MIMO Wireless Channel and How to Determine Its Capacity Under Different Conditions

In MIMO we talked a lot about receive antenna diversity or transmit antenna diversity. The more diversity you have, the easier it is to fight channel fading. Diversity is characterized by the number of independent fading branches or paths (paths). The next important term is the data pipeline. This term comes from fluid dynamics. Pipes are used to transport water to tanks / reservoirs. The greater the number of pipes, the more water will enter the tank / reservoir. This is similar to the data pipeline, but the similarity with fluid dynamics is over. Consider the case where there are two pipes between the transmitter and the receiver.

Increasing the bandwidth is not the only way to get more capacity from the technology. You can have multiple channels in the same bandwidth. Essentially, this is MIMO (Multiple Input Multiple Output). MIMO is multiple channels in space-time. These channels are on the same bandwidth, but in some respects they are quite different from each other (eg spatially oriented or some encoded "signatures") so they qualify as separate channels . Then, under ideal conditions, the capacity of these individual channels (MIMO stream) is added. Shannon's bondage still applies. So far, this equation was not that simple, so the channel is a matrix of individual MIMO streams and the capacity is a vector addition of each capacity. However, it is important that this constraint is applied. I did not infringe it

Large MIMO (Multiple Input Multiple Output) antennas use multiple antennas and multi - user MIMO (MU - MIMO) to increase sector throughput and capacity density. Each antenna is individually controlled and can be embedded in the radio transceiver assembly. Nokia claims that the capacity of the 64-Tx / 64-Rx antenna system has increased five-fold. The term "large-scale MIMO" was first created by Dr. Thomas L. Marzetta, researcher of Nokia Bell Labs in 2010, and was launched on 4G network such as Softbank in Japan.

In recent years, antenna technology has achieved incredible improvements, namely Massive MIMO and MU-MIMO. Large-scale MIMO (Multiple Input Multiple Output) technology refers to the idea of ​​equipping a radio transceiver with multiple antennas and has been shown to improve the spectral efficiency of radio links. Massive MIMO essentially extends the MU - MIMO (Multi - User MIMO) concept already popular in LTE networks by increasing the number of antennas far more than the number of simultaneous users.