The document discusses MIMO (Multiple Input Multiple Output) systems. It motivates MIMO by explaining how system designers aim to achieve high data rates and quality while minimizing complexity, transmission power, and bandwidth. It describes MIMO antenna configurations including SISO and MIMO. MIMO systems use multiple transmit and receive antennas to achieve high capacity. The document outlines diversity as a design criterion for MIMO systems to achieve reliable reception. It also discusses Alamouti's space-time coding scheme and how MIMO can be combined with OFDM to further improve performance. In conclusions, MIMO brings us closer to gigabit speeds while also providing reliable communications.

1. MIMO(A SHORT DISSCUSSION)
PRESENTED BY-PRITAM MOHANTY
REGD.NO-0901304189
GUIDED BY-Mr. Shakti Narayana Mishra(lect. In ECE dept.)
DEPT.-ELECTRONICS AND COMMUNICATION ENGINEERING
GANDHI INSTITUTE OF TECHNOLOGY AND MANAGEMENT
BHUBANESWAR

2. CONTENTS
 Motivations for the development of MIMO
systems
 MIMO Antenna Configuration
 Design Criterion for MIMO Systems (Diversity )
 MIMO-OFDM
 Conclusions

3. Aspirations of a
System Designer Achieve
High data rate “Channel Capacity (C)”
Quality
Minimize Probability of Error
(Pe)
Minimize complexity/cost of
System
Real-life Issues Minimize transmission power
Minimize Bandwidth

4. Antenna Configurations
 Single-Input-Single-Output (SISO) antenna system
User data stream
channel
User data stream
 1Gbps barrier can be achieved using this
configuration if you are allowed to use much power
and as much BW
 A combination a smart modulation, coding and
multiplexing techniques have yielded good results but
far from the 1Gbps barrier

5. MIMO Antenna Configuration
 Use multiple transmit and multiple receive antennas for a
1 1
single user
2 2
User data stream User data stream
. channel .
. .
. .
. .
. .
MT MR
 Now this system promises enormous data rates!

6. MIMO System Model
h11
s1 y1
h12
s2 . y2 User data stream
User data stream
. .
. .
. Channel
. .
sM Matrix H yM
s y
TRANSMITTED RECEIVED
VECTOR y = Hs + n VECTOR
MT
h11 h21 …….. hM1
h12 h22 …….. hM2
Where H = MR
. . …….. .
h1M h2M …….. hMM

7. Capacity of MIMO Channels
 We assume M RX and N TX antennas. The capacity
in bits/sec/Hz of a MIMO channel under an
average transmitter power constraint is given by
C = log 2 [det(IM + p/N H H*) b/s/Hz]

8. Capacity (contd)
 The capacity expression presented was over one realization
of the channel. Capacity is a random variable and has to be
averaged over infinite realizations to obtain the true
ergodic capacity. Outage capacity is another metric that is
used to capture this
 So MIMO promises enormous rates theoretically! Can we exploit this
practically?

9. DIVERSITY:
 Reliable reception is achieved when multiple
independently-faded replicas of the data symbol
can be obtained at the receiver end.
 The maximal diversity gain dmax is the total
number of independent signal paths that exist
between the transmitter and receiver
 The higher my diversity gain, the lower my Pe

10. Alamouti’s Scheme - Diversity
 Transmission/reception scheme easy to implement
 Space diversity because of antenna transmission. Time
diversity because of transmission over 2 symbol periods
 Consider (2, MR) system
1. Receiver uses combining and ML detection
2. rs = 1
+
• If you are working with a (2,2)
system, stick with Alamouti!
𝑥1 −𝑥2
+
• Widely used scheme: CDMA 𝑥2 −𝑥1
2000, WCDMA and IEEE 802.16-
2004 OFDM-256

11. Orthogonal Frequency Division
Multiplexing(OFDM)
 It is a special kind of FDM
 The spacing between carriers are such that they are
orthogonal to one another
 Therefore no need of guard band between carriers.
11

12. MIMO-OFDM
 OFDM extends directly to MIMO channels with the IFFT/FFT
and CP operations being performed at each of the transmit and
receive antennas. MIMO-OFDM decouples the frequency-
selective MIMO channel into a set of parallel MIMO channels
with the input–output relation for the ith (i = 0, 2,…,L-1) tone,
yi = Hisi + ni i = 0, 2,…, L-1

13. Conclusions
 MIMO Systems are getting us closer to the 1Gbps
landmark
 At the same time, they provide reliable
communications
 Different architectures available for use
 Developing efficient network protocols for a
MIMO PHY layer is an area of open research

14. References
(1) “Layered Space-Time Architecture for
Wireless Communication in a Fading
Environment When using Multi-Element
Antennas”, G.J.Foschini, Bell Labs Tech
Journal, 1996
(2) “An Overview of MIMO Communications – A
Key to Gigabit Wireless”, A.J Paulraj,
Gore, Nabar and Bolcskei, IEEE Trans
Comm, 2003
(3) “Improving Fairness and Throughput of Ad
Hoc Networks Using Multiple
Antennas”, Park, Choi and
Nettles, submitted Mobicom 2004

15. THANK YOU