Pre5G uses technological innovation to outline the 5G blueprint
As mobile broadband networks penetrate into all areas of society, people are full of expectations for 5G, the fifth-generation mobile communication technology that is fully connected and can increase capacity by thousands of times.
However, 5G still has many issues worthy of discussion from demand definition to key technical routes. It is generally believed that commercial use will be after 2020.
In June 2014, ZTE Wireless CTO Dr. Xiang Jiying first proposed the Pre5G concept at the Global 5G Technology Summit held in the Netherlands, bringing 5G technology forward to the 4G era for the first time.
In fact, Pre5G is a concept driven by customer needs, and ZTE has just made some abstractions.
First of all, customers generally report that 5G research has been carried out for several years. Why can no one clearly explain what 5G is? There are many people trying to define 5G, but there has never been an authoritative definition.
Secondly, 5G will not be commercially available until at least 2020. The first reaction of most customers is "there are still 6 years, it has nothing to do with me, let others study it first."
After ZTE proposed the "Pre5G concept", I unexpectedly discovered that it was no longer necessary to come up with an "accurate 5G definition" immediately.
Moreover, since Pre5G can be used based on 4G terminals, it is no longer after 2020, butThis may have been in 2015 or 2016, so many customers immediately had strong interest.
Simply put, Pre5G contains four elements: (1) Since it is related to 5G, it must use 5G technology.
(2) It brings users a user experience that is much higher than 4G and close to 5G.
For example, the throughput rate is doubled, the delay is reduced, and so on.
(3) The time point is much earlier than 2020.
(4) It can be based on existing air interfaces, or even directly use old 4G terminals.
Some customers questioned that 5G has not been defined yet, how to define Pre5G? Although 5G is indeed not defined from a standard perspective, it has been defined in terms of requirements and key technologies. Well defined, at least some of the technologies are already recognized as 5G technologies.
So based on these recognized 5G technologies and 5G requirements, there is no problem for us to define Pre5G.
Based on the above characteristics of Pre5G, the difference between Pre5G, 4G+ and 5G can be clearly defined.
The performance of Pre5G clearly exceeds the definition of the 4G+ standard, but it does not need to rely on the standard definition of 5G and can be achieved based only on standard 4G.
Therefore, even if the Pre5G stage does not appear in the standard, there will be a Pre5G stage between 4G+ and 5G at the implementation level.
At present, ZTE has made outstanding progress in Pre5G technology. The related Massive MIMO (massive multi-antenna) and UDN (ultra-dense network) technologies have commercial capabilities. This is objectively due to As the world's leading telecommunications equipment supplier, ZTE has an in-depth understanding of 4G and 5G.
Therefore, although ZTE is the first company in the industry to clearly propose Pre5G technology defines and implements the commercialization of Pre5G, but the concept of Pre5G is driven by customer needs.
Massive MIMO
November 2014 , ZTE and China Mobile completed the world's first TD-LTE3D/Massive Pre-commercial test of MIMO base station.
The test was initiated and organized by China Mobile Research Institute and used ZTE’s latest 64-port 128-antenna 3D/Massive MIMO baseband radio integrated outdoor base station.
This test focused on verifying 3D/Massive MIMO's comprehensive and deep coverage capability for high-rise buildings
In the existing network, the ordinary 8-antenna vertical beam is fixed and the vertical coverage angle is small, resulting in poor deep coverage in high-rise buildings, high interference in high-rise buildings, and SINR received by terminals. and low throughput rate, leading to poor high-level user experience, which has becomeThis is a major problem faced by operators.
3D/Massive MIMO antennas have 3D beam forming capabilities. This test shows that the 3D/Massive MIMO base station can fully and deeply cover a 35-story high-rise office building, and its data throughput rate is far better than that of an 8-antenna base station. On the 35th floor, its data The throughput rate is 3.36 times that of the 8-antenna base station.
This test proves that 3D/Massive MIMO is a good technology for solving high-rise coverage. Only one station can solve the problem that traditional base stations can solve with multiple stations.
The test results basically meet the pre-commercial requirements, marking ZTE’s completion of the Pre5G pre-commercial base station field test and taking a solid step towards 5G.
Massive MIMO is one of the most important core technologies in 5G, and it can even be said to be the only technology that can exponentially improve spectrum efficiency (most other technologies only improve space utilization efficiency, such as building sites more densely, using more more spectrum resources, etc.).
