Why there is restriction for SR transmission only in PUCCH format 0 and 1?

Question

in same PUCCH occasion if UE has more than one PUCCH resource for SR transmission then How UE selects the resource.

Answer 1

For SR transmission, PUCCH format 1 is used. PUCCH format 1,1a,1b.
These formats used by 3GPP for SR due to convenient Physical resource allocation mapping .
Location of PUCCH resources are on the edge of bandwidth allocated.SR indication is transmitted based on the configured sr-PUCCHResourceIndex in the SFN and sub-frame number. The timing and physical control channel configuration for SR transmission can be configured in higher layer signaling message.

Comments

Hi,
Thank you, But what is convenient in PUCCH format 1 for SR, why not other PUCCH format?

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Basically PUCCH format 1,1a,1b choose for SR, 1 bit HARQ/SR & 2 bit HARQ/SR.
PUCCH format 1 does not takes any bits per subframe & also there is No Ack/Nack which is suitable for SR. Enodeb only detects the presence of energy in the PUCCH channel & SR information only involves the request in order to get the resources.   
I think this is the reason why PUCCH format 1 use SR only.