计算机网络

采用更好理解的方式,分为5层

应用层:直接为用户应用进程提供服务,到运输层到应用的信息进行处理(解密,以何种方式展示给你,比如文字消息:正楷?,行书?),然后可以展示给你。

运输层:负责运输网络层的信息给应用层,主要功能包括分用和复用。

分用:就是把接收到来自网络层分开交付给应用层相应的进程(有端口号)

复用:所有来着应用进程的数据(加头信息,有IP???和端口,只加端口???)进行封装,然后发送到网络层

网络层:为交换网上的不同主机之间提供通信服务,有IP协议,选择合适的路由(路径),使源主机传下来的数据,能够通过网络中的路由器找到目的主机。(一种协议,更像概念上的,只是教你如何找路径)。

数据链路层:两个主机之间数据传输,总是在一段一段的链路上,相邻两个点之间,是点对点直接传送的。需要专门的链路层协议,数据链路层将网络层交下来的IP数据报组装成帧(framing),在两个相邻结点间的链路上“透明”地传送帧(frame)中的数据(有同步信息:有没有完全送到,地址信息:发到哪里?差错控制:有错,马上停止,重发)。

物理层(physical
layer):在物理层上传送的数据的单位是比特,物理层的任务就是透明地传送比特流。(可以理解为物理媒介,如双绞线、同轴电缆、光缆、无线信道等,很小很小一个个单元,1
bit 1bit的往下传)。

主要功能:

(1)gNB:Radio Resource Management,无线资源管理;Radio Bearer Control,无线承载控制;Radio
Admission Control无线接入控制; Connection Mobility Control 连接移动性控制;Measurement
configuration & Provision;测量配置和规定;Dynamic Resource Allocation 动态资源分配(安排)

(2)AMF:NAS (Non-access stratum) Security非接入层安全;idle State Mobility
Handling空闲状态移动处理

(3)UPF:Mobility Anchoring移动性锚定;PDU handling协议数据单元处理

(4)SMF(Session Management function):UE IP address allocation UE IP地址分配; PDU
Session Control 协议数据单元会话控制

4.3 Network Interfaces

网络接口

1.NG interface

NG User Plane:The NG user plane interface (NG-U) is defined between the NG-RAN
node and the UPF. The user plane protocol stack of the NG interface is shown on
Figure 4.3.1.1-1. The transport network layer is built on IP transport and
GTP-U is used on top of UDP/IP to carry the user plane PDUs between the NG-RAN
node and the UPF.

NG-U,连接NG-RAN和UPF,NG接口用户面协议栈

运输网络层在IP传输层之上,使用GPRS Tunneling
Protocol-User(GPRS隧道协议:用户,在UDP/IP之上)传递在NG-RAN节点和UPF的用户面数据协议单元。

NG-U provides non-guaranteed delivery of user plane PDUs between the NG-RAN
node and the UPF.

NG-U使用的UDP协议,不能保证完全准确的传送。

NG Control Plane:

The NG control plane interface (NG-C) is defined between the NG-RAN node and
the AMF. The control plane protocol stack of the NG interface is shown on
Figure 4.3.1.2-1. The transport network layer is built on IP transport. For the
reliable transport of signalling messages, SCTP is added on top of IP. The
application layer signalling protocol is referred to as NGAP (NG Application
Protocol). The SCTP layer provides guaranteed delivery of application layer
messages. In the transport, IP layer point-to-point transmission is used to
deliver the signalling PDUs.

NG-C在
NG-RAN节点和AMF之间,运输网络层在IP传输层之上,为了可靠的信令传输,SCTP添加在IP层之上,应用层信令协议被称为NGAP,SCTP(Stream
Control Transmission Protocol)保证了应用层消息的可靠的传输,在运输IP层点对点传输被用于传输信令协议数据单元。

NG-C provides the following functions:

* NG interface management;
NG接口管理

* UE context management;
UE上下文管理

* UE mobility management;
UE移动性管理

* Transport of NAS messages;
NAS信息传输

* Paging;
寻呼

* PDU Session Management;
协议数据单元会话管理

* Configuration Transfer;
配置转移

* Warning Message Transmission.
警告消息传输

与控制有关的NGAP,有AP存在,采用TCP/IP协议???

Xn interface

Xn User Plane:The Xn User plane (Xn-U) interface is defined between two NG-RAN
nodes. The user plane protocol stack on the Xn interface is shown in Figure
4.3.2.1-1. The transport network layer is built on IP transport and GTP-U is
used on top of UDP/IP to carry the user plane
PDUs.Xn-U(用户面)在两个NG-RAN节点之间,运输网络层在IP运输层之上,用GTP-U协议(UDP/IP)来传输用户面PDUs

Xn Control Plane:The Xn control plane interface (Xn-C) is defined between two
NG-RAN nodes. The control plane protocol stack of the Xn interface is shown on
Figure 4.3.2.2-1. The transport network layer is built on SCTP on top of IP.
The application layer signalling protocol is referred to as XnAP (Xn
Application Protocol). The SCTP layer provides the guaranteed delivery of
application layer messages. In the transport IP layer point-to-point
transmission is used to deliver the signalling PDUs.

Xn-C在两个NG-RAN节点之间,应用层信令协议称为XnAP,SCTP(Stream Control Transmission
Protocol)层协议保证应用层的信息的可靠传输。在IP层点对点传输被用于传递信令数据

Xn-C functions:

*
Xn interface management; Xn接口管理;

*
UE mobility management, including context transfer and RAN
paging:UE移动性管理,包括上下文传输和RAN寻呼:

*
Dual connectivity.双连接(4G和5G???)

4.4 Radio Protocol Architecture

无线协议架构

* User Plane
The figure below shows the protocol stack for the user plane, where SDAP,
PDCP, RLC and MAC sublayers (terminated in gNB on the network side) perform the
functions listed in subclause 6.

SDAP(Service Data Adaptation Protocol),PDCP(Packet Data Convergence Protocol),
RLC(Radio Link Control)and MAC子层终结于gNB网络侧

* Control Plane
PDCP, RLC and MAC(subclause 6),

RRC(subclause 7),radio resource control

NAS(Non-access stratum) control protocol(非接入层控制协议)

NAS control protocol (terminated in AMF on the network side) performs the
functions listed in 3GPP TS 23.501 [3]), for instance: authentication, mobility
management, security control…认证,移动管理和安全控制

4.5 Multi-RAT Dual Connectivity

多RAT双连接(Radio Access Technology)

NG-RAN supports Multi-RAT Dual Connectivity (MR-DC) operation whereby a UE in
RRC_CONNECTED is configured to utilise radio resources provided by two distinct
schedulers, located in two different NG-RAN nodes connected via a non-ideal
backhaul and providing either E-UTRA (i.e. if the node is an ng-eNB) or NR
access (i.e. if the node is a gNB). Further details of MR-DC operation can be
found in 3GPP TS 37.340 [21].

NG-RAN支持多接入双连接操作,从而一个UE在RRC_CONNECTED状态下被配置为利用两个不同调度程序提供的无线资源,调度程序位于两个不同的NG-RAN节点中(通过非理想的回程连接)并且提供E-UTRA或者NR接入。

技术
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