Subject: Re: [its] novel use case for intra-vehicular wireless

From: Alison Chaiken <[email-masked]>
Date: Sat, 4 May 2013 10:14:41 -0700

Michael Richardson <[email-masked]> offers:
> It seems to me that distributing 5V/12V is possibly easier than data cables.

Every data cable in a car is a custom part that dealers and their
distributors must stock.  Consider the pain that the parts
distribution problem causes smaller companies with limited
distribution, and how much of a barrier to entry to new markets the
parts problem represents.     Tesla, for example, does not plan to
have a dealer network.    Also, cables have weight, especially copper
ones.   While wireless in the car initially struck me as crazy,
further consideration shows that there are a lot of advantages,
particularly for aftermarket devices with long battery life.    What
zeroconf, lightweight association protocol these devices might use
(6LoWPAN?) and whether they would be routable from outside the car are
the questions that pertain to IETF's areas of concern.

Ethernet has had difficulty making inroads because pulling coax with
adequate thermal stability and durability through body panels is slow
and expensive.    New demonstrations of twisted-pair Ethernet via
Broadcom's new BroadR-Reach PHY are slowly prying that door open.

User interface studies show that drivers can operate a display with at
most 4 segments while driving.    Mercedes and BMW reperesentatives in
a panel discussion organized by German-American Business Association a
year ago said that big consoles in the dash will be displaced by
smaller touchscreens dispersed around the cabin in coming model years.

> I realize that CAN has done lots in the space of data+power already.

CAN is going away, although it will be with us for a long time.    CAN
is too slow, too hard to interoperate with other buses, and is
insecure at OSI level 2 in a way that higher levels can only partly
fix.

-- 
Alison Chaiken                           [email-masked]
650-279-5600                            http://{she-devel.com,
exerciseforthereader.org}
The intermediary between the head and the hands must be the heart.
-- Thea von Harbou

---

From: Rex Buddenberg <[email-masked]>
Date: Sat, 04 May 2013 14:52:37 -0700

This requires a reply.

Having spent ~40 years or so in the comms business one way or another,
one of the things I've learned is never to do with radio what you can do
with wireline.  There are lots of reasons, but a couple of the enduring
ones are:
  - capacity.  The diff is about four orders of magnitude.  Or in terms
that might make a bit more impact: a radio channel is about 1/10,000 the
size attainable in a wired (either LAN or terrestrial-WAN) pipe.  
  - error rate.  Converse to the capacity issue, the error rate in radio
is about three orders of magnitude greater than wireline.  

These are physics issues, not standards or engineering ones.  Use the
radio to reach to mobile.  

More in line below:

On Sat, 2013-05-04 at 10:14 -0700, Alison Chaiken wrote:
> Every data cable in a car is a custom part 

Which is a good reason to shift to UTP ethernet throughout.  
     Several industries have gone through this custom cable evolution
and the end is usually the same.  
  - Navy ships have gone through this and ended up with multimode fiber
as the backbone (between compartments, penetrations of watertight
bulkheads) and wired ethernet elsewhere.  (There's no problem lighting
up a compartment with Wi-Fi).  
  - About 15 years ago, the rage was hybrid cables in your house -- a
bundle of fiber, coax and UTP put in before the drywall goes up.  Nope,
not anymore.  Run ethernet.  (Again, there's no problem with WiFi at the
fringe).
  - PLCs seem to reappear on about a 7 year cycle.  Only to get blown
away with mainstream internet.  Usually ethernet again.  
  - electrical power industry.  The legacy SCADA systems were stovepipe
top-bottom 15 years ago.  Increasingly they're internet style -- the
standard SCADA application looks a lot like SNMP.  
  - ... more....

>  Also, cables have weight, especially copper
> ones.  

So do it and do it once.  

There is a tail-dog issue here and know which is which.  It's a usual
habit in each of these industries to fix upon legacy end systems and try
to work from there.  Legacy end systems tend to be pretty dumb; they
require some computing to finish the data back at the other end of the
comms pipe.  That usually results in poor modularization which usually
results in a marketplace dead end.  The point of the internet is that
the smarts shift from the center to the edge ... and CPU horsepower
remains cheap ... so the end systems get smarter (and more modular).  It
makes a lot of sense in the information systems design to start with
'routable network' at the foundation ... work from there.  

>  While wireless in the car initially struck me as crazy,

No it's not, but keep it in its place.  I wouldn't use it for any of the
automobile sensor/control functions.  But it makes perfect sense to
light up a WiFi hotspot so your iPad has something to latch onto.
     For the WiFi to make sense, you have to get beyond the automobile
control discussion to the payload -- what's the four wheels supposed to
do?  If it's an ambulance, then you want to be able to use the same
diagnostic instruments you have in the hospital ICU in the ambulance.  

> Ethernet has had difficulty making inroads because pulling coax 

Coax?  I haven't seen operational Thicknet or Thinnet in a couple
decades now.  UTP hit the big time in the late '80s.

