Tutorial MIMO Communications with Applications to (B)3G and 4G Systems
Introduction
Juha Ylitalo
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 1
Introduction
Short historical note Advantages of multi-antenna techniques Adaptive antennas
- Beamforming: spatial focusing of correlated signals - Rx/Tx diversity: combining of decorrelated signals - MIMO: increasing spectral efficiency/ data rates
Simple example: SINR improvement Definition of MIMO Spatial correlation matrix Example: Diversity & MIMO in WCDMA
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 2
Historical Note
Multiple antenna transmission used by Marconi in 1901
Four 61m high tower antennas (circular array) Morse signal for "S" from England to Signal Hill, St. John, Newfoundland, distance 3425km
Submarine sonar during 1910's Acoustic sensor arrays 1910's RF radars 1940's Ultrasonic scanners from 1960's
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 3
Advantages of Multiple Antenna Techniques
Resistivity to fading (quality) Increased coverage Demonstration by Lucent Increased capacity with 8 Tx /12 Rx antennas: Increased data rate 1.2 Mbit/s in 30kHz Improved spectral efficiency Reduced power consumption Reduced cost of wireless network
Some challenges: - RF: Linear power amplifiers, calibration - Complex algorithms: DSP requirements, cost - Network planning & optimisation
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 4
Adaptive Antennas
An adaptive antenna system consists of several antenna elements, whose signals are processed adaptively in order to exploit the spatial dimension of the mobile radio channel.
Weight Adaptation
RF
IF
RF
IF
RF
IF
Baseband processing
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 5
Adaptive Antenna Operation
Conventional BTS:
radiation pattern covers the whole cell area
Smart Antenna BTS:
adaptive radiation pattern, "spatial filter" transmission/reception only to/from the desired user direction minimise antenna gain to direction of other users
Conventional BTS radiation pattern
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
Smart Antenna BTS
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 6
Beamforming (beam steering)
Beamforming = phasing the antenna array elements Only Direction-of-Arrival (DOA) parameter needed in both TX and RX: simple and robust Suits especially well to FDD systems
0 -5 -10 -15 -20 -25 -30 DOA = 0 deg. 1 DOA = 30 deg.
2
M=8
Array Gain [dB]
-50
0 Azimuth [deg]
50
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 7
RX Diversity
De-correlated (statistically independent) signals received spatial and polarisation diversity arrangements combining of fading signals:
Maximum Ratio Combining (MRC) Interference Rejection Combining (IRC)
dB
10 5 0 -5 -10 4MRC 2MRC -15 0 0.5
Received signal power
RX RX RX RX
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
1.5 2 2.5 Seconds, 3km/h
WCDMA WCDMA Transceiver Transceiver
Combined received signal
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 8
Transmission Diversity
Multiple antennas available at the BTS Terminal: only one antenna
-> downlink suffers from lack of diversity
Uncorrelated fading
Downlink: Use TX instead of RX diversity TX diversity gain:
Signal #1
Base station
(1) Gain against fading
Signal #2
Gain against fading Feedback modes: coherent combining ("beamforming") gain
Downlink capacity improvement RX diversity in terminal is coming soon enabling RX diversity at UE, MIMO,
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
(2) Coherent combining gain (only feedback modes)
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 9
SISO, SIMO, MISO, MIMO
Single-Input, Single-Output channel suffers from fading Single-Input, Multiple-Output channel: RX diversity Multiple-Input, Single-Output channel: TX diversity, Beamforming
SISO Data stream radio channel Data stream
SIMO Data stream radio channel Combiner
Data stream
Data stream
MISO radio channel
Data stream
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 10
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
Definition of MIMO
Multiple-Input, Multiple-Output channel Mapping of a data stream to multiple parallel data streams and de-mapping multiple received data streams into a single data stream Aims at high spectral efficiency / high data rate
M antennas N antennas
Data stream
Serial/ parallel mapping
MIMO radio channel Parallel/ serial mapping
Data stream
Rxx
HMN
Ryy
Requires rich scattering environment
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 11
TX diversity& Beamforming vs. MIMO
Maximum Gain: Transmit Diversity/ BF
V1 V2
s1, s2, s3, s4
Same signal on all antennas, i.e. conventional Tx diversity/ BF
V3 V4 a)
Maximum Capacity: Parallel channel transmission
s1 s2
V1 V2
s3
V3 V4
Different signals on Tx antennas. i.e. true MIMO
s4
b) BLAST (PARC) type of transmission scheme is considered as MIMO, whereas WCDMA STTD is a hybrid, considered as a Tx diversity scheme
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 12
Channel capacity (Shannon)
Represents the maximum error-free bit rate Capacity depends on the specific channel realization, noise, and transmitted signal power. Single-input single-output (SISO) channel
y (t ) = x(t ) + n(t )
Multi-input multi-output (MIMO) channel
P 2 C = log2 1 + 2 n
y(t ) = Hx(t ) + n(t )
1 H C = log 2 det I + 2 HQH n
Q is the covariance matrix of the transmitted vector
Tutorial #2: MIMO Communications with Applications to (B)3G and 4G Systems Introduction
J. Ylitalo & M. Juntti, University of Oulu, Dept. Electrical and Inform. Eng., Centre for Wireless Communications (CWC) 13
