Periodic noise in very low frequency power-line communications

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.