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Application of a phantom circuit for xDSL communications

: Oswald, E.

Rohling, H. ; TU Hamburg-Harburg, Institut für Nachrichtentechnik:
13th International OFDM-Workshop, InOWo'08. Proceedings : August 27th - 28th, 2008 at the Hotel Atlantic, Hamburg, Germany
Hamburg, 2008
International OFDM-Workshop (InOWo) <13, 2008, Hamburg>
Conference Paper
Fraunhofer ESK ()

Around the turn of the twentieth century a method that allowed for a third voice communications channel over two copper pairs was developed. The third channel was known as the "Phantom Circuit". Over the years communicating with the phantom circuit became less and less worth while until it was abandoned completely.
Today researchers in the area of DSL technology view the phantom circuit as the method for squeezing the last bit of bandwidth out of copper twisted pair communications.
It is the objective of this contribution to first clarify whether communication at DSL frequencies is at all possible over a phantom circuit, and secondly whether it can be used to increase the possible transfer rate and/or the distances over which these transfer rates can be achieved.
For test purposes phantom circuit interface boards were fabricated using interface transformers that are currently implemented in VDSL2 systems. Results of measurements show that xDSL communication is possible using a phantom circuit. Higher throughput rates and/or longer ranges for a fixed data rate were achieved.