Method of handling uplink synchronization and related communication device

A mobile device of a wireless communication system for handling uplink synchronization, the mobile device capable of receiving and transmitting on a plurality of component carriers, the mobile device comprising:

• a processor for executing a program;
• and
• a storage unit coupled to the processor for storing the program;
• wherein the program instructs the processor to perform the following steps:
• performing a first random access procedure on a first component carrier of the plurality of component carriers to establish uplink synchronization on the first component carrier;
• and
• performing a second random access procedure on at least a component carrier of the plurality of component carriers to establish uplink synchronization on the at least a component carrier, which comprises:
• receiving at least a random access preamble assigned by a network of the wireless communication system for the at least a component carrier;
• sending at least a random access preamble message including the at least a random access preamble to the network;
• and
• receiving a random access response message on the first component carrier corresponding to the at least a random access preamble message from the network, wherein the random access response message includes at least a timing advance value determined by the network according to the at least a random access preamble message.

A method of handling uplink synchronization for a mobile device capable of receiving and transmitting on a plurality of component carriers in a wireless communication system, the method comprising:

• performing a random access procedure on a first component carrier of component carriers with the same timing advance value to obtain a timing advance value;
• and
• managing a plurality of time alignment timers each corresponding to some of the plurality of component carriers for indicating a synchronization state on the component carriers with the same timing advance value, wherein the managing step comprises:
• starting or restarting the time alignment timer when a timing advance command in a random access response message of the random access procedure is received for the first component carrier, and a random access preamble of the random access procedure is not selected by the mobile device or the time alignment timer is not running.

A mobile device of a wireless communication system for handling uplink synchronization, the mobile device capable of receiving and transmitting on a plurality of component carriers, the mobile device comprising:

• a processor for executing a program;
• and
• a storage unit coupled to the processor for storing the program;
• wherein the program instructs the processor to perform the following steps:
• performing a random access procedure on a first component carrier of component carriers with the same timing advance value to obtain the timing advance value;
• and
• managing a plurality of time alignment timers each corresponding to some of the plurality of component carriers for indicating a synchronization state on the component carriers with the same timing advance value, wherein the managing step comprises:
• starting or restarting the time alignment timer when a timing advance command in a random access response message of the random access procedure is received for the first component carrier, and a random access preamble of the random access procedure is not selected by the mobile device or the time alignment timer is not running.