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AWR1243: MIMO setting

Morteza Varasteh
Prodigy 20 points
Part Number: AWR1243

Dear team, 

I am trying to use the radar AWR1243 in the TDM-MIMO setting (3TX and 4RX). 

1) My first question is how can I make sure on the mmWave studio software that this setting is applied and it is NOT BPM-MIMO?

2) second question is a bit technical and I would appreciate your patience in addressing it: in the 3x4 TDM-MIMO setting, assuming that e.g. we have #of_chirp_loops=33, we have 33 chirps (denoted as C_{m,n} where m is the index of chirp and n is the index of the transmit antenna) from each transmit antenna sent simultaneously as below: 

C_{1,1}, C_{1,2}, C_{1,3}, C_{2,1}, C_{2,2}, C_{2,3}, C_{3,1}, C_{3,2}, C_{3,3}, ....., C_{33,1}, C_{33,2}, C_{33,3}

This means we have 3 frames sent at the same time (orthogonal in time). Each frame has 33 chirps with chirp_repeatition_period=3*chirp_cycle_time

Assuming 6 frames transmitted, at the receiver side (after collecting IQ ADC samples), we have a tensor (denoted by T) of size (6,33,300,4) where 6 is the number of frames, 33 is the number of chirps per loop, 300 is the number of ADC samples per chirp and 4 is the number of Rx antennas. Am I correct to say that T[0,:,:,0], T[1,:,:,0], T[2,:,:,0] are in the following form:

T[0,:,:,0] =[S_{1,1}, S_{2,1}, S_{3,1}, ..., S_{33,1}].T

T[1,:,:,0] =[S_{1,2}, S_{2,2}, S_{3,2}, ..., S_{33,2}].T

T[2,:,:,0] =[S_{1,3}, S_{2,3}, S_{3,3}, ..., S_{33,3}].T

where S_{m,n} are the ADC samples of m-th chrip transmitted from the n-th antenna

I am not sure if what i said above is correct or not but if it then it has conflicts with what I have read in this PDF (https://www.ti.com/lit/an/swra554a/swra554a.pdf?ts=1701272993127&ref_url=https%253A%252F%252Fdev.ti.com%252F) (it is in page 6. Please see the part that I have attached as an image below):

I am facing a huge issue digesting the transmission structure in TDM-MIMO mode. I would deeply appreciate it if you could let me know whether I am correct or not and if not please kindly explain what is the correct way.

Many thanks.

  • 0
    TI__Mastermind 20605 points

    Hi Morteza,

    Please find my responses as follows:

    1. You would have to look at the chirp configuration sequence that you have used while configuring the mmWave device. You can additionally see if the BPM is enabled in the BPM config.
      • Morteza Varasteh said:
        This means we have 3 frames sent at the same time (orthogonal in time). Each frame has 33 chirps with chirp_repeatition_period=3*chirp_cycle_time
      We refer to this entire sequence as one frame conventionally.
      Following this, I'm unsure of your tensor breakdown of the frames sequenced but I can break it as follows: (This should also comply with the document)
      1. First would be the number of samples for a given chirp (Say 300 samples)
      2. We have 4 receivers, so each would have 300 samples (300 x 4)
      3. This would be for 1 unique chirp from one transmitter, which would repeat for each of the 3 in a TDM scheme (300 x 4 x 3)
      4. Each of these unique chirps are looped 33 times so you have (300 x 4 x 3 x 33)
      5. From d. we obtain something that we commonly refer to as a frame. If you, let's say have 6 frames, then you will end up with something like (300 x 4 x 3 x 33 x 6). 

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    Prodigy 20 points

    Dear Kaushik,

    Many thanks for your quick reply. I got my full answer with the first question. On the second question, Let us assume that as you said a frame is a summation of the transmitted signals from the three Tx antennas (in TDM mode). I am still not sure if I get the same results on my recordings. 

    Please see the screenshots below that represent the setting I have used for my recording

    I am assuming that the parameter No_chirp_Loops = 33 is for each transmit antenna which overall makes the number of chirps in a frame (according to the conventional definition) equal to 99

    When I extract the data samples (before reshaping into a matrix) I have 10137600 IQ samples which is as below

    100(frames) * 33(number of chirp loops) * 384(number of ADC samples) * 4(receive antennas) * 2(I and Q samples)

    According to what you said, I am and I was expecting to see another 3 because of transmit antennas but at least the number of samples that I get does not confirm this. 

    Many thanks in advance for your patience and guidance. 

    Morteza. 

  • 0 in reply to Morteza Varasteh
    TI__Mastermind 20605 points

    Hi Morteza,

    Can you confirm if you configured the 3 unique chirps with Tx0, Tx1 and Tx2 individually by setting it in ChirpCfg? Your Frame cfg would also have to reflect the chirp indices to be looped.

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    Prodigy 20 points

    Thanks a lot Kaushik,

    I think you have spotted the problem. I didnt configure that part. Please could you provide some complementary information on how I can do that appropriately? Link or pdf should suffice.

    Many thanks!

  • 0 in reply to Morteza Varasteh
    TI__Mastermind 20605 points

    Hi Morteza,

    I highly recommend you go through the mmwave_studio_user_guide.pdf which can be found in the docs folder of your mmwave Studio installation. Additionally, you can also refer to the example lua scripts that might be available in your Studio installation folder to understand typical API call sequences.

    Regards,

    Kaushik

  • 0 in reply to Kaushik Gowda
    Prodigy 20 points

    Thank you very much, Kaushik,

    I had already reviewed the user guide before posing this question. However, I didn't find any information in the document regarding the MIMO configuration for 3 transmit and 4 receive antennas. In my own search, both through the mmWave Studio User Guide and online resources, I encountered a similar issue. The guide covers a wide range of topics but does not provide specific instructions for this particular setup. Additionally, an online search did not yield precise results for configuring mmWave Studio in this specific MIMO scenario.

    I would greatly appreciate it if you could provide more specific details or guidance. Would it be possible for you to explain the configuration process here? Your expertise on this matter would be highly valuable.

    Thank you so very much

  • +1 in reply to Morteza Varasteh
    TI__Mastermind 20605 points

    Hi Morteza,

    There is no additional documentation here. Users are typically expected to go through the documentation and understand how to use these APIs from the examples.

    FYI, this is the API call sequence that you would have to do for a typical 3 Tx and 4 Rx MIMO.

    ar1.ChirpConfig(0, 0, 0, 0, 0, 0, 0, 0, 0, 1)          -> Chirp 1
    ar1.ChirpConfig(1, 1, 0, 0, 0, 0, 0, 0, 1, 0)          -> Chirp 2
    ar1.ChirpConfig(2, 2, 0, 0, 0, 0, 0, 1, 0, 0)          -> Chirp 3
    These will be the unique chirps from each of the Tx. The same will be looped nLoops number of times. The same API will be called every time you click "Set" on the chirp config tab.
    All the 4 receiver channels to be enabled in ChannelCfg config API.

    Regards,

    Kauhsik

  • +1 in reply to Kaushik Gowda
    Prodigy 20 points

    Thanks Kaushik, 

    I found its corresponding place in the lua file as well as on the mmWavestudio. Now the dimensions are as I expect. Thanks a lot again for your patient answers. 

    Best,

    M