Re: Problems with packet communication using BPSK
Okay, got it now. So in '1', I am feeding the samples received by LimeSDR Mini to FLL, polyphase clock sync and costas loop for synchronization. Since it does not have any known reference signal appended to data, it will not take care of phase ambiguity at receiver and so my data is not exactly same as what is being transmitted and there are some bit inversions. However in '2' , I am appending header with preamble and other information to the payload to create packet which is transmitted by Lime SDR Mini. This data is received over the air by another SDR which uses correlation estimator to calculate the correlation as well as the phase, amplitude and time estimation used by the blocks downstream in the receiver. This is where I have issues when my RX doesn't detect or parse any packet. Thanks and Regards SG
Re: Problems with packet communication using BPSK
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 "AA.." or "5.". 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 >
Re: Problems with packet communication using BPSK
Hi! I know that without any packet structure in '1', the received data is being decoded as "AA.." or "5.". 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
Re: Problems with packet communication using BPSK
Did you account for the 0-180 phase ambiguity when demodulating BPSK? This would produce an inverted bitstream which wouldn't be noticeable when transmitting alternating 1s & 0s. @(^.^)@ Ed On 8/10/20 2:50 AM, 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
Problems with packet communication using BPSK
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
