MIMO (Multiple Input Multiple Output) systems use multiple antennas at both the transmitter and receiver to improve communication performance. MIMO offers various diversity modes like time, frequency, and space diversity to decrease fading. It can also do spatial multiplexing to increase capacity without additional power or bandwidth. MIMO is used in many wireless standards like 802.11n, LTE, and is key to improving data rates towards 1Gbps while maintaining reliability. However, MIMO systems also face challenges of increased hardware complexity, power consumption, and processing requirements.

1. MULTIPLE INPUT MULTIPLE
OUTPUT(MIMO) SYSTEMS
Presented By:
SHAHNEEL SIDDIQUI
BE-VI

2. Contents of Presentation
• Introduction of SISO & SIMO Systems/Antenna’s
• Introduction of MIMO Systems
• Diversity Modes
• Formats/Features of MIMO Systems
• MIMO Standards
• Why MIMO systems are useful ?
• Advantages & Disadvantages of MIMO Systems
• Conclusion

3. SISO Systems
• Assume we have an antenna, which transmits a signal x1at a frequency f
• As the signal propagates through an environment, the signal is faded, which
is modeled as a multiplicative coefficient h1. The received signal y1 will be
h1x1.
fading h1
y1 = h1x1
transmit receive
x1

4. SIMO Systems
• There will be two received signals y1 and y2 with different fading
coefficients h1 and h2.
• The effect upon the signal x for a given path (from a transmit antenna to a
receive antenna) is called a channel.
y1 = h1x1
transmit receive
x1
fading h1
y2 = h2x1

5. MIMO Introduction
• Systems with more than one input and/or more than one output
are known as Multi-Input Multi-Output systems
• With 2 transmitting antennas and 2 receiving antennas, we
actually add a degree of freedom!
• Multiple Input MultipleOutput technology uses multiple
antennas to make use of reflected signals to provide gains in
channel robustness and throughput.
• It is effectively a radio antenna technology as it uses multiple
antennas at the transmitter and receiver to enable a variety of
signal paths to carry the data transmit receive
x2
x1
fading h4
y1
y2

6. MIMO Model

7. MIMO Systems

8. Diversity Modes
• Time diversity: Using time diversity, a message may be transmitted at
different times, e.g. using different timeslots and channel coding.
• 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.
• Space diversity : This form of diversity uses different angles of polarization to
transmit the signal

9. Formats
• Spatial Diversity
• Signal copies are transferred from multiple antennas or received at
more than one antenna
• It is provided by employing an array of antennas, with a minimum
separation of λ/2 between neighbouring antennas

10. Formats Contd.
• Spatial Multiplexing
• The system is able to carry more than one data stream over one
frequency, simultaneously

11. MIMO Standards
Standard Technology
WLAN 802.11n OFDM
WiMAX 802.16-2004 OFDM/OFDMA
WiMAX 802.16e OFDMA
3GPP Release 7 WCDMA
3GPP Release 8 (LTE) OFDMA
802.20 OFDM
802.22 OFDM

12. Why MIMO?
• Systems with MIMO
• Significant increase in spectral efficiency and data rates
• High Quality of Service (QoS)
• Wide coverage
• Systems without MIMO
• Suffers from Co–channel interference and signal level fading
• It provides a limited bandwidth
• Power falls off with distance

13. Advantages of MIMO Systems
• Diversity decreases the fading and increases coverage and improves QoS
• Multiplexing increases capacity and spectral efficiency with no additional
power or bandwidth expenditure
• Allows large number of users
• Higher Data rates
• Lower Bit Error Rate
• Improved reliability and coverage

14. • Hardware complexity:
• Each antenna needs a radio-frequency (RF) unit
• Powerful digital signal processing (DSP) unit required
• Software complexity:
• Most signal processing algorithms are computationally intensive
• Power consumption:
• Battery lifetime of mobile devices
• Thermal problems
Disadvantages of MIMO Systems

15. Conclusions
• MIMO Systems are getting us closer to the 1Gbps landmark
• At the same time, they provide reliable communications
• MIMO introduces diversity & multiplexing
• 4G (LTE) uses MIMO technology
• Base for implementing next G-network

16. Thank you ! 
Questions are welcomed