Wireless local area networks (LANs), typified by IEEE (Institute of Electrical and Electronics Engineers) 802.11, have in recent years been widespread, leading to an increase in the information amount of transmitted contents and the number of wireless LAN-capable products. Therefore, to improve the efficiency of communication over an entire network, the standard IEEE 802.11 is still being enhanced.
In the 802.11ac standard, which is an example enhanced version of the standard IEEE 802.11, multi-user multi-input multi-output (MU-MIMO) is employed for a downlink (DL). MU-MIMO is a technique for allowing transmission of a plurality of signals during the same period of time through space-division multiplexing. The technique can improve the efficiency of use of frequencies, for example.
However, different communication apparatuses may transmit frames during different transmission time periods. In this case, the number of multiplexed frames fluctuates during a period of time when the frames are received. Therefore, the reception power of a communication apparatus that receives multiplexed frames fluctuates during the reception time period. The fluctuation of the reception power may have an influence on the performance of reception. To address this problem, a technique of transmitting frames during equal transmission time periods has been proposed.
For example, Patent Literature 1 describes a communication apparatus that appropriately adds a padding to a plurality of frames having different transmission time periods and thereby transmits the plurality of frames during equal transmission time periods.
In addition, Patent Literature 2 describes a communication method in which a communication apparatus serving as an access point (AP) transmits uplink (UL) permission information designating a transmission time period of a UL frame and a communication apparatus receiving the UL permission information transmits a UL frame over the designated transmission time period.