5G上行

本文探讨了5G上行面临的问题,包括上行覆盖不足,主要由高频段穿透损耗大、手机发射功率有限导致。接着介绍了EN-DC双连接技术,通过4G与5G结合提供更好的网络体验。最后,提出了两种5G内部覆盖增强方案:辅助上行(SUL)和载波聚合(CA),以提升上行覆盖和性能。

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一、上行覆盖不足

由于2.6G/3.5G的频率较高,跟3/4G所用的2.1GHZ或者1.8GHZ相比,穿透损耗大、信号衰减快。此外手机体积小能力弱,且由于辐射指标的限制,在TDD双发场景下也就最大26dBm(0.4瓦),平均23dBm(0.2瓦)的发射功率,路径上还要经历重重折损,离基站稍微远点,还没到达基站就衰减殆尽了。

 

二、EN-DC双连接

5G的非独立组网(NSA)模式,最常用的选项3x(option3x),4G负责控制面,5G作为容量的补充。这种方式也叫EN-DC(EnodeB NR Dual Connectify)双连接。

EN-DC UL:3.5/2.6+2.1GHZ   DL:3.5/2.6+2.1GHZ
4G UL/DL:2.1GHZ

 

三、5G内部覆盖增强方案

5G频率域 频率范围 名称
Contents Foreword 7 1 Scope 8 2 References 8 3 Abbreviations and Definitions 9 3.1 Abbreviations 9 3.2 Definitions 9 4 Overall Architecture and Functional Split 10 4.1 Overall Architecture 10 4.2 Functional Split 11 4.3 Network Interfaces 13 4.3.1 NG Interface 13 4.3.1.1 NG User Plane 13 4.3.1.2 NG Control Plane 13 4.3.2 Xn Interface 14 4.3.2.1 Xn User Plane 14 4.3.2.2 Xn Control Plane 14 4.4 Radio Protocol Architecture 15 4.4.1 User Plane 15 4.4.2 Control Plane 15 4.5 Multi-RAT Dual Connectivity 16 5 Physical Layer 16 5.1 Waveform, numerology and frame structure 16 5.2 Downlink 17 5.2.1 Downlink transmission scheme 17 5.2.2 Physical-layer processing for physical downlink shared channel 17 5.2.3 Physical downlink control channels 18 5.2.4 Synchronization signal and PBCH 18 5.2.5 Physical layer procedures 19 5.2.5.1 Link adaptation 19 5.2.5.2 Power Control 19 5.2.5.3 Cell search 19 5.2.5.4 HARQ 19 5.3 Uplink 19 5.3.1 Uplink transmission scheme 19 5.3.2 Physical-layer processing for physical uplink shared channel 19 5.3.3 Physical uplink control channel 20 5.3.4 Random access 21 5.3.5 Physical layer procedures 21 5.3.5.1 Link adaptation 21 5.3.5.2 Uplink Power control 21 5.3.5.3 Uplink timing control 21 5.3.5.4 HARQ 21 5.4 Carrier aggregation 21 5.4.1 Carrier aggregation 21 5.4.2 Supplemental Uplink 22 5.5 Transport Channels 22 6 Layer 2 23 6.1 Overview 23 6.2 MAC Sublayer 24 6.2.1 Services and Functions 24 6.2.2 Logical Channels 25 6.2.3 Mapping to Transport Channels 25 6.2.4 HARQ 25 6.3 RLC Sublayer 25 6.3.1 Transmission Modes 25 6.3.2 Services and Functions 26 6.3.3 ARQ 26 6.4 PDCP Sublayer 26 6.4.1 Services and Functions 26 6.5 SDAP Sublayer 27 6.6 L2 Data Flow 27 6.7 Carrier Aggregation 27 6.8 Dual Connectivity 29 6.9 Supplementary Uplink 29 6.10 Bandwidth Adaptation 29 7 RRC 30 7.1 Services and Functions 30 7.2 Protocol States 31 7.3 System Information Handling 31 7.4 Access Control 32 7.5 UE Capability Retrieval framework 32 7.6 Transport of NAS Messages 33 7.7 Carrier Aggregation 33 7.8 Bandwidth Adaptation 33 8 NG Identities 33 8.1 UE Identities 33 8.2 Network Identities 33 9 Mobility and State Transitions 34 9.1 Overview 34 9.2 Intra-NR 34 9.2.1 Mobility in RRC_IDLE 34 9.2.1.1 Cell Selection 34 9.2.1.2 Cell Reselection 35 9.2.2 Mobility in RRC_INACTIVE 35 9.2.2.1 Overview 35 9.2.2.2 Cell Reselection 36 9.2.2.3 RAN-Based Notification Area 36 9.2.2.4 State Transitions 37 9.2.2.4.1 UE triggered transition from RRC_INACTIVE to RRC_CONNECTED 37 9.2.2.4.2 Network triggered transition from RRC_INACTIVE to RRC_CONNECTED 37 9.2.2.5 RNA update 38 9.2.3 Mobility in RRC_CONNECTED 38 9.2.3.1 Overview 38 9.2.3.2 Handover 39 9.2.3.2.1 C-Plane Handling 39 9.2.3.2.2 U-Plane Handling 41 9.2.4 Measurements 41 9.2.5 Paging 43 9.2.6 Random Access Procedure 43 9.2.7 Radio Link Failure 44 9.3 Inter RAT 44 9.3.1 Intra 5GC 44 9.3.1.1 Cell Reselection 44 9.3.1.2 Handover 45 9.3.1.3 Measurements 45 9.3.2 From 5GC to EPC 45 9.3.2.1 Cell Reselection 45 9.3.2.2 