Department of Electrical and Computer Engineering,
Wireless Networking and Communications Group,
The University of Texas at Austin,
Austin, TX 78712 USA
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Paper Draft - Presentation Slides - Software Release
Our Magazine Article on Smart Grid Communications Diversity
Smart Grid Communications Project
Q2. The average coded BER vs. SNR plots show a shift in the shape
of the curve for the MRC combiner of the PLC/wireless channels vs.
However, the slope of the curve is the same, and this does not
indicate an improvement due to diversity.
A2. Due to the independence of the PLC and wireless links, we would expect to see twice the diversity order play out in the communication performance. At high SNR, we would expect to see a doubling in the slope in the average BER on a log scale vs. SNR in dB curves for the hybrid system vs. that of a single link. In the paper, we used convolutional coding and Viterbi decoding, and swept SNR values from -6 dB to 4 dB for binary phase shift keying (BPSK) and -4 dB to 8 dB for differential BPSK using the testbed. For the average coded BER on a log scale vs. SNR in dB for BPSK, the slopes for the two data points with the highest SNR values are -1.1835 for the PLC link, -1.1896 for the Wireless Communications link, and -1.4652 for the MRC. The SNR range that we considered is too low to see the dramatic increase in the slope. We will seek to verify that as SNR increases, the average BER of the hybrid system decreases more rapidly (i.e. higher slope) than the BER of a single link. (Note: Prof. Naofal Al-Dhahir at The University of Texas at Dallas contributed to this answer.)
Q3. Did you consider simply selecting the link with the higher SNR?
A3. We didn't try this approach. From eyeballing the average coded BER rate vs. SNR curves, choosing the link with the higher SNR would not perform as well as the proposed MRC approach, except in the case of an exteme difference in SNRs in which selecting the link with the higher SNR would give the same result as the proposed MRC approach.
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Last Updated 05/29/18.