Brief Analysis on how to integrate TD Smart Antenna with MIMO

MIMO, as a mainstream solution for the long-term evolution of TD, has been basically established. by increasing the number of antennas at the transmitting end and the receiving end, we can improve the spectrum utilization to meet the increasing demand for wireless communication capacity. So how does the TD system evolve from an existing Smart Antenna System to multi-antenna MIMO? MIMO indicates that the last path of the smart antenna can be carried together with the smart antenna?

Integration is a joy and sorrow

How can smart antennas and MIMO be integrated? It can only be said that if we want to find a fusion solution that does not conflict with MIMO implementation, it is to replace a single ordinary antenna with a single Smart Antenna and add a shaping module before each smart antenna. Each Smart Antenna has a wavelength interval of 10 times.

In principle, this fusion improves the channel reliability by using multi-antenna space-time encoding, while the beam shaped by smart antennas improves link coverage. If this system has been implemented, you can think of the problem to analyze its performance.

It is not difficult to find that the maximum number of users in a single time slot of a smart antenna is limited by the number of its array sources. Only a few levels of users with zero traps can be generated. for services that exceed the maximum number of users, the gain of smart antennas cannot be guaranteed, which greatly limits the system throughput. Furthermore, if we want to compare it with a MIMO system composed of a common antenna, the number of arrays of a single smart antenna is much higher than that of a single common antenna, but can the gain be comparable to that of multiple common antennas, this is also unknown. Without a doubt, even if the integration solution was established, it was a mixed blessing.

Integration implementation

Most of the Solutions for replacing a single ordinary antenna with a single Smart Antenna agree with the proposed fusion solution, but there are some problems:

From the perspective of smart antennas, due to the large size of smart antennas, the spatial distribution is more difficult to have a 10-fold wavelength interval than that of ordinary antennas, which poses a great challenge to the antenna layout;

The beam of a smart antenna is a High-Intensity Computing Unit. Simultaneous computing of multiple smart antennas brings a great deal of load to the hardware at the base station end, or even the base station end cannot carry the load;

Even if the base station can carry the data, multiple shaped modules will bring about processing latency, which is also a major obstacle for TD;

For multi-user sources, bit streams encoded when they are empty are disordered, and the beam shaping unit needs to determine the corresponding users for each bit. This undoubtedly increases the complexity of hardware;

For MIMO, increasing the number of antennas will increase the encoding complexity exponentially. In today's effort to reduce hardware complexity, integration may be a little worse.

Path

There are also other solutions for the integration of smart antennas and MIMO. For example, the smart antenna is used as the receiving antenna, and the ordinary antenna is used as the sending scheme. I will not mention it here. In short, even if it is integrated, smart antennas are also tied to MIMO systems. For integration, it is more out of consideration for the use of existing smart antennas, in order to minimize the operator's operating costs. Inevitably, the difference in the concept of smart antennas and MIMO poses a huge challenge.

For example, how to increase the number of service users? We may introduce the concept of grouping in MIMO to divide all antennas into several groups, each serving a set of fixed users. For example, if the two antennas are bound to a group and serve users 1-16, the number of users is doubled. Of course, the price we pay is that the diversity effect is halved or even more. The above is an extreme effect. We can also make an antenna serve users 1-8, another user serves users 4-12, and users in each group can be different at this time. The choice of users is undoubtedly the advantage of smart antennas, in order to find a compromise between throughput and diversity. Therefore, the advantages of smart antennas in MIMO systems need to be carefully designed.

Similarly, for hardware complexity, certain performance will be sacrificed to achieve integration. After all, what MIMO brings to smart antennas is an outstanding leader. Does a Smart Antenna keep up with it or stop it? How far can it go in a wireless network system?

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