# Re: [10GBT] More on Fixed Point Decoder of the (1024, 833) Code

Sailesh,
I do not know what you mean by '1D LLR estimator'. If you mean the a
posteriori LLR's of the coded bits coming from the channel, we just
follow the basics:
We assume that all points of the 12 PAM constellation are equi-probable
and their probabilities are independent across dimensions. It follows
immediately that the channel LLR's are separable across dimensions, i.e.
for each bit, one only need to consider the received signal on the wire
that carried the bit.
(One may argue that this method is 'suboptimal', however it is
well-known that the loss due to this approximation is very very small.)
The derivation of bit LLR's from the received 1D symbols is also
straightforward.
One good example can be found in ungerboeck_2_0904.pdf.
Regards,
Dariush
-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
Behalf Of sailesh rao
Sent: Tuesday, October 05, 2004 5:36 AM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] More on Fixed Point Decoder of the (1024, 833) Code
Dariush,
Please specify the 1D LLR estimator used in these simulations.
Thanks,
Sailesh.
srao@phyten.com
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