wireless communications lab
TRANSCRIPT
Wireless Communications Lab
Wireless Networking and Communications GroupDepartment of Electrical and Computer Engineering
The University of Texas at Austin, Austin TX USAENS 435
http://[email protected]
Robert W. Heath Jr. Ph.D, P.E.KE5NCG
Wednesday, September 4, 13
OutlineReview 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 ReviewInstructor: 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 fulfillmentCommunications / Networking and Signal Processing
Graduate: Counts as a CommNetS course
Class will be video recorded but please come to class
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Wednesday, September 4, 13
OutlineReview 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
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The Cellular Concept
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Base stations serve multiple subscribers
Frequencies are geographically reused in cells
Handoff provides seamless connection
Base Station (BS)
Co-ChannelInterference
Mobile Station (MS)or
User Equipment (UE)The same frequency is
reused in multiple clusters
Handoff
Cell
Cluster
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Evolution of Cellular Systems
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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.
1G
Most of you in have never used 1G
:-(
Wednesday, September 4, 13
Evolution of Cellular Systems
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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)
2G
Most of you have a 2G compatible
phone
Wednesday, September 4, 13
Evolution of Cellular Systems
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Third generation systems - known as 3G
Conceived in the 1990’s
Deployed in the 2000’s
Digital voice plus data
Video telephony
Higher capacity
CDMA (code division multiple access)
Examples: 3GPP WCDMA, HSDPA, etc.
3GPP2 cdma2000, 1xEV, 1xEV-DO, 1xEV-DV, etc.
3G
Most of you use 3G on a daily basis
Wednesday, September 4, 13
Evolution of Cellular Systems
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After 3G, cellular systems began fine-grained development3GPP 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
4G devices are now being sold
Have one?
Wednesday, September 4, 13
Evolution of Cellular Systems
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Fifth generation systems - known as 5G
3GPP after Release 14 will likely be considered 5G
Development is ongoing
Possible technologies that could make 5GMassive MIMO - hundreds of antennas at the base station
Millimeter wave - use millimeter wave spectrum to obtain larger bandwidth
New concepts supported by 5GDevice-to-device
Machine-to-machine
Vehicle-to-vehicle
5G
Active area of research, good area of senior design and PhD dissertations
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Wireless is Everywhere
cellular networks local area networks
personal area networks emerging applications
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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
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IEEE 802.11 Wireless LANIEEE is the Institute of Electrical and Electronics Engineers
Main professional society for electrical engineers
Everyone should become a student member of the IEEE
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)
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digression
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IEEE 802.11 Subgroups
802.11: 1/2Mbps in 2.4GHz band, FHSS or DSSS
802.11a: extend to 5GHz ban, 54Mbps, OFDM
802.11b: (WiFi) DSSS with 11Mbps in 2.4GHz band
802.11g: similar to 802.11a but for 2.4GHz
802.11n: MIMO enhancement, 100-200Mbps
802.11ac: Very high throughput < 6GHz carrierMore bandwidth aggregation, more MIMO, multiuser MIMO
802.11ad: Very high throughput > 6GHz carrierExploits 60GHz unlicensed bands, lots of antennas, beamforming
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11 11b 11g 11n 11ac 11ad
many more subgroups, some successful and some not
Discussion has started on beyond 11ac/adWednesday, September 4, 13
Wireless is Everywhere
cellular networks local area networks
personal area networks emerging applications
Wednesday, September 4, 13
Personal Area Networks (PAN)
Lower range connectivity compared to WLANCable replacement is one of the primary applications
Has an ad hoc network architecture (usually called a piconet)
IEEE 802.15 is the main standardExamples are Bluetooth used for keyboards and handsfree headsets
Upcoming 802.15.3c uses 60GHz for HDMI cable replacement
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Set-top Box
10 Gbps
6 Gbps
5 Gbps
PAN / LAN boundaries are blurring
Wednesday, September 4, 13
Wireless is Everywhere
cellular networks local area networks
personal area networks emerging applications
Wednesday, September 4, 13
Emerging Applications
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body area networks
car area networks
mobile ad hoc networks
powerline communication
vehicular area networks
underwater communication
Wednesday, September 4, 13
OutlineReview 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
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Physical Layer
MAC
LogicalLink
Control
Network Layer
Transport Layer
Session Layer
Presentation Layer
Data LinkLayer
Application Layer
OSI Network Model
Antennas & Circuits
Signal Processing Algorithms
Focus of this class
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Typical Digital Communication Sys.
