Abstract: A method of message retransmission and a user equipment (UE) using the same are provided, which are adapted for performing a discovery procedure of the proximity service (ProSe). The UE includes a transceiver and a processor. The transceiver is used to transmit and receive a wireless signal. The processor is coupled to the transceiver and configured to perform the following steps. A first message used for an authorization request of the ProSe is transmitted through the transceiver, and a first timer is started. If a second message responding to the first message is not received through the transceiver when the first timer is expired, a second timer is started. And, the first message is not transmitted through the transceiver before the second timer is expired.

Abstract: The present disclosure proposes a method of setting an attach attempt counter value by a network applicable under the circumstance when a UE attempts to attach to a network control entity of the network. The proposed method would include the UE transmitting an attach request message to a network. After transmitting the attach request message, the UE may receive an attach reject message in response to an attach failure. The attach reject message would contain an attach attempt counter value set by the network so as to generate a received attach attempt counter value which would overwrite whatever value that was currently stored in the attach attempt counter. The UE could then determine whether to continue attempting to attach to the network according to the attach attempt counter value received from the attach reject message.

Abstract: The present disclosure proposes a method for managing a tracking area identity (TAI) list to be used by a user equipment (UE), a user equipment using the same, and a communication system using the same. The present disclosure would include a UE which stores a forbidden TAI list. A mobility management entity (MME) would transmit a first message which includes a TAI List to the UE. The UE would then determine whether the TAI list and the forbidden TAI list contain a first tracking area which is on both the TAI list and the forbidden tracking area list. If that is the case, the UE may either remove the first tracking area from the TAI list or the UE may remove the first track area from the forbidden tracking area list. After the revision of the TAI list is complete, the UE may synchronize the TAI with the MME.

Abstract: A method of message retransmission and a user equipment (UE) using the same are provided, which are adapted for performing a discovery procedure of the proximity service (ProSe). The UE includes a transceiver and a processor. The transceiver is used to transmit and receive a wireless signal. The processor is coupled to the transceiver and configured to perform the following steps. A first message used for an authorization request of the ProSe is transmitted through the transceiver, and a first timer is started. If a second message responding to the first message is not received through the transceiver when the first timer is expired, a second timer is started. And, the first message is not transmitted through the transceiver before the second timer is expired.

Abstract: The present disclosure proposes a method for managing a tracking area identity (TAI) list to be used by a user equipment (UE), a user equipment using the same, and a communication system using the same. The present disclosure would include a UE which stores a forbidden TAI list. A mobility management entity (MME) would transmit a first message which includes a TAI List to the UE. The UE would then determine whether the TAI list and the forbidden TAI list contain a first tracking area which is on both the TAI list and the forbidden tracking area list. If that is the case, the UE may either remove the first tracking area from the TAI list or the UE may remove the first track area from the forbidden tracking area list. After the revision of the TAI list is complete, the UE may synchronize the TAI with the MME.

Abstract: The present disclosure proposes a status indicating method applicable to a user equipment and a user equipment using the same method. The proposed call status indicating method would include establishing a radio resource connection (RRC), performing a subscriber authentication procedure in response to establishing the RRC connection, transmitting or receiving a call setup message in which the call status is indicated within the call setup message in response to performing the subscriber authentication procedure, and performing a radio bearer setup procedure in response to transmitting or receiving the call status embedded in the call setup message. The call status would be indicated in an information element (IE) of the setup message such as an Important Status IE of the setup message.

Abstract: The present disclosure proposes a method of setting an attach attempt counter value by a network applicable under the circumstance when a UE attempts to attach to a network control entity of the network. The proposed method would include the UE transmitting an attach request message to a network. After transmitting the attach request message, the UE may receive an attach reject message in response to an attach failure. The attach reject message would contain an attach attempt counter value set by the network so as to generate a received attach attempt counter value which would overwrite whatever value that was currently stored in the attach attempt counter. The UE could then determine whether to continue attempting to attach to the network according to the attach attempt counter value received from the attach reject message.