The mobile station continuously searches for Pilots to detect the presence of other CDMA signals that have the same carrier frequency and measures the strength (received Ec/Nt) of the pilots. 
When the mobile station detects a Pilot of sufficient strength that is not associated with the serving cell/sector, it sends a message to the serving base station. The cellular network decides which neighbor base stations can be involved in a Handoff. 
Handoff Candidate divided in Four Category in CDMA,
  • Active Set : The pilots associated with the Forward Traffic Channels assigned to the mobile station. 
  • Candidate Set :The pilots that are not currently in the active set but have been received by the mobile station with sufficient strength to indicate that the associated Forward Traffic Channels could be successfully demodulated. 
  • Neighbor Set : The pilots that are not currently in the Active Set or the Candidate Set and are likely candidates for Handoff. 
  • Remaining Set : The set of all possible pilots in the current on the current CDMA frequency assignment, excluding the pilots in the Neighbor Set, the Candidate Set, and the Active.