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 >