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HANDBOOK ON GREEN INFORMATION AND COMMUNICATION SYSTEMS Chapter 15 Energy Efficient MIMO-OFDM Systems Zimran Rafique and Boon-Chong Seet Auckland University of Technology – PowerPoint PPT presentation

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Title: HANDBOOK ON GREEN INFORMATION AND COMMUNICATION SYSTEMS


1
HANDBOOK ON GREEN INFORMATION AND COMMUNICATION
SYSTEMS
Chapter 15 Energy Efficient MIMO-OFDM Systems
Zimran Rafique and Boon-Chong Seet Auckland
University of Technology New Zealand
2
Table of Contents
3
INTRODUCTION
  • Due to multimedia applications, wireless systems
    with higher data rate are required
  • Higher data rates necessitate more energy per bit
    for a given bit error rate (BER)
  • Thus, overall system energy consumption will
    increase
  • Corresponding increase in CO2 emission threatens
    climate change and contributes to global warming
  • Energy efficient designs for high data-rate
    wireless systems is a crucial issue to be
    addressed

4
INTRODUCTION
  • Multi-Input-Multi-Output (MIMO) systems
  • In late 1990s, MIMO techniques were proposed to
    achieve higher data rates and smaller BER with
    the same transmit power and bandwidth required by
    single antenna system
  • Orthogonal Frequency Division Multiplexing (OFDM)
  • OFDM is a multi carrier modulation technique
    which has the capability to mitigate the effect
    of inter-symbol-interference (ISI) at the
    receiver side

5
INTRODUCTION
  • Fourier based OFDM (FOFDM)
  • Wavelet based OFDM (WOFDM)
  • In conventional OFDM, complex exponential Fourier
    bases are used to generate orthogonal subcarriers
    consist of a series of orthogonal sine/cosine
    functions
  • In WOFDM, wavelet bases are used to generate
    orthogonal carriers. These bases are generated
    using symmetric or asymmetric QMF structure of
    delay or delay-free type

6
INTRODUCTION
  • MIMO-OFDM
  • MIMO techniques are used with OFDM (MIMO-OFDM) to
    enhance the system performance
  • MIMO-OFDM systems are capable of increasing the
    channel capacity even under severe channel
    conditions
  • Provide two dimensional space-frequency coding
    (SFC) in space and frequency using individual
    subcarriers of an OFDM symbol or three
    dimensional coding called space-time-frequency
    coding (STFC) to achieve larger diversity and
    coding gains
  • OFDM can also be used in multi-user cooperative
    communication system by assigning subcarrier to
    different users for overall transmit power
    reduction

7
Multiple Antenna System
  • More than one antennas are used on transmitting
  • and/or receiving side
  • By using spatial multiplexing, data rate can be
  • increased
  • By using spatial diversity, BER can be improved
  • SNR can be improved at the receiver and
  • co-channel interference (CCI) can be
    eliminated
  • along with beam forming techniques

MIMO wireless communication system
8
Multiple Antenna System
  • Spatial Multiplexing Techniques
  • The number of users, or data rate of a single
    user, can be increased by the factor of number
  • of transmitting antennas (Nt) for the same
    transmission power and bandwidth
  • Individual transmitter antenna power is scaled by
    1/ Nt, thus the total power remains
  • constant and independent of number of Nt
  • At the receiver, the transmitted signals are
    retrieved from received sequences (layers)
  • by using detection algorithms

