mimo in 4g wireless
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Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
MIMO Introduction Realizing Benefits from MIMO Antenna Diversity, Beamforming and SDMApplications of MIMO in WiFi, WiMax and LTE Future of MIMO
MIMO in 4G Wireless
Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
Introduction Multiple Input Multiple Outputo Multiple Tx & Rx Antennas
Multiple radio channels
Tx Rx
1 1
2 2
M N
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Introduction Multiple Input Multiple Outputo Multiple Tx & Rx Antennas
Multiple radio channels
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What came before MIMO?
SISOo Single Input Single Output
Tx Rx
1 1
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What came before MIMO?
SISOo Single Input Single Output
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What came before MIMO?
SIMOo Single Input Multiple Output
Tx Rx
1 1
2
N
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What came before MIMO?
SIMOo Single Input Multiple Output
TxRx
Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
What came before MIMO?
MISOo Multiple Input Single Output
Tx Rx
1 1
2
M
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What came before MIMO?
MISOo Multiple Input Single Output
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Finally MIMO! MIMOo Multiple Input Multiple Output
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Interactive Question #1 Which Antenna configuration is depicted by the following figure?
1. SISO2. SIMO3. MISO4. MIMO
TxRx
Rx
Rx
Rx
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Promises of MIMO Robust Radio Channel
o Effects of fading and multipath interference mitigatedo No breaks in voice calls or data
Higher Throughputo Faster downloadso More Mbps with existing spectrum and power
Enables 4G Wireless Broadband applicationso WLAN (IEEE 802.11n/ad)o WiMAX (IEEE 802.16m)o LTE-A (3GPP Rel 10)
IIs this handset in your future?
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Realizing MIMO Promises
Antenna Diversityo Receive Diversityo Transmit Diversity
Beamforming Space Division Multiplexing (SDM)
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Multipath Propagation
I20 -30 dB Fading
+ =no signal
TxRx
Path 3
Path 2
Path 1
+ =
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Multipath Propagation
I Inter Symbol Interference (ISI)
time
Path 1
Path 2
Path 3
++
s1 s2
s1, s2 s2
s1 s2
TxRx
Path 3
Path 2
Path 1
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Receive Diversity Mitigates Effects of Multipath Propagation Enhances Signal to Noise Ratio (SNR) SIMO Configuration
TxRx
λ/2 λ/2
ISignals combined from multiple antennas
TxRx
λ/2 λ/2
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• • •
• Max SNR
ISelection Combining
Receive Diversity Mitigates Effects of Multipath Propagation Enhances Signal to Noise Ratio (SNR) SIMO Configuration
TxRx
λ/2 λ/2
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IEqual Gain Combining
• • •
• 1/3 1/3 1/3
Mitigates Effects of Multipath Propagation Enhances Signal to Noise Ratio (SNR) SIMO Configuration
Receive Diversity
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TxRx
IMaximal Ratio Combining
• • •
• 3/6 2/6 1/6
λ/2 λ/2
Receive Diversity Mitigates Effects of Multipath Propagation Enhances Signal to Noise Ratio (SNR) SIMO Configuration
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Transmit Diversity Redundant copies of signal transmitted across space and time Space Time Block Codes (STBC) used
o 50 – 200 ns time delay inserted in transmission paths Mitigates Effects of Multipath Propagation Enhances Signal to Noise Ratio (SNR) MISO Configuration
time
Ant 1
Ant 2
Ant 3
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Interactive Question #2 What is not a benefit of Antenna Diversity?
1. Diversity Gain2. Enhanced Signal to Noise Ratio3. Increased Bandwidth4. Redundant Copies of Signal
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Beamforming
Radio Beam
Controls shape and direction of radio signals Used on Transmit or Receive Antenna Arrays Extends range of radio signals in a direction
o Signals from multiple antennas add up constructively to maximize receiver gain
Mitigates Effects of Multipath Propagation
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Radio Beam
Beamforming Controls shape and direction of radio signals Used on Transmit or Receive Antenna Arrays Extends range of radio signals in a direction
o Signals from multiple antennas add up constructively to maximize receiver gain
Mitigates Effects of Multipath Propagation
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Space Division Multiplexing (SDM) Different signals transmitted and received simultaneously over same RF bandwidth Exploits spatial separation provided by MIMO Configuration Achieves Higher Throughput Ideal for RF channels with High Signal to Noise Ratio (SNR)
Tx Rx
1 1
2 2
M N
M X N MIMOλ/2
λ/2
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Space Division Multiplexing (SDM) Signal Path Coefficients (h11….hMN) represent amplitude and phase response for each signal path
o Determined during training sequence– Tx generates known training signal– Rx processes training signal to estimate path responses
Tx Rx
1 1
2 2
M N
M X N MIMO
h11
h1Nh21
h22
hM2
hMN
λ/2
λ/2
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Space Division Multiplexing (SDM) MIMO channel represented as matrix of signal path coefficients, H Receivers use H-1 to spatially demultiplex the original transmitted signals
o T = H-1 R
IReceived Signals
IMIMO ChannelITransmitted
Signals
Rx1
Rx2
RxN
••
•
₌
h11 h21 • • hM1
h21 h22 • • hM2
• • • • •
• • • • •
hM1 hM2 • • hMN
Tx1
Tx2
TxM
••
•
R H T
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Interactive Question #3 Which technique will you recommend when the radio channel is very noisy (SNR is low)?
