Cognitive Radio System Testbed Demonstration

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Cognitive Radio System Testbed Demonstration

• Dr. Kyutae Lim (ktlim_at_ece.gatech.edu)
• Associate Director of Technology
• Georgia Electronic Design Center,
  www.gedcenter.org
• Georgia Institute of Technology

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Cognitive Radio Testbed Overview
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Cognitive Radio Testbed

• Cognitive Radio Testbed was built in Georgia
  Electronic Design Center, Georgia Tech, Atlanta,
  GA.
• Perform the real time demonstration of various
  operations in CR system.
• Perform the industrial level of evaluation for
  PHY/MAG and Sensing Technologies.
• CR Testbed has flexibility in H/W and S/W.
• Testbed configuration and test procedure can be
  set by WG and Tiger team.
• We hope CR testbed to contribute for forging IEEE
  802.22 Standard.

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CR Testbed System Configuration
Signal Generation
Signal Reception
TV Antenna
DTV Test Receiver
AMP
Vector Signal Analyzer
DTV Sig Gen
Spectrum Analyzer
Vector Sig Gen
ADC Data Acquisition
Receiver Module
4 CH DAC
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Photo of Cognitive Radio Testbed
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System Specification
Name Specification
SMU 200A Vector Signal Generator Dual RF path A (100 kHz 6 GHz), B (100 kHz 3 GHz) I/Q baseband modulation bandwidth 56 MHz
FSQ 40 Vector Signal Analyzer RF input 20 Hz 40 GHz Standard GSM/EDGE, FM, CDMA2K, Bluetooth, WLAN, WiMax
SFU TV Signal Generator RF output 100 kHz 3 GHz Standard Digital TV ATSC, DVB-T/H/C/S, DMB-T, DIRECTV, T-DMB/DAB Analog TV, Arbitrary signal Test stream generator Noise AWGN, phase noise, impulsive noise Fading static path, pure dopler, rayleigh, rice, const. phase
Tuner RF input 50 878 MHz IF out at 44 MHz / 6-MHz SAW filter can be bypassed NF 8 dB / RF VGA gain control -12 38 dB
DAQ (ADC) PCI-interface Dual channel / 12-bit resolution Max. 400 MSample/sec Input Dynamic Range 100 mV 5 V
DAC PCI-interface 4 channel / 12-bit resolution Max. 300 MSample/sec
EFA TV Test Receiver ATSC/8VSB Demodulation
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Demo.1 Cognitive Radio System Concept

• Purpose Basic CR operation principle
• Spectrum Sensing
• Co-existance of Incumbent and WRAN
• Interference mitigation
• Frequency agile operation

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Testbed Configuration Demo.1
Signal Generation
Signal Reception
TV Antenna
DTV Test Receiver
AMP
Vector Signal Analyzer
DTV Sig Gen
Spectrum Analyzer
Vector Sig Gen
ADC Data Acquisition
Receiver Module
4 CH DAC
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Spectrum Sensing (TV signals only)
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WRAN Interferer (overlapped)
WiMax signal used as WRAN
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OFDMA Constellation / EVM
OFDMA communication failed. No constellation. EVM
does not meet the criteria
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TVs-WRAN Co-Existence (WRAN in vacant channel)
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OFDMA Constellation / EVM
OFDMA communication working well. Good
constellation. EVM meet the criteria
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Dynamic Frequency Switching - I- New primary
user signal into the WRAN channel -
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OFDMA Constellation / EVM
Communication failed.
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Dynamic Frequency Switching - II- WRAN signal
move to another vacant channel -
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OFDMA Constellation / EVM
Communication in work.
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Demo.2 Evaluation of Spectrum Sensing Technology

• Purpose Verifying Various Spectrum Sensing
  Technologies
• Generating Spectrum Environment
• Energy Detection MRSS
• Feature Detection AAC

