Abstract
The traffic demand of wireless networks is expected to increase 1000-fold over the next decade. In anticipation of such increasing data demand for dense networks with a large number of stations, IEEE 802.11ax has introduced key technologies for capacity improvement including Orthogonal Frequency-Division Multiple Access (OFDMA), multi-user multi-input multi-output (MU-MIMO), and greater bandwidth. However, IEEE 802.11ax has yet to fully define a specific scheduling framework, on which the throughput improvement of networks significantly depends. Even within a 20 MHz of bandwidth, users experience heterogeneous channel orthogonality characteristics across sub-carriers, which prevents access points (APs) from achieving the ideal multi-user gain. Moreover, frequency selectivity increases as bandwidth scales and correspondingly severely deteriorates multi-user MIMO performance. In this work, we develop a novel channel adaptation scheme, named selectivity-aware multi-user MIMO (SAMU), to combat the issue of frequency selectivity and support coexistence among users in the network by jointly assigning subsets of sub-carriers to selected users and implementing downlink MU-MIMO. To do so, we first investigate the channel characteristics of an indoor environment. We then consider the frequency selectivity of current and emerging WiFi channel bandwidths to optimize multi-user MIMO by dividing the occupied sub-carrier resources into equally sized sub-channels according to the level of frequency selectivity. In our design, each sub-channel is allocated according to the largest bandwidth that can be considered frequency-flat, and an optimal subset of users is chosen to serve in each sub-channel according to spatial orthogonality. As a result, we support more simultaneous users than current 802.11 designs and achieve a significant performance improvement for all users in the network. Additionally, we propose a selectivity-aware high efficiency (SA-HE) mode, which is based on and fully backward compatible with the existing IEEE 802.11ax standard. Finally, over emulated and real indoor channels, we show that SAMU can achieve as much as 84.8% throughput improvement compared to existing multi-user MIMO schemes in IEEE 802.11ax.
Highlights
To address the exponentially increasing traffic demand in wireless networks, the Wireless fidelity (WiFi) community is currently developing IEEE 802.11ax to improve the efficiency of WiFi networks in dense scenarios [1, 2]
2 We develop protocols and algorithms for a selectivity-aware multi-user multi-input multi-output (MU-MIMO) scheme, selectivity-aware multi-user MIMO (SAMU), which considers the degree to which frequency selectivity is present on the channel, allocates frequency-flat sub-channels, and chooses an optimal subset of users for each sub-channel to improve the spatial efficiency of the network
We set the total number of users served by an Access point (AP) to be 256 and use an equal-power echo channel in this experiment
Summary
To address the exponentially increasing traffic demand in wireless networks, the WiFi community is currently developing IEEE 802.11ax to improve the efficiency of WiFi networks in dense scenarios [1, 2]. The AP attempts to select an optimal subset of users that maximizes the overall spatial efficiency. Optimal user selection is usually based on the traffic demands of and channel characteristics experienced by all the users. With frequency selectivity, a subset of users may have good spatial reuse on some carrier frequencies due to the orthogonality of the sub-channels experienced by each user, but poor orthogonality on other frequencies due to the frequency diversity across the channel bandwidth. The critical enhancements of implementing OFDMA and MU-MIMO from the latest IEEE 802.11ax draft standard are known to independently improve the system capacity. There is currently no such scheme to adapt the bandwidth of MU-MIMO WiFi according to the frequency selectivity of the channel
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: EURASIP Journal on Wireless Communications and Networking
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
