Testing of Wireless Modulation made easy Hugo Landman

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Testing of Wireless Modulation made easyHugo
Landman emv Benelux BVemv Benelux B.V.
Frankrijklaan 7, ITC Boskoop 2391 PX
HAZERSWOUDE DORP The Netherlands tel 31 172
423 000 fax [phone] www.emv.nl
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Agenda

• Introduction to Digital Wireless communication
• Digital Modulation Basics
• Impairments
• Generation of Modulated Signals with AWGs
• The Modular Solution HW SW
• Small demo (if time permits)

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Digital Modulation Areas of Application

• Wireless
• Satellite
• Mobile Telephony
• Radio Links
• Broadcast
• Networking
• Radar, Navigation
• Sensor and Sensor Networks
• Wired
• CATV
• ADSL, Cable Modems
• Optical

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Wireless Everywhere

• Wireless have expanded to companies out of the
  tradional RF business (Military, Radio and
  Satellite Communications, Broadcast)
• Consumer Electronics
• Computer
• Automotive
• Retailers
• Payment and identification systems
• Medical

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Going Digital

• Digital modulations technologies are being used
  in new services and devices and applied to more
  traditional area of applications
• Broadcast
• Digital TV DVB, DMB-T, ATSC, ISDB-T
• Digital Radio DAB, satellite radio (XM, Sirius),
  AM/SW DRM
• Radar
• Short Range UWB radar
• Digital pulse compression technologies

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Complex Wireless Technology

• The need to use the available spectrum
  efficiently is fueling the continuous development
  and improvement of new wireless technologies
• Higher order modulation schemes
• More sophisticated multiple access and spectrum
  sharing methodologies
• CDMA
• Spread-spectrum radio
• OFDMA
• Better channel coding and error protecting codes
• Implementation of new services on the existing
  wireless infrastructure
• Modulation schemes specially designed to work in
  dificult channel conditions or mobile reception
• Boom of the OFDM technology
• Extensive research on MIMO and Beam Forming
  architectures

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Technology Trends

• Wireless Networks
• OFDM
• MIMO
• Short range Networks
• UWB (Cable substitution)
• Ultra-low power (Zigbee)
• Mobile telephony
• Beam forming
• OFDMA
• Broadcast
• Different OFDM schemes (COFDM, TDS-OFDM)
• Mobile Reception

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DIGITAL MODULATION BASICS
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Modulation for Wireless

• Media
• Carrier
• The 3 essential parameters
• Amplitude value A(t) ? Amplitude Modulation
• Frequency value f(t) ? Frequency Modulation
• Phase value f(t) ? Phase Modulation

V(t) A cos(2pfc t F)
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Transmission of a Digital Message

• Basically, its the same as Analog Modulation
  Methods
• ASK Amplitude shift keying
• FSK Frequency shift keying
• PSK Phase shift keying
• Digital modulation Amplitude, frequency and/or
  Phase are used to represent a digital state

V(t) A(t) cos(2pfc t F)
V(t) A(t) cos(2pf(t) t F)
V(t) A(t) cos(2pf(t) t F(t))
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Digital Modulation in Modern Wireless Systems
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Digital Modulation Block Diagram
Raw Data
Convert to Symbols
Compression, Error Correction, Encryption
01 10 10 10 01 01
011010100101
110101
I - Signal
00
01
Low Pass Filter
To IQ Modulator
Q - Signal
Low Pass Filter
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10
Modulation Mapping
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Quadrature Digital Modulation

• Data can be splitted to modulate orthogonal
  carriers (In-Phase and Quadrature) at the same
  carrier frequency

cos(2pfct)
I
LPF
fc
BPF
90
90
90
LPF
Q
sin(2pfct)
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IQ Mapping (Constellation Diagram)

• Example (QPSK)

• What is Mapping
• Translate a Symbol to a point in the IQ space

Q
(11)
(01)
I
(00)
(10)
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Differential Modulation

• DQPSK(Differential QPSK)
• The value is based on the transitions between 2
  points

• QPSK(Quadrature PSK)
• Assign the value to points in IQ Space

Q
(01)
(00)
I
(11)
(10)
00 0 01 90 10 -90 11 180
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Higher Order Modulation

• ?/4 DQPSK
• The value is based on the transitions between 2
  points
• Eliminates Zero Crossings