In principle, Massive MIMO has two main functions. First, it can form semi-dynamic targeted coverage for broadcast channels (CRS, PBCH, etc.), while traditional antennas can only form static coverage. Therefore, the coverage of Massive MIMO is better and more targeted.
Second, for PDSCH, a fully dynamic digital waveform can be formed, thus greatly improving cell capacity.
Simulation shows that compared with 8 antennas, the capacity is increased by 4 to 6 times, which is unachievable by any previous technology.
It is generally believed that 100 times of 5G’s thousands of times capacity comes from more cells and more spectrum, while only 8 to 10 times comes from improvements in spectrum efficiency.
Therefore, it can be said that the adoption of Massive MIMO has brought the spectrum efficiency experience close to the requirements of 5G.
Massive MIMO increases the number of antenna ports from the traditional 8 to close to or even more than 100.
When the number of antennas increases to hundreds, the use of the traditional 4G channel feedback mechanism will inevitably generate a lot of overhead. Even just the reference signal (RS) It can account for more than 80% of the overall resources.
To this end, a lot of research has been done on channel feedback in 5G, and a consensus has been reached that the channel feedback mechanism of 4G must be significantly modified.
In this case, Massive MIMO sounds very different from 4G and is a brand new technology.
However, further research shows that in TDD mode, uplink and downlink symmetry can be used to predict downlink channels through uplink channel estimation.
This supports channel measurement of hundreds of channels without adding feedback channels.
Compared with the direct feedback mode, this method has better and faster performance.
UDN< /p>
UDN (Ultra-dense network) is also another 5G A key technology.
In 4G, the number of small cells is still relatively small, so in 4G, Small cells are involved. The cell technology focuses more on the interference with the macro network (Hetnet), but does not pay much attention to the interference between small cells.
5G UDN is deployed ultra-densely, so the interference between small cells becomes a problem. The main contradiction.
ZTE has discovered through research that ZTE’s Cloud Radio technology in 4G macro networks can in principle be used to suppress interference between small cells.
So it can be considered that, 5G UDN technology is ZTE 4G Cloud A natural evolution of Radio
This is because, essentially, small Intercell interference is the same as Macro-Macro interference, which is a networking problem of homogeneous networks.
ZTE has evolved Cloud Radio to UDN and proposed Virtual Cell technology.
The cell is a physical cell, and the Cell ID is used to identify the cell. All communications of the UE are based on the Cell ID.
In the virtual cell, the Cell ID becomes unimportant or even disappears, and is dynamically generated by the network for specific users. The "UE ID", from the user's point of view, it is equivalent to a virtual logical site that follows their movements, so the smoothness and performance of the business are greatly improved.
MUSA
MUSA(multi-user shared access) is a 5G technology proposed by ZTE.
Traditional communication technologies (such as 4G) use an "orthogonal" method to distinguish users, that is, different users are assigned different freedoms. degree (time, subcarrier, or space), two users cannot share the same degree of freedom .
MUSA assigns a code sequence to each user, and then assigns these users to the same degree of freedom.
Different from traditional 3G code division multiple access, MUSA. The codes assigned to users can be non-orthogonal and only play a role in spreading.
Then at the same time.How to distinguish the signals of different users in a degree of freedom requires the help of SIC receiving technology (successive interference cancellation). For example, for two users, one far and one near, the far user needs to be allocated more power, so for the near user The interference is very large.
Conventional receivers cannot handle this situation well. The nonlinear SIC receiver can first decode the data of the remote user and perform interference cancellation, thereby Smoothly extract your own data.
On the surface, it seems that the user has obtained additional data, but it does not violate the rules of communication. It just makes the data traffic distribution more balanced. For example, traditional communication methods can only be used at the complete expense of the remote user. Obtain maximum system capacity, but MUSA can ensure larger system capacity under relatively loose conditions while ensuring balance among users.
There are currently many studies on non-orthogonal communication. The characteristics of ZTE MUSA are: obvious performance improvement and controllable complexity.
In addition, due to the code domain method, it can support the access of a large number of users, and due to the use of non-orthogonal detection, synchronization is not required in principle, which is beneficial to improving battery life, so MUSA's uplink technology is very suitable For MTC IoT applications.
In addition, ZTE invested heavily in the development of 4G vector processor chips a few years ago because the chip platform has a flexible software-scalable architecture and super processing capabilities. , so the hardware can be kept unchanged and the instruction set can be simply adjusted to meet the requirements of Pre5G or even 5G.
