Communication system with radio interworking capability and related user equipment

A communication system, comprising:

• a communication station, comprising:
• a transceiving circuit;
• a storage device configured to operably store an ANDSF (Access Network Discovery and Selection Function) rule set and a RAN (Radio Access Network) rule, wherein the RAN rule comprises one or more RAN validity conditions and a traffic specification, the ANDSF rule set comprises one or more ANDSF rules and each ANDSF rule comprises one or more ANDSF validity conditions and a prioritized network list;
• and
• a processor module, coupled with the transceiving circuit and the storage device, configured to operably control the transceiving circuit to transmit the ANDSF rule set and the RAN rule;
• multiple access points comprising a target access point;
• and
• a user equipment, comprising:
• a first communication circuit configured to operably receive the ANDSF rule set and the RAN rule transmitted from the transceiving circuit;
• a second communication circuit configured to operably communicate with the multiple access points;
• a memory device configured to operably store the ANDSF rule set and the RAN rule received by the first communication circuit;
• and
• a control circuit, coupled with the first communication circuit, the second communication circuit, and the memory device, configured to operably:
• select a target ANDSF rule out of the ANDSF rule set;
• determine whether the user equipment fulfills all validity conditions of the target ANDSF rule;
• select a target access network out of a prioritized network list defined by the target ANDSF rule when all validity conditions of the target ANDSF rule are fulfilled, wherein each of the valid conditions of the target ANDSF rule indicates at least one of:
• a location of the user equipment, and a time of a day;
• control the second communication circuit to scan the target access network so as to determine whether the target access network is present or not;
• determine whether the target access network fulfills all validity conditions of the RAN rule when the target access network is present, wherein each of the valid conditions of the RAN rule indicates at least one of:
• a traffic load of a RAN, a signal quality of the RAN, and a performance level of the RAN;
• and
• control the second communication circuit to steer traffic specified in the target ANDSF rule or traffic specified in the RAN rule to the target access point of the target access network when the target access network fulfills all validity conditions of the RAN rule,
• wherein the control circuit is further configured to operably compare a priority level of the target ANDSF rule with a priority level of the RAN rule so as to determine which traffic to be steered to the target access point, and
• wherein when the priority level of the target ANDSF rule is higher than the priority level of the RAN rule, the control circuit controls the second communication circuit to steer traffic specified in the target ANDSF rule to the target access point of the target access network.