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SourceChannelCoding
Modulation Analog Processing
Sink ChannelDecoding
Demodulation Analog Processing
transmitter
receiver
Propagation Medium
SourceCoding
SourceDecoding real
world
channel
digital analog
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DSP Approach to Wireless
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Use systems approach for communication
Inputs System Outputs
0110110 h[n]
h(t)
0110110
time
time
time
time
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Wireless Communications Lab @ UTPremises of the course
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 ideasLearn 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
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Developed and tested over 7 years
EE 471C / EE 381V
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Technical Concepts in the CourseDSP Models for communication
Sampling, up/down conversion, baseband vs. passband, complex baseband
Power spectrum, bandwidth, pulse-shaping
Basics of digital communicationQAM modulation, ML detection
Dealing with impairmentsChannel 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
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Content of the CourseDigital comm overviewSignals, stochastic processesTransforms, sampling theormFrequency response, power spectrum, bandwidthUpconversion, downconversion, complex basebandQuadrature pulse amplitude modulationOptimal pulse shapesMaximum likelihood detection in AWGNSample timing offset, sample timing algorithmsFrequency selective channels, least squares channel estimationFrequency offset estimation and correction, frequency domain equalizationSingle carrier frequency domain equalization, OFDM, the cyclic prefixIEEE 802.11a, GSM standardIntroduction to propagation, large-scale fading, link budgets, path-lossSmall-scale fading, coherence time, coherence bandwidthProbability of error in fading channelsSources of diversity, Alalmouti space-time code, maximum ratio combiningIntroduction to MIMO communication, spatial multiplexingIntroduction to MIMO-OFDM, highlights of the IEEE 802.11n standard
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Mathematical preliminaries
Basic digital comm
Channel impairments
StandardsFading
MIMO
Wednesday, September 4, 13
OutlineReview 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
Located in ENS 113
Lab has ten workstations for transmit / receiveWork in teams of 2, same team the whole semester
Use your windows laptop to connect (need GigEthernet)
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NI USRP 2921
ethernet cable
MIMOcable
antennas
Wednesday, September 4, 13
How this Fits with the Lab
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Source ChannelCoding
Modulation D/A RF Upconversion
Sink ChannelDecoding
Demodulation A/D RF Downconversion
channel
transmitter
receiver
Laptop with LabVIEW NI USRP 2921Real world
(all digital signal processing)
Wednesday, September 4, 13
Content of the CourseDigital comm overviewSignals, stochastic processesTransforms, sampling theormFrequency response, power spectrum, bandwidthUpconversion, downconversion, complex basebandQuadrature pulse amplitude modulationOptimal pulse shapesMaximum likelihood detection in AWGNSample timing offset, sample timing algorithmsFrequency selective channels, least squares channel estimationFrequency offset estimation and correction, frequency domain equalizationSingle carrier frequency domain equalization, OFDM, the cyclic prefixIEEE 802.11a, GSM standardIntroduction to propagation, large-scale fading, link budgets, path-lossSmall-scale fading, coherence time, coherence bandwidthProbability of error in fading channelsSources of diversity, Alalmouti space-time code, maximum ratio combiningIntroduction to MIMO communication, spatial multiplexingIntroduction to MIMO-OFDM, highlights of the IEEE 802.11n standard
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Donein the Lab
Wednesday, September 4, 13
Lab MaterialLaboratory manual
DIGITAL COMMUNICATIONS: Physical Layer Exploration Using the NI USRP
141 pages
8 Laboratory experiments
Lab experimentsBackground information
Include prelab to be completed prior to lab
Laboratory experiments
Postlab
Complete software framework
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Dr. Robert W. Heath, University of Texas at Austin
DIGITAL COMMUNICATIONS
PHYSICAL LAYER EXPLORATION LAB USING THE NI USRP™ PLATFORM
front.pdf 1 9/12/11 4:46 PM
Included with the Digital Communications Teaching Bundlehttp://sine.ni.com/nips/cds/view/p/lang/en/nid/210385
free!!
