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UE initial attach procedure :

  1. RSSI scan.
  2. Subframe and frame synchronization using pss and sss.
  3. listening to Cell specific reference signals
  4. MIB info
  5. SIB1
  6. SIB2

and so on...

From documents available in Internet, I came to know that, when we power on UE, it will perform RSSI (Reference signal strength indicator) scan within the configured bandwidth channel.(let's say 1.4Mhz,3,5,10,15,20Mhz) and will create a list of cells which signal strength is more than threshold value . As per the resource grid I have seen in this site, every 0th and 4th OFDMA symbol will carry info about Reference signal.

Question 1 : How UE will decode 0th and 4th OFDMA symbol before slot, Sub frame and Frame synchronization? As of I know, from the data received from 0th and 4th OFDMA symbol UE will find the strength of signal i.e RSSI value.(Please correct me, if I am wrong)

In order to exactly index 0th and 4th symbol, first UE has to find symbol boundary, right? As of I know symbol boundary will be carried out in later stage using cyclic prefix.

Question 2 : In RSSI scan, will UE derive RSRP and RSRQ values?

Question 3 : If UE derives RSRP & RSRQ info in RSSI scan, then why again after pss and sss synchronization, UE will listen to Cell Specific Reference signal?

Question 4 : What and all info will UE get in listening to cell specific reference signals after synchronization ?

Forgive me, If my question was not properly asked, please help me by considering some time in editing the question. Thanks in advance for your valuable time & support.

Murali Krishna Bellamkonda
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1 Answers1

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  1. It doesn't. The UE will need to do PSS/SSS detection first.
  2. RSRP requires looking at a subset of the blocks for determining RSSI so nominally the UE has the information it needs to compute RSRP and RSRQ.
  3. The cell specific reference is used to determine how to equalize. Also RSRP and RSRQ aren't static values, they generally change with time. (For example, if a UE moves away from the tower, we can expect the RSRP to decrease). The UE is always listening to the cell specific reference signal.
  4. See question 3. The cell specific reference is used for equalization.
hiandbaii
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