What is prach frequency offset in LTE?
PRACH Frequency Offset
| System Bandwidth | Resource Block Offset Range | Resource Block Offset Default Value |
|---|---|---|
| 5 MHz | 0 to 19 | 0 |
| 10 MHz | 0 to 44 | 0 |
| 15 MHz | 0 to 69 | 0 |
| 20 MHz | 0 to 94 | 0 |
What is prach preamble in LTE?
The position of LTE random access preamble is defined by PRACH frequency offset parameter carried in SIB-2. LTE UE selects the sequence from these two groups based on size of uplink packet and radio conditions. This helps eNodeB to calculate PUSCH resources needed for UE uplink transfer.
What is LTE prach?
PRACHPhysical Random Access Channel is the Physical Random Access Channel and is used by UEs to request an uplink allocation from the base station. In the frequency domain, PRACH spans 6 resource blocks of spectrum. The frequency location of PRACH is determined by upper layers. …
What is prach configuration index?
The PRACH Configuration Index (prachConfIndex) parameter specifies the index, which informs UE of which frame number and which subframe number (SFN) within the frame has PRACH resources. RACH root sequence’s planning is dependent on PRACH cyclic shift.
Why is Rach needed?
Another purpose of RACH process is to obtain the resource for Msg3 (Message 3). RRC Connection Request is one example of Msg3 and there are several different types of Msg3 depending on situation.
What is prach occasion?
a PRACH occasion in a PRACH slot is valid if it is within UL symbols, or. a PRACH occasion in a PRACH slot is valid if it does not precede a SS/PBCH block in the PRACH slot and starts at least Ngap symbols after a last downlink symbol and at least Ngap symbols after a last SS/PBCH block transmission symbol.
What is prach resource index in LTE?
The PRACH mask index identifies which PRACH resources the UE is allowed to use for its access attempt (see 36.32, section 7.3). More specifically, the mask defines in whichPRACH (or PRACHs) within a frame a UE can transmit a Random Access Preamble.
What is prach used for?
Physical Random Access Channel (PRACH) is an uplink channel used by UE for connection request purpose. PRACH is used to carry the RACH transport channel data.
Who determines prach configuration index?
For example, if PRACH Configuration Index is 10 as shown in the following example, the preamble format 0 is used. The you may ask ‘Who determines PRACH Configuration index?’ . The answer is ‘eNB determines it via prach-Configindex IE in SIB2’.
What is RACH failure LTE?
If the UE does not receive a response within the random access window or fails to verify the response, the response fails. In this case, if the number of random access attempts is smaller than the upper limit, the UE retries random access. Otherwise, random access fails.