The use of D2D IEEE 802.11aa communications will reduce the amount of IEEE 802.11ak airtime required for Extended IEEE 802.11ai each fransmission by functionalities allowing higher data IEEE 802.11aq rates and avoiding the IEEE 802.11ay use of the AP as a : relay.Beamforming is IEEE 802.11ad an interesting feature for D2D communication ::: IEEE 802.11ax because it may allow PHY/MAC IEEE 802.11ac concurrent transmissions inside the same WLAN IEEE 802.11n by different groups of nodes. IEEE 802.11ah >t 20092010201120122013201420152016201720182019 Feature Amendment Objective Handoff duration below 100 ms by Fast handoff between APs IEEE 802.11ai-2016 implementing preemptive channel sensing and user authentication. STAs with D2D capability can decide to D2D/WiFi Direct WiFi Alliance feature create their own WLAN to communicate directly. Multi-technology APs and 1EEE802.11ak-2017 Interconnection of multiple WLANs. bridging capabilities Video traffic 1EEE8v02.11aa-2012 Stream prioritization and groupcast differentiation mechanisms. APs provide pre-association information AP/service selection lEEE802.11aq-2018 about the services offered to help STAs to choose between multiple APs Figure 6.Upcoming IEEE 802.11 amendments. with an external hard disk and instantaneous file very fast millimeter-wave communications.In exchange between a mobile phone and a pro- this situation,the STAs of any of those networks jector/smart television.The use of D2D com- should be able to communicate with the STAs in munications will reduce the amount of airtime any of the other WLANs.This is the aim of the required for each transmission by allowing higher IEEE 802.11ak-2017 amendment,which focuses data rates and avoiding the use of the aP as a on adding bridging capabilities to WLANs. relay.Beamforming is an interesting feature for Finally,next-generation WLANs will use traf- D2D communication because it may allow con- fic differentiation,flow admission control,and current transmissions inside the same WLAN by groupcast mechanisms from the IEEE 802.11e- different groups of nodes. 2007,IEEE802.11ae-2012 and IEEE802.11aa- IEEE 802.11ax-2019 aims to operate in the 2012 amendments to support multimedia traffic 2.4 and 5 GHz bands by superseding and inte- with the required QoS.Also,further advances in grating the IEEE 802.11n-2009 and IEEE power saving mechanisms are expected to keep 802.11ac-2013 amendments.In a few years,every WLAN energy consumption as low as possible. single AP will most likely implement two IEEE 802.11ax-2019 instances that independently oper- CONCLUSION ate at 2.4 and 5 GHz,with a IEEE 802.11ah-2016 We have reviewed some technological options instance at 1 GHz for M2M and long-range com- that could be included in the IEEE 802.11ax- munications,and one IEEE 802.11ad-2012 (or 2019 amendment for next-generation WLANs. the future IEEE 802.11ay-202x)at 60 GHz for Individually,all those solutions offer some per- IEEE Wireless Communications.February 2016 45IEEE Wireless Communications • February 2016 45 with an external hard disk and instantaneous file exchange between a mobile phone and a pro￾jector/smart television. The use of D2D com￾munications will reduce the amount of airtime required for each transmission by allowing higher data rates and avoiding the use of the AP as a relay. Beamforming is an interesting feature for D2D communication because it may allow con￾current transmissions inside the same WLAN by different groups of nodes. IEEE 802.11ax-2019 aims to operate in the 2.4 and 5 GHz bands by superseding and inte￾grating the IEEE 802.11n-2009 and IEEE 802.11ac-2013 amendments. In a few years, every single AP will most likely implement two IEEE 802.11ax-2019 instances that independently oper￾ate at 2.4 and 5 GHz, with a IEEE 802.11ah-2016 instance at 1 GHz for M2M and long-range com￾munications, and one IEEE 802.11ad-2012 (or the future IEEE 802.11ay-202x) at 60 GHz for very fast millimeter-wave communications. In this situation, the STAs of any of those networks should be able to communicate with the STAs in any of the other WLANs. This is the aim of the IEEE 802.11ak-2017 amendment, which focuses on adding bridging capabilities to WLANs. Finally, next-generation WLANs will use traf￾fic differentiation, flow admission control, and groupcast mechanisms from the IEEE 802.11e- 2007, IEEE 802.11ae-2012 and IEEE 802.11aa- 2012 amendments to support multimedia traffic with the required QoS. Also, further advances in power saving mechanisms are expected to keep WLAN energy consumption as low as possible. Conclusion We have reviewed some technological options that could be included in the IEEE 802.11ax- 2019 amendment for next-generation WLANs. Individually, all those solutions offer some per￾Figure 6. Upcoming IEEE 802.11 amendments. 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 t Extended functionalities IEEE 802.11ay PHY/MAC Feature Amendment Objective Fast handoff between APs IEEE 802.11ai-2016 Handoff duration below 100 ms by implementing preemptive channel sensing and user authentication. D2D/WiFi Direct WiFi Alliance feature STAs with D2D capability can decide to create their own WLAN to communicate directly. Multi-technology APs and bridging capabilities IEEE 802.11ak-2017 Interconnection of multiple WLANs. Video traffic differentiation IEEE 8v02.11aa-2012 Stream prioritization and groupcast mechanisms. AP/service selection IEEE 802.11aq-2018 APs provide pre-association information about the services offered to help STAs to choose between multiple APs IEEE 802.11ah IEEE 802.11ax IEEE 802.11aq IEEE 802.11ad IEEE 802.11ai IEEE 802.11ak IEEE 802.11aa IEEE 802.11ac IEEE 802.11n The use of D2D communications will reduce the amount of airtime required for each transmission by allowing higher data rates and avoiding the use of the AP as a relay. Beamforming is an interesting feature for D2D communication because it may allow concurrent transmissions inside the same WLAN by different groups of nodes