IEEE 802.11 ax is a type of WLAN in the IEEE 802.11 set of types of WLANs. It is designed to improve overall spectral efficiency especially in dense deployment scenarios. It is still in a very early stage of development, but is predicted to have a top speed of around 10 Gb/s (as tested by Huawei), it works in 2.4 and/or 5 GHz, in addition to MIMO and MU-MIMO it introduces OFDMA technique to improve spectral efficiency and also higher order 1024 QAM modulation support for better throughputs. Though the nominal data rate is just 37% higher comparing with 802.11ac, the new amendment will allow achieving 4X increase of user throughput thanks to more efficient spectrum usage. It is due to be publicly released in 2019.
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Technical improvements
The 802.11ax amendment will bring several key improvements over 802.11ac. 802.11ax addresses frequency bands between 1 GHz and 6 GHz. Therefore, unlike 802.11ac, 802.11ax will also operate in the unlicensed 2.4 GHz band. To meet the goal of supporting dense 802.11 deployments the following features have been approved.
Study Group High Efficiency WLAN
In 2012 and 2013, IEEE 802.11 received various submissions in its Standing Committee (SC) Wireless Next Generation (WNG) looking at issues of IEEE 802.11ac and potential solutions for future WLANs. Immediately after the publication of IEEE 802.11ac in March 2013, the IEEE 802.11 Working Group (WG) established Study Group (SG) High Efficiency WLAN (HEW).
SG HEW received a high number of technical contributions discussing various technologies such as Full Duplex Radios, OFDMA, Uplink MU-MIMO, and other enhancements. Other submissions debated potential use cases and requirements. SG HEW also developed the Project Authorization Request (PAR) and Criteria for Standards Development (CSD) documents that set the scope and are needed to approve a new Task Group (TG). SG HEW held it last meeting in March 2014. Afterwards, SG HEW was replaced by 802.11 TGax.
Task Group 802.11ax
During its first meeting TGax elected Osama Aboul-Magd as chairman and Yasuhiko Inoue as secretary. In September 2014, the two vice-chairmen Simone Merlin and Ron Porat were elected. Because of the comprehensive set of requirements and technical solutions foreseen, in November 2014 TGax decided to create four (sub) ad hoc groups. In January 2015, TGax elected Eric Wong, Reza Hedayat, and Brian Hart as chairmen of a MAC ad hoc group, Bo Sun, Jianhan Liu, and Yakun Sun as chairmen of a PHY ad hoc group, Sigurd Schelstraete, Kiseon Ryu, and Kaushik Josiam as chairmen of a Multi-user ad hoc group, and Laurent Cariou, Guido Hiertz, and Jae Seung Lee as chairmen of a Spatial Reuse ad hoc group. Continuing the work of SG HEW, TGax developed documents describing simulation scenarios, according channel models, and related evaluation methodologies. TGax furthermore decided to implement a development process previously applied in 802.11ac. The process foresaw creation a specification framework document (SFD) that collects requirements and desired features of the 802.11ax amendment. Various submissions contributed to the SFD. According to the TGax selection procedures a feature or mechanism was added to the SFD once it was approved by a 75% majority. Beginning of 2016 SFD development ended and on 2 March 2016 a draft specification was uploaded. This submission specification forms the basis of the first of 802.11ax draft amendment.
