CU） and the distributed unit （DU） in order to support more flexible transport networks and provide enhanced user experience. However, such functional split may also introduce some new technical issues. In this pa- per, we study the data fast retransmission issue introduced by this functional split in different scenarios and solutions are provided to handle this issue. With the fast data retransmis- sion mechanism proposed in this paper, the retransmitted da- ta packets could be identified and handled with high priority. In this way, the data delivery between the CU and DU in 5G RAN is assured.

General Architecture of Centralized Unit and Distributed Unit for New Radio

In new radio （NR） access technology, the radio access network （RAN） architecture is split into two kinds of entities, i.e., the centralized unit （CU） and the distributed unit （DU）, to enhance the network flexibility. In this split architecture, one CU is able to control several DUs, which enables the function of base-band central control and remote service for users. In this paper, the general aspects of CU-DU split architecture are introduced, including the split method, interface functions （control plane functions and user plane functions）, mobility scenarios and other CU-DU related issues. The simulations show the performance of Options 2 and 3 for CU-DU split.

NR中集中式网元和分布式网元架构现状与进展

在新空口(NR)接入技术中,无线接入网络架构被分割成2种实体:集中式网元(CU)和分布式网元(DU)。认为在这种分离的架构中,通过一个CU控制多个DU的方式,可以同时实现基带集中控制功能和针对用户的远端服务功能。介绍了CU-DU分离架构的基本特性,包括分割方式、接口功能(控制面功能和用户面功能)、移动性场景以及其他CU-DU相关特性和最新进展,为下一代无线接入网络技术研究提供参考。

Enabling Energy Efficiency in 5G Network

The mobile Internet and Internet of Things are considered the main driving forc⁃es of 5G,as they require an ultra-dense deployment of small base stations to meet the in⁃creasing traffic demands.5G new radio(NR)access is designed to enable denser network deployments,while leading to a significant concern about the network energy consump⁃tion.Energy consumption is a main part of network operational expense(OPEX),and base stations work as the main energy consumption equipment in the radio access network(RAN).In order to achieve RAN energy efficiency(EE),switching off cells is a strategy to reduce the energy consumption of networks during off-peak conditions.This paper intro⁃duces NR cell switching on/off schemes in 3GPP to achieve energy efficiency in 5G RAN,including intra-system energy saving(ES)scheme and inter-system ES scheme.Addition⁃ally,NR architectural features including central unit/distributed unit(CU/DU)split and dual connectivity(DC)are also considered in NR energy saving.How to apply artificial in⁃telligence(AI)into 5G networks is a new topic in 3GPP,and we also propose a machine learning(ML)based scheme to save energy by switching off the cell selected relying on the load prediction.According to the experiment results in the real wireless environment,the ML based ES scheme can reduce more power consumption than the conventional ES scheme without load prediction.

RAN Centric Data Collection for New Radio

Self-organizing network(SON)and minimization of driver tests(MDT)are functions designed for Long Term Evolution(LTE)system.SON is designed for network deployment by automatic configuration.MDT is designed for network performance evaluation by automatic signalling procedure.However,these functions do not support new features in new radio(NR)access technology,e.g.,multiple radio access technology(RAT)-dual connectivity(MR-DC),central unit-distribute unit(CU-DU)split architecture,beam,etc.Therefore,how to support these features is a challenge for the industry.This paper provides analysis for these problems and provides the summary of SON/MDT functions progress in3 GPP.The analysis includes sub functions such as inter/intra system mobility robustness enhancement,inter/intra system mobility load balance,measurement qualities and mechanism of MDT,energy saving mechanism and procedure,RACH procedure optimization,PCI selection optimization,coverage and capacity optimization,and quality of service(QoS)monitoring mechanism.In addition,this paper also provides an initial thought on artificial intelligence(AI)algorithms applied to SON/MDT functions in NR,so called Smart Grid.

General Introduction of Non General Introduction of Non-Terrestrial Networks for New Radio

In the new radio(NR)access technology,non-terrestrial networks(NTN)are intro-duced to meet the requirement of anywhere and anytime connections from the world market.With the introduction of NTN,the NR system is able to offer the wide-area coverage and en-sure the service availability for users.In this paper,the general aspects of NTN are intro-duced,including the NTN architecture overview,the impact of NTN on next-generation radio access network(NG-RAN)interface functions,mobility scenarios and other NTN related is-sues.The current progress in 3GPP Release 17 is also provided.