# My preamble bits not enough for locking the timing recovery for a gaussian channel

I have chosen the preamble to be 48 bits (16 bits for carrier recovery+16 bits for timing recovery+ 16 bits for AGC of 30dB + 16 bits for phase ambiguity) As channel is gaussian and there is no much frequency offset i was thinking number of bits would be ok? but i am seeing sometimes they is timing error? I choose the preamble length based on some sample application? Is there any criteria to choose the preamble properly? Does it depend on snr, data rate ...

• Any specific reason for not using all the 48 bits for all of these 3 tasks. The algorithms for each of these task could perform better with access to all 48 bits Jun 4 '20 at 15:25

Timing recovery is implemented as a control loop (measure the timing error and adjust the sample offset) and therefore would have an acquisition time depending on the control loop parameters (loop BW). A reasonable estimate for acquisition time assuming the start of acquisition is in the linear capture range of the loop is the first order 10% to 90% rise time estimate of $$t_r = 0.35/BW$$ where $$t_r$$ is the estimated rise time from 10% to 90% and $$BW$$ is the loop BW in Hz. This is accurate for a first order loop and a reasonable estimate whenever there is a dominant pole as that would set the settling time.