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[boost]

[boost]

I can't seem to find what it stands for either

[roseway]

The function is H(f) which is channel gain plotted against frequency. It can be expressed in two forms: HLin(f) in which the gain is expressed in linear increments, and HLog(f) in which the gain is expressed in logarithmic increments. In the context of DSL, gain is always a lot less than 1, so the logarithmic values are all negative. H is presumably just the mathematical symbol used for gain in this context.

[boost]

H Linear
H Logarithmic

Arbitrary or otherwise, 'H' must stand for something?

[4candles]

If it does, it doesn't seem to be googlable (is that a word? - it should be  ).

I suspect it's an arbitrary symbol, as roseway suggests, in the same way that impedance is 'Z' and inductance 'L'.

[konrado5]

Perhaps it does mean channel, because Hlog is channel response.

[kitz]

I'd also go with CHannel Characteristics Function
According to TR-090 5.5.1

Sub-Carrier Number (1..J)
 Channel Characteristics Function Linear Representation Scale (HLINSCds/ HLINSCus)
 Channel Characteristics Function Linear Representation (HLINpsds /HLINpsus)
 Channel Characteristics Function Logarithmic Measurement Time (HLOGMTds / HLOGMTus)
 Channel Characteristics Function Logarithmic Representation (HLOGpsds/ HLOGpsus)
 Quiet Line Noise PSD Measurement Time (QLNMTds / QLNMTus)
 Quiet Line Noise PSD (QLNpsds / QLNpsus)
 Signal-to-Noise Ratio Measurement Time (SNRMTds / SNRMTus)
 Signal-to-Noise Ratio (SNRpsds / SNRpsus)

[renluop]

Is it just a coincidence that Windows Regedit uses HKey preceding Software etc? I,ve long wondered why the H.

[kitz]

Ive always thought that stood for hotkey

[atkinsong]

The Windows registry is split up into Hives, hence the abbreviation for HiveKey.

[WWWombat]

I thought roseway might have been right: H = Gain.

In electronics, the gain of a transistor is usually written a h_FE; a very common parameter.

When you look in detail, it might not be quite so obvious:
Etymology of h_FE shows that this term is actually one of many "h-parameters" ... and they aren't all gain.

In other places, the channel characteristics seem to call "H" the "Transfer Function", which seems to be a mathematical model to represent the output vs input of a black box (in this case a length of copper pair)
Wikipedia's page on Transfer Functions shows H(s) defined as a transfer function.

I guess in this case, the transfer function does indeed represent gain (or loss).

JDSU seem to call it Transfer Function too.

^{Edit: Fix URL & typo for transistor}

[burakkucat]

Having done some reading, I believe transfer function is, indeed, the correct definition.

JDSU seem to call it Transfer Function too.

Hmm . . . Somehow I don't think that is a correct link! 

[WWWombat]

Ahem