1. Space Division Multiplexing (SDM)2. Transmit Antenna Diversity3. Space Time Block Codes (STBC)4. Time Division Multiplexing (TDM)
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Multiplexing Rate in MIMO
Base Station
1 1
22
3
Single User
3 X 2 MIMOMultiplexing Rate = 2
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
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Multiplexing Rate in MIMO Multiplexing Rate
o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
Base Station
1 1
22
3
3 X 2 MIMOMultiplexing Rate = 2
Single User
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Multiplexing Rate in MIMO
Base Station
1 1
22
3
Single User
3 X 2 MIMOMultiplexing Rate = 2
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
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Multiplexing Rate in MIMO
Base Station
1 1
22
3
Single User
3 X 2 MIMOMultiplexing Rate = 2
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
Copyright © USPurtek LLC, 2012 All Rights Reserved. No part of this publication may be reproduced without the prior written permission of USPurtek LLC, uspurtek.com
Multiplexing Rate in MIMO
Base Station
1 1
22
3
Single User
3 X 2 MIMOMultiplexing Rate = 2
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
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Multiplexing Rate in MIMO
Base Station
1 1
22
3
Single User
3 X 2 MIMOMultiplexing Rate = 2
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
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Multiplexing Rate in MIMO
Base Station
1 1
22
3
3 X 2 MIMOMultiplexing Rate = 2
Single User
Multiplexing Rate o Number of distinctive data streams that can be received correctly and simultaneously
– For MxN MIMO, it is the min (M,N)
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Diversity Gain in MIMO For narrow band system with slow fadingo Product of M & N
Base Station
1 1
22
3
Single User
3 X 2 MIMODiversity Gain = 6
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Trade Off is Possible For 5x4 MIMO oCase 1: Reliable Mode
– Multiplexing Rate = 2– Diversity Gain = 3x2 = 6
Multiplexing & Diversity Combo
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Multiplexing & Diversity Combo
Trade Off is Possible For 5x4 MIMO oCase 2: High Rate Mode
– Multiplexing Rate = 3– Diversity Gain = 2x1 = 2
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MIMO in WiFi IEEE 802.11n standard has adopted MIMOo Antenna Diversity upto 4 x 4o Tx Beamformingo Space Division Multiplexing (SDM)
2.4/5 GHz ISM bando 20/40 MHz Bandwidth
PHY Data rates upto 600 Mbpso Throughput > 200 Mbps
Extended Rangeo Indoor 70 mo Outdoor 250 m
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MIMO in WiFi Antennas for Access Pointo Narrowband Monopole
λ/2 λ/2
λ/4
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MIMO in WiFi Antennas for Access Pointo Multiband Compact
Top View
2.4 GHz5 GHz
RF Cable
Ground
Multiband Antenna Element
Antenna Element
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MIMO in WiFi Antennas for Portable Deviceso Tradeoffs between design, performance and placement
Antenna Feed Point
Ground Plane
Antenna Configuration: Case1
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MIMO in WiFi Antennas for Portable Deviceso Tradeoffs between design, performance and placement
Antenna Feed Point
Ground Plane
Antenna Configuration: Case2
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Interactive Question #4 What is the recommended physical separation between Antenna elements of a MIMO system?
1. λ/42. Depends on the wireless standard3. Minimum λ/24. Does not matter
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MIMO in WiMax IEEE 802.16m has full featured MIMOo Antenna Diversity o Beamformingo Space Division Multiplexing (SDM)
2.3-2.4, 3.3-3.4 GHz (country specific)o 5-10 MHz Bandwidth
Enhanced Throughputo 1 Gbps for fixed stationso 100 Mbps for mobile stations
Single or Multi User MIMOo SU-MIMOo MU-MIMO
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MIMO in LTE-A 3GPP Rel 10 (LTE-A) has full featured MIMOo Antenna Diversity o Beamformingo Space Division Multiplexing (SDM)
22 Freq. bands covering 698-3600 MHzo Scalable Bandwidth (20-100 MHz)
Enhanced Throughputo 1 Gbps Downlinko 500 Mbps Uplink
Single or Multi User MIMOo SU-MIMOo MU-MIMO
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SU-MIMO Single User gets the benefit of full
Throughput
Base Station
1 1
22
3
3 X 2 MIMO
Single User
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SU-MIMO
1
1
2
2
3
3 X 2 MIMO
Base Station
Single User
Single User gets the benefit of full Throughput
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MU-MIMO Multiple Users share full Throughput
11
22
3
Base Station Multiple
Users
3
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A Glimpse of the Future Massive MIMO & WiGig (IEEE 802.11ad)o 60 GHz unlicensed band
– 4 channels of 2 GHz eacho Upto 7 Gbps data rateso mm Wave MIMO Antenna Arrays
– small λ ( 5 mm) means very small antenna
λ /2 = 2.5 mmDistance between elements
1 cm
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A Glimpse of the Future
256 elements
16 elements
Massive MIMO & WiGig (IEEE 802.11ad)o 60 GHz unlicensed band
– 4 channels of 2 GHz eacho Upto 7 Gbps data rateso mm Wave MIMO Antenna Arrays
– small λ ( 5 mm) means very small antenna
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Bibliography“An Introduction to MU-MIMO Downlink” IEEE Communications Magazine, October 2004 “MIMO-OFDM based air interface” IEEE Communications Magazine, January 2005 “Downlink MIMO in LTE-A” IEEE Communications Magazine, February 2012 “Understanding IEEE 802.11n amendment” IEEE Circuits and Systems Magazine 1Q 2008 “Advancement of MIMO in WiMax” IEEE Communications Magazine June 2009 “MIMO in WiMax and LTE” IEEE Communications Magazine May 2010 “MIMO-OFDM Wireless Systems” IEEE Wireless Communications August 2006 “Antennas for WiFi Connectivity” Proceedings of the IEEE July 2012 “Overview of Mobile WiMax – Technology and Evolution” IEEE Communications Magazine October 2008 The ARRL Handbook for Radio Communications, 2010
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