# Question about digital\_ofdm\_mapper\_bcv class and d\_msg variable

**URL:** <https://www.ruby-forum.com/t/question-about-digital-ofdm-mapper-bcv-class-and-d-msg-variable/222151>\
**Category:** GNU Radio\
**Created:** [August 15, 2012, 10:18am UTC](https://www.ruby-forum.com/t/question-about-digital-ofdm-mapper-bcv-class-and-d-msg-variable/222151 "2012-08-15T10:18:48Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\
**Post date:** [August 15, 2012, 10:18am UTC](https://www.ruby-forum.com/t/question-about-digital-ofdm-mapper-bcv-class-and-d-msg-variable/222151/1 "2012-08-15T10:18:48Z")

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Hello everyone,

In the current implementation of the digital\_ofdm\_mapper\_bcv::work()  
method  
only one packet of 528 size(in other words d\_msg-\>length() == 528) is  
consumed each time in order to create a symbol.  
I tried to modify the method to consume more of those packets but it  
still  
not works.  
So the question is if there is a way to change the packet size of the  
msg  
(d\_msg-\>length()) from 528 to another integer.I could not find where  
this  
value is given yet.

Thans in advance,  
Lampros.

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**Author:** ![Lampros\_Katsikas](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/6de8d8/32.png) [@Lampros\_Katsikas](https://www.ruby-forum.com/u/Lampros_Katsikas)\
**Post date:** [August 27, 2012, 2:00pm UTC](https://www.ruby-forum.com/t/question-about-digital-ofdm-mapper-bcv-class-and-d-msg-variable/222151/2 "2012-08-27T14:00:23Z")

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On Wed, Aug 15, 2012 at 4:17 AM, Lampros Katsikas  
[removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> Thans in advance,  
> Lampros.

You can change the lengths of most parts of the symbol and packet. If  
you run the benchmark\_tx.py script with ‘-h’, you’ll see the list of  
options. The ‘-s’ allows you to specify the length of the packet  
(default = 400 bytes), the number of subcarriers (–fft-length), the  
number of used subcarriers (–occupied-tones) and the length of the  
cyclic prefix (–cp-length).

You should be able to make the OFDM code work on more than one symbol  
at a time, which should help a bit in the performance. The  
book-keeping starts to get nasty, so to make it easier on us when we  
put this together, we decided to get it right by only using one symbol  
at a time.

Tom

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**Author:** ![Lampros\_Katsikas](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/l/6de8d8/32.png) [@Lampros\_Katsikas](https://www.ruby-forum.com/u/Lampros_Katsikas)\
**Post date:** [August 27, 2012, 2:01pm UTC](https://www.ruby-forum.com/t/question-about-digital-ofdm-mapper-bcv-class-and-d-msg-variable/222151/3 "2012-08-27T14:01:13Z")

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Thank you very much for your reply but this is not what i was looking  
for…  
Its my fault because didn’t tell you what exactly i would like to do!

So, i don’t want just to run the benchmark\_tx.py to see its behaviour  
but i  
would like if possible to give the packet\_size as a parameter or even  
set  
it statically with another size in order to handle bigger packets at  
the  
work method of the digital\_ofdm\_mapper\_bcv class.  
I have already checked the gr\_buffer and gr\_msg\_queue files from  
gnuradio\_core folder but i havent seen anything yet.

Thank you in advance,  
Lampros.

2012/8/22 Tom R. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid)