G’day all
Note: this e-mail is important if you care about IEEE 802.11ax/be (aka Wi-Fi 6/7) operation in the 6 GHz band
During the mid-session plenary in Irvine, I presented
11-20-0057r2. The presentation outlined some of the outstanding issues related to the completion of ETSI BRAN work on Harmonised Standards for operation in the 5 & 6 GHz bands in Europe. I noted that while ETSI BRAN’s work is technically focused on operation
in Europe, it will have a global influence on how IEEE 802.11 is implemented and coexistence with technologies such as LAA & NR-U.
One of the two issues I highlighted was the proposal from some members of ETSI BRAN (two cellular focused companies in particular) that the rules in EN 303 687 (6 GHz Harmonised Standard) be written so that IEEE 802.11ax/be will no longer
be able to use its traditional Preamble Detection/Energy Detection (PD/ED) mechanism and thresholds (at -82 dBm for PD and -62 dBm for ED) in the 6 GHz band. Instead, it is proposed by these companies that IEEE 802.11ax/be be restricted to using an ED threshold
of -72 dBm in a typical environment.
This restriction is being proposed by these companies primarily as a result of 3GPP choosing not to take advantage of the well proven, and arguably more sophisticated, PD/ED mechanism. There is a now a fear by these companies that this
choice by 3GPP will result in LAA and NR-U obtaining less access in the 6 GHz band than 802.11ax/be equipment. In some cases, this might actually be true, particularly with the increasing use of OFDMA by 802.11ax/be in 6 GHz. In other cases, it is not. The
reality is complicated because coexistence between systems using heterogenous access across a wide diversity of use cases is inherently complicated. I would encourage those interested in the details to review the various submissions over the last five years
to
IEEE 802.11 Coex SC and
ETSI BRAN (via 802.11 members only site).
Some LAA & NR-U stakeholders are now attempting to mitigate their fears by insisting IEEE 802.11 be restricted from using the PD/ED mechanism (and thresholds) that has proved so successful for over 20 years. Instead of embracing PD/ED as
defined by IEEE 802.11, or even working with the IEEE 802.11 WG to define a form of PD/ED that works for both 802.11 and LAA/NR-U, they are proposing to restrict the operation of all technologies in 6 GHz, including IEEE 802.11, to ED-only at -72 dBm.
Interestingly, these stakeholders assert this restriction will make EN 303 687 more
technology neutral (a concept that is also contentiously asserted to be important in the context of ETSI Harmonised Standards). It is hard to believe that stopping IEEE 802.11 from doing something it has done for 20 years is
technology neutral. Indeed, an analysis of the legal definition of technology neutrality shows a more
technology neutral approach is to allow any technology to adopt ED-only at -72 dBm or PD/ED with its traditional thresholds (PD/ED + ED-only). However, the mere discussion of a legal concept like
technology neutrality just highlights the complexity of the debate.
During the Coex SC session on Thu PM1 in Irvine, a proposal was made that IEEE 802.11 WG should agree to a position in relation to the PD/ED issue. In particular, it was proposed by me (see
11-20-0171-02) that IEEE 802.11 WG recommend to ETSI BRAN that they adopt the PD/ED + ED-only mechanisms and thresholds from EN 301 893 (5 GHz) in EN 303 687 (6 GHz), as follows:
It is the IEEE 802.11 Working Group’s view that there is insufficient evidence at this time to revise the compromise established for 5 GHz (in EN 301 893) when considering 6 GHz operation (in EN 303 687). The
IEEE 802.11 Working Group therefore recommends that ETSI BRAN use the 5 GHz listening mechanism (as defined in EN 301 893) for 6 GHz operation (as defined in EN 303 687) too. This approach is aligned with the current draft of 802.11ax. Of course, the IEEE
802.11 Working Group will consider changing its recommendation if additional compelling evidence becomes available.
There was not sufficient support for this proposed position (and not many people in the room). The motion failed 5/4/10 (from memory). A few arguments were made against it. One speaker claimed such a position was not useful to progress
the debate in ETSI BRAN at this time, although he could not articulate a significant harm either. Other speakers took a view that seemed to be biased against the interests of IEEE 802.11. On the other side, a few speakers emphasized the importance of the IEEE
802.11 WG taking a position rather than passively standing by while the right to use PD/ED in 6 GHz was removed. The majority of the small number of people in the room (anyone can vote in a SC) were unable to take a position at the time.
I would like to make progress on this topic in Atlanta in March 2020. Indeed, the timing of the Atlanta meeting means any agreed position could be liaised to ETSI BRAN in time for their meeting the following week. At this time, my assumption
is that IEEE 802.11 WG would like 802.11ax/be to continue to use the PD/ED mechanism because that is what is documented in the 802.11ax draft. However, it is worth testing that assumption …
ACTION: Please respond to this e-mail (unicast or broadcast) if you believe that it is
acceptable for 802.11ax/be to be restricted to an ED threshold of -72 dBm in 6 GHz! If so, it would also be useful for you to articulate your reasoning.
This is not a mandatory ballot or survey, but it is requested that any responses be sent in the next 2-3 weeks to allow me time to collate them for the next Coex SC meeting. While I am not explicitly requesting those supporting the
opposite view (status quo) to do anything, I would welcome their perspectives too.
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Andrew Myles Chair, IEEE 802.11 Coex SC
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Andrew Myles |
Cisco Systems Limited |
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