# Equalization for non-coherent FSK burst modem

Started by January 27, 2014
```On 06/02/14 16:25, mite_learner wrote:
> I am also planning to do frequency hopping. Would that benefit me against
> multipath distortion?

Slow frequency hopping: no. It purpose it to reduce detectability

Fast frequency hopping: yes, but AFAIK nobody bothers since they
use direct sequence spread spectrum has essentially the same
properties and is easy to implement.

OFDM uses more processing power in order to protect against channel
```
```<snip>
..
>>>
>>>For the block version you can use something like this in Matlab. What
>>we're doing here is basically solving the W-H Equation for the filter
>>taps.
>>>
>>>function zeq = cma(z,Neq)
>>>
>>>    [dummy,R]=corrmtx(z,Neq-1);
>>>    P=xcorr(z,z./abs(z),(Neq-1)/2);
>>>    W=R\P;W=W/sum(abs(W));
>>>    zeq = filter(W,1,z);
>>>
>>>end
>>>
>>>John
>>>
>>
>>
>>I am also planning to do frequency hopping. Would that benefit me
against
>>multipath distortion?
>>
>>ML
>
>Not much.   It really only helps if you would have otherwise picked a
>channel that was in a deep fade.  If the system is smart enough to not
>do that, and/or to move channels when it loses lock due to a fade,
>then FH isn't going to help to mitigate frequency-selective fading.
>If the signal bandwidth is wider than the channel coherence bandwidth,
>it'll help even less.
>
>FH is mostly an interference mitigation/suppression technique.
>
>
>Eric Jacobsen
>Anchor Hill Communications
>http://www.anchorhill.com
>

Hi Eric, thanks for your feedback. Yes, FH is mostly an interference
mitigation/suppression technique. I want to use it against multipath
interference as well at fast hopping rates :)

ML

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```
```>On 06/02/14 16:25, mite_learner wrote:
>> I am also planning to do frequency hopping. Would that benefit me
against
>> multipath distortion?
>
>Slow frequency hopping: no. It purpose it to reduce detectability
>
>Fast frequency hopping: yes, but AFAIK nobody bothers since they
>use direct sequence spread spectrum has essentially the same
>properties and is easy to implement.
>
>OFDM uses more processing power in order to protect against channel