Re: Ofdm transceiver with more than 16QAM

[Marcus Müller]

You don't need to measure it. You need to ask yourself *why* a
constellation with many points might not work well with a low SNR.

Then you have your answer.

On 11.11.20 14:03, pv@koalatech.pt wrote:
> I don know how can I measure the SNR with QAM modulation. There is only
> a MPSK SNR probe.
> Can you tell me how to measure SNR with MQAM?
> 
> Thanks for your help,
> Pedro Viegas
> 
> Citando Marcus Müller <mmueller@gnuradio.org>:
> 
>> Hi. this is a typical question like I'd ask it when talking a student
>> through a test for a digital comms computer lab. So here's a hint:
>>
>> "Constellations with very many points" don't always work. It has to do
>> with SNR. Can you explain what the problem is with low SNR?
>>
>> Best regards,
>> Marcus
>>
>> On 10.11.20 12:56, pv@koalatech.pt wrote:
>>> Hi, I'm trying to make an OFDM transmission of a png file (9.3 kB) with
>>> 256QAM with the gnuradio
>>> example of OFDM transmitter / receiver. The USRP I'm using is the ettus
>>> n210 with the cbx daughter board. With the QPSK and 16QAM modulations it
>>> works, but with 64QAM or 256QAM I can´t receive the file, sometimes it
>>> receives some packets but most of the time it doesn't receive any byte.
>>> Can anyone help me with with this problem?
>>>
>>> Thanks in advance.
>>> Pedro Viegas
> 
>