In previous videos, we explained thatresources are allocated dynamically.
在之前的视频中，我们解释了资源是动态分配的。
But how does the eNodeB inform theterminals of which resource is dedicated to which UE?In this video we will study the principles of allocation in L. T. E further.但是eNodeB如何通知终端哪个资源专用于哪个UE？在这个视频中，我们将进一步研究L. T. E中的分配原则。
And then, we will have a look atunderlying signalling exchanges.然后，我们将看看底层的信令交换。
So at the end, you will understandhow a terminal is informed that it is going to receivedata and how he can ask the eNodeBfor a resource to send data.因此，最后，您将了解终端如何被告知它将接收数据以及如何向eNodeB请求资源发送数据。
There are three main rules about allocation in L. T. E.Firstly: everything is centralized by the eNode B for both thedownlink and the uplink.关于L. T. E.的分配有三个主要规则：首先，eNode B为下行链路和上行链路集中所有内容。
So, a mobile cannot transmit if it has not been given permission.因此，如果未获得许可，移动设备将无法进行传输。
Secondly, as discussed in previous videos: resources areonly allocated when there is an actual need to transmit.其次，正如之前的视频中所讨论的：资源仅在实际需要传输时分配。
And thirdly: At each sub-frame, so everymillisecond, the eNode B publishes an allocationtable to inform the mobiles of theresource allocation for both the uplink and the downlink.第三：在每个子帧，每毫秒，eNode B发布一个分配表，以通知移动台上行链路和下行链路的资源分配。
Before continuing we have to make a point about addresses.在继续之前，我们必须指出地址。
Obviously, we need addresses to identify the terminals.显然，我们需要地址来识别终端。
We could use the same identifiers introduced in theprevious lessons of this MOOC (IMSI, GUTI, and so on).我们可以使用此MOOC（IMSI，GUTI等）之前课程中引入的相同标识符。
But these are not really suited to our requirementsas they are unique within the whole network.但这些并不适合我们的要求，因为它们在整个网络中是独一无二的。
However, in our case, the geographic range is limited toone single cell, because the scheduling ishandled independently by each eNodeB.但是，在我们的例子中，地理范围限于一个单个小区，因为调度由每个eNodeB独立处理。
And we need these addresses to be as short as possible,because they are used frequently.我们需要这些地址尽可能短，因为它们经常使用。
Remember that an allocation table is published every millisecond.请记住，每毫秒发布一个分配表。
So, L. T. E introduces a new identifier the RNTI:Radio Network Temporary Identifier.因此，L.T.E引入了RNTI的新标识符：无线电网络临时标识符。
It is managed by the eNode B and valid only within its cell.它由eNode B管理，仅在其单元内有效。
When a terminal arrives in a cell, the eNode B assigns ita new RNTI.当终端到达小区时，eNode B为其分配新的RNTI。
The RNTI is coded on 16 bits.RNTI以16位编码。
This is much shorter than other identifiers but stillallows for approximately 65 thousand mobiles per cell.这比其他标识符短得多，但仍然允许每个单元大约65,000个移动设备。
Let’s look at how things work on the downlink, so whendata is transferred TO the terminal.让我们来看看下行链路上的工作原理，以便将数据传输到终端。
We have seen that the eNodeB can use one or severalresource blocks per sub-frame to communicate with a given UE.我们已经看到eNodeB可以使用每个子帧的一个或多个资源块来与给定UE通信。
At the beginning of the sub-frame, the eNodeB publishesa kind of map of the sub-frame to let terminals knowwhich Resource Blocks hold data that are intended for them.在子帧的开始处，eNodeB发布一种子帧的映射，以使终端知道哪些资源块保存了针对它们的数据。
This is what we will call “allocation table” in this MOOC.这就是我们在这个MOOC中称之为“分配表”的内容。
For this sub-frame, the allocation tablehere is published in the blue space.对于此子帧，此处的分配表将在蓝色空间中发布。
Resource blocks 12 and 13 hereare allocated to the mobile with RNTI 63, this green mobile.这里的资源块12和13通过RNTI 63（这个绿色移动台）分配给移动台。
In the same way, resourceblocks 4 to 7 are allocated tothe mobile number 62, the red one.以相同的方式，资源块4到7被分配给移动号码62，红色的移动号码。
One advantage of doing this is energy saving.这样做的一个优点是节能。
If a mobile notices that no data is sent to him on this sub-frame,it can turns to standby mode until the next sub-frame.如果移动设备注意到在该子帧上没有数据发送给他，则它可以转到待机模式直到下一个子帧。
And even if it has to receive data, for example our green phone here,it can avoid wasting energydecoding data not intended for it andfocus its efforts only on its own resource blocks.即使它必须接收数据，例如我们的绿色电话，它也可以避免浪费能源解码数据，而不是仅仅针对自己的资源块。
