Wireless Communications Lab
Robert W. Heath Jr. Ph.D, P.E.
KE5NCG
Wireless Networking and Communications Group
Department of Electrical and Computer Engineering
The University of Texas at Austin, Austin TX USA
ENS 435
http://www.profheath.org
rheath@utexas.edu
Wednesday, September 4, 13
Outline
Review of the syllabus
Introduction to wireless communication
A DSP approach to wireless
Connection to the lab
How the course works
2
Wednesday, September 4, 13
Syllabus Review
Instructor: Robert W. Heath Jr.
TA:Yingzhe Li
EE 471C Prerequisites: EE 345S or EE 351M or EE 360K
Reading Materials
Based on course reader already posted to Blackboard
Occasional updates to reader will be made
All previous homework and exam problems in reader
Undergrad: Tech area fulfillment
Communications / Networking and Signal Processing
Graduate: Counts as a CommNetS course
Class will be video recorded but please come to class
3
Wednesday, September 4, 13
Outline
Review of the syllabus
Introduction to wireless communication
A DSP approach to wireless
Connection to the lab
How the course works
4
Wednesday, September 4, 13
Wireless is Everywhere
cellular networks
local area networks
personal area networks
emerging applications
Wednesday, September 4, 13
The Cellular Concept
Co-Channel
Interference
Handoff
Base Station (BS)
Mobile Station (MS)
or
User Equipment (UE)
Cell
The same frequency is
reused in multiple clusters
Cluster
Base stations serve multiple subscribers
Frequencies are geographically reused in cells
Handoff provides seamless connection
6
Wednesday, September 4, 13
Evolution of Cellular Systems
1G
First generation systems - known after the fact as 1G
Conceived in the 1960’s
Deployed in the late 1970’s / early 1980’s
Built around analog technology, FM modulation
Limited data, little security
Expensive due to analog technology
Little roaming
Examples AMPS, NTT, NMT-450, etc.
Most of you in have
never used 1G
:-(
7
Wednesday, September 4, 13
Evolution of Cellular Systems
2G
Second generation systems - known as 2G
Conceived in the 1980’s
Deployed in the 1990’s
Digital Voice
More subscribers per bandwidth, some data
Enabled roaming in Europe (GSM), not in US (IS-95, IS-136)
Examples GSM, IS-95, IS-136, PDC, EDGE (2.5G)
Most of you have a
2G compatible
phone
8
Wednesday, September 4, 13
Evolution of Cellular Systems
3G
Third generation systems - known as 3G
Conceived in the 1990’s
Deployed in the 2000’s
Digital voice plus data
Video telephony
Most of you use 3G
on a daily basis
Higher capacity
CDMA (code division multiple access)
Examples: 3GPP WCDMA, HSDPA, etc.
3GPP2 cdma2000, 1xEV, 1xEV-DO, 1xEV-DV, etc.
9
Wednesday, September 4, 13
Evolution of Cellular Systems
4G
After 3G, cellular systems began fine-grained development
3GPP updates were made in stages e.g. R7, R8, R9, R10, R11, etc
Transition to 4G happened at Release 10 known as 3GPP LTE Advanced
Fourth generation systems - known as 4G
IP based backbone, supports VoIP
OFDMA allows efficient resource allocation
MIMO (multiple antennas 8 @ base station, 4 at handset)
Higher data rates
3GPP Long Term Evolution Advanced
4G devices are
now being sold
Have one?
