Transmission between 2 bladeRF boards

[k8000]

Hello everyone

I am currently working on a OFDM related project where I need to transmit information from one bladeRF board to another. I have implemented this same system using GNU Radio in a loopback fashion on a single bladeRF where I connect the transmitter and receiver of the boards. When implementing on a single board the system works perfectly.

The problem starts when I try to transmit between two bladeRF boards. When working with 2 bladeRF boards, there seems to be something affecting the received signal where I observe a sort of pulsating that takes place in that the amplitude seems to have some sort of envelope as the signal is being received. This pulsating effect, however, does not continue for the whole duration of the signal reception, only for a portion of it but it repeats at consistent intervals. When looking at the frequency spectrum of the transmitted signal there seems to be an intrinsic DC spike that always exists no matter what I transmit. I suspect this could be an issue but what confuses me is that the system works on one bladeRF board.

I've tried different methods to remove this DC component at the transmitter to no avail. The next thing I suspect are IQ imbalances but I am not sure how I can solve these in GNU radio using the osmocom block. I tried generating the automatic gain control using https://github.com/Nuand/bladeRF/wiki/D ... Correction but it does not seem to make any difference. Any suggestions on this would be much appreciated. Thank you

[lilycollins9x]

Your suspicions about the DC spike are well-founded. Continuous DC offsets in the transmitted signal can produce amplitude variations in the received signal, which manifests as the oscillation effect you are seeing.
bitlife

[duringaccurate]

The cause may lie in the persistent DC Deviation in the transmitted signal

tunnel rush

[NellyAurora]

The presence of continuous DC offsets in the transmitted signal can cause fluctuations in the amplitude of the received signal, resulting in the oscillation effect that you are observing heardle 80s

[charith123]

Pls take it easy on me I am new to SDRs

challenge I've encountered while conducting an experiment involving two Nuand BladeRF 2.0 micro xa4 software-defined radios (SDRs).

Experiment Overview:

I aim to establish a communication setup where one BladeRF serves as a transmitter and the other as a receiver. The objective is to transmit a simple message in ASCII text format which we would convert to binary and send and convert back to ASCII, and successfully receive and interpret it.

Progress So Far:

I've successfully set up both BladeRF devices on separate computers – one for transmitting and the other for receiving.

During a test run, I created a binary file using a Python script and utilized the following commands for transmission:
On the transmitter:
```bladeRF> tx config file=samples.bin format=bin```
```bladeRF> tx start```
```bladeRF> tx```
On the receiver:
```bladeRF> rx config file=samples.bin format=bin n=10```
```bladeRF> rx start```
```bladeRF> rx```

I've ensured that the sample rate, frequency, and power levels are appropriately configured on both the transmitter and receiver.

Issue Encountered:

Despite believing that the message was transmitted successfully, upon attempting to open the file on the receiving laptop, the received binary did not resemble what was sent.

I would greatly appreciate any assistance someone can offer in resolving this issue.

[righthalfplane]

I find in general a very common problem is to over drive the transmitter or receiver - so, try turning the gain down.

In the video -

Transmitting and Receiving OFDM Data with the gnuradio-companion
https://youtu.be/A3aJDPcvrHg

I transmitted from one room to another using a Blade xA5 and a HackRF One. The biggest problem was fiddling with the gains until it worked.

[jeffreestar]

I find in general a very common problem is to over drive the transmitter or receiver - so, try turning the gain down.

In the video -

Transmitting and Receiving OFDM Data with the gnuradio-companion
https://youtu.be/A3aJDPcvrHg slice masters

I transmitted from one room to another using a Blade xA5 and a HackRF One. The biggest problem was fiddling with the gains until it worked.

As you mentioned, IQ imbalances can significantly impact the performance of your system. The osmocom block in GNU Radio allows you to perform IQ imbalance correction. Ensure that you properly configure and enable this block in your GNU Radio flowgraph. You may need to experiment with different correction parameters to achieve the best results.