Handover 45 9.3.2.3 Measurements 45 9.3.2.4 Data Forwarding 45 9.4 Roaming and Access Restrictions 46 10 Scheduling 46 10.1 Basic Scheduler Operation 46 10.2 Downlink Scheduling 46 10.3 Uplink Scheduling 47 10.4 Measurements to Support Scheduler Operation 47 10.5 Rate Control 47 10.5.1 Downlink 47 10.5.2 Uplink 48 10.6 Activation/Deactivation Mechanism 48 11 UE Power Saving 48 12 QoS 49 13 Security 50 13.1 Overview and Principles 50 13.2 Security Termination Points 51 13.3 State Transitions and Mobility 51 14 UE Capabilities 51 15 Self-Configuration and Self-Optimisation 51 15.1 Definitions 51 15.2 UE Support for self-configuration and self-optimisation 51 15.3 Self-configuration 52 15.3.1 Dynamic configuration of the NG-C interface 52 15.3.1.1 Prerequisites 52 15.3.1.2 SCTP initialization 52 15.3.1.3 Application layer initialization 52 15.3.2 Dynamic Configuration of the Xn interface 52 15.3.2.1 Prerequisites 52 15.3.2.2 SCTP initialization 52 15.3.2.3 Application layer initialization 52 15.3.3 Automatic Neighbour Cell Relation Function 52 15.3.3.1 General 52 15.3.3.2 Intra-system – intra NR Automatic Neighbour Cell Relation Function 52 15.3.3.3 Intra-system – intra E-UTRA Automatic Neighbour Cell Relation Function 53 15.3.3.4 Intra-system – inter RAT Automatic Neighbour Cell Relation Function 53 15.3.3.5 Inter-system Automatic Neighbour Cell Relation Function 53 15.3.4 Xn-C TNL address discovery 53 16 Verticals Support 53 16.1 URLLC 53 16.1.1 Overview 53 16.1.2 LCP Restrictions 53 16.1.3 Packet Duplication 53 16.2 IMS Voice 54 16.3 Network Slicing 54 16.3.1 General Principles and Requirements 54 16.3.2 CN Instance and NW Slice Selection 55 16.3.2.1 CN-RAN interaction and internal RAN aspects 55 16.3.2.2 Radio Interface Aspects 55 16.3.3 Resource Isolation and Management 55 16.3.4 Signalling Aspects 56 16.3.4.1 General 56 16.3.4.2 CN Instance and NW Slice Selection 56 16.3.4.3 UE Context Handling 56 16.3.4.4 PDU Session Handling 57 16.3.4.5 Mobility 58 16.4 Public Warning System 59 Annex A (informative): QoS Handling in RAN 60 A.1 PDU Session Establishment 60 A.2 New QoS Flow without Explicit Signalling 60 A.3 New QoS Flow with NAS Reflective QoS and Explicit RRC Signalling 61 A.4 New QoS Flow with Explicit Signalling 62 A.5 Release of QoS Flow with Explicit Signalling 63 A.6 UE Initiated UL QoS Flow 64 Annex B (informative): Deployment Scenarios 66 B.1 Supplementary Uplink 66 Annex C (informative): Change history 67
### 5G 上行同步机制及其实现 #### 同步的重要性 在无线通信系统中,特别是对于第五代移动网络(5G),上行链路的同步至关重要。它确保基站能够准确接收来自多个用户的信号并区分这些信号的时间和频率偏移[^1]。 #### 初始接入过程中的定时调整 当终端设备首次连接到网络时,会通过随机接入信道(RACH)发送前导序列给基站。基站接收到该前导序列后,计算出时间提前量(Timing Advance, TA)。TA用于补偿由于距离差异引起的传播延迟,从而使得不同位置的UE能够在相同的时间窗口内传输数据至gNodeB[^2]。 #### 基于PUSCH的持续跟踪 除了初始阶段外,在正常业务期间也需要维持精确的时间对齐。物理上行共享信道(PUSCH)承载着主要的数据负载,并且其帧结构设计允许周期性的反馈来微调每个UE的具体发射时刻。这种闭环控制可以适应快速变化的环境条件比如高速运动场景下的多普勒效应影响等。 ```python def calculate_timing_advance(distance_to_base_station): speed_of_light = 3e8 # meters per second timing_advance = distance_to_base_station / speed_of_light * 1e6 # microseconds return timing_advance distance_km = float(input("Enter the approximate distance from UE to gNodeB in kilometers: ")) timing_adjustment_us = calculate_timing_advance(distance_km * 1000) print(f"The required Timing Advance is approximately {timing_adjustment_us:.2f} µs.") ``` 上述代码片段展示了如何基于用户设备与基站之间的直线距离粗略估算所需的时间提前量。 #### 频率偏差校正 另外一方面,考虑到实际操作环境中不可避免的存在载频误差问题,则需依赖参考信号如DM-RS(Demodulation Reference Signal),通过对它们的相关处理得到估计值进而实施相应的纠正措施以保持上下行间的一致性。 ---
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