Post network entry connection method in millimeter wave communication system and related apparatuses using the same

In one of the exemplary embodiments, the disclosure is directed to a post network entry connection method applicable to a user equipment. The method would include not limited to: receiving a time unit which may include a payload region and a downlink header region which may include a first BQMR for a first scan beam and a second BQMR for a second scan beam; obtaining a first reference signal from the first BQMR and a second reference signal from the second BQMR; calculating a first signal quality measurement by using the first reference signal and calculating a second signal quality measurement by using the second reference signal; selecting the first scan beam based on the first signal quality measurement being better than at least the second signal quality measurement; and transmitting the first signal quality measurement which corresponds to the first scan beam via another time unit.