Research On Beamforming Technology For IEEE802.11ax

IEEE 802.11 series of standards has gone through nearly 20 years, the data transmission rate changed from IEEE 802.11n Mbit/s to nowdays IEEE 802.1 lac Gbit/s, having been made considerable progress.However,in order to cope with the growing demand for wireless communications quality,IEEE 802.11 working group began to study the next major evolution of the WLAN standard—EEEE 802.11ax,which mainly aimed at those scenes that have high density of network equipments and large wireless access demands.Different from previous IEEE 802.11 standard,802.11 ax standard is to study how to enhance the user experience, such as the users’average throughput, in the edge of the user’s throughput and a single area of the throughput, etc. Beamforming technology has great advantages in expanding the AP coverage, suppressing the interference between users and improving the edge of the user’s throughput, especially in dense scenes, the enhanced beamforming technology is used to suppress the co-channel interference and to improve the signal to noise ratio of the received signal become more important.In this paper, we mainly study 802.11 ax downlink beamforming transmission scheme based on the existing beamforming (especially 802.11ac) technology, which mainly includes two parts:channel sounding and beamforming algorithms. For channel sounding, on the research of the existing channel sounding scheme and take the new features of 802.11ax into account, we design an efficient channel sounding scheme, expecially suitable for 802.11 ax dense scenes, which can reduce the polling overhead and is easy to implement.Then, to further reduce the CSI feedback overhead, we explore the subcarrier grouping technique in 802.11 ax. Combined with the proposed channel sounding scheme can not only reduce the polling overhead, but also reduce the CSI feedback overhead. For beamforming algorithms,we mainly discussed several linear beamforming algorithms which are widely used in WLAN system,such as SVD and GMD single-user beamforming and CI (channel inverse)、RI (regularized channel inverse)、BD (block diagonalization) multi-user beamforming and GZI algorithm which has less computational complexity than BD. In addition, we build a platform of 802.11 ax DL PHY, and simulate link level performance for those beamforming algorithms in the channel D model.The results show that under different modulation cardinality,using different beamforming technology can further improve system performance, regardless of single-user beamforming or multi-user beamforming.