Go homepage(回首页) Upload pictures (上传图片) Write articles (发文字帖)
The author:(作者)aaapublished in(发表于) 2013/12/6 12:32:40 Popular science： with the 4G standard， FDD and TD who is faster，
Popular science: with the 4G standard, TD and the FDD who-TDLTE,FDD,4G faster, operator-IT information Popular science: with the 4G standard, FDD and TD who is faster
Ministry recently, TD-LTE standard 4G were issued to three operators licences did not release LTE FDD. What is the difference between these two standards? FDD speed is said to be right?
4G based on the LTE standard has currently two, namely, the LTE TDD and LTE FDD (LTE TDD internally used to be known as the TD-LTE). Name will have an intuitive impression, different branches of the two standards are based on LTE, similarity over 90%. Next we use the traffic to, for example, concrete analysis of the differences between the two:
Resources, TD-LTE province, FDD speed
LTE FDD using frequency division duplex, TD-LTE is a time division duplex. We put aside such jerky terms, in a more simple way to explain:
First of all, mobile Internet, uplink and downlink channels must be established to: for example, you click on the micro-hand opportunity through upstream channel sends a request, and micro-server via the downlink channel, bring you the latest unread messages to your mobile phone. Under normal circumstances, we use this line (download) more, uplink (uploading) only very little time.
In order to build up the uplink and downlink channels FDD frequency to split, on the frequency of two symmetric, then one of the downloads, it tube upload. But like the two-lane, two cars in the direction of noninterference, unblocked. On your mobile phone, is the feeling of speed.
TD-LTE another way. It uses one frequency, responsible for both uploading and is responsible for downloading. Benefits is than FDD province has a frequency occupies, resources utilization more high (actually TD-LTE to avoid interference, needs reserved larger protection with, also will consumption some resources); TDD of disadvantages also is obviously, because is "line road" Shang ran two-way "traffic", TD-LTE only through time to control traffic (hours duplex), a will let download of flow through, a will and let upload of flow through. On the phone side, than some FDD Suman.
At present, the downlink speeds of 150Mbps,TD-LTE theory to LTE FDD downlink speeds of 100Mbps.
Second, TD-LTE for the hotspot coverage, FDD for wide area coverage
We come across such a situation in life: first, directions of traffic jams in the city, next to the out of town on the road in the direction of traffic is scarce. This is certainly a waste of resources.
Mobile Internet in the process, a phenomenon more common: people using cell phones, more reading, viewing, and downloading, little time for upload. Therefore, if your phone's wireless network is visible, you will find the download channel data stream, upload channel is rarely used.
TD-LTE has the advantage that he would upload and download channels into one, then through time to flexibly control, such as the time allocated to download 70%, upload and 30%, so that you will find the entire channel traffic is always full, better resource utilization.
Since TD-LTE so the economy, but it also cannot be used in all.
In user-intensive hotspots area, band resources on edge, and that's when FDD "dual carriageway" is quite a waste, TDD is more suitable. But TDD uplink limited coverage is less than the base station FDD and, therefore, non-hot-spot coverage area (suburbs, towns and roads), TDD need to build more than FDD base stations, the cost is too high.
Finish third, difference, TD-LTE FDD combined net?
FDD and TD-LTE, the two branches of the LTE standard has his merits, but the underlying technology is very similar between the two. Experts say TD-LTE and LTE FDD can be thought of as a total system, is only in the business to realize there is a technical difference.
Therefore, international TD-LTE FDD hybrid networking model, leveraging their respective strengths, TD-LTE for the hotspot coverage, FDD for wide area coverage.
Due to having a common technology base, FDD and TD-LTE in a mixed networking has a very good future. ITU in developing 4G this is the year when desired--namely to minimize the differences between different standard physical layer, network standards and ultimately to fusion.
Mobile 4G network in Hong Kong with a TD-LTE FDD hybrid network and the accumulated experience in this area. From information received, the Ministry is also an upcoming carrier validation of hybrid networks.
To summarise:
Fundamentals of TD-LTE and LTE FDD essentially common set of standards, has some differences in business technology. TD-LTE savings channel resources for hot concentrated regional coverage; FDD's theoretical top speed faster, the base station cover a wide, suitable for wide area coverage, such as suburbs, highway and railway.
Mixed group of the two networks, would be a better choice.