Spatial multiplexing system architecture with Nt
transmitting and Nr receiving antennas
9
Multiple Antenna System
Spatial Multiplexing Techniques
,
D-BLAST
10
Multiple Antenna System
Spatial Multiplexing Techniques
D-BLAST
11
Multiple Antenna System
Spatial Multiplexing Techniques
D-BLAST
12
Multiple Antenna System
Spatial Multiplexing Techniques
V-BLAST
13
Multiple Antenna System
Spatial Multiplexing Techniques
V-BLAST
14
Multiple Antenna System
Spatial Multiplexing Techniques
V-BLAST
15
Multiple Antenna System
Spatial Multiplexing Techniques
V-BLAST
16
Multiple Antenna System
Spatial Multiplexing Techniques
V-BLAST
17
Multiple Antenna System
Spatial Multiplexing Techniques
Turbo-BLAST
18
Multiple Antenna System
Spatial Multiplexing Techniques
Turbo-BLAST
19
Multiple Antenna System
Spatial Multiplexing Techniques
Turbo-BLAST
20
Multiple Antenna System
Space Time Coding Techniques
  • By using space and time (two-dimensional coding),
    multiple antenna setups can be used to attain
    coding gain and diversity gain for the same bit
    rate, transmission power and bandwidth as
    compared single antenna system
  • Information bits are transmitted according to
    some pre-defined transmission sequence
  • At the receiver, the received signals are
    combined by using optimal combining scheme
    followed by a decision rule for maximum
    likelihood detection

Space-time coding system architecture with Nt
transmitting and Nr receiving antennas
21
Multiple Antenna System
Space Time Coding Techniques
Alamouti STC Technique
22
Multiple Antenna System
Space Time Coding Techniques
Alamouti STC Technique
23
Multiple Antenna System
Space Time Coding Techniques
Space-Time Trellis Coding ( STTC) Technique
24
Multiple Antenna System
Space Time Coding Techniques
Space-Time Trellis Coding ( STTC) Technique
PSK 4-state space-time code with two transmitting
antennas
Time-delay diversity with 2 antennas
25
Multiple Antenna System
Space Time Coding Techniques
Orthogonal Space-Time Block Coding ( OSTBC)
Technique
26
Multiple Antenna System
Space Time Coding Techniques
Orthogonal Space-Time Block Coding ( OSTBC)
Technique
27
Multiple Antenna System
Space Time Coding Techniques
Space-Time Vector Coding ( STVC) Technique
28
Multiple Antenna System
Space Time Coding Techniques
Space-Time Vector Coding ( STVC) Technique
29
Multiple Antenna System
Beam-Forming
  • Multiple antennas capable of steering lobes and
    nulls of antenna beam
  • Co-channel interference cancellation can be done
    to improve SNR
  • and to reduce delay spread of the channel

A beam-former with Nt transmitting and Nr
receiving antennas
30
Multiple Antenna System
Beam-Forming
Delay-Sum Beam-Former
A Simple Delay-Sum Beam-Former
31
Multiple Antenna System
Beam-Forming
V-BLAST MIMO System with Beam-Former
V-BLAST MIMO system with beam-former
32
Multiple Antenna System
Multi-Functional MIMO Systems
  • Capable for achieving multiplexing gain,
    diversity gain and beamforming gain
  • Has Nt transmit antenna arrays (AAs) which are
    sufficiently apart to experience independent
    fading
  • LAA numbers of elements of each AA are spaced at
    a distance of ?/2 for achieving beamforming gain
  • Receiver is equipped with Nr receiving antennas

Multi-functional MIMO system
33
Multiple Antenna System
Virtual MIMO (V-MIMO) Systems
Models
  • Also known as cooperative MIMO systems
  • Proposed primarily for energy and physically
    constrained wireless nodes (e.g. sensor nodes)
  • to realize the advantages of MIMO techniques,
    which is otherwise not possible
  • V-MIMO systems are distributed in nature because
    multiple nodes are placed at different
  • physical locations to cooperate with each
    other
  • V-MIMO systems may also have problems such as
    time and frequency asynchronism