10
Wednesday, September 4, 13
Evolution of Cellular Systems
5G
Fifth generation systems - known as 5G
3GPP after Release 14 will likely be considered 5G
Development is ongoing
Possible technologies that could make 5G
Massive MIMO - hundreds of antennas at the base station
Millimeter wave - use millimeter wave spectrum to obtain larger bandwidth
New concepts supported by 5G
Device-to-device
Machine-to-machine
Vehicle-to-vehicle
Active area of
research, good area
of senior design and
PhD dissertations
11
Wednesday, September 4, 13
Wireless is Everywhere
cellular networks
local area networks
personal area networks
emerging applications
Wednesday, September 4, 13
The Wireless LAN Concept
Wireless LANs provide wireless Internet access (and LAN)
Access Points (APs) serve multiple clients
Uses unlicensed frequency bands
Little to no coordination between adjacent APs
13
Wednesday, September 4, 13
IEEE 802.11 Wireless LAN
IEEE is the Institute of Electrical and Electronics Engineers
Main professional society for electrical engineers
Everyone should become a student member of the IEEE
digression
You might also want to join COMSOC (communications society), SPSOC
(signal processing society), and ITSOC (information theory society)
IEEE 802 is a group that develop local area network and
metropolitan area network standards, focusing on the PHY,
MAC, and LINK layers
IEEE 802.11 is WLAN working group (members develop
standards + vote)
14
Wednesday, September 4, 13
IEEE 802.11 Subgroups
11
11b
11g
11n
11ac
11ad
802.11: 1/2Mbps in 2.4GHz band, FHSS or DSSS
many more
802.11b: (WiFi) DSSS with 11Mbps in 2.4GHz band subgroups,
some
802.11g: similar to 802.11a but for 2.4GHz
successful
802.11n: MIMO enhancement, 100-200Mbps
and some
not
802.11ac:Very high throughput < 6GHz carrier
802.11a: extend to 5GHz ban, 54Mbps, OFDM
More bandwidth aggregation, more MIMO, multiuser MIMO
802.11ad:Very high throughput > 6GHz carrier
Exploits 60GHz unlicensed bands, lots of antennas, beamforming
Discussion has started on beyond 11ac/ad
Wednesday, September 4, 13
15
Wireless is Everywhere
cellular networks
local area networks
personal area networks
emerging applications
Wednesday, September 4, 13
Personal Area Networks (PAN)
10 Gbps
5 Gbps
6 Gbps
Set-top Box
Lower range connectivity compared to WLAN
Cable replacement is one of the primary applications
Has an ad hoc network architecture (usually called a piconet)
IEEE 802.15 is the main standard
Examples are Bluetooth used for keyboards and handsfree headsets
Upcoming 802.15.3c uses 60GHz for HDMI cable replacement
PAN / LAN boundaries are blurring
17
Wednesday, September 4, 13
Wireless is Everywhere
cellular networks
local area networks
personal area networks
emerging applications
Wednesday, September 4, 13
Emerging Applications
body area
networks
powerline
communication
car area
networks
vehicular area
networks
mobile ad hoc
networks
underwater
communication
19
Wednesday, September 4, 13
Outline
Review of the syllabus
Introduction to wireless communication
A DSP approach to wireless
Connection to the lab
How the course works
20
Wednesday, September 4, 13
The Network Stack
OSI Network Model
Focus of this class
Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Logical
Link
Data Link
Control
Layer
MAC
Physical Layer
Signal Processing
Algorithms
Antennas &
Circuits
21
Wednesday, September 4, 13
Typical Digital Communication Sys.
transmitter
Source
Source
Coding
Channel
Coding
Modulation
Analog
Processing
Propagation
Medium
Sink
Source
Decoding
Channel
Decoding
Demodulation
Analog
Processing
real
world
channel
receiver
digital
analog
22
Wednesday, September 4, 13
DSP Approach to Wireless
Inputs
System
0110110
h[n]
Outputs
0110110
h(t)
time
time
time
time
Use systems approach for communication
23
Wednesday, September 4, 13
Wireless Communications Lab @ UT
Premises of the course
EE 471C / EE 381V
Analog communication is no longer required
Wireless communication can be learned by all EEs
Wireless communication can be taught without a communication background
You can implement what you learn while you learn it
Key ideas
Learn digital communication from a digital signal processing perspective
Incorporate modulation, channel estimation, equalization, synchronization
Use algorithmic design examples, not comprehensive theory
Leverage flexible software defined radio prototyping
Exploit LabVIEW & USRP
Developed and tested over 7 years
24
Wednesday, September 4, 13
Technical Concepts in the Course
DSP Models for communication
Sampling, up/down conversion, baseband vs. passband, complex baseband
Power spectrum, bandwidth, pulse-shaping
Basics of digital communication
QAM modulation, ML detection
Dealing with impairments
Channel estimation
Frame/sample/carrier frequency offset synchronization
Equalization, single carrier frequency domain equalization
OFDM
Standards: GSM, IEEE 802.11a, IEEE 802.11n
Channel models: large scale, small scale, coherence