• 8PSK(8-PSK)
• Assign the value to points in IQ Space
• 3 points per symbol

Q
Q
(11)
(110)
(001)
(011)
(00)
(01)
I
(111)
I
(10)
(100)
(000)
00 -45 01 135 10 -135 11 45
(010)
(101)
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More Higher Order Modulation
Q

• 16QAM(16-Quadrature Amplitude Modulation)
• Each IQ symbol location is represented by 4 data
  bits
• 64QAM (64-Quadrature Amplitude Modulation)
• Each symbol is now worth 5 bits

(011100)
(010100)
(110100)
(111100)
(000100)
(001100)
(101100)
(100100)
(011101)
(010101)
(110101)
(111101)
(000101)
(001101)
(101101)
(100101)
(011111)
(010111)
(110111)
(111111)
(000111)
(001111)
(101111)
(100111)
I
(011110)
(010110)
(110110)
(111110)
(000110)
(001110)
(101110)
(100110)
(011010)
(010010)
(110010)
(111010)
(000010)
(001010)
(101010)
(100010)
(011011)
(010011)
(110011)
(111011)
(000011)
(001011)
(101011)
(100011)
(011001)
(010001)
(110001)
(111001)
(000001)
(001001)
(101001)
(100001)
(011000)
(010000)
(110000)
(111000)
(000000)
(001000)
(101000)
(100000)
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Why Not Just Keep Going?

• Errors in IQ modulation create symbol errors in
  transmission
• Vector Errors are created (whats that?)
• Noise in the transmission channel create symbol
  errors
• Inaccuracies in the receiver creates errors
• Signal-to-noise requirements increase with higher
  order modulations

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Symbol Rate and Bit Rate

• Modulation type determines number of bits per
  symbol
• BPSK 1 bit/symbol
• DBPSK 1 bit/symbol
• QPSK 2 bit/symbol
• p/4 DQPSK 2 bit/symbol
• DQPSK 2 bit/symbol
• 8PSK 3 bit/symbol
• 16QAM 4 bit/symbol
• 64QAM 5 bit/symbol
• 256QAM 6 bit/symbol
• For a fixed symbol rate, having more bits will
  provide a faster transfer rate

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Others

• 32QAM
• ADSL etc
• 256QAM
• Microwave Communication
• Some Cable Modem
• 1024QAM
• Still experimental
• OQPSK
• Offset QPSK
• Used to avoid zero crossings
• DQPSK
• And many, many more

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Filters, For Spectrum Control
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Filters Alter The Signal
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Sources of Error

• IQ Quadrature modulation

cos(2pfct)
I
LPF
fc
BPF
90
90
90
LPF
Q
sin(2pfct)
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Errors Receiving the Signal

• IQ Quadrature demodulation
• This could be your customers receiver

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Impairments

• Ideal, no impairments

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Amplitude Modulation

• Amplitude Modulation

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Impairments

• Compression

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Impairments

• Phase Noise

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Impairments

• Gaussian Noise C/N 20 dB

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Impairments

• Wrapping Errors on Repeating Signals

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Summary

• Digital modulation is cheaper, faster, more
  accurate, more efficient, more secure
• Higher order modulation is used for greater
  transmission rates in the same spectrum occupancy
• Higher order modulation is more susceptible to
  noise
• Baseband filters are used to control spectrum

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Generation of Modulated Signals with AWGs
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Generating Digitally Modulated Signals with AWGs

• Why AWG for Digital Modulation Applications?
• Baseband Generation(I,Q) ?IQ Modulator
• IF Generation ?Up-converter
• Direct Digital Generation

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Why AWG for Digital Modulation Applications?

• AWGs are capable of generating any modulation
  scheme without any specialized hardware.
• Available bandwidth only limited by analog BW and
  maximum sample rate.
• Simultaneous multiple, dissimilar signal
  generation capability (multi-carrier).
• No practical limits for symbol speed.
• Multiple impairments can be easily added to the
  signal.
• Pre-distortion techniques are easy to implement.

