2. INTRODUCTION
MIMO is an acronym that stands for Multiple Input Multiple Output.
It is an antenna diversity technology that is used both in transmission and
receiver equipment for wireless radio communication.
Here can be various MIMO configurations. For example, a 2x2 MIMO
configuration is 2 antennas to transmit signals (from base station) and 2 antennas
to receive signals (mobile terminal).
Exploit multipath instead of mitigating it.
3. Types of Smart antennas
There are two types of smart antennas are there:
1. Adaptive array antenna
2. Switched beam array antenna
4. Different MIMO Configurations
• Single Input Single Output (SISO)
• Simplest form, no diversity and no additional processing
required.
• Limited in its performance , more impact by interference
and fading then other.
• Bandwidth is limited by Shannon’s law and throughput
being dependent upon channel bandwidth and SNR.
SISO - Single Input Single Output
5.
6. Cont..
• Multiple Input Single Output (MIMO)
• Also termed as transmit diversity, here same data is
transmitted redundantly from two transmitter antennas and
receiver receive the optimum one.
• Multiple antennas and redundancy coding/processing
transfer to the transmitter and also advantages in terms of
space for antennas and reducing the level of processing.
MISO - Multiple Input Single Output
7. Advantages
■ Improved system capacities
■ Higher permissible signal bandwidths
■ Space division multiple access (SDMA)
■ Higher signal-to-interference ratios
■ Increased frequency reuse
■ Sidelobe canceling or null steering
■ Multipath mitigation
■ Constant modulus restoration to phase modulatedsignals
■ Blind adaptation
■ Improved angle-of-arrival estimation and directionfinding
■ Instantaneous tracking of moving sources
■ Reduced speckle in radar imaging
■ Clutter suppression
■ Increased degrees of freedom
■ Improved array resolution
■ MIMO compatibility in both communications and radar
8. Drawbacks
■ There transceivers are much more complex than traditional
• base station
■ The antenna needs separate transceiver chains for each array
antenna element and accurate real-time calibration for each of
them
■ The antenna beam forming is computationally intensive, i.e., smart
antenna base stations must be equipped withvery powerful digital
signal processors
• This leads to increase the system costs in short term, but since the benefits
outweigh the costs, it will be less expensive in long run
9. Conclusion
• MIMO systems have enabled a huge step forward since they can increase
significantly both the coverage and the capacity of cellular systems.
• The performance improvements resulting from the use of MIMO systems are due
to array gain, diversity gain, spatial multiplexing gain, and interference
reduction.
• The capacity of Receive or Transmit Diversity grows logarithmically with the
number of antennas
• Capacity of MEMO increases linearly with the number of antennas.
• Using Spatial Diversity:
• The SNR increases and Pe decreases when using MIMO
• There is a trade off between Spatial Multiplexing and Spatial Diversity gain.
10. References
• Ahmed El Zooghby, Smart Antenna Engineering; Artech House, Inc.: 2005.
• C.A. Balanis “Antenna theory analysis and design”, John Wiley and Sons
• Allen, B.; Ghavami, M. Adaptive Array Systems: Fundamentals and Applications;
John Wiley & Sons Inc.: 2005.
• Liberti, J., and T. Rappaport, Smart Antennas for Wireless Communications: IS-95
and Third Generation CDMAApplications, Prentice Hall New York, 1999.
• Lehne, PH & Pettersen, M & Telenor R&D. 1999, An overview of smart antenna
technology for mobile communications systems, IEEE Communications Surveys,
http://www.comsoc.org/pubs/surveys.
• Martin Cooper, Marc Goldburg, ”Intelligent Antennas: Spatial Division Multiple
Access” Annual Review of Communications,1996.
• Jack H. Winters “Smart Antenna Techniques and Their Application to Wireless Ad
Hoc Networks” .
• Murali Kiruba “Smart Antennas for Wireless Mobile Communication” ITtoolbox
Wireless- 15592, 22 Oct 2004.