科普：同是4G标准，TD和FDD谁更快 - TDLTE,FDD,4G,运营商 - IT资讯科普：同是4G标准，TD和FDD谁更快
工信部近日向三家运营商发放了TD-LTE标准的4G牌照，并没有发放LTE FDD的。这两大标准之间到底有何区别？据说FDD速度更快是真的吗？
目前基于LTE的4G标准有两个，分别为LTE FDD和LTE TDD（国内习惯于将LTE TDD称为TD-LTE）。看名字大家会有直观的印象，两大标准都是基于LTE的不同分支，相似度超过90%。接下来我们用交通来举例，具体分析一下两者间的差异：
一、TD-LTE省资源，FDD速度快
LTE FDD采用的是频分双工，TD-LTE则是时分双工。我们抛开这些生涩的术语，用更简单的方式解释一下：
首先，手机想上网，必须要建立上行和下行的通道：例如，你点击微信，手机会通过上行通道发送一个请求，然后微信服务器通过下行通道，把你最新的未读消息传到你的手机上。一般情况下，我们使用下行（下载）的时间比较多，而上行（上传）的时间很少。
为了建立起上行和下行的通道，FDD通过频率来分割，在两个对称频率上，一个管下载，一个管上传。就好像是双车道，两个方向的汽车互不干扰，畅通无阻。表现在你的手机上，就是速度很快的感觉。
TD-LTE采用另一种方式。它只用一个频率，既负责上传，又负责下载。好处是比FDD省了一个频率占用，资源利用率更高（实际上TD-LTE为了避免干扰，需要预留较大保护带，也会消耗一些资源）；TDD的缺点也很明显，因为是“单行道”上跑双向“车流”，TD-LTE只能通过时间来控制交通（时分双工），一会让下载的流量通过，一会又让上传的流量通过。表现在手机端，会比FDD网速慢一些。
目前，LTE FDD理论下行速度为150Mbps，TD-LTE理论下行速度为100Mbps。
二、TD-LTE适合热点区域覆盖，FDD适合广域覆盖
我们在生活中遇到过这种情况：上班高峰期，进城方向的交通拥堵不堪，旁边出城方向的马路上却车流稀少。这无疑是一种资源的浪费。
在手机上网过程中，这种现象更普遍：人们使用手机，更多的是阅读、观赏和下载，很少的时间用于上传。因此，如果手机的无线网络是可见的，你会发现下载通道上数据川流不息，上传通道却很少被使用。
TD-LTE的优势在于，他将上传和下载通道合并为一个，然后通过时间来灵活控制，例如分配给下载的时间占70%，上传占30%，这样，你会发现整个通道的车流总是满的，资源利用率更高。
既然TD-LTE如此经济，却也不能全部采用。
在用户密集的热点区域，频段资源很紧张，这时候，FDD的“双车道”就显得很浪费，TDD更适合。但由于TDD在上行方面受限，基站覆盖范围小于FDD，因此，在非热点的在广覆盖区域（城郊、乡镇和公路）上，TDD需要比FDD建设更多基站，成本太高。
三、说完区别，TD-LTE与FDD能混合组网吗？
FDD和TD-LTE这两个LTE的分支标准各有所长，但两者间基础技术非常相似。有专家表示，TD-LTE和LTE FDD完全可以看做一个系统，仅是在业务实现上有一定的技术区别。
因此，国际上有了将TD-LTE与FDD混合组网的模式，发挥两者各自长处，TD-LTE用于热点区域覆盖，FDD用于广域覆盖。
由于有着共同的技术基础，TD-LTE与FDD在混合组网方面有着非常好的前景。这也是当年国际电联在制定4G标准时所期望实现的——即尽量降低不同标准之间物理层的差异，让网络标准最终走向融合。
中移动在香港的4G网络中即采用了TD-LTE与FDD混合组网的方式，积累的这方面的经验。从目前得到的消息看，工信部也即将组织运营商开展混合组网的验证。
最后总结一下：
TD-LTE与LTE FDD本质上共用一套标准基础，在业务实现的技术上有着一定差别。TD-LTE节省频道资源，适合热点集中区域覆盖；FDD的理论最高速度更快，基站覆盖更广，适合郊区、公路铁路等广域覆盖。
两者混合组网，是更好的选择。
赞