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Testbed Configuration Demo.2
Signal Generation
Signal Reception
TV Antenna
DTV Test Receiver
AMP
Vector Signal Analyzer
DTV Sig Gen
Spectrum Analyzer
Vector Sig Gen
ADC Data Acquisition
Receiver Module
4 CH DAC
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Dual Sensing Strategy (presented Mar 06)
Begin Sensing
Energy Detection for wide band (Analog, RSSI,
MRSS, FFT)
Fine/Feature Detection for single channel
MAC (Select single channel)
FFT
CSFD
Field Sync
Optimum Radiometer
Spectrum Usage Database (BS)
Multi-cycle Detector
AAC
Spectral Correlation
ATSC Segment Sync
occupied?
Y
End Sensing
N
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Input Signal Spectrum / Time-domain Waveform
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Coarse MRSS
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Fine MRSS with Threshold Detection
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AAC for OFDM (WLAN 802.11a)
Get two clues (due to short and long preamble) !!
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An Example of Scheduling Algorithm for DFH
WRAN A
Channel 1
WRAN B
Channel 2
Channel 3

• A WRAN system maintains two channels (operating
  channel and candidate channel)
• If WRAN BSes can communicate each other to
  schedule the time switching to the candidate
  channel, collision can be completely avoided.
• Even if collision occurs on the candidate
  channel, it is only in very short time (about
  quite time).

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Demo.3 Evaluation of protecting Incumbent user
from WRAN signal

• Generation of various fading environment
• DTV Signal quality measurement in Fading
• Coexistence of DTV and WRAN
• Signal quality measure for DTV and WRAN

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Testbed Configuration Demo.3
Signal Generation
Signal Reception
TV Antenna
DTV Test Receiver
AMP
Vector Signal Analyzer
DTV Sig Gen
Spectrum Analyzer
Vector Sig Gen
ADC Data Acquisition
Receiver Module
4 CH DAC
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ATSC Test 1 Fading (1)

• ATSC with Fading channel environment
• ATSC
• Ch. 39 (center freq 623 MHz)
• Level -10 dBm
• Fading
• Rayleigh (Pass loss 3 dB, freq ratio 1.00)
• EASY3 for DTV test
• Number of DTV signals and Fading parameters can
  be easily adjusted

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ATSC Test 1 Fading (2)
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ATSC Test 1 Fading (3)
Signal quality can be measured
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ATSC Test 1 Fading (4)


Various graphs enables signal quality analysis
for DTV signal
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ATSC Test 2 w/ WiMax (1)

• ATSC with Fading plus OFDMA signal to the
  adjacent channel
• ATSC
• Ch. 39 (center freq 623 MHz)
• Level -10 dBm
• No fading
• WRAN (WiMax signal is used)
• Freq 616.5 MHz, BW 7 MHz
• Level 0 dBm

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ATSC Test 2 w/ WRAN (2)

• Spectrum

ATSC
WiMax Mask
WiMax
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ATSC Test 2 w/ WRAN (3)
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ATSC Test 2 w/ WRAN (4)
Signal quality is little bit degraded due to
OFDM signal at adjacent channel
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ATSC Test 2 w/ WRAN (5)
OFDM signal
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ATSC Test 2 w/ WRAN (6)

• OFDM (WiMax) performance

Still OK!
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Summary

• CR Testbed has built in GEDC, Georgia Tech
• Maximum H/W flexibility
• Full S/W control MATLAB
• Easy to expand for evaluating Sensing,
  Interference, MAC, PHY
• CR Testbed has been demonstrated
• CR Concept and frequency agile operation
• Spectrum sensing technology evaluation
• Emulation of various fading channel environment
• Evaluation of WRAN signal to interfere DTV
  reception

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Suggestion

• Realistic spectrum environment can generated
  repeatedly.
• The testbed can be customized to perform various
  test/evaluation.
• The parameters and figure-of-merit can be defined
  by WG.
• Standard procedure for evaluation can be defined
  by WG.
• Lets use this testbed for standard evaluation
  platform for PHY and Sensing technology !!!