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Outline of Lab Manual
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“book” — 2011/9/29 — 15:18 — page v — #5 !!
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Contents
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
v
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Sample Pages
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“book” — 2011/9/29 — 15:18 — page 51 — #63 !!
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Lab 3: Synchronization:Symbol Timing Recovery in Narrowband
Channels
Summary
In this lab you will consider the problem of symbol timing recovery alsoknown as symbol synchronization. Timing recovery is one of several syn-chronization tasks; others will be considered in future labs.
The wireless communication channel is not well modeled by simple ad-ditive white Gaussian noise. A more realistic channel model also includesattenuation, phase shifts, and propagation delays. Perhaps the simplest chan-nel model is known as the frequency flat channel. The frequency flat channelcreates the received signal
z(t) = !ej"x(t ! #d) + v(t), (1)
where ! is an attenuation, " is a phase shift, and #d is the delay.The objective of this lab is to correct for the delay caused by #d in discrete-
time. The approach will be to determine an amount of delay k̂ and then todelay the filtered received signal by k̂ prior to downsampling. This willmodified the receiver processing as illustrated in Figure 1.
Two algorithms will be implemented for symbol synchronization in thislab: the maximum energy method and the Early Late gate algorithm. Themaximum energy method attempts to find the sample point that maximizesthe average received energy. The early–late gate algorithm implements adiscrete-time version of a continuous-time optimization to maximize a certain
C/D
SymbolSync
M
TM
( )z t [ ]RXg n
k̂
k̂z
T =z
Figure 1: Receiver with symbol synchronization after the digital matched filtering.
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“book” — 2011/9/29 — 15:18 — page 43 — #55 !!
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Lab 2: Part 2 Pulse Shaping and Matched Filtering 43
Figure 3: Hierarchy of code framework for new simulator.
top rx.vi and provides each with the appropriate inputs. The parts of thesimulator you will be modifying are located in transmitter.vi and receiver.vishown in Figures 4 and 5 respectively.
You will be putting your VIs into transmitter.vi and receiver.vi, replacingthe locked versions that are already there. After doing this, you will thenopen up simulator.vi, that you will use to confirm your VIs operate correctlybefore implementing them on the NI-USRP.
Notice that pulse shaping.vi and matched filtering.vi do not take any pa-rameters as inputs. All of the pulse shaping and oversampling parameters youneed to use for these VIs can be accessed from the modulation parameters incluster. After building these VIs, replace the existing code in the simulatorwith your code. Replace a subVI in the transmitter or receiver with your code
Figure 4: Block diagram of transmitter.vi.
Wednesday, September 4, 13
OutlineReview 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 StructureLectures
Lecturing on document camera or white board
Focus on DSP approach to communication
Laboratory sessionsLabs performed in groups of 2 (same all semester)
Implement pre-lab ahead of lab in simulation
Experiments performed during the session
AssignmentsPre-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
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except first lab, you have to learn LabVIEW
there is a lot of stuff here but you can do it!
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Grad versus UndergradLectures, assignments, homeworks all the same
Graduate course requires a final projectLiterature 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
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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 waysBasics 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
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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 waysEmphasis 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
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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 AustinFrame / 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 projectCan leverage your ongoing research
Can help you find a research advisor
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Wednesday, September 4, 13
Preparation for Next WeekReading
Chapter 1 and 2 of course notes (posted shortly)
LectureIntroduction to digital communication
LabNo 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!
HomeworkHomework #1 will be posted shortly, due next week
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Questions?
Wednesday, September 4, 13
Wednesday, September 4, 13