Hungtran,
The user will not have to perform the call more than once to go through, even though the indicator SDCCH failure rate is “high”. Just take your experience as a reference : how many times do you have to push the “call” button to make or answer a call ? only once…
Those failures are counting the “automatic” RACH attempts of the mobiles, as well as ghost RACH, etc… If you don’t agree, then perform drive-tests and experience the SDCCH failures. You’ll see that it’ll never happen.
This threshold is always the same, whichever the network. I told you already… alcatel officially recommend a threshold of 20%.
Contact the RTAC for additional infos…