Subject: [its] Finalized 802.11p adapter vs 802.11a adapter with AR5414 Chipset

From: Song Gao <[email-masked]>
Date: Thu, 17 Oct 2013 08:19:41 -0500

Hello,

We are research lab in Auburn University. We are trying to implement
DSRC communication on trucks and we need some help on choosing
devices.

We were about to order DCMA-86P2[1] from Unex until we noticed that
some of 802.11a cards [2] in our lab have the same chipset (AR5414),
which is also able to work on 802.11p frequencies. Since the chipset
is the same, we assume driver (ath5k based) would behave the same on
both devices.

We are wondering if there's any advantage that finalized 802.11p
adapter (e.g. the Unex one) would give over using AR5414 powered
802.11a card?

Other advices on adapters or drivers would also be much appreciated!

Thanks in advance!

[1] http://unex.com.tw/product/dcma-86p2
[2] http://www.mikrotik.com/pdf/R52.pdf

--
Song Gao
http://song.gao.io/

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From: "Konstantin A. Khait" <[email-masked]>
Date: Thu, 17 Oct 2013 18:24:41 +0400

You can download proper drivers for OpenWrt from our github.

Hello,

Thanks in advance!

--
Song Gao
http://song.gao.io/
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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 18 Oct 2013 09:39:27 +0200

The unex and mikrotik specs are on the web sites that you referred.

What I am looking for in a card/driver combination is its max
transmitted power level.  I need it to reach as much as 33 dBm, in order
to have vehicle-to-vehicle communications over a distance of as much as
1km, in a single IP hop, offering a bandwidth of 12 Mbit/s.

The unex specs seem to approach this (specs say Peak Transmit Power 29
dBm), whereas the microtik spec seems to say max 19dBm.

Where I live the regulator imposes that for 802.11a/b/g/n to be "Radio
LAN" and use a max of 20dBm (approx. 50m distance), but for "ITS" -
presumably 802.11p - it allows for 33 dBm (approx. 1km distance).

This 33dBm-vs-20dBm may be a matter of driver, or of hardware.  I.e.
same hardware with different driver knob values may reach both power
levels.  Or it may be a matter of hardware: a particular hardware may
never reach 33dBm regardless of effort put in driver.

The specs are important.

Yours,

Alex

Le 17/10/2013 15:19, Song Gao a écrit :
> [1] http://unex.com.tw/product/dcma-86p2 [2]
> http://www.mikrotik.com/pdf/R52.pdf
>
> -- Song Gao http://song.gao.io/
> _______________________________________________ its mailing list
> [email-masked] https://www.ietf.org/mailman/listinfo/its
>
>

---

From: "Konstantin A. Khait" <[email-masked]>
Date: Fri, 18 Oct 2013 12:36:32 +0400

Guys,

We did lab and field test of Unex DC86 and several Mikrotik modules. We 
also did some reverse engineering of the schematics. Unex module seems to 
be full analog of R5H, which is now out of production. R52H and R52nM are 
having less output power, but it doesn't significantly affect the field 
performance, which is much more affected by applied antenna.
Actually we have drivers for 802.11p for both ATH5K and ATH9K in public 
domain. For 9k Mikrotik produces several modern models with up to 1000mW 
output. So, there are no reasons to pay extra costs for Unex. They don't do 
anything special.

Thanks,
Kostia

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From: Alexandru Petrescu <[email-masked]>
Date: Fri, 18 Oct 2013 11:13:54 +0200

Thanks!  That is good to know and to prefer cheaper hardware/driver. 
That should be done for any initial and next steps.

Le 18/10/2013 10:36, Konstantin A. Khait a écrit :[...]

> domain.

That is good to know.

> For 9k Mikrotik produces several modern models with up to 1000mW

1000mW is approximately 30 dBm.

But, it seems to me,

EU/ETSI allows for 33 dBm (2Watt).

US/FCC allows for 44.8 dBm (30Watt).

Looking forward for any hardware/driver able to do that.

Alex

FCC-03-324A1.pdf
en_302663v010201p.pdf

> output. So, there are no reasons to pay extra costs for Unex. They don't
> do anything special.
>
> Thanks,
> Kostia
>
>

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From: Song Gao <[email-masked]>
Date: Fri, 18 Oct 2013 10:40:47 -0500

Thanks Alex and Konstantin. That's quite informative!

-- 
Song Gao
https://song.gao.io/

On October 18, 2013 at 4:14:27 AM, Alexandru Petrescu ([email-masked]) wrote:

That is good to know.

But, it seems to me,

Alex

FCC-03-324A1.pdf
en_302663v010201p.pdf

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From: Henry Ptasinski <[email-masked]>
Date: Thu, 17 Oct 2013 10:24:05 -0600

>From the specs, Unex has optimized the RF design on the DCMA-86P2 for
better rejection of signals outside the DSRC band.  The board also has
higher TX power and better RX sensitivity.  Overall performance (range,
throughput, interference rejection) in DSRC applications should be
better with the Unex cards.  Depending on the specific research you're
planning on doing, the extra performance may or may not be relevant.

On the other hand, the Unex board will perform worse in non-DSRC
frequencies.  If you need to use the boards for anything other than
DSRC, the regular 802.11a cards would likely be a better general-purpose
choice.

---
Henry Ptasinski
[email-masked]

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From: Henry Ptasinski <[email-masked]>
Date: Fri, 18 Oct 2013 12:34:49 -0600

> never reach 33dBm regardless of effort put in driver.

Absolutely.

Given the added power handling, heat dissipation, etc required to get to
29dBm, most hardware labeled as 20 dBm really wont be able to go that high.

Also note that pushing a card past it's certified transmit power, if
possible in SW, may overdrive the RF front end.  This could result in a
distorted spectrum (e.g. significantly increased sidelobes) that is out
of regulatory compliance.

I think that FCC limit on 11a is 29 dBm transmiter power (in the 5.725 ‐
5.825 GHz band), which can be coupled with a max 6 dBi antanna, for a
max 35 dBm EIRP.

---
Henry Ptasinski
[email-masked]