MIMO Systems and It's Applications
- MIMO system was invented to increase the system's capacity. Here capacity of the system increases linearly with the number of antennas at transmitter and receiver increases. But there is a main issue arises in MIMO system is that interference between multiple antenna elements.
- MIMO is an important feature of Wi-Fi 4 and 5, as well as 3G and 4G cellular networks. This method was developed to improve the capacity of a channel by sending many data streams simultaneously over a single channel. In a MIMO system, all simultaneous data streams are encoded orthogonally multiplexed, which lowers interference. Massive MIMO is widely utilized in 5G to achieve large capacity and communicate via beam forming or directional transmission.
- Here in MIMO systems we can use different types of diversity (time, space, and frequency diversity - three are three main type of diversity) to improve Quality of service (QoS) by reducing inter-element (antenna) interference. We can use different types of different types of polarization and pattern diversity, i.e., LP (linearly polarized antennas), CP (circularly polarized antennas), etc. to cancel interference between MIMO antenna elements. That diversity techniques are widely used in WLAN systems.
- Diversity is a technique where, especially, in case of MIMO system, multiple antennas can enable multiple data streams between transmitter and receiver simultaneously. Now, interference occurs in that system if there is no diversity. We know in case of time diversity you can send multiple signals to multiple devices using different time slots. Similar thing happens in TDM (time division multiplexing) modulation system. You know in 2G GSM we use TDM to connect 8 devices to BS thru same channel by 8 different time slots.
