What is T_ADD,T_DROP and T_TDROP in CDMA?
Pilot Detection Threshold (T_ADD)
Any Pilot that is strong but is not in the Handoff Direction Message is a source of interference. This Pilot should be immediately moved into the active set for handoff to avoid voice/data degradation or a possible drop call. T_ADD affects the percentage of MS in handoff. It should be low enough to quickly add useful Pilots and high enough to avoid false alarms due to noise.
Pilot Drop Threshold (T_DROP)
This affects the percentage of MS in handoff. It should be low enough to avoid dropping a good Pilot that goes into a short fade . It should be high enough not to remove quickly useful Pilots in the active or candidate state.
Pilot Drop Timer (T_TDROP)
This is a timer. Whenever the strength of a Pilot in the active set falls below a value of T_DROP, a timer is started by the MS. If the Pilot strength goes back above T_DROP, the timer is reset; otherwise the timer expires when a T_TDROP has elapsed since the Pilot strength has fallen below T_DROP. Every MS maintain a handoff drop timer for each Pilot in the Active and Candidate Sets.