Now, let’s talk about uplink, so when a mobile needs to send data.现在，我们来谈谈上行链路，这样当移动设备需要发送数据时。
Uplink uses the same principle as downlink.上行链路使用与下行链路相同的原理。
Resources are allocated by the eNodeB.资源由eNodeB分配。
And an allocation table is published at the same time asthe table for the downlink.并且分配表与下行链路表同时发布。
However, there are some differences because the eNode Bdoes not know when the terminals need to transmit.但是，存在一些差异，因为eNode B不知道终端何时需要传输。
So, before transmitting, the terminals first have tomake a request to the eNodeB.因此，在发送之前，终端首先必须向eNodeB发出请求。
It’s a bit of a paradox because, in order to transmit,the terminal has to transmit a request.这有点悖论，因为为了传输，终端必须传输请求。
We’ll see later on how this problem is solved.我们稍后会看到这个问题是如何解决的。
For the moment, just consider that the UE can send such a request.目前，只需考虑UE可以发送这样的请求。
And that, in response, the eNode B allocates it aresource in the next allocation table.并且，作为响应，eNode B在下一个分配表中为其分配资源。
When the mobile receives this information, it has toprepare a transport block, to encode it, to modulate it,etc, as we have seen in the previous videos.当移动设备接收到这些信息时，它必须准备一个传输块，对其进行编码，调制它等，正如我们在之前的视频中看到的那样。
So, the UE is not ready to transmit its message immediately.因此，UE尚未准备好立即发送其消息。
That’s why the allocation table published by the eNode Bfor the uplink is actually for the fourth upcoming sub-frame.这就是eNode B为上行链路发布的分配表实际上是第四个即将到来的子帧的原因。
In other words, for what is going to happen in 4 milliseconds.换句话说，对于将在4毫秒内发生的事情。
This graphic shows the L. T. E frame patterns for downlink and uplink.
此图显示了下行链路和上行链路的L. T. E帧模式。
In both cases, resources are reserved to transmit controldata and user data separately.在这两种情况下，都保留资源以分别传输控制数据和用户数据。
On the downlink, the control channel is shown in blue.在下行链路上，控制信道显示为蓝色。
In particular, it transports the allocation tables ofuplink and downlink.特别是，它传输上行链路和下行链路的分配表。
It uses the first resource elements of each sub-frame.它使用每个子帧的第一个资源元素。
This should remind you of the resource elements in purplewhen we saw Resource Blocks.当我们看到资源块时，这应该提醒您紫色的资源元素。
The rest makes up the data channel that is usedto transfer the user data.其余部分组成用于传输用户数据的数据通道。
On the uplink,the control channel is displayed in gray.在上行链路上，控制信道以灰色显示。
It is made up of the resource blocks situated at either end of the band.它由位于频段两端的资源块组成。
And resource blocks transporting data arelocated at the center of the band.传输数据的资源块位于频段的中心。
Earlier, I told you I was going to explain how terminalscan transmit a request to the base station, when theyactually don’t have a resource to transmit.早些时候，我告诉过你我将解释终端如何在没有资源传输的情况下向基站发送请求。
Well, they send their request on this uplink control channel.
好吧，他们在这个上行链路控制信道上发送请求。
For this channel L. T. E, specifies a special access mechanism which givesthe right to transmit, in turn, to each terminal of the cell.对于这个频道，L.T.E，规定了一种特殊的接入机制，它赋予了向小区的每个终端传输的权利。
Just a quick word to explain that L. T. E generalizes the notion of “channel.”In fact, the standard defines numerous channels withrather barbarian acronyms.只是一个简单的词来解释L. T. E概括了“频道”的概念。事实上，该标准定义了许多频道而不是野蛮的缩略词。
You can see here the names of channels, for example,PDSCH, PDCCH, PUCCH, etc.您可以在此处看到频道的名称，例如PDSCH，PDCCH，PUCCH等。
But, don’t worry.但是，不要担心。
We won’t get down to that level of detail.我们不会达到这个细节水平。
For this course, just keep in mind that we differentiatebetween data channels and control channels.对于本课程，请记住，我们区分数据通道和控制通道。
In a nutshell, allocation is managed by the eNode B forboth uplink and downlink.简而言之，分配由eNode B管理，用于上行链路和下行链路。
And resources are only allocated when there is a need for transmission.
并且仅在需要传输时分配资源。
Exchanges about allocationare made on dedicated control channels.关于分配的交换是在专用控制信道上进行的。
On the uplink, the terminal must first make a requeston the control channel, before being allocated resources,which can be used 4 sub-frames later.在上行链路上，终端必须首先在控制信道上发出请求，然后才能分配资源，以后可以使用4个子帧。
转载于:https://www.cnblogs.com/sec875/articles/9959083.html