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IQ Modulation Block Diagram
Baseband I Signal
I
N level D/A
Base Band Filter
AM Modulator
0
Data Source
Symbol Mapping
Local Oscilator
Phase Splitter
Adder
IF/RF Signal
?/2
Q
N level D/A
AM Modulator
Base Band Filter
Baseband Q Signal
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BB Generation (I,Q) ?IQ Modulator

• Carrier frequency only limited by the IQ
  modulator
• Phase/Amplitude matching for I and Q signals
  paths is critical
• Moderate/low sample rate requirements for the AWG
• Maximum symbol rate and number of carriers also
  limited by the IQ modulator modulation bandwidth

2 CHANNEL AWG
IQ MODULATOR
CH1 I Signal
RF Signal
CH2 Q Signal
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IF Generation ?Up-Converter

• Carrier frequency only limited by the
  up-converter
• Phase/Amplitude matching for I and Q signals is
  perfect because they are combined mathematically
  and obtained physically from a single D/A
  converter
• Medium sample rate requirements for the AWG
• Maximum symbol rate and number of carriers also
  limited by the up-converter conversion bandwidth

1 CHANNEL AWG
UPCONVERTER
CH1 IF Signal
RF Signal
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Direct Digital Generation

• No additional equipment required
• Carrier frequency limited by maximum sample rate
  and analog bandwidth
• Phase/Amplitude matching for I and Q components
  is perfect
• Symbol rate and number of carriers unlimited
• D/A and analog linearity are critical
• Extremely long record lengths required

HIGH SPEED 1 CHANNEL AWG
CH1 RF Signal
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Where to Connect the AWGs?
I
LPF
IQ Baseband - 2Ch
I
fi
IF - 1Ch
BPF
RF - 1Ch High Speed
IF
90
90
90
fol
LPF
Q
I
LPF
IF
fi
BPF
90
90
fol
LPF
Q
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THE TABOR MODULAR SOLUTIONHW SW
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The Modular Tool

• Features
• Basic handling
• Embedded analysis tools
• Advanced handling
• Channel coded signals
• Impairments
• Data import/export

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Features (I)

• Baseband (IQ) and IF/RF (DDS) signal generation.
• Multiple carrier capability with independent
  definition of modulation parameters for each
  carrier.
• High modulation quality supporting AWGs with more
  than 16 bit D/A converters.
• Automatic wrap-around spurious free signals.
• Fast compilation speed ideal to handle ultra long
  record lengths with direct file creation in the
  target instrument.
• Support of channel coded signals for applications
  in CDMA, W-CDMA and DVB environments.

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Features (II)

• Support of user defined base band filtering,
  modulation scheme, symbol list, modulation
  envelopes, and payload data.
• Linear, non-linear, and multi-path impairments.
• Built-in analysis including phase, constellation
  and eye diagrams, signal density and histogram
  display and CCDF power analysis.
• Support of ASCII export formats for spreadsheet
  and scientific calculation software packages.
• Runs under Windows 98/Me/XP/2000/NT with
  GPIB/USB/Ethernet connection to the target
  instrument.

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ModularInstrument Support

• Instruments Supported
• WW2571/2
• WW1281A
• WW2074
• WW1071/2
• WW5061/2
• Interfaces Supported
• GPIB
• USB
• Ethernet, TCP/IP
• Record Length
• User defined

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ModularMulti-Carrier Generation
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ModularEmbedded Analysis
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Embedded AnalysisSpectrum Display

• Spectrum is shown up to the Nyquist frequency
  (Sr/2).
• Input data is quantized to an ideal DAC converter
  based in the target AWG resolution.
• Blue cursor shows the position of the anchor
  carrier in the spectral display.
• Calculations are based in the first 8192 samples.

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Embedded AnalysisZoom and Constellation

• Zoom and Constellation displays show I vs. Q
  highlighting phase transitions and symbol
  locations respectively
• Graph is autoscaled and amplitude values are
  derived from the dimensionless amplitude
  parameter specified in the Carrier Edition Window

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Embedded AnalysisHistogram

• Histogram display gives a qualitative statistical
  view of the signal distribution in the IQ plane.
• Gray Scale information is derived from a three
  dimensional data base built with up to 500,000
  samples.
• Vertical and horizontal histograms can be defined
  in specific areas using two XY cursors.
• ? can control gray scale distribution.