Alleged Illegal actions of DensiFi SIG
On 16 June 2016 IEEE 802.11 voting member and TGax attendee Graham Smith filed a complaint with the IEEE 802.11 WG chairman Adrian Stephens about alleged dominance in TGax. In his e-mail to the chairman, G. Smith complaints about his technical contributions being excluded from the 802.11ax draft amendment because of various entities engaging their employees in illegal agreements. Because of the complaint, the 802.11 WG chairman formed an investigation team. Since the WG chairman declares himself conflicted he appointed the 802.11 WG 2nd Vice Chair Dorothy Stanley as Investigating Officer (IO). For interviewing TGax members and the creation of a report the IO has been furthermore supported Roger Marks and Mike Montenmurro. Over a period of two months, the IO and her team conducted interviews, reviewed documents, and collected evidence regarding the complaint. On 9 November 2016, the IO published her report. The report reveals that the secret Special Interest Group (SIG) called DensiFi applied illegal tricks over a period of at least two years. The report revealed that this cartel had Intel, LGE, Broadcom, Marvell, MediaTek, Qualcomm, Huawei, Orange, NTT, NTT DoCoMo, Samsung, ZTE, Apple, Cisco, Sony, Toshiba, Newracom, and Quantenna as member companies. According to the report the "investigating team conclude that dominance has occurred through the mechanism of ‘superior leverage, strength or representation’ with the effect of excluding viewpoints of non-SIG participants from ‘fair and equitable consideration’ within the 802.11ax Task Group."
Although Broadcom’s legal department proposed the IEEE 802 Executive Committee (EC) rejecting "the investigating team’s findings" the EC welcomed the report and approved actions against DensiFi without any dissenting vote. The actions foresaw to reduce "the vote of all individuals affiliated with DensiFi SIG members as a single vote in WG and TG motions and letter ballots related to 802.11ax until such time […] the SIG is no longer active."
In his submission and a related email the 802.11 WG chairman explained his interpretation of the actions against DensiFi. The chairman announced that he would re-instantiate voting rights of each voting member affiliated with a company participating in DensiFi once such company declared independence from the cartel. In his email to the chairman the appellant G. Smith predicted that according to the interpretation former DensiFi "members will effectively face zero consequences as a result of their 3 years(?) of activity […] against the rules and interests of 802.11. It is quite obvious that […] we will see all the DensiFy [sic] companies send in their letters so that by the next meeting it will be business as usual." Beginning 2016-11-30 former DensiFi member companies started declaring their independence from the SIG. On 15 December 2016 the two last companies declared independence. In their statements, Cisco, Samsung, and Marvel equally explain that "all operations of DensiFi SIG ended on 2016-12-03 at 01:00 UTC." At its January 2017 meeting the 802.11 WG chairman reported therefore, "no 802.11 members remain subject to special measures." In his report the chairman also informed that an appeal was filed against the IEEE-SA Standards Board’s declaration that it "ratified the actions taken 11 November 2016 by the IEEE 802 LMSC Sponsor in connection with the 802 TGax complaint." The appellants complain that "the remedies adopted ‘prove[d] to be insufficient’ as implemented and thus do not constitute or provide for any meaningful ‘corrective action’".
Because of the DensiFi scandal, inappropriate behavior in 802.11ai and prior cases of dominance the IEEE 802 EC created new instructions highlighting that attendees "have an obligation to act and vote as an individual and not under the direction of any other individual or group. Your obligation to act and vote as an individual applies in all cases, regardless of any external commitments, agreements, contracts, or orders. […] By participating in IEEE 802 meetings, you accept these requirements. If you do not agree to these policies then you shall not participate."
Letter ballot on draft 1.0 of 802.11ax
Between 1 December 2016 and 8 January 2017 the IEEE 802.11 WG held a letter ballot on the first draft of 802.11ax. This ballot failed with only 58% approval. In response to the ballot, TGax received 7,418 comments. Because of the large number of comments to be addressed, the TGax Chairman Osama Aboul-Magd assumed that the approval of draft 2.0 of 802.11ax will be delayed to September 2017. Consequently, publication of the 802.11ax amendment is expected to delay until 2019.
In response to the TGax Chairman’s call for verification of the 802.11ax PAR several simulation results were presented. In 2016, various simulation results indicated that the goal of four times performance improvement defined in the PAR might not be achievable. As it became evident that the 802.11ax draft amendment might not meet the intended performance improvements, TGax decided to modify the simulation scenario assumptions for generating more favorable results. Further simulation studies are expected.