Re: Problems with packet communication using BPSK

[Marcus Müller]

When you don't correct for the phase of your channel (including all
filters and devices), you don't know whether your 0° or your 180° symbol
is the binary 0 or 1. A PLL only corrects the rotation of your
constellation so that it's a valid constellation, not necessary the same
rotation as at the transmitter.

Best regards,
Marcus

On 11.08.20 13:19, Shruti Gupta wrote:
> Hi!
> 
> I know that without any packet structure in '1', the received data is
> being decoded as "AAAAAA......" or "55555.....". Is that what you meant
> by inverted bit stream? I am not really clear about what you meant by
> phase ambiguity?
> 
> Thanks
> SG
> 
> 
> On 10/08/20 12:20 pm, Shruti Gupta wrote:
>>
>> Hi all!
>>
>> I am working on implementing  BPSK communication system with SDR in
>> GNURadio. I tried implementing packet-communication in GNURadio using
>> two systems each acting as TX and RX. Using the examples provided in
>> gr-digital , I tried running TX and RX with LimeSDR Mini, but was
>> unable to get them to work. In order to identify and solve the issues,
>> I moved on to implementing everything in step-wise approach, as in-
>>
>>  1. Transmit just alternating 1’s and 0’s using BPSK modulation and
>>     receiving it on other end using synchronization and demodulation.
>>  2. Introduce packet structure into the previous raw-communication
>> model .
>>  3. Then add FEC into the system and finally include CRC and achieve
>>     the same packet-communication as provided with gr-digital.
>>
>> In this step-wise approach, I was able to get raw communication model
>> (point 1 in above) work properly. However, I am not able to get packet
>> version (number 2) working. I used the same system settings just the
>> introduction of packet structure at TX and correlation estimation &
>> header-payload demux at RX but still no luck. Is there some issue with
>> the way I am implementing packet formation at TX or the correlation
>> estimator is the problem? You can find my implementation at following
>> link:
>>
>> https://drive.google.com/drive/folders/1TIWhNuVmclenhLj4qJK2HT-er6RoCcco?usp=sharing
>>
>>
>> Any suggestions/pointers in order to resolve the issue will be helpful.
>>
>> Thanks and Regards
>> SG
>