Dear Kartik,

The length tag name in the OFDM transmitter and the Length Tag key
parameter in Stream to Tagged Stream block is the same.It is set properly.

Also, I get the error only when I try to reconfigure a flow graph. Could
you please let me know the correct way to reconfigure a flow graph when
they are using tags.

Thanks,
Damindra

On Sat, Dec 24, 2016 at 4:00 AM, Kartik Patel <[email protected]>
wrote:

> Hi Damindra,
>
> In the OFDM Transmitter block, check the parameter *Length Tag Name*.
> Value of that parameter should be same as *Length Tag Key* parameter in 
> *Stream
> to Tagged Stream* block.
>
> See *gr-digital/examples/ofdm/tx_ofdm.grc* for an example.
>
> Regards,
> Kartik Patel
>
>
>
> On Sat, Dec 24, 2016 4:19 AM, Damindra Bandara [email protected]
> wrote:
>
>> Hi,
>>
>> I am trying to dynamically reconfigure some parameters of a flow graph.
>> My flow graph is as follows.
>>
>> File source --> stream to tagged stream --> OFDM transmitter --> usrp sink
>>
>> In the top_block I do the following.
>>
>> tb.stop()
>> tb.wait()
>> <do the reconfiguration>
>> tb.start()
>>
>> I have done parameter reconfiguration earlier(before introducing OFDM TX)
>> and it worked fine. However now when I try to do the reconfiguration I get
>> the following error.
>>
>> FATAL: Missing a required length tag on port 0 at item #160
>> thread[thread-per-block[2]: <block crc32_bb (16)>]: Missing length tag.
>> FATAL: Missing a required length tag on port 0 at item #160
>> thread[thread-per-block[18]: <block crc32_bb (27)>]: Missing length tag.
>> SSFATAL: Missing a required length tag on port 0 at item #0
>> FATAL: Missing a required length tag on port 0 at item #0
>> thread[thread-per-block[86]: <block ofdm_frame_equalizer_vcvc (62)>]:
>> Missing length tag.
>> thread[thread-per-block[53]: <block ofdm_frame_equalizer_vcvc (93)>]:
>> Missing length tag.
>> LLLLLLLLUU
>>
>> I appreciate if someone could help me to figure out what is causing this
>> issue and  how to fix it.
>>
>> Thank you,
>> Damindra
>>
>>
>> --
>> Damindra Savithri Bandara,
>> Ph.D. in Information Technology (Candidate)
>> George Mason University,
>> Fairfax,
>> Virginia
>>
>


-- 
Damindra Savithri Bandara,
Ph.D. in Information Technology (Candidate)
George Mason University,
Fairfax,
Virginia
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