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What's Difference Of TDD LTE And FDD LTE

- Nov 07, 2018 -

The 4G name is the fourth generation mobile phone mobile communication standard, including TD-LTE (foreign called LTE-TDD, called different, meaning the same) and FDD-LTE. China Mobile uses TD-LTE, and China Unicom and China Telecom use a hybrid network of TD-LTE and FDD-LTE. So what do we mean by LTE? LTE is the abbreviation of English Long Term Evolution, which literally means long-term evolution technology.


LTE is technically considered to be 3.9G. But we usually call them 4G, because they have 100Mbps data download capability (referred to as cat.3 downlink bandwidth), which is about 10 times faster than 3G network speed. It is also a key process for 3G evolution to technology 4G.


The specific difference between TD-LTE and FDD-LTE


The main difference between FDD and TDD is that different duplex modes are used. Frequency division duplex (FDD) and time division duplex (TDD) are two different duplex modes. The FDD is received and transmitted on two separate symmetric frequency channels, and the guard band is used to separate the receive and transmit channels. The disadvantage of FDD is that it must use pairs of frequencies, relying on frequency to distinguish between uplink and downlink, and its unidirectional resources are continuous in time. Although FDD can fully utilize the uplink and downlink spectrum when supporting symmetric services, spectrum utilization will be greatly reduced when supporting asymmetric services.

In contrast, TDD uses time to separate the receive and transmit channels. It is carried out in one channel. In the mobile communication system of the TDD mode, different time slots using the same frequency carrier are received and transmitted as bearers of the channel, and time resources are allocated in two directions. The base station sends a signal to the mobile station during a certain period of time, and the time interval in the middle is sent by the mobile station to the base station, and the base station and the mobile station must cooperate in order to work smoothly.


In theory, the advantage of FDD is bigger than TDD, which makes many potential 4G users feel excited and determined to use Unicom's LTE-FDD. However, in terms of current form, the author believes that the use of mobile or Unicom Telecom's network is actually There is not much impact. In terms of network coverage, the coverage of LTE-TDD is much larger than that of LTE-FDD. For the speed of 4G, whether it is LTE-TDD or LTE-FDD, it has very good speed, enough for users now. Use, and the user does not have much need to choose to change operators in order to experience the difference between FDD and TDD.


From the current point of view, the Ministry of Industry and Information Technology has allocated 130Mhz of TDD-LTE bandwidth usage to China Mobile, which can cover more mobile customers and provide better access services. The mobile layout strategy is low transmission power and high coverage density. So far, China Mobile's 4G coverage is still very good, and many small counties already have mobile 4G networks. Because of its preconceptions on the 4G network, China Mobile has a slight advantage in 4G competition.

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