Multiple antennas: receive, transmit, MIMO
25
Wednesday, September 4, 13
Content of the Course
Digital comm overview
Signals, stochastic processes
Mathematical
preliminaries
Transforms, sampling theorm
Frequency response, power spectrum, bandwidth
Upconversion, downconversion, complex baseband
Quadrature pulse amplitude modulation
Basic digital comm
Optimal pulse shapes
Maximum likelihood detection in AWGN
Sample timing offset, sample timing algorithms
Channel impairments
Frequency selective channels, least squares channel estimation
Frequency offset estimation and correction, frequency domain equalization
Single carrier frequency domain equalization, OFDM, the cyclic prefix
Standards
IEEE 802.11a, GSM standard
Introduction to propagation, large-scale fading, link budgets, path-loss
Fading
Small-scale fading, coherence time, coherence bandwidth
Probability of error in fading channels
Sources of diversity, Alalmouti space-time code, maximum ratio combining
MIMO
Introduction to MIMO communication, spatial multiplexing
Introduction to MIMO-OFDM, highlights of the IEEE 802.11n standard
26
Wednesday, September 4, 13
Outline
Review of the syllabus
Introduction to wireless communication
A DSP approach to wireless
Connection to the lab
How the course works
27
Wednesday, September 4, 13
The Lab
ethernet
cable
NI USRP 2921
antennas
MIMO
cable
Located in ENS 113
Lab has ten workstations for transmit / receive
Work in teams of 2, same team the whole semester
Use your windows laptop to connect (need GigEthernet)
28
Wednesday, September 4, 13
How this Fits with the Lab
transmitter
Source
Channel
Coding
Modulation
D/A
RF
Upconversion
channel
receiver
Sink
Channel
Decoding
Demodulation
Laptop with LabVIEW
(all digital signal processing)
A/D
RF
Downconversion
NI USRP 2921
Real
world
29
Wednesday, September 4, 13
Content of the Course
Digital comm overview
Signals, stochastic processes
Transforms, sampling theorm
Frequency response, power spectrum, bandwidth
Upconversion, downconversion, complex baseband
Quadrature pulse amplitude modulation
Optimal pulse shapes
Maximum likelihood detection in AWGN
Sample timing offset, sample timing algorithms
Frequency selective channels, least squares channel estimation
Frequency offset estimation and correction, frequency domain equalization
Single carrier frequency domain equalization, OFDM, the cyclic prefix
IEEE 802.11a, GSM standard
Introduction to propagation, large-scale fading, link budgets, path-loss
Small-scale fading, coherence time, coherence bandwidth
Probability of error in fading channels
Sources of diversity, Alalmouti space-time code, maximum ratio combining
Introduction to MIMO communication, spatial multiplexing
Introduction to MIMO-OFDM, highlights of the IEEE 802.11n standard
Done
in the Lab
30
Wednesday, September 4, 13
Lab Material
free!!
Laboratory manual
DIGITAL COMMUNICATIONS: Physical Layer Exploration Using the NI USRP
front.pdf
1
9/12/11
4:46 PM
141 pages
8 Laboratory experiments
Lab experiments
Background information
Include prelab to be completed prior to lab
Laboratory experiments
Postlab
Complete software framework
DIGITAL COMMUNICATIONS
PHYSICAL LAYER EXPLORATION LAB USING THE NI USRP™ PLATFORM
Dr. Robert W. Heath, University of Texas at Austin
Included with the Digital Communications Teaching Bundle
http://sine.ni.com/nips/cds/view/p/lang/en/nid/210385
Wednesday, September 4, 13
31
Contents
Outline of Lab Manual
Preface
vii
About the Author
xi
Lab 1: Part 1 Introduction to NI LabVIEW
1
Lab 1: Part 2 Introduction to NI RF Hardware
10
Lab 2: Part 1 Modulation and Detection
22
Lab 2: Part 2 Pulse Shaping and Matched Filtering
35
Lab 3: Synchronization
51
Lab 4: Channel Estimation & Equalization
63
Lab 5: Frame Detection & Frequency Offset Correction
82
Lab 6: OFDM Modulation & Frequency Domain Equalization
99
Lab 7: Synchronization in OFDM Systems
115
Lab 8: Channel Coding in OFDM Systems
130
Appendix A: Reference for Common LabVIEW VIs
139
Bibliography
141
32
Wednesday, September 4, 13
!
Sample Pages
!
!
“book” — 2011/9/29 — 15:18 — page 43 — #55
Lab 2: Part 2 Pulse Shaping and Matched Filtering
!
!
!
“book” — 2011/9/29 — 15:18 — page 51 — #63
!
!
Lab 3: Synchronization:
Symbol Timing Recovery in Narrowband
Channels
43
Summary
In this lab you will consider the problem of symbol timing recovery also
known as symbol synchronization. Timing recovery is one of several synchronization tasks; others will be considered in future labs.
The wireless communication channel is not well modeled by simple additive white Gaussian noise. A more realistic channel model also includes
attenuation, phase shifts, and propagation delays. Perhaps the simplest channel model is known as the frequency flat channel. The frequency flat channel
creates the received signal
z(t)
Figure 3: Hierarchy of code framework for new simulator.
=
αej φ x(t − τd ) + v(t),
(1)
where α is an attenuation, φ is a phase shift, and τd is the delay.
