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Transmission time for sending JPEG still image

  1. Apr 11, 2014 #1
    Hi all... I am trying to design digital modem to send 3 things,, audio, data and image, the problem that when I try to send image 640x480 pixel, with JPEJ format, I need to get a value for a transmission time by using the type of modulation scheme and symbol rate, my question is what the relation that could I use between transmission time , modulation scheme and symbol rate??
    Please help me. I am really stuck in this problem,,,
    Thanks in advance
  2. jcsd
  3. Apr 12, 2014 #2


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    Science Advisor
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    Gold Member

    I suspect there is more to the question but the short answer would be..

    Transmission time = Number of bits to be transmitted (including overheads) / Bit rate of the system.

    The problem is that both are variable. The number of bits in a JPEG file depends on the image detail. The bit rate of the system may vary depending on the line quality.
  4. Apr 12, 2014 #3
    Thanks for your response..
  5. Apr 12, 2014 #4
    Digital modem design

    Hello.. I need a help with my design study, I am asked to design modem for UHF, 2 GHz, for rescue helicopter with speed 200km/h, to send 3 types of data, speech, image and onboard instrument data,,, I nearly finish my design,,, but I stuck in point,, as a part from my design I need to use adaptive modulation, I was given to values for SNR, 50dB for 20% of time and 20dB for 50% of time!! the problem that I do not understand! what is the reason for these percentage,, where should I implement them? To make it more clear, for worst case of my design I used SNR 20 dB , this leads me to use 8-QAM scheme, and best case when SNR 50 dB this leads me to use 256-QAM, I assumed another values in between these two SNR values, to get another M-QAM schemes. So should I multiply these (%) with the SNR values that correlated to or what??? Please help me..
    I hope that I clarified the problem,,
    Thank you in advance...
  6. Apr 12, 2014 #5


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    Staff: Mentor

    Calm down, calm down. Everything's going to be allright.

    What frequency band would you like to use? What is your link budget?
  7. Apr 13, 2014 #6
    Thanks berkeman.. The band width need to use it was 10kHz, the modem will operate on 2GHz frequency,,and the onboard instrument produces data about 200 bps (fixed),, and each modem will have SNR 50db for 20%of time and 20db for 50% of time,,,these are all my given parameters..
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