Method for reducing sounding overhead by shortening trigger-based physical layer protocol data unit duration for trigger-based implicit feedback, and associated apparatus

An access point (AP) device, for reducing sounding overhead by shortening trigger-based (TB) physical layer (PHY) protocol data unit (PPDU) duration (TB-PPDU duration) for trigger-based implicit feedback, the AP device comprising:

• a processing circuit, arranged to control operations of the AP device;
• and
• at least one communication control circuit, coupled to the processing circuit, arranged to perform communication control, wherein the at least one communication control circuit is arranged to perform wireless communication operations with at least one other device within a wireless communication system for the AP device, wherein a non-access-point station (non-AP STA) device is wirelessly linking to the AP device, and a number of sounding dimension of the non-AP STA device is less than a maximum number of spatial streams of the AP device;
• wherein:
• the AP device is arranged to transmit a first frame regarding TB-sounding as well as a trigger frame, with at least one field of at least one frame among the first frame and the trigger frame being set to shorten the TB-PPDU duration;
• and
• the AP device is arranged to receive a sounding feedback having the TB-PPDU duration to be the trigger-based implicit feedback, for use of generating a beamforming steering matrix for transmission beamforming, wherein the at least one field is set to shorten a time for receiving a useless part within the sounding feedback, for reducing the sounding overhead.