1. A method of improving performance of a multi-subscriber-identification-module (multi-SIM) wireless communication device having a first radio frequency (RF) resource associated with at least a first SIM and a second RF resource associated with a second SIM, wherein the first RF resource is enabled to support operations on at least the first SIM, the method comprising: detecting that the second RF resource is in a deactivated state; determining whether the first RF resource is in idle mode; and in response to determining that the first RF resource is in idle mode: identifying idle-mode tasks associated with the first SIM to be performed by the first RF resource; identifying parallelism parameters that provide criteria to assist scheduling simultaneous idle-mode tasks; identifying possible parallel task combination sets based on the identified idle-mode tasks associated with the first SIM and the parallelism parameters; selecting a parallel task combination set; and assigning at least one of the identified idle-mode tasks associated with the first SIM to each of the first and second RF resources according to the selected parallel task combination set.