In depth interpretation of 5g key technologies

5G As 4G The continuation of , There won't be much change in the core network , Its key technologies focus on the wireless part . that 5G What are the key technologies , Let's list some key technologies , Of course , It should be more than that .

1. Non orthogonal multiple access technology （Non-Orthogonal Multiple Access,NOMA）

We know 3G Direct sequence code division multiple access （Direct Sequence CDMA ,DS-CDMA） technology , The receiving end of the mobile phone uses Rake Receiver , Because of its non orthogonal property , You have to use fast power control （Fast transmission power control ,TPC) To solve the problem of the distance between the mobile phone and the community - Near problem . and 4G The network adopts orthogonal frequency division multiple access （OFDM） technology ,OFDM It can not only overcome the problem of multipath interference , And and MIMO Technical cooperation , Greatly improve the data rate . Due to multi-user orthogonality , There is no distance between the cell phone and the community - Near problem , Fast power control was abandoned , And use AMC（ Adaptive coding ） To realize link adaptation .NOMA What we hope to achieve is , recollect 3G The principle of non orthogonal multi-user multiplexing in the era , And integrate it into the present 4G OFDM In technology .

from 2G,3G To 4G, Multiuser multiplexing technology is nothing more than in the time domain 、 frequency domain 、 Make an article on the code field , and NOMA stay OFDM A dimension is added on the basis of —— Power domain . The purpose of adding this power domain is , Using different path loss of each user to realize multi-user multiplexing . Realize multi-user multiplexing in power domain , It is necessary to install a... At the receiving end SIC（ Continuous interference cancellation ）, Through this interference eliminator , Plus channel coding （ Such as Turbo code Or low density parity check code （LDPC) etc. ）, The signals of different users can be distinguished at the receiving end .

NOMA The difference of different path loss can be used to stack the multi-channel transmission signals , So as to improve the signal gain . It enables all mobile devices within the same cell coverage to obtain the maximum accessible bandwidth , It can solve the network challenges caused by large-scale connections .NOMA Another advantage of is , There is no need to know... For each channel CSI（ Channel status information ）, It is expected to achieve better performance in high-speed mobile scenarios , And can build a better mobile node backhaul link .

2. FBMC（ Filter group multicarrier technology ）

stay OFDM In the system , Each subcarrier is orthogonal to each other in time domain , Their spectrums overlap , Therefore, it has high spectrum efficiency .OFDM Technology is generally used in data transmission of wireless systems , stay OFDM In the system , Due to the multipath effect of wireless channel , Thus, interference is generated between symbols . In order to eliminate symbol interference (ISl), Insert a protection interval between symbols . The general method of inserting protection interval is to set zero between symbols , That is, the first symbol is sent and stays for a period of time ( Don't send any messages ), Then send the second symbol . stay OFDM In the system , In this way, inter symbol interference is weakened or eliminated , Because the orthogonality between subcarriers is destroyed , This leads to interference between subcarriers (ICI). therefore , This method OFDM Cannot be used in the system . stay OFDM In the system , In order to eliminate ISI, And it can eliminate ICI, Usually, the protection interval is determined by CP（Cycle Prefix , Cyclic prefix to ) act as .CP It's the overhead , Do not transmit valid data , This reduces the spectral efficiency . and FBMC Multi carrier transmission is realized by using a group of non overlapping band limited subcarriers ,FMC The inter carrier interference caused by frequency offset is very small , Unwanted CP（ Cyclic prefix ）, Greatly improve the frequency efficiency .

3. Millimeter wave （millimetre waves ,mmWaves)

What is millimeter wave ？ frequency 30GHz To 300GHz, Wavelength range 10 To 1 mm . Due to a sufficient amount of available bandwidth , High antenna gain , Millimeter wave technology can support ultra-high transmission rate , And the beam is narrow , Be flexible and controllable , Can connect a large number of devices .

4. On a large scale MIMO technology （3D /Massive MIMO）

MIMO Technology has been widely used in WIFI、LTE etc. . Theoretically , More antennas , The higher the spectral efficiency and transmission reliability . On a large scale MIMO The technology can be realized by some inexpensive low-power antenna components , It provides a broad prospect for mobile communication in high frequency band , It can double the radio spectrum efficiency , Enhance network coverage and system capacity , Help operators maximize the use of existing station sites and spectrum resources . We start with a 20 Take the antenna physical plane of square centimeter as an example , If these antennas are arranged in a grid at half wavelength intervals , be ： If the operating frequency band is 3.5GHz, Can be deployed 16 Secondary antenna .

5. Cognitive radio technology （Cognitive radio spectrum sensing techniques）

The biggest feature of cognitive radio technology is that it can dynamically select wireless channels . Without interference , Mobile phones constantly sense frequencies , Select and use the available wireless spectrum .

6. Ultra wideband spectrum

Channel capacity and bandwidth SNR In direct proportion to , In order to satisfy the 5G The Internet Gpbs Level data rate , Need more bandwidth . The higher the frequency is. , The more bandwidth , The higher the channel capacity . therefore , High band continuous bandwidth becomes 5G The inevitable choice of . Thanks to some effective technologies to improve spectral efficiency （ such as ： On a large scale MIMO）, Even with relatively simple modulation techniques （ such as QPSK), It can also be realized in 1Ghz On the Super bandwidth of 10Gpbs The transmission rate of .

7. Super density heterogeneous network （ultra-dense Hetnets）

Three dimensional layered network （HetNet） Refer to , A large number of microcells are deployed in the macro cellular network layer （Microcell）、 Tiny honeycomb （Picocell）、 Femtocells （Femtocell） Wait for the access point , To meet data capacity growth requirements . here we are 5G Time , More things - Object connection access network ,HetNet The density of will increase greatly .

8. Multi technology carrier aggregation （multi-technology carrier aggregation）

The future network is an integrated network , Carrier aggregation technology should not only realize LTE Intra carrier aggregation , It also extends to 5G、WIFI And so on . Multi technology carrier aggregation technology and HetNet Together , It will realize the seamless connection between all things .