I am trying to think of a way in which the base station (BS) can send say 100 bits of feedback to devices in my cell. My confusion is what is a good way to send this feedback bits.

This is during the initial access phase. My thought is to use the downlink broadcast channel from base station to all the users. I read that the PBCH is used to transmit the MIB (master information block). This is a small data packet that all the UEs must decode after detecting a cell using the synchronization signals.

I also read the following:

The MIB itself has 24 bits, plus a 16 bit CRC. These 40 bits are encoded as a 1920 bit codeword so that the MIB can be decoded even with very bad signal quality. An UE that receives the PBCH with good SNR is able to decode the MIB from just the 480 bits of a single PBCH transmission, speeding up the decoding process.

So maybe if I have 100 bits, I can send it alongside the MIB the same way?

Can you say this seems like a good approach.

  • $\begingroup$ What do you mean by "send it alongside the MIB the same way"? The MIB is a fixed message* sent over a fixed time unit and a fixed frequency unit over the air. Also, you need to tell us what are those feedback bits as before the initial access, there is no exchange whatsoever between the BS and the devices, then nothing to feedback. $\endgroup$
    – AlexTP
    Aug 26, 2023 at 9:57
  • $\begingroup$ For (*), there is one bit that is unused (or has not been used yet) in the MIB and you can exploit it. But I am not sure that I understand well what you want to do. $\endgroup$
    – AlexTP
    Aug 26, 2023 at 9:59
  • $\begingroup$ @AlexTP I am in the phase of active device discovery. For example, say there are 100 devices in the system and only 10 are active which is unknown to BS. So I am doing some initial signaling to identify the active devices. Basically, the devices will send a signature sequence simultaneously and BS uses that to identify an estimate set. Now, I want to convey this info back to the device saying "Hey, I found out you are active, I can go ahead and assign you resources (something like that)". This is the feedback I am talking about. $\endgroup$
    – wanderer
    Oct 5, 2023 at 16:32
  • $\begingroup$ I don't know how to support what you want to do with the LTE/5G protocols. $\endgroup$
    – AlexTP
    Oct 11, 2023 at 7:47


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