MIMO System

img

Multiple-input Multiple-output (MIMO)

A MIMO system can simply be defined as a transmission system equipped with various number of transmit antenna of at least two antennas and receive antennas great than one minimum of two. They are widely used in radio frequency technology (RF) such as in Wi-Fi, Long term evolution (LTE) and so on.

What made MIMO to be MIMO is the number of transmit antenna and the mode of transmission as shown below. If a transmission system is equipped with only one transmit antenna and one receive antenna then it becomes a SISO system, i.e. single-input single-output.

img

Now let’s talk about the mode of transmission.

Let us consider a MIMO system with Tx transmit antenna and Rx receive antenna. At every transmission instant of time t all the transmit antenna Tx are active at the same time. Likewise, the receive antenna too.

Meanwhile, with a SISO system only one antenna is active at every transmission instant (it can’t use more than one as the whole system only have one Tx antenna and one Rx antenna).

Since more than one data is transmitted via different transmit antenna Tx at the same time t, this increases the capacity of the MIMO system.

However, there is degradation in terms of performance of MIMO system and this can be improved using various diversity techniques. Also, antenna synchronization is required at the transmitter since all Tx most be active for transmission

Several different diversity modes are available in and each provides a unique number of benefits:

  1. Time diversity: Using time diversity, a message may be transmitted at different times, e.g. using different timeslots and channel coding.
  2. Frequency diversity: This form of diversity uses different frequencies. It may be in the form of using different channels, or technologies such as spread spectrum/OFDM.
  3. Space diversity : Space diversity used in the broadest sense of the definition is used as the basis for MIMO. It uses antennas located in different positions to take advantage of the different radio paths that exist in a typical terrestrial environment.

We have seen such diversity techniques in signal space time, space time block code, Alamouti, spatial modulation and so on. All this diversity techniques are in our product catalogue.

  • Tags
  • Simulation code
  • Self explanatory
  • Detailed system model

Please Note:

About Author
Autor MathsCodes

Our mission is to create a platform that simplifies digital signal processing as much as possible.