In France, in a mobile network, there are typically acouple of MMEs and 20 million UEs (user equipement).在法国，在移动网络中，通常有几个MME和2000万UE（用户设备）。
One MME should thus typically manage10 million subscribers.因此，一个MME通常应该管理1000万订户。
How an MME can manage the different states and activitiesof several million UE at the same time?MME如何同时管理数百万UE的不同状态和活动？
The question we will be looking at in this video ishow to structure exchanges in a simple way tofacilitate these exchanges between one MMEand the millions of UE it manages.我们将在本视频中讨论的问题是如何以简单的方式构建交换，以促进一个MME与其管理的数百万UE之间的这些交换。
Here we represent a single terminal (UE) witha base station (eNode B) and an MME.这里，我们表示具有基站（eNode B）和MME的单个终端（UE）。
We might think that each message transmitted by anindividual terminal has an identity.我们可能会认为单个终端发送的每条消息都有一个标识。
So, when the MME receives the message, it knows whichterminal it came from.因此，当MME收到消息时，它知道它来自哪个终端。
One terminal identity that does not change isthe IMSI (International Mobile Subscriber Identity) but there would be a problem ofconfidentiality if the IMSI was sent on the radio interface.不改变的一个终端标识是IMSI（国际移动订户身份），但是如果IMSI是在无线电接口上发送的，则存在机密性问题。
A hacker who is listening to the radio wavescan identify who is in the cell.正在收听无线电波的黑客可以识别谁在小区中。
So, perhaps we could think of the GUTI(Globally Unique Temporary Identity).所以，也许我们可以想到GUTI（全球唯一的临时身份）。
But this GUTI is renewed for reasons of security.但出于安全考虑，此GUTI已续订。
If the GUTI changes,the MME would need to remember that it’s the same terminal,so managing this is going to be a bit complicated.如果GUTI发生变化，MME需要记住它是同一个终端，因此管理它会有点复杂。
So we need another solution.所以我们需要另一种方案。
In terms of radio transmission, each terminalwith a radio connection is identified by anRNTI (Radio Network Temporary Identifier),which is allocated by the eNB.在无线电传输方面，具有无线电连接的每个终端由RNTI（无线电网络临时标识符）识别，RNTI由eNB分配。
Within the radio connection there can be datamessages and control messages: for example, the change ofa security key or an association request to the network.在无线电连接中，可以存在数据消息和控制消息：例如，安全密钥的改变或对网络的关联请求。
Here, we only consider control messages, in otherwords signaling messages, exchanged between theterminal and the MME.这里，我们仅考虑在终端和MME之间交换的控制消息，换言之，信令消息。
Each signaling message from a given terminal istransported on a logical channel which is identifiedby an LCID (Logical Channel Identifier).来自给定终端的每个信令消息在逻辑信道上传输，该逻辑信道由LCID（逻辑信道标识符）识别。
Hence, a signaling radio beareris identified for each terminal by anRNTI plus an LCID.因此，通过RNTI加LCID为每个终端识别信令无线电承载。
A protocol calledS1-AP or Application Protocolon the S1 Interface is defined between the eNode B and the MME.在eNode B和MME之间定义S1接口上称为S1-AP或应用协议的协议。
The solution to managemultiple dialogs is to reuse the same principle oftunnel we saw in the previous video but in a slightly different way:the S1-AP protocol is connection-orientedand there will be as many connections as there are terminals connected.管理多个对话框的解决方案是重用我们在前一个视频中看到的相同的隧道原理，但方式略有不同：S1-AP协议是面向连接的，并且连接的终端将有尽可能多的连接。
We have one connection per UE and, just likewe used tunnel identifiers at each endpoint of thetunnel, we are going to use connection identifiers:one identifier at each endpoint.我们每个UE有一个连接，就像我们在隧道的每个端点使用隧道标识符一样，我们将使用连接标识符：每个端点都有一个标识符。
We’ll associate the signaling bearerand the S1-AP connection.我们将信令承载和S1-AP连接相关联。
This association is made at the eNode B level.该关联在eNode B级别进行。
Let’s look at an example to better understand it.让我们看一个例子来更好地理解它。
Imagine a terminal, an eNode B, an MME,an established radio connection,an S1-AP connection that wepresume has been established.想象一下终端，eNode B，MME，已建立的无线连接，我们认为已经建立的S1-AP连接。
Each connection is referenced at each endpointby an identifier.每个端点都通过标识符引用每个连接。
Here, we’ve taken an example where we’ve given thehexadecimal identifier, for instance 03-FE-01on the eNode B side.这里，我们举了一个例子，我们给出了十六进制标识符，例如eNode B端的03-FE-01。
When the terminal sends a message, forexample, a specific request to the network,this message includes, in the header,the LCID value in a radio block associated with an RNTIcorresponding to the cell phone.当终端向网络发送消息（例如，特定请求）时，该消息在头部中包括与对应于蜂窝电话的RNTI相关联的无线电块中的LCID值。
The eNode B has in memory a lookup table.eNode B在内存中具有查找表。
Each RNTI and LCID is associatedwith the local connection identifier andthe connection identifier of the distant entity,in this case the MME, as well as the IPaddress of the MME.每个RNTI和LCID与本地连接标识符和远程实体的连接标识符相关联，在这种情况下是MME，以及MME的IP地址。
This way, when the signaling message is retransmitted,by the ENode B it includes the connection identifier onthe MME side and the connection identifieron the eNode B side.这样，当重新发送信令消息时，ENode B包括MME侧的连接标识符和eNode B侧的连接标识符。
Compared to what we have seen in the presentation ontunnels, the choice was made here to set bothidentifiers systematically in each message, inorder to easily keep the reference of a connection when aterminal is moving to a new cell.与我们在隧道演示中看到的相比，这里选择在每个消息中系统地设置两个标识符，以便在终端移动到新小区时容易地保持连接的引用。
To summarize, for each UE active in the network,a specific connection is set up between the eNodeB thatserves the UE and the MME.总而言之，对于在网络中活动的每个UE，在为UE服务的eNodeB与MME之间建立特定连接。
There are as many connections as the number of UEscontrolled by the MME and each connection isreferenced by a pair of connection identifiers, one oneach side of the connection.存在与由MME控制的UE的数量一样多的连接，并且每个连接由一对连接标识符引用，连接的每一侧各有一个连接标识符。
转载于:https://www.cnblogs.com/sec875/articles/10020654.html
