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Very low frequency (VLF) power line communications (PLC) presently has widespread use in AMR/AMI deployments and may also be useful for smart grid applications, largely due to its excellent propagative properties. However, noise within the VLF band is more energetic than at higher frequencies and without effective mitigation algorithms degrades channel capacity, possibly to the point of making the band impractical. Recent work has demonstrated that PLC noise in the low frequency band (LF) and above is effectively modeled as a cyclostationary random process. We present measurements of actual power line noise and argue that the cyclostationary model is unnecessarily restrictive and that VLF PLC channel may be modeled as having a non-trivial wide-sense periodic component. We demonstrate the preponderance of periodic noise in this band by means of constrained covariance estimation from power line noise measurements. This has important ramifications for receiver design and when employed appropriately will increase the post-processed SNR, making VLF PLC a more attractive prospect for smart grid communications.

This paper addresses power-line communication (PLC) for automated metering infrastructure (AMI) and automated meter reading (AMR) applications in North America, with specific focus on the physical layer. FCC regulations permit powerline communication systems in the US to use the band from 9 kHz to roughly 500 kHz. This paper presents channel and noise characteristics in this band, based on field tests. It is shown that the main challenge in communicating in this band is severe signal attenuation by service transformers. In rural areas, these transformers supply eight or fewer end points on average. Consequently, it is not economical to use a bridge device across each transformer. Rather, one router is placed on the medium voltage line for every few service transformers. We consider the channel between a concentrator or a router on the medium voltage line (around 7.2 kV), and low-voltage (around 110V) end points connected to transformers some distance away on the medium voltage line. The signal-to-noise ratios observed in such a link, and implications for signal design, are studied. Data is provided on all modem connection scenarios, including medium voltage to low voltage (MV− − − −>LV), low voltage to medium voltage (LV− − − −>MV), and medium voltage to medium voltage (MV− − − −>MV). These results are intended to define requirements for a PHY / MAC communication system that can support the AMI application in such channel conditions.

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