1. ©2012 Aclara Technologies LLC David W. Rieken, Zhixi Li, and Chris Fleck Advanced Systems Research & Development Aclara Technologies, LLC St. Louis, MO, USA VLF-band Power Line Channel Sounding

2. ©2012 Aclara Technologies LLC Summary  VLF band (1-9 KHz) – Not regulated by the FCC – Legacy AMI systems (e.g. TWACS, Turtle) – Good signal propagation properties? – Signal frequency is higher than mains, but still low enough to permit long distance comms – Presents unique challenges to PLC because of low data rate and significant mains interference  Overview – VLF-band channel sounding – Experimental setup – Survey results

3. ©2012 Aclara Technologies LLC Channel sounding algorithm: signal model 3

4. ©2012 Aclara Technologies LLC Channel sounding algorithm: transmitted signal 4

5. ©2012 Aclara Technologies LLC Channel sounding algorithm: sounding procedure 5

6. ©2012 Aclara Technologies LLC Channel sounding algorithm: periodic noise cancelation 6

7. ©2012 Aclara Technologies LLC Experiment setup 7

8. ©2012 Aclara Technologies LLC Experiment setup: transmission point 8

9. ©2012 Aclara Technologies LLC Experiment setup: receive point 9

10. ©2012 Aclara Technologies LLC Analysis: convolution with sounding signal 10 Spreading signal so that it is orthogonal to mains makes detection in low SNR channels easy.

11. ©2012 Aclara Technologies LLC Survey results: Illinois site 11

12. ©2012 Aclara Technologies LLC Survey results: Missouri site 12

13. ©2012 Aclara Technologies LLC SNR Analysis 13

14. ©2012 Aclara Technologies LLC SNR analysis: Illinois site (7.2 mi link) 14

15. ©2012 Aclara Technologies LLC SNR analysis: Illinois site (7.2 mi link) 15

16. ©2012 Aclara Technologies LLC SNR analysis: Missouri site (25.2 mi link) 16

17. ©2012 Aclara Technologies LLC SNR analysis: Missouri site (25.2 mi link) 17

18. ©2012 Aclara Technologies LLC Survey results: SNR by band 18

19. ©2012 Aclara Technologies LLC Conclusions 19  Any VLF-band PLC system must – Accommodate a wide range of link strengths – Leverage higher concentrator data rates than endpoint data rates – Maximize system throughput, rather than instantaneous data rate  Analysis shortcomings – Sampling rate offset – Time-varying channel IPR