Building installations with UTP tend to go through a couple phases.  One
is 'hub per room' distribution which minimizes cabling.  But the second
stage is to buy a big honkin' hub, stick it in a wiring closet and pull
all the cable on the floor into that wiring closet -- lots more cable
run, but lots more management/troubleshooting sanity.  I don't know how
a discussion in an automobile would come out, but we've been here
before.  

> with

There are several flavors of ethernet that may be germane here.  All
share the same layer 3 interface, MAC, framing and addressing.  The only
diffs worth haggling are in the cable:
 - 'normal' ethernet cable usually comes with a 'Cat 5' label on the
box.  This cable usually has four pairs and the Cat 5 has to do with the
number of twists/inch (noise cancellation reasons).  Noise on the cable
length itself is usually not a problem, the crosstalk issues appear at
the hubs (near end crosstalk where 15689  cables are all crammed into
the hub cheek-by-jowl).  
 - earlier ethernet (10BaseT) uses two of the four pairs, the others are
idle.  So some el-cheapo cables only had two pairs in them (patch cords
packed in your shiny new laptop, often).
 - with fast ethernet (100BaseT) at least some implementations used all
four pairs.  
 - Power over Ethernet is a trick that will undoubtedly be useful in
automobiles -- grab a couple wires in the cable and energize them with
48v DC.  The 48v is legacy telco, but the trick should work with 12v
automotive too.  
 - fiber Phy is common with ethernet.  Often used for campus
installations, run between buildings where the runs are >100 meters.  
    Both the UTP and fiber implementations are physically point-point
between hub and end system.  This may not be what you want in a car.  So
it might indeed be worthwhile resurrecting a coax implementation and
push the shared use back out onto the cable.  I know of no company
actually doing that, though.  

> most 4 segments while driving.  

User interface?  What to do with LAN?  (I do agree with human-factors
discussions on minimizing driver distractions, but that's a different
discussion)

> insecure at OSI level 2 in a way that higher levels can only partly

Is CAN a routable network?  If its not, then you'll need to build some
layer 7 gateways.  Probably easier to phase it out.  Loop back to the
other-industry evolution notes above.  

Does anyone in [its] remember the SAE Ring Bus standardization effort?
Late '80s.  Was definitely intended for automotive use; eclipsed by FDDI
(better technical solution all 'round and chipsets were actually being
built).  But why did the effort not pan out?

---

From: Dave Crocker <[email-masked]>
Date: Sat, 04 May 2013 17:03:53 -0700

> with wireline.  There are lots of reasons, but a couple of the enduring

Yes, but...

System design, integration and operations issues can create a mixture of 
tradeoffs that make one or the other choice of wire or wireless far better.

We used to get television only over the air and telephone only over wires.

Today, dominant usage has swapped these choices.

I'm not trying to negate the factors of capacity and error rate that you 
cite, but merely to observe that they are but two of a larger set. Their 
importance in the mixture diminishes, for example as capacity demand 
reduces and upper-layer recovery mechanisms make errors (of certain 
types) less relevant.

I'm also not taking a position on the particular choices in this thread. 
  To me what is important is how those choices are evaluated.

>>   Also, cables have weight, especially copper

I did that with Cat 5 in my house, some years aback, and now can't get 
reliable Gigabit networking in my house.  And yes, this has had a 
noticeable effect when trying to access my storage/media server...

> User interface?  What to do with LAN?

The ability to physically distribute functions easily, but still have 
them interact well, could reasonably prompt having other design issues, 
such as UI human processing limits, dominate the choices.

d/

-- 
Dave Crocker
Brandenburg InternetWorking
bbiw.net

---

From: Michael Richardson <[email-masked]>
Date: Mon, 06 May 2013 09:08:31 -0400

>>>>> "Alison" == Alison Chaiken <[email-masked]> writes:

    Alison> Every data cable in a car is a custom part that dealers and
    Alison> their distributors must stock.  Consider the pain that the
    Alison> parts distribution problem causes smaller companies with
    Alison> limited distribution, and how much of a barrier to entry to
    Alison> new markets the parts problem represents.  Tesla, for

It seems that you are agreeing with me that data cables are hard, but 
are you also saying that a single power lead (assuming chassis ground)
is also hard?

-- 
]               Never tell me the odds!                 | ipv6 mesh networks [ 
]   Michael Richardson, Sandelman Software Works        | network architect  [ 
]     [email-masked]  http://www.sandelman.ca/        |   ruby on rails    [

---

From: Alexandru Petrescu <[email-masked]>
Date: Thu, 16 May 2013 20:27:22 +0200

Le 04/05/2013 19:14, Alison Chaiken a écrit :
[...]
> CAN is going away, although it will be with us for a long time.
> CAN is too slow, too hard to interoperate with other buses, and is

I am not an expert of CAN.

But I wouldn't see it disappearing altogether.

I can see is that it becomes cheaper and cheaper, more and more
available.  I can see it multiplies (several CANs) in a vehicle, not
that it disappears.  I.e. several non-IP CANs, several IP subnets,
several WiFi and bluetooth - all within one cabin.

Alex