On Feb 16, 6:45 am, Vladimir Vassilevsky <antispam_bo...@hotmail.com>
wrote:
> Oli Charlesworth wrote:
>
> > Soft decoders are typically designed to use Euclidean distance as the
> > metric; therefore it is correct to square each difference component.
>
> No, this is not a correct statement.
> It depends on what is the channel and what are the signals.
>
> Vladimir Vassilevsky
>
> DSP and Mixed Signal Design Consultant
>
> http://www.abvolt.com
For the AWGN channel, the soft decoder uses the Euclidean distance as
the metric. To reduce the complexity, only the cross-correlation
between the received signal and the modulation constellation is used.
For the BPSK system, (0,1) is mapped to (1, -1).
Reply by Vladimir Vassilevsky●February 16, 20072007-02-16
Oli Charlesworth wrote:
>
> Soft decoders are typically designed to use Euclidean distance as the
> metric; therefore it is correct to square each difference component.
No, this is not a correct statement.
It depends on what is the channel and what are the signals.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
Reply by Vladimir Vassilevsky●February 16, 20072007-02-16
JAlbertoDJ wrote:
> In the hard decsion case, if I receive [0,1] say, then the metric
> compared to [0,0] is 1.
It depends.
Suppose I received [0.9,1.1] in the soft
> decision case. Is the metric compared to [0,1]...
>
> (0.9)^2 + (1.1)^2 ??? or 0.9 + 1.1 ?????
It depends.
>
> Note: 0.9 is the correlation for a symbol 0
> Note: 1.1 is the correlation for a symbol 1
>
> Both correlations have been calculated by Quadrature Receiver (nocoherent
> detection)
The metric is the generalized distance between the reference vectors and
the received vector. It depends on what signal vectors corresponds to
[0,1], [0,0] and such.
Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com
Reply by Oli Charlesworth●February 16, 20072007-02-16
On Feb 16, 9:53 am, "JAlbertoDJ" <nietoro...@yahoo.es> wrote:
> In the hard decsion case, if I receive [0,1] say, then the metric
> compared to [0,0] is 1. Suppose I received [0.9,1.1] in the soft
> decision case. Is the metric compared to [0,1]...
>
> (0.9)^2 + (1.1)^2 ??? or 0.9 + 1.1 ?????
Soft decoders are typically designed to use Euclidean distance as the
metric; therefore it is correct to square each difference component.
Therefore, the metric for [0.9, 1.1] vs. [0, 1] is:
(0.9 - 0)^2 + (1.1 - 1)^2
--
Oli
Reply by JAlbertoDJ●February 16, 20072007-02-16
In the hard decsion case, if I receive [0,1] say, then the metric
compared to [0,0] is 1. Suppose I received [0.9,1.1] in the soft
decision case. Is the metric compared to [0,1]...
(0.9)^2 + (1.1)^2 ??? or 0.9 + 1.1 ?????
Note: 0.9 is the correlation for a symbol 0
Note: 1.1 is the correlation for a symbol 1
Both correlations have been calculated by Quadrature Receiver (nocoherent
detection)