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Hi all,

  I have this doubt in implementation of viterbi decoder in FPGA

  While the trace-back unit decodes the single bit after tracing back the
path of length 5*L, next input to the viterbi decoder should not be given.
But if the input data is continuous, trace-back operation should be
completed within single clock input period.

  So to fulfil the above requirement,i considered a clock for trace-back
unit of 5*L times faster than input clock and it is working fine. Is this
the correct way of implementing or is there an alternate implementation
possible with using trace-back unit clock of same period as input clock.

I referred few IP cores like xilinx, Altera, Lattice,etc on this info. But
nowhere this delay of 5*L clock cyles is specified or usage of higher clock
frequency is mentioned.

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san_jack wrote:

> Hi all,
> 
>   I have this doubt in implementation of viterbi decoder in FPGA
> 
>   While the trace-back unit decodes the single bit after tracing back the
> path of length 5*L, next input to the viterbi decoder should not be given.
> But if the input data is continuous, trace-back operation should be
> completed within single clock input period.

Yes.

>   So to fulfil the above requirement,i considered a clock for trace-back
> unit of 5*L times faster than input clock and it is working fine. Is this
> the correct way of implementing or is there an alternate implementation
> possible with using trace-back unit clock of same period as input clock.

????
You don't have to do the full 5L retrace. You only have to update all 
paths by one step.

> I referred few IP cores like xilinx, Altera, Lattice,etc on this info. But
> nowhere this delay of 5*L clock cyles is specified or usage of higher clock
> frequency is mentioned.

Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

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>But as per the viterbi algorithm, traverse of trace-back for 5,6 times of
constraint length yields the correct decoded path. So for decoding each bit
I should traverse minimum 5L paths.

>
>san_jack wrote:
>
>> Hi all,
>> 
>>   I have this doubt in implementation of viterbi decoder in FPGA
>> 
>>   While the trace-back unit decodes the single bit after tracing back
the
>> path of length 5*L, next input to the viterbi decoder should not be
given.
>> But if the input data is continuous, trace-back operation should be
>> completed within single clock input period.
>
>Yes.
>
>>   So to fulfil the above requirement,i considered a clock for
trace-back
>> unit of 5*L times faster than input clock and it is working fine. Is
this
>> the correct way of implementing or is there an alternate
implementation
>> possible with using trace-back unit clock of same period as input
clock.
>
>????
>You don't have to do the full 5L retrace. You only have to update all 
>paths by one step.
>
>> I referred few IP cores like xilinx, Altera, Lattice,etc on this info.
But
>> nowhere this delay of 5*L clock cyles is specified or usage of higher
clock
>> frequency is mentioned.
>
>Vladimir Vassilevsky
>DSP and Mixed Signal Design Consultant
>http://www.abvolt.com
>

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san_jack wrote:

>>But as per the viterbi algorithm, traverse of trace-back for 5,6 times of
> 
> constraint length yields the correct decoded path. So for decoding each bit
> I should traverse minimum 5L paths.
> 
> 
>>san_jack wrote:
>>
>>
>>>Hi all,
>>>
>>>  I have this doubt in implementation of viterbi decoder in FPGA
>>>
>>>  While the trace-back unit decodes the single bit after tracing back
> 
> the
> 
>>>path of length 5*L, next input to the viterbi decoder should not be
> 
> given.
> 
>>>But if the input data is continuous, trace-back operation should be
>>>completed within single clock input period.
>>
>>Yes.
>>
>>
>>>  So to fulfil the above requirement,i considered a clock for
> 
> trace-back
> 
>>>unit of 5*L times faster than input clock and it is working fine. Is
> 
> this
> 
>>>the correct way of implementing or is there an alternate
> 
> implementation
> 
>>>possible with using trace-back unit clock of same period as input
> 
> clock.
> 
>>????
>>You don't have to do the full 5L retrace. You only have to update all 
>>paths by one step.
>>
>>
>>>I referred few IP cores like xilinx, Altera, Lattice,etc on this info.
> 
> But
> 
>>>nowhere this delay of 5*L clock cyles is specified or usage of higher
> 
> clock
> 
>>>frequency is mentioned.
>>
>>Vladimir Vassilevsky
>>DSP and Mixed Signal Design Consultant
>>http://www.abvolt.com
>>

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