In 5G, I think 1 resource block (RB) carrier is 12 subcarriers. So one user uses 12 subcarriers. But in some research, 612 subcarriers are used for channel estimation research. Is it okay to use more than 12 subcarriers in actual 5G communication?
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- $\begingroup$ Hi Ryo! Please don't forget to accept answers to questions you've asked! Thank you. $\endgroup$Marcus Müller– Marcus Müller2023-10-15 09:04:26 +00:00Commented Oct 15, 2023 at 9:04
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6 Channel estimation doesn't require resource blocks that are allocated to a single user
So, yes, that's sensible: there's pilots all over all subcarriers inserted at regular intervals, and every user knows their position.
- $\begingroup$ Thank you for your reply. Sorry for the long post. Is my understanding below correct? Assuming downlink communication, there are 612 subcarriers and 14 time slots are transmitted. Assume that one resource block is allocated to each user. The user who receives the signal performs a Fourier transform on the allocated 12 frequencies. As a result, each user receives a signal of 12 subcarriers x 14 time slots. After that, channel estimation and equalization are performed. $\endgroup$Ryo Onishi– Ryo Onishi2023-10-15 21:54:51 +00:00Commented Oct 15, 2023 at 21:54
- $\begingroup$ However, in the research, it was as if one user were receiving the received data of 612 subcarriers x 14 time slots. Then, the 612 x 14 data was input to machine learning (CNN) to perform channel estimation. Is it possible to receive 612 subcarriers in a real scenario? $\endgroup$Ryo Onishi– Ryo Onishi2023-10-15 21:55:24 +00:00Commented Oct 15, 2023 at 21:55
- $\begingroup$ No, that understanding is not correct. The FFT will be over the full bandwidth, usually, exactly because otherwise it's hard to get channel state information. Of course it is possible to receive all subcarriers at once. Have you looked at at 4G/5G time/frequency frame diagram? There's phases where there's synchronization and pilot symbols everywhere, and of course in a scenario where one user gets all the availalable spectrum, they will have to receive all of it. $\endgroup$Marcus Müller– Marcus Müller2023-10-15 22:01:01 +00:00Commented Oct 15, 2023 at 22:01
- $\begingroup$ You might really want to take a step back and look at OFDM theory. An OFDM receiver will not do a sub-band FFT, that makes no sense, it loses the ability to time- and frequency synchronize. I think you're already thinking about optimizing a system with machine learning which you haven't fully understood the very basis of! $\endgroup$Marcus Müller– Marcus Müller2023-10-15 22:03:45 +00:00Commented Oct 15, 2023 at 22:03
- $\begingroup$ Thank you very much! I will study this ieeexplore.ieee.org/ielx7/6287639/8948470/… $\endgroup$Ryo Onishi– Ryo Onishi2023-10-15 23:43:18 +00:00Commented Oct 15, 2023 at 23:43
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2 A single resource block is 12 consecutive subcarriers, it is really just a unit of bandwidth. 5G allocations can be more than a single resource block, for example, the synchronization signals in 5G use 20 resource blocks during their transmission.
- $\begingroup$ Thanks .Is synchronization done on the first few symbols of a resource block? After that, do you also use 20 resource blocks? $\endgroup$Ryo Onishi– Ryo Onishi2023-10-15 21:34:10 +00:00Commented Oct 15, 2023 at 21:34
- $\begingroup$ In 5G, the synchronization signals are sent periodically, where the period can be flexible depending on the exact setup being used. $\endgroup$Engineer– Engineer2023-10-16 01:05:29 +00:00Commented Oct 16, 2023 at 1:05