Re: [ipwave] Risks for the future of OCB mode at 5.9GHz

Alexandre Petrescu <> Mon, 15 February 2021 11:37 UTC

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From: Alexandre Petrescu <>
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Date: Mon, 15 Feb 2021 12:37:21 +0100
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Subject: Re: [ipwave] Risks for the future of OCB mode at 5.9GHz
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A colleague pointed me to a video presentation of the problem of ITS-G5
vs C-V2X of January 21, 2021.  The presentation is brief.  It describes
this DSRC-vs-5G to be a problem because there are two standards, too
complex for deployers, and there is uncertainty for vehicle users.  IMHO
this uncertainty means : should I buy a Ford (C-V2X) or a VW (ITS-G5).
The presenter gives his oppinion: probably C-V2X will win.

Starting at around 21:02 (21min, 2 seconds) and lasts for about 2 minutes:

It is interesting to note how he compares the problem to the VHS vs
Betacam (presumably 5G is more of VHS, and ITS-G5/DSRC more of Betacam).
  Certainly, in around 1995 one would no longer work on anything Betacam.
  But they were both overcome by DVD and Bluray later, and now by 8K.

Also, the notion of direct communications in cellular systems (w/o base
station) existed long before 5G's PC5: 3G tried it too but it did not
work.  On another hand, in 3G there were no chips doing direct comm, no
spectrum, but in 5G there are.

All in all, I am not sure how will this unfold.

Possibly one way forward is to consider IP:
IP-over-PC5, and CAM-over-IP.

With IP tools at hand, the deployer would abstract from the DSRC-vs-PC5

What do you think is a possible way forward in the DSRC-vs-PC5 problem?


Le 12/02/2021 à 11:51, Alexandre Petrescu a écrit :
> I take advantage of a private message I received, in order to explain
> this in English, and to the public email list.
> I have some doubts about the future of OCB mode of WiFi.
> The recent re-allocation of spectrum by FCC in USA divides the space
>  typically used for OCB mode of 802.11 into a space for C-V2X (a 
> different mode than 802.11) and a space for WiFi.
> The C-V2X already ate the OCB mode at cca 5.8-5.9GHz, by allocation.
>  The WiFi is highly likely to eat the OCB mode at cca 5.4-5.8GHz. The
> reason of this is that WiFi is always and will always be looking at
> increasing the bandwidth; that increase can be achieved by widening
> the bands.  This is what WiFi 6E does when claiming to offer 4Gbit/s
> at 6GHz ('6' is a coincidence).
> In the past, what FCC did in USA at 5.9GHz was simply replicated in 
> Europe and other parts of the world.  Even if today much RSU 
> deployment exists in Europe (refs available) that runs OCB at
> 5.9GHz, and VW Golf 8s send CAMs to each other, many indicators point
> that it might be that these will disappear.  Such indicators are,
> for example, lack of OCB mode in smartphones, pushes from industry 
> alliance 5GAA towards 5G-V2X, lack of FCC reply to IPv6-over-OCB 
> comment, and other declarations.
> It is for these reasons that I tend to think the future of OCB mode 
> of 802.11 at around 5.9GHz is probably at risk.
> Alex
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