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ScientificWorldJournal. 2014;2014:920937. doi: 10.1155/2014/920937. Epub 2014 Jul 24.

Beamforming transmission in IEEE 802.11ac under time-varying channels.

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Department of Information and Communication Engineering, Yeungnam University, Gyeongsan 712-749, Republic of Korea.
School of Information and Communication Engineering, Chungbuk National University, Cheongju 361-763, Republic of Korea.


The IEEE 802.11ac wireless local area network (WLAN) standard has adopted beamforming (BF) schemes to improve spectral efficiency and throughput with multiple antennas. To design the transmit beam, a channel sounding process to feedback channel state information (CSI) is required. Due to sounding overhead, throughput increases with the amount of transmit data under static channels. Under practical channel conditions with mobility, however, the mismatch between the transmit beam and the channel at transmission time causes performance loss when transmission duration after channel sounding is too long. When the fading rate, payload size, and operating signal-to-noise ratio are given, the optimal transmission duration (i.e., packet length) can be determined to maximize throughput. The relationship between packet length and throughput is also investigated for single-user and multiuser BF modes.

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