When to use Extend Cyclic Prefix (ECP)?

Hi Experts,
What is the difference between Normal & Extend Cyclic Prefix?
In Which case we will use ECP?
Most of the Operator will use Normal CP?
What about Extended CP?

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Extended Cyclic Prefix (ECP) is for SCS 60 KHz and for large cells.
ECP in 5G has only 12 symbols instead of 14 symbols.
Extended Cyclic Prefix is used for cells with large delay paths.

Complementary reading: What is CP (Cyclic Prefix) in LTE?

In 4G as well it’s same where subcarrier spacing 15 KHz.

Is that PRACH config you’re refering?

Nope, it’s the number of symbols and duration of symbols that is different for extended prefix.

PRACH config indicates subframe in which RACH transmit it’s huge table.
For 5G we have different config index used for FR1 and FR2.
Short PRACH format for 5G.
Long PRACH format for 4G.

Is any there any specific reasons why ECP is not used often?
Why we are using major NCP?

Main reason being planning and implementation.
I’ve done for dense cluster cities only but, in my knowledge I never seen extended cp used.
In Link Budget as well, we have option to select.
On which cell radius depend.

Extended CP reduces throughput compared to normal prefix.

Is it set by default by the time of implementation?
Can we configure it according to signal multipath variations?

We have parameter to select.

Thanks. So due to signal delay, Throughput will be less by using ECP?

Throughput is lower because we use 12 symbols instead of 14 symbols.

Never seen it used too… not even on high speed trains, etc.

Extended CP is used where is large propagation delays, like over 1-2 km delay path, large villages with hills around, etc.

Other usage of Extended Cyclic Prefix is for MBMS service, where resource block used extended cyclic prefix having 3 symbols in time domain and 24 subcarrier having 7.5 KHz subcarrier spacing.

ECP may be used in cases such as island sites, sea sites where UE are very far from BTS, large propagation.
It can impove coverage but reduce capacity.
And very few UE can support ECP, so it’s not deployed much in practice.

Normal CP can handle a propagation delay of ~1.4 KM ( 4.69 microseconds), whereas ECP can handle a propagation delay of ~5 KM (16.67 microseconds).