When I turn on a terminal, it establishes a radio connection.当我打开终端时，它建立了无线电连接。
If I don’t use my terminal, if I leave it in my pocket,are the connections still maintained?如果我不使用我的终端，如果我把它放在口袋里，连接是否仍然保持？
Alternatively, if I want to maintain a radio connection,won’t it consume too much energy?或者，如果我想保持无线电连接，它会不会消耗太多能量？
We are going to answer these two questionsin this video.我们将在此视频中回答这两个问题。
At power up, we have already seen the establishment of a default bearer.在加电时，我们已经看到了默认承载的建立。
A packet that arrives from thenetwork must be routedas quickly as possible.必须尽快路由从网络到达的数据包。
Likewise, a packet that is created because I have an apprunning on my terminal must also be transmitted asquickly as possible.同样，由于我的终端上运行的应用程序而创建的数据包也必须尽快传输。
When using my terminal, I can move (as long as I am notdriving my car of course) an active radio connectionrequires signal measurements from different base stationsto be sent regularly in order to detectwhether the terminal is getting farther from one basestation and closer to another.当我使用我的终端时，我可以移动（只要我当然不开车），有效的无线电连接需要定期发送来自不同基站的信号测量，以便检测终端是否离一个基站越来越近 并且更接近另一个。
If I’m not using my terminal, maintaining this radioconnection requires regular exchangesof measurements and checks to ensure that the terminal isstill covered by the same cell.如果我没有使用我的终端，保持这种无线电连接需要定期交换测量和检查，以确保终端仍然被同一个小区覆盖。
All that would entail the expenditure of a lot of energy.所有这些都需要耗费大量精力。
And the batteries would not last long.电池不会持续很长时间。
Furthermore, for each radio connection,an RNTI should be allocated.此外，对于每个无线电连接，应分配RNTI。
RNTIs are 16 bits in length, whichmakes over 65,000 available.RNTI长度为16位，超过65,000可用。
65,000 seems a huge number butit isn’t that large.65,000似乎是一个巨大的数字，但它并不是那么大。
So, we’re going to avoid maintaining the radio connection all the time.因此，我们将一直避免维持无线电连接。
What is implemented is a time-outwhen the radio connection is inactive.实现的是无线电连接不活动时的超时。
As long as I’m using my terminal, that is to say, as longas user data is being transmitted, theconnection is maintained and theinactivity timer is reset.只要我正在使用我的终端，也就是说，只要正在传输用户数据，就会保持连接并重置不活动定时器。
You can see it here.你可以在这里看到它。
There’s no more activity.没有更多的活动。
The timer is counting down.计时器正在倒计时。
It’s counting down, but the user, for example, loads a Web page.它倒计时，但用户，例如，加载网页。
There is activity once again.再次有活动。
The timer is reset.计时器重置。
When the value reaches zero,in other words, when no application has sent any messagefor a defined period of time, the radio connection is released.当值达到零时，换句话说，当没有应用程序在指定的时间段内发送任何消息时，将释放无线电连接。
This timer is placedin the eNodeB and is started at the end of an exchange.此计时器位于eNodeB中，并在交换结束时启动。
At the end of the time out, the RRCconnection is released and the UEloses its RNTI.在超时结束时，释放RRC连接并且UE丢失其RNTI。
A radio connection is abit like a leash between a dog and his master.无线电连接有点像狗和他的主人之间的皮带。
Note that the dog is the UE and the master is the eNodeB.注意，狗是UE，主设备是eNodeB。
Sometimes, to allow the dog to freely run, themaster removes the leash.有时，为了让狗自由奔跑，主人移除了皮带。
This is the radio connection release procedure.这是无线电连接释放程序。
If we look at the network, we have here a representation ofall the connections and tunnels.如果我们查看网络，我们在这里有所有连接和隧道的表示。
We have already seen these diagrams in previous sequences.我们已经在之前的序列中看到过这些图表。
If there is radio activity, the connectionand all tunnels are maintained.如果存在无线电活动，则保持连接和所有隧道。
If there is no activitythe radio connection is released.如果没有活动，则释放无线电连接。
But, if we release the radio connection, that means thenetwork loses awareness of the cell of the UE.但是，如果我们释放无线电连接，则意味着网络失去对UE的小区的认识。
So, the terminalcan move or change base stationswithout the network necessarily being aware.因此，终端可以在没有网络必须知道的情况下移动或改变基站。
We’ll see this in week six.我们将在第六周看到这一点。
This means that the networkno longer knows precisely under which eNodeBthe terminal is located.这意味着网络不再精确地知道终端位于哪个eNodeB下。
There is no reason to maintain an S1 bearer betweenthe eNodeB and the serving gateway.没有理由在eNodeB和服务网关之间维持S1承载。
There is no reason to maintain an S1-AP connection.没有理由维持S1-AP连接。
So, when werelease the radio connection we release the S1 bearer andthe S1-AP connection at the same time.因此，当我们释放无线电连接时，我们同时释放S1承载和S1-AP连接。
This is referred to as an ECM state.这被称为ECM状态。
In the ECM_Idle state,there is no radio connection; thenetwork is unaware of the precise location of the terminal.在ECM_Idle状态下，没有无线连接; 网络不知道终端的精确位置。
On the other hand, the terminal remains connectedto the network.另一方面，终端保持连接到网络。
However, during the ECM_Connected state, the radioconnection is active, an RNTI isallocated and there are signaling anduser bearers.然而，在ECM_Connected状态期间，无线电连接是活动的，分配了RNTI并且存在信令和用户承载。
Bearers and tunnels are alwaysmaintained between the SGW, the PGW and the MME.SGW，PGW和MME之间始终保持着承载和隧道。
A timer is managed by the eNodeB.计时器由eNodeB管理。
In case of inactivity of the UE, theradio bearers, the S1-AP connection and the S1 bearer are released.在UE不活动的情况下，释放无线电承载，S1-AP连接和S1承载。
There are, therefore, frequent switches between theECM_Connected and ECM_Idle states.因此，ECM_Connected和ECM_Idle状态之间频繁切换。
转载于:https://www.cnblogs.com/sec875/articles/10039082.html
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