An engineer who claimed to be a technical house was unwilling to see some unobtrusive debates about the 4G two-standard FDD and TDD with many imaginary components, so he decided to give some technical-only students. Let's take a lesson. Here are a few key points he summed up: Don't talk about the difference between TDD and FDD, the frequency is the root of life. In 4G, the ratio of TDD and FDD is 90%. From a technical point of view, they are all the same in the following six aspects: they all use OFDM multiple access, Turbo code encoding, up to 350KM/h mobility, all support VoLTE voice solution, Full IP system architecture, flexible configuration from 1.4M to 20M channel bandwidth. In fact, as a user, you don't need to care about these seemingly inscrutable technical languages, let alone they are all the same, that is, different nuances, as long as they have no effect on the experience of the cricket, do not need to care. For example, it is often said that FDD requires paired frequencies and high frequency requirements, so it is not as good as TDD. Having said that, the frequency has something to do with the people? As long as the frequency is allocated to the operators for national reasons, as long as the frequency of FDD is sufficient, it is not required to be high, and it has nothing to do with the people. Unless the frequency bandwidth allocated to FDD is not wide enough, when the user reaches a certain scale and the operator wants to serve more users on this frequency, the experience will drop. The direct result may be that the network speed drops. This is like a highway, beyond the maximum traffic restrictions, everyone can only block on the highway, think about the free high-speed tragedy every holiday, I think everyone understands. But who is this wider highway in the future? Just remember the two numbers: TDD has a frequency bandwidth of 190M and FDD is 120M. For operators, frequency is crucial, and the same is true for one system! This is also the best frequency for Europe to give its own FDD. In China, the Ministry of Industry and Information Technology has strongly allocated the best frequency to TDD. Don't talk about different business experiences, FDD and TDD have their own advantages and disadvantages. Let's look at the support of the application scenario. It is often said that the TDD system is better than the FDD system. To put it bluntly, it is possible to use the frequency of fragmentation. (Note: It is to find a complete segment in the world, and the frequency of unoccupied is getting harder and harder. Merchants can only see the stitches to find the frequency), or the frequency utilization is high. The advantage of TDD over FDD is that his support for asymmetric services is more flexible than FDD. What is an asymmetric business? Most Internet businesses are asymmetric. The voice service is a symmetric service. The so-called symmetry is that the amount of data on the uplink and downlink of your terminal is not the same. Using mobile phones to watch videos, watch news, map navigation, and play games, we need a lot of data to go down from the Internet. At this time, the TDD system has an advantage, because he allocates uplink and downlink channels according to time slices, he can flexibly follow It is necessary to configure the uplink and downlink channels, as long as the allocation ratio of the next time slice is changed. But TDD is not without its drawbacks. It is a time-synchronized system that is sensitive to the Doppler effect, so when it is too fast, it is not as good as FDD. For example, the ITU requires the TDD system to move at a speed of 120 km/h, and the FDD system requires a moving speed of 500 km/h. This is mainly because FDD is a system of continuous control, and TDD is a system of time division control. At high speeds, the Doppler effect causes fast fading. The higher the speed, the higher the fading conversion frequency and the deeper the fading depth. In other words, if you cover high-speed rail, FDD coverage is a good choice, and the user experience will be better than TDD coverage. Of course, this is the case where the base station distribution intervals of FDD and TDD are the same. Don't talk about who is who's spring, no base station site, no network coverage, everything is air In fact, simply comparing FDD and TDD, or mixing network gods, is of little significance. The three operators who can give users a better experience still have to rely on network resources to decide. The most important thing is who can do the job well, do it fast, do more, and do the province. To be straightforward, the number of existing base stations, whoever has more, will dominate. First, network upgrades can be made on existing base stations to quickly cover; instead, the cycle of base station location is shortened. Now the property is so embarrassing, of course, whoever has more existing sites, who can cover it faster. Both TDD and FDD are high frequencies, which require the same network quality, and the number of base stations of the operators must be close in size. Whether you are TDD or FDD, or a hybrid network, there is no need for base station resources, and it is impossible to have a good network coverage. The Shenma technology will become air. Don't talk about the cheaper fees, there is a terminal that is not a rogue Some people say that there are thousands of terminals for global FDD, and hundreds of terminals that support TDD. What industry is mature, terminal costs are low, and all kinds of gods and horses have their own opinions. These people have forgotten that, technically, there are actually few real terminals that meet the multi-mode requirements of Telecom and China Unicom. There are many foreign terminals, but they can't get into the network brightly. They can't be included in the contract machine plan because they don't meet the technical requirements of TDD and FDD hybrid networking. Of course, the tariff is also the selling point of the three major operators, but this thing is actually nothing to say, one is cheaper than one, you 48, I 49, you free combination package, my unified package. The cost of playing is more fancy, your mobile phone is still a 3G mobile phone, so what is the user's feelings? 12V Transformer,Small Transformer,Transformer 24V,Led Transformer Ninghai Yingjiao Electrical Co., Ltd. , https://www.yingjiaoadapter.com