Description:
TDD and FDD are actually two duplex modes. FDD is called frequency division duplex, and TDD is called time division duplex.
FDD is actually very simple. Data has both uplink and downlink. When you talk on the phone, the other party hears the uplink data, and in turn, you hear the downlink data. These two kinds of data transmission use different frequencies, which are generally called Symmetrical frequency, in order to prevent interference, there must be a certain interval between frequencies, and the interval frequency cannot carry services, so the shortcomings of FDD come out and waste frequency resources. FDD is the most widely used, like all GSM networks, Telecom's CDMA, CDMA2000, and China Unicom's WCDMA all use FDD.
TDD technology is relatively complex, requiring both uplink and downlink to be performed on the same frequency. In simple terms, it is to control the delay of uplink and downlink data within an imperceptible time. In order to ensure effective isolation of uplink and downlink, the synchronization time is very high, so the introduction of For satellite synchronization, each base station will have a GPS antenna, which can explain why the signal of the TDD network is not good. TDD has high requirements for time delay, which makes it impossible for a base station to cover a large area and the distance is long. , the delay is not easy to control, generally there will be a state where the other party can hear your speech, but you cannot hear the other person's speech. The term is called mismatch between upstream and downstream. TDD main network: TD-SCDMA is mobile 3G. In fact, WIFI is also this technology. In the past, PHS was also this technology.
First of all, TDD and FDD are two branches of the LTE (LTE is strictly 3.9G in the strict sense, LTE-Adavaced is 4G) standard formulated by the 3GPP standards organization, of which the 3GPP standards organization is the organization that formulates communication standards.
Second, the difference between TDD and FDD is very small, mainly reflected in the frame format of the physical layer. In layman's terms, if 4G is compared to an 8-lane road, then FDD adopts a 4-4 lane configuration, while TDD can adopt a variety of flexible methods, either 3-5 or 2-6.
Third, from the perspective of market performance, there are more than 200 operators using FDD in the world, and no more than 20 operators adopting TDD. The market is the litmus test for the best technology. Generally speaking, FDD technology is better than TDD technology. The technical advantage is reflected in the same set of 4G equipment, and the FDD standard is cheaper than the TDD standard, which is why China Unicom mainly promotes FDD. As for mobile push TDD, it is mainly assigned by the country's administrative orders.
TDD and FDD are actually two duplex modes. FDD is called frequency division duplex, and TDD is called time division duplex.
FDD is actually very simple. Data has both uplink and downlink. When you talk on the phone, the other party hears the uplink data, and in turn, you hear the downlink data. These two kinds of data transmission use different frequencies, which are generally called Symmetrical frequency, in order to prevent interference, there must be a certain interval between frequencies, and the interval frequency cannot carry services, so the shortcomings of FDD come out and waste frequency resources. FDD is the most widely used, like all GSM networks, Telecom's CDMA, CDMA2000, and China Unicom's WCDMA all use FDD.
TDD technology is relatively complex, requiring both uplink and downlink to be performed on the same frequency. In simple terms, it is to control the delay of uplink and downlink data within an imperceptible time. In order to ensure effective isolation of uplink and downlink, the synchronization time is very high, so the introduction of For satellite synchronization, each base station will have a GPS antenna, which can explain why the signal of the TDD network is not good. TDD has high requirements for time delay, which makes it impossible for a base station to cover a large area and the distance is long. , the delay is not easy to control, generally there will be a state where the other party can hear your speech, but you cannot hear the other person's speech. The term is called mismatch between upstream and downstream. TDD main network: TD-SCDMA is mobile 3G. In fact, WIFI is also this technology. In the past, PHS was also this technology.
First of all, TDD and FDD are two branches of the LTE (LTE is strictly 3.9G in the strict sense, LTE-Adavaced is 4G) standard formulated by the 3GPP standards organization, of which the 3GPP standards organization is the organization that formulates communication standards.
Second, the difference between TDD and FDD is very small, mainly reflected in the frame format of the physical layer. In layman's terms, if 4G is compared to an 8-lane road, then FDD adopts a 4-4 lane configuration, while TDD can adopt a variety of flexible methods, either 3-5 or 2-6.
Third, from the perspective of market performance, there are more than 200 operators using FDD in the world, and no more than 20 operators adopting TDD. The market is the litmus test for the best technology. Generally speaking, FDD technology is better than TDD technology. The technical advantage is reflected in the same set of 4G equipment, and the FDD standard is cheaper than the TDD standard, which is why China Unicom mainly promotes FDD. As for mobile push TDD, it is mainly assigned by the country's administrative orders.