The objective of this lab is to correct for the delay caused by τd in discretetime. The approach will be to determine an amount of delay k̂ and then to
delay the filtered received signal by k̂ prior to downsampling. This will
modified the receiver processing as illustrated in Figure 1.
Two algorithms will be implemented for symbol synchronization in this
lab: the maximum energy method and the Early Late gate algorithm. The
maximum energy method attempts to find the sample point that maximizes
the average received energy. The early–late gate algorithm implements a
discrete-time version of a continuous-time optimization to maximize a certain
top rx.vi and provides each with the appropriate inputs. The parts of the
simulator you will be modifying are located in transmitter.vi and receiver.vi
shown in Figures 4 and 5 respectively.
You will be putting your VIs into transmitter.vi and receiver.vi, replacing
the locked versions that are already there. After doing this, you will then
open up simulator.vi, that you will use to confirm your VIs operate correctly
before implementing them on the NI-USRP.
Notice that pulse shaping.vi and matched filtering.vi do not take any parameters as inputs. All of the pulse shaping and oversampling parameters you
need to use for these VIs can be accessed from the modulation parameters in
cluster. After building these VIs, replace the existing code in the simulator
with your code. Replace a subVI in the transmitter or receiver with your code
z (t )
C/D
Tz =
ˆ
zk
g RX [n]
M
kˆ
T
M
Symbol
Sync
Figure 1: Receiver with symbol synchronization after the digital matched filtering.
Figure 4: Block diagram of transmitter.vi.
!
!
Wednesday, September 4, 13
!
!
!
51
!
!
!
33
Outline
Review of the syllabus
Introduction to wireless communication
A DSP approach to wireless
Connection to the lab
How the course works
34
Wednesday, September 4, 13
Overall Course Structure
Lectures
Lecturing on document camera or white board
Focus on DSP approach to communication
Laboratory sessions
Labs performed in groups of 2 (same all semester)
Implement pre-lab ahead of lab in simulation
Experiments performed during the session
except first lab,
you have to learn
LabVIEW
Assignments
Pre-labs prepare for lab, turned in prior to lab, performed in groups
Homework due every week, supplement the theory portions of the lab
Lab reports summarize lab findings, due week after completion of a lab
there is a lot of stuff here but you can do it!
35
Wednesday, September 4, 13
Grad versus Undergrad
Lectures, assignments, homeworks all the same
Graduate course requires a final project
Literature review, or
Implementation, or
Research paper
Final grading of undergrad and grad sections is independent
Please note the grading is not dependent
Seriously, the grades are computed differently
This doesn’t mean, however, that you should slack off in either case
36
Wednesday, September 4, 13
Is this just a rip-off of EE 445S?
In short, no…
EE 345S deals with real-time DSP
Emphasis is on DSP background and real-time implementation issues
Digital modem used as significant design example
EE 471C differs in the following ways
Basics of DSP assumed already known(thus the prereq)
Emphasis is on wireless communication using your existing DSP toolset
Build a real wireless modem that operates over the air
Programming is in LabVIEW, less concern for real-time implementation
Discuss many new topics including symbol/frame/frequency synchronization,
standards, fading, bit error rate analysis, and wireless cellular systems
37
Wednesday, September 4, 13
What about 360K?
Again not really
EE 360K deals with digital communication
Emphasis is on mathematical theory
Note: Grad digital comm is even more theory :-(
EE 371C differs in the following ways
Emphasis is on wireless digital communication
Examine complete physical layer system
Cover many topics to build intuition
Implement every topic in the lab
Discuss features of current standards & why certain design choices were made
Build a real wireless modem that operates over the air
38
Wednesday, September 4, 13
Why Should I Take EE 381V?
If you are a grad student, you may wonder why you should take
this course?
Many topics not found in other graduate course at UT Austin
Frame / frequency offset synchronization
Channel estimation
Software defined radio
GSM and IEEE 802.11a system design issues
Single carrier frequency domain equalization
OFDM with channel estimation and synchronization
You have the opportunity to conduct a research project
Can leverage your ongoing research
Can help you find a research advisor
39
Wednesday, September 4, 13
Preparation for Next Week
Reading
Chapter 1 and 2 of course notes (posted shortly)
Lecture
Introduction to digital communication
Lab
No lab next week but there will be a LabVIEW tutorial given by the TA
Lab 1.1 will be posted next week
Primarily involves learning LabVIEW - start early!
Homework
Homework #1 will be posted shortly, due next week
40
Wednesday, September 4, 13
Questions?
Wednesday, September 4, 13
Wednesday, September 4, 13