What is the architecture of the 4G network?
4G网络的架构是什么？
We have seen the principal elements, but we can ask ourselves if all these pieces are connected directly to each other.
我们已经看到了主要元素，但我们可以问自己，所有这些部分是否直接相互连接。
And, do all the pieces of equipment communicate with each other?
并且，所有设备是否相互通信？
These are the questions we will answer in this video.
以下是我们将在本视频中回答的问题。
As we’ve said, a 4G network is made up of a set of eNodeBs,a few Serving Gateways, a few MMEs, a few PGW and an HSS.
正如我们所说，4G网络由一组eNodeB，一些服务网关，一些MME，一些PGW和一个HSS组成。
All these nodes are connected to the IP network of the mobile operator.
所有这些节点都连接到移动运营商的IP网络。
All the equipment of the 4G network have the IP protocol stack and we could say, in plain language, speak IP.
4G网络的所有设备都有IP协议栈，我们可以用简单的语言说IP。
The operator’s IP network is made up of a set of interconnected routers.
运营商的IP网络由一组互连的路由器组成。
The pieces of equipment communicate even if they are not directly linked to each other, from the moment there are routers between them: this is the principle of the IP protocol which is going to take care of retransmission by successive hops.
从它们之间存在路由器的那一刻起，即使它们没有彼此直接链接，这些设备也进行通信：这是IP协议的原理，它将通过连续的跳跃来处理重传。
Consequently, we can now define logical interfaces between nodes even they are not physically connected.
因此，我们现在可以定义节点之间的逻辑接口，即使它们没有物理连接。
Let’s first simplify the network and show only the essential elements.
让我们首先简化网络，只显示基本要素。
We have here a certain network topology and what we can see is that it’s just an IP network belonging to the mobile operator and the 4G nodes are connected to it.
我们在这里有一定的网络拓扑结构，我们可以看到它只是一个属于移动运营商的IP网络，4G节点与它相连。
We’ll define a certain number of interfaces, for example,between two eNodeBs, between an eNodeB and a Serving Gateway and so on.
我们将定义一定数量的接口，例如，在两个eNodeB之间，eNodeB和服务网关之间等等。
Each interface is specified, because, above the IP, there will be communication protocols specialized in mobility management or the exchange of data taking mobility into account.
指定每个接口，因为在IP之上，将存在专用于移动性管理或考虑移动性的数据交换的通信协议。
The first interface we see is called the SG-I interface,"I"for Internet.
我们看到的第一个接口称为SG-I接口，“I”表示Internet。
It’s the interface between the P-Gateway and the external IP network that we can interpret as the Internet.
它是P-Gateway和外部IP网络之间的接口，我们可以将其解释为Internet。
Each interface is numbered.
每个接口都有编号。
I’m using these numbers in the course because those are the ones used by the professionals, but there is no need to remember them.
我在课程中使用这些数字，因为那些是专业人士使用的数字，但没有必要记住它们。
The S5 interface is found between the S‑Gateway and the P-Gateway of the same 4G network.
S5接口位于同一4G网络的S-Gateway和P-Gateway之间。
The interface is used to exchange user data and a few signaling messages.
该接口用于交换用户数据和一些信令消息。
There’s also the interface between the S-Gateway and the MME since the MME is the control equipment and it must also control, for certain functions, the S-Gateway.
由于MME是控制设备，因此S-Gateway和MME之间也有接口，并且对于某些功能，它还必须控制S-Gateway。
The S11 interface between the MME and the S-Gateway is only used to exchange signaling.
MME和S-Gateway之间的S11接口仅用于交换信令。
We have the interface between the MME and the HSS called S6a, which also only does signaling.
我们在MME和HSS之间有一个叫做S6a的接口，它也只做信令。
The interface between the eNode B and the MME called S1-MME, there again, is only for the exchange of signaling.
eNode B和被称为S1-MME的MME之间的接口再次仅用于信令的交换。
Between the eNodeB and the S-Gateway, we have the S1U interface.
在eNodeB和S-Gateway之间，我们有S1U接口。
Here it’s only for transporting user data, there is no exchange of signaling.
这里仅用于传输用户数据，没有信令交换。
The X2 interface is the one between two eNodeB.
X2接口是两个eNodeB之间的接口。
Both signaling and user data are transported.
传输信令和用户数据。
Finally, an extremely important interface, the Uu interface: transmission on the radio channel.
最后，一个极其重要的接口，Uu接口：无线电信道上的传输。
The UU interface is therefore situated between the terminal (the UE) and the eNodeB.
因此，UU接口位于终端（UE）和eNodeB之间。
Here again, user data and signaling messages are transported.
这里再次传输用户数据和信令消息。
Now let’s look at the interconnection of various mobile networks.
现在让我们来看看各种移动网络的互连。
This is the principle of international roaming.
这是国际漫游的原则。
I am a citizen of country F and I go to country B.
我是F国的公民，我去了B国。
I’ll be taken care of by a local eNodeB, a local S-Gateway, and a local MME.
我将由本地eNodeB，本地S-Gateway和本地MME负责。
Because we’re staying inside the network, we have the same interfaces that we’ve just seen.
因为我们留在网络中，所以我们拥有与之相同的界面。
That doesn’t change between country B and country F.
这在B国和F国之间没有变化。
However, in one of the possible implementations,the S-Gateway will communicate with the P‑Gateway of my originating network.
但是，在一种可能的实现中，S-Gateway将与我的始发网络的P-Gateway通信。
Here, it’s an interface that is slightly different from the S5 interface between the S‑Gateway and the P‑Gateway of the same network, the S8 interface is between the S-Gateway and P-Gateway of different networks.
这里，它是一个与同一网络的S-Gateway和P-Gateway之间的S5接口略有不同的接口，S8接口位于不同网络的S-Gateway和P-Gateway之间。
For this course, we won’t distinguish between them because that would take us too far into uninteresting technical details and these details are not useful for us to understand the general concepts.
对于本课程，我们不会区分它们，因为这会让我们对无趣的技术细节有太多的了解，这些细节对我们理解一般概念没有用。
Here’s is a representation of all nodes of a 4G network.
这是4G网络的所有节点的表示。
There is additional equipment that we won’t be looking at, other than in this video.
除了这个视频外，还有其他我们不会看的设备。
The EIR, Equipment Identity Register,is the terminal data base for terminals which have been stolen.
EIR，设备识别寄存器，是被盗终端的终端数据库。
The interface between the MME and the EIR is called S13.
MME和EIR之间的接口称为S13。
We also have the PCRF, Policy and Charging Rules Function, which takes care of managing quality of service and there is a Gx interface between the P-Gateway and the PCRF.
我们还有PCRF，策略和计费规则功能，它负责管理服务质量，P-Gateway和PCRF之间有一个Gx接口。
In this mooc, we will consider the nodes that should be present in every 4G network.
在这个mooc中，我们将考虑每个4G网络中应该存在的节点。
We’ll use this representation throughout this course.
我们将在整个课程中使用此表示法。
It summarizes the 4G architecture:the eNodeBs, which cover the territory, the MME and HSS which manage the control function, the SGW and PGW through which the user data is routed.
它总结了4G架构：覆盖领土的eNodeB，管理控制功能的MME和HSS，用于通过其路由用户数据的SGW和PGW。
转载于:https://www.cnblogs.com/sec875/articles/9865076.html
