LabVIEW Multicore Real-Time Multi- LabVIEW Multicore Real-Time Multi- Input Muli-Output Discrete Input Muli-Output Discrete Multitone Transceiver Testbed Multitone Transceiver Testbed Yousof Mortazavi, Aditya Chopra, and Prof. Brian L. Evans Wireless Networking and Communications Group The University of Texas at Austin
LabVIEW Multicore Real-Time Multi-Input Muli -Output Discrete Multitone Transceiver Testbed. Yousof Mortazavi , Aditya Chopra, and Prof. Brian L. Evans Wireless Networking and Communications Group The University of Texas at Austin. Introduction. Discrete Multitone Modulation. - PowerPoint PPT Presentation
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◦ LabVIEW Real-Time Vis Accesses hardware Calls DLL functions
◦ C++ Dynamic Link Library (DLL) Digital discrete-time baseband processing – Generates/processes samples sent/received
to/from hardware◦ Real-time operating system
Runs on target to guarantee real-time performance
Desktop PC◦ TCP/IP link to real-time target◦ Asynchronous visualization and control using
LabVIEW
Evolution of the TestbedEvolution of the Testbed
Bit AllocationBit Allocation Fixed amount of energy available to transmit per
DMT symbol DMT allows different number of bits transmitted on
each tone Adapt bit allocation to maximize throughput or
SNR margin on each tone Hughes Hartog bit allocation algorithm [1987]
implemented
Far-End Crosstalk Far-End Crosstalk CancellationCancellationFar End Crosstalk provides significant
deterioration in bit rate
Using vectored DMT [Ginis &Cioffi, 2002] multiple receivers operate together to cancel crosstalk
Other crosstalk cancellation methods◦ Linear: zero-forcing equalizer◦ Non-linear: successive interference
cancellation
SlicerSlicer
Vectored DMTVectored DMT
QHYQHYSuccessiveInterferenceCancellation
SuccessiveInterferenceCancellation
Estimate channel
matrix H
H = Q R
Training (per-tone)Training (per-tone)
• Uses channel estimate and both received signals to effectively cancel crosstalk
y0
y1
For each tone, H, Q and R are 2x2 matrices
Q RSymbol decoding Symbol decoding
(per-tone)(per-tone)
Experimental ResultsExperimental Results• System Parameters
• 256 tones per DMT symbol• Maximum Transmitted Voltage 5.0V• Receiver noise floor ~ -60dB
• 1000ft CAT-5 cable
• Inter-twisted pairs for maximum far-end crosstalk
• Far-end crosstalk limits SNR to ~10dB
Experimental ResultsExperimental Results
SIC – Successive Interference Cancellation
Target CPU UtilizationTarget CPU Utilization
ReferencesReferencesD. Hughes-Hartog, ”Ensemble
modem structure for imperfect transmission media.” U.S. Patents Nos. 4,679,227 (July 1987), 4,731,816 (March 1988), and 4,833,706 (May 1989)
G. Ginis and J. Cioffi, “Vectored transmission for digital subscriber line systems,” IEEE J. Select. Areas Commun., vol. 20, no. 5, pp. 1085-1104, Jun. 2002
BackupBackup
Analog Front-EndAnalog Front-End
• Hybrid circuits from Texas Instruments– Line Driver / “2-wire to 4-
wire” Interface
• Custom passive analog filters from TTE– Serve as anti-aliasing