Method of handling random access procedure and related communication device

A method of handling random access procedure for a network in a wireless communications system, the method comprising:

• configuring a plurality of access points or a plurality of component carriers with at least one of a plurality of physical random access channel (PRACH) resources, a plurality of preamble formats, and a plurality of preamble sequences;
• whereby a mobile device of the wireless communication system uses at least one of the plurality of PRACH resources, the plurality of preamble formats, and the plurality of preamble sequences to access at least one of the plurality of access points or the plurality of component carriers when performing at least a random access procedure;
• after the mobile device accesses on at least one of the plurality of PRACH resources with at least a preamble transmission, determining which access points or component carriers the mobile device accesses to according to at least one of the accessed PRACH resources, used preamble formats, and used preamble sequences, or determining which access points or component carriers the mobile device accesses to according to at least one of uplink transmission resources that the mobile device accesses to, a temporary cell radio network temporary identifiers (T-CRNTIs) used by the mobile device, a modulation and coding schemes (MCSs) used by the mobile device, a reference signal cyclic shift values used by the mobile device, and an indications for a uplink transmission when receiving the uplink transmissions;
• and
• utilizing at least one of the plurality of access points which receive the at least a preamble to respond to the mobile device at least a random access response (RAR) message addressed by at least a random access radio network temporary identifier (RA-RNTI) associated with the at least one of the accessed PRACH resources.