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I'm currently not sure if I understood DSSS correctly. Following example: We have a shared RF network with around a thousand of users and we want to use CDMA. The RF link should allow the streaming of a 4k video. If we use Gold Codes to generate the spreading code we would need around one thousand different codes which means one code also has the length of around one thousand bits. A 4k video requires around 20 Megabits/s. XORing this data stream with the spreading code leads to a 20Gigabits/s data stream. Using QPSK, a bandwidth of 20Ghz and a DAC with a sampling rate of 40GS/s would be required

This appears to be quite a lot to me. Where is my misunderstanding ?

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  • $\begingroup$ You may be able to trim the symbol rate (and, hence, bandwidth), depending on your available channel. But you're already using two bits per symbol, and going up to 16QAM is probably as much as is practical for radio, so you're not going to save much. $\endgroup$
    – TimWescott
    Commented Oct 21, 2023 at 17:15

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You're misunderstanding nothing.

Is that so surprising? You designed your system so that all your 1000 users can simultaneously get 20 Mb/s, so a total data rate of 1000 users · 20 Mb/s / user = 20 Gb/s.

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