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Embedded AnalysisEye Diagram
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Embedded AnalysisIQ Time-Domain Display
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Advanced HandlingMulti-Carrier Assistant

• It is a simplified version of the Carrier Editor
  designed to ease the definition of multi-carrier
  signals made of similar carriers.
• Once the set-up is defined, a regular (editable)
  carrier list is created.
• There are several controls devoted to facilitate
  the creation of uncorrelated carriers.

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Advanced FeaturesLinear Impairments
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Advanced FeaturesNon Linear Impairments
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Advanced FeaturesPower Ramping
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Advanced HandlingMulti Path
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Advanced FeaturesImport Data

• Filter File
• Externally defined baseband filter.
• It must be defined with 50 samples per symbol
  period.

• IQ File
• File containing envelope or symbol samples
• Data File
• Input data in binary ASCII format (100101011)
• Symbol Map
• User Defined Symbol Map using the Symbol Map
  Edition Tool.

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Advanced FeaturesUser Defined Symbol Maps
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Advanced FeaturesExport Data
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The Tabor Solutions

• Four different application cathegories targeted
• Education
• IF/Baseband
• Multichannel
• High-Speed
• There is a good match between these market
  cathegories and specific Tabor WW generators
• Education WW5061/2 and WW1071/2
• IF/Baseband WW2571/2A
• Multichannel WW2074
• High-speed WW1281

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Education

• Single or Dual Channel models
• Allowing to generate IF and I/Q signals with a
  single instrument.
• 50 or 100MS/s, 14bit Vertical Resolution and up
  to 4M waveform memory
• to generate complex, realistic,
  high-dynamic-range wireless signals with EVM less
  than 0.5.
• Easy signal set-up
• Stand-alone operation
• Allows off-line signal generation and analysis
• Basic and advanced analog and digital modulation
  support
• Easy implementation of complex modulation
  concepts
• Linear impairment addition and visualization
• Real-world impairments can be simulated and
  played-back
• Cost Effective Solution

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IF/Baseband (I)

• Single or Dual Channel models
• Capable of generating IF and I/Q signals with a
  single instrument.
• 250MS/s, 16bit Vertical Resolution and up to 4M
  waveform memory
• To generate complex, realistic,
  high-dynamic-range wireless signals with EVM less
  than 0.25.
• Digital signal generation
• Digital outputs to easily test modern
  Software-Defined-Radio architectures
• Basic and advanced modulation schemes support
• Supporting from basic BPSK signals up to full
  featured 3G downlink scenarios
• real-world signals to stress any design

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IF/Baseband (II)

• High-speed compilation time
• Allowing interactive creation of multiple
  mega-sample IF/RF/Baseband waveforms
• High calculation accuracy
• Support up to 16 bit vertical resolution, while
  keeping the full available dynamic range
• Multi Carrier signal support
• Allowing simultaneous creation of multiple,
  dissimilar carriers in both baseband and IF/RF
• Linear and non linear impairments, multi-path,
  and power-ramping support
• To directly create real-world signals to stress
  any design

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Multi-Channel

• Four Channel models
• Capable of generating IF and I/Q signals
  simultaneously with a single instrument
• 50, 100 and 200MS/s, 16bit Vertical Resolution
  and up to 4M waveform memory
• To generate complex, realistic,
  highest-dynamic-range wireless signals with EVM
  less than 0.25
• Multiple IF signal generation
• For Ease creation of MIMO scenarios
• Simultaneous dissimilar signal generation
• Allows testing more than one DUT simultaneously.
• Special modulation architectures support
• Allows creating advanced baseband arrangements,
  such as Polar Modulation
• Dynamic range improvement
• Allows improving multi-carrier signals quality by
  splitting the signal between multiple channels

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High-Speed

• Single or Dual Channel models
• Capable of generating I/Q, IF and RF signals with
  a single instrument
• 1.2GS/s, 12bit Vertical Resolution and up to 16M
  waveform memory
• To generate complex, realistic,
  high-dynamic-range wireless signals with EVM less
  than 1 at 400MHz IF/RF carrier frequency
• High sampling rates and bandwidth
• To test serial data links in any wireless design
• Multiple signal type support
• To create non-hoping baseband for UWB-MBOA
  signals.
• Multi Carrier signal support
• Allowing simultaneous creation of multiple,
  dissimilar carriers in both baseband and IF/RF
• Linear and non linear impairments, multi-path,
  and power-ramping support
• To directly create real-world signals to stress
  any design

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Questions?