Virtual-MIMO system models
34
Multiple Antenna System
Virtual MIMO Systems
Models
Virtual-MIMO system models
35
Multiple Antenna System
Virtual MIMO Systems
Transmission-Delay for Model-d
36
Multiple Antenna System
Energy Efficiency of MIMO Systems
37
Multiple Antenna System
Energy Efficiency of MIMO Systems
38
Multiple Antenna System
Energy Efficiency of MIMO Systems
39
Multiple Antenna System
Energy Efficiency of MIMO Systems
Transmitter and receiver architecture
(In-Phase/Quadrature-Phase) for FOFDM and QAM
(analog)
40
Multiple Antenna System
Energy Efficiency of MIMO Systems
41
Multiple Antenna System
Energy Efficiency of MIMO Systems
42
Multiple Antenna System
Energy Efficiency of MIMO Systems
43
OFDM WOFDM
OFDM
44
OFDM WOFDM
Orthogonality Principle of OFDM
Comparison of the bandwidth utilization for
FDM and OFDM
45
OFDM WOFDM
Fourier based OFDM (FOFDM)
46
OFDM WOFDM
Fourier based OFDM (FOFDM)
A basic FOFDM based communication system
47
OFDM WOFDM
Fourier based OFDM (FOFDM)
FOFDM modulator and demodulator with filter bank
structure
48
OFDM WOFDM
Wavelet based OFDM (WOFDM)
Constellation Diagram of WOFDM
49
OFDM WOFDM
Wavelet based OFDM (WOFDM)
50
OFDM WOFDM
Wavelet based OFDM (WOFDM)
51
OFDM WOFDM
Wavelet based OFDM (WOFDM)
WOFDM modulator and demodulator using symmetric
QMF filter bank structure
52
OFDM WOFDM
Wavelet based OFDM (WOFDM)
53
Multiple Antenna OFDM Systems
  • Most of the MIMO techniques have been developed
    with the assumption of
  • flat fading channel
  • For broadband frequency selective wireless
    channel, the combination of MIMO and
  • OFDM (MIMO-OFDM) was proposed to mitigate the
    effect of ISI and ICI
  • In MIMO techniques, CSI is usually required at
    transmitter and/or receive side,
  • thus OFDM is also used in MIMO systems to
    estimate CSI

MIMO-OFDM system with Nt transmitting and Nr
receiving Antennas
54
Multiple Antenna OFDM Systems
MIMO Techniques with FOFDM
55
Multiple Antenna OFDM Systems
MIMO Techniques with FOFDM
56
Multiple Antenna OFDM Systems
MIMO Techniques with FOFDM
57
Multiple Antenna OFDM Systems
MIMO Techniques with FOFDM
Co-operative communication in a multi user
scenario using FOFDM
58
Multiple Antenna OFDM Systems
MIMO Techniques with WOFDM
Transmitter and receiver architecture for WOFDM
(analog)
59
Conclusion
  • The underlying principles and techniques of
    MIMO-OFDM systems for energy efficient
  • wireless communications are presented
  • Multi-antenna systems with spatial multiplexing,
    space-time coding and beamforming
  • techniques are introduced
  • To improve BER, SNR, throughput, and energy
    efficiency, multi-functional MIMO and
  • virtual MIMO systems are discussed along with
    energy efficiency analysis
  • The basic principles of FOFDM and WOFDM and
    their applications in true (co-located)
  • and virtual (cooperative) MIMO wireless
    systems are described
  • MIMO-OFDM is a promising solution for energy
    efficient high data rate wireless networks
  • WOFDM can be used for SFC, STFC, as well as
    cooperative communication systems

60
Conclusion
  • Potential directions for future work
  • New wavelet basis can be designed according to
    wireless channel conditions to
  • improve the overall system performance
  • Multifunctional MIMO performance can be
    evaluated using WOFDM/FOFDM
  • True and virtual MIMO-OFDM systems can be
    implemented to verify the theoretical results
  • Physical layer architecture performance of
    MIMO-OFDM system along with medium
  • access control (MAC) layer protocols
    can be explored
  • New MAC layer protocols can be proposed for true
    and virtual MIMO-OFDM systems
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