Scrambling in 1000Base-T


In 1000Base-T Ethernet, the scrambling at the master side is different from the scrambling at the slave side. Is someone knows the reason?

At the master side, the polynomonial is: 1 + X13 + X33, whereas at the slave side, the polynomial is: 1 + X20 + X33.

Is it a question of energy spreading?

Thanks for your advice, Michelot

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Hi Michelot,

I think no. The separare scramblers makes the two opposite streams more uncorrelated, which helps symbol recovery at the receiving end.

Let's try an example, if it is correct!

The length of the pseudocode is 2v33 = (2v10)v3.3 bits, around 10v10 bits, that's make 10v4 seconds at 1 Gbit/s, that is around 3 hours.

Suppose a transmitting of IDLE. If the scramblers were same, the both end will transmit the same signal after a period of 3 hours. In this case, with the echo and crosstalk cancellations, perhaps it should be difficult to detect a start of MAC frame.

Is it your advice? Mchelot

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