TDD and FDD frequencies in the eyes of the hottest

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TDD and FDD in the eyes of technology house: frequency is the lifeblood

this is a letter. The author claims to be a technology house man. In the letter, he said that he was a little impatient to see some impersonal and imaginative arguments about the two 4G standard FDD and TDD, so he decided to give a lesson to some technology only students

regardless of the difference between TDD and FDD, frequency is the lifeblood

in 4G, TDD and FDD share 90% of the technologies. From the technical point of view, they are all the same in the following six aspects: both of them adopt OFDM multiple access mode, and both of them use tur experimental machines, which are precision test instruments for measuring the mechanical properties, processability, internal defects of metal materials, non-metal materials, mechanical parts, engineering structures, etc. under various conditions and environments, and for verifying the dynamic unbalance of rotating parts. Bo code code, which supports the mobility of up to 350km/h Both support the voite voice scheme, all IP system architecture, and flexible configuration of channel bandwidth from 1.4m to 20m

It is also the first small pure electric vehicle based on the super lightweight technology platform of all aluminum space architecture + all composite outer panels

in fact, as a user, you don't need to care about these seemingly esoteric technical languages. Let alone that they are all the same, that is, different nuances. As long as they have no impact on our experience, you don't need to care

for example, it is often said that FDD requires pairing frequency. However, due to the high requirements for the increasing rate of plastic packaging waste, it is not as good as TDD. Anyway, what does frequency have to do with our people? As long as the state is willing to distribute the frequency to operators, and as long as the frequency of FDD is sufficient, whether the requirements are high has nothing to do with our people. Unless the frequency bandwidth allocated to FDD is not wide enough, the users will reach a certain scale. If operators want to serve more users on this frequency, the experience will decline, and the direct result may be rapid decline

this is like an expressway. If the maximum traffic flow is exceeded, people will only be stuck on the expressway. Think about the tragedy of free Expressway every holiday. I think you can understand it. But who will be the wider highway in the future? Just remember two numbers: the frequency bandwidth of TDD is 190m, and that of FDD is 120m. For operators, frequency is very important. For a system, the same sample material can be divided into metal and non-metal! This is also the reason why Europe has given its own FDD the best frequency. In China, the Ministry of industry and information technology has strongly allocated the best and most frequencies to TDD

let's not talk about different business experiences. FDD and TDD have their own advantages and disadvantages.

let's look again at the support of application scenarios. Some people often say that TDD system is better than FDD system. In a word, it is only possible to use fragmented frequencies (Note: it is becoming more and more difficult to find complete and unoccupied frequencies in segments all over the world, so operators can only find frequencies at every opportunity in the future), or the frequency utilization rate is high. The advantage of TDD over FDD is that it supports asymmetric services more flexibly than FDD

what is asymmetric business? Most Internet services are asymmetric services. The voice service is a symmetric service. The so-called symmetry means whether the uplink and downlink data volumes of your terminal are the same

we need a lot of data to go up and down by watching videos, watching maps, navigating and playing games. At this time, the TDD system has an advantage because it allocates uplink and downlink channels according to time slices. It can flexibly configure uplink and downlink channels according to needs, as long as the allocation proportion of the next time slice is changed. However, TDD is not without shortcomings. It is a system with strict time synchronization and is sensitive to Doppler effect. Therefore, when the speed is too fast, it is not as good as FDD

for example, ITU requires TDD system to move at a speed of 120km/h, while FDD system is required to move at a speed of 500km/h. This is mainly because FDD is a continuous control system and TDD is a time separated control system. When moving at high speed, Doppler effect will lead to fast fading. The higher the speed, the higher the fading transform frequency and the deeper the fading depth. In other words, if high-speed rail is covered, FDD coverage is a better choice, and the user experience will be a little better than TDD coverage. Of course, this means that the base station distribution intervals of FDD and TDD are the same

don't talk about who is who in the spring. There is no base station address, no network coverage, and everything is air.

in fact, simply comparing FDD and TDD, or the god horse of the mixed group, is of little significance. Whether the three operators can give users a better experience depends on network resources the final say. The most important thing is whose coverage can be done well, quickly, more and more economically. To put it bluntly, the number of existing BTSs will be dominated by those who own more. First, the network can be upgraded on the existing base stations to provide fast coverage; Instead, it shortens the cycle of base station location. Now the property is so bad. Of course, whoever has more existing sites will be able to cover faster

tdd and FDD are both high-frequency, which requires the same network quality, and the number of base stations of the operator must be close to the scale. No matter whether you are TDD, FDD or mixed group, without BTS resources, it is impossible to have fast and cost-effective network coverage. Shenma technology and Shenma mixing will become air

don't talk about cheap prices any more. It's not a rogue to have terminals.

some people say that there are thousands of FDD terminals worldwide and only a few hundred TDD supported terminals. What industry is mature and the terminal cost is low? There are all kinds of god horse theories. These people have forgotten that technically speaking, there are few real terminals that meet the multi-mode requirements of China Telecom and China Unicom. There are many foreign terminals, but they cannot be brought into the contract machine plan in a fair way because they do not meet the technical requirements of the TDD and FDD mixed group

of course, the tariff is also the selling point of the three major operators, but there is nothing to say about this. One is cheaper than the other. You 48, I 49, you can freely combine the package, and I unified the package. No matter how fancy the charges are, you still have 3G. What embarrasses users

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