LTE SRS rules

 

SRS is used to predict channel quality for UL。According to the standard, SRS should follow the rules,

 

PUCCH:

• PUCCH 2/2a/2b
  • SRS region should not overlap with PUCCH 2/2a/2b, as PUCCH 2/2a/2b can not be shortened
  • If a UE has PUCCH 2/2a/2b to send, no SRS can be scheduled in the same subframe
• For PUCCH 1/1a/1b
  • SRS region could overlap with PUCCH 1/1a/2a.
  • If Simul-AN-and-SRS = FALSE, UE should not send SRS at its SRS opportunity if this UE has PUCCH 1/1a/1b to send
  • If Simul-An-and-SRS = TRUE, Cell-specific SRS = TRUE, Ue should use shortened PUCCH. If it is UE’s SRS opportunity, it sends out SRS.

 

PUSCH

• UE’s PUSCH should be shortened,
  • if it overlap with Cell specific SRS region
  • If it has SRS to send (SC-OFDM property, no overlap in the last symbol; 212 5.2.4.1)
• If UE is sending PUSCH corresponding to RAR or the retransmission of it, UE should not send SRS
•  

 

PRACH

• In UpPTS, whenever SRS transmission instance overlaps with the PRACH region for preamble format 4 or exceeds the range of uplink system bandwidth configured in the cell, the UE shall not transmit SRS

 

Note: If CQI is sent in PUSCH, SRS should be sent