Subject: [Gen-art] review of draft-ietf-ecrit-framework-10.txt

From: Francis Dupont <[email-masked]>
Date: Mon, 08 Mar 2010 16:44:44 +0100

I have been selected as the General Area Review Team (Gen-ART)
reviewer for this draft (for background on Gen-ART, please see
http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html).

Please resolve these comments along with any other Last Call comments
you may receive.

Document: draft-ietf-ecrit-framework-10.txt
Reviewer: Francis Dupont
Review Date: 2010-03-05
IETF LC End Date: 2010-03-10
IESG Telechat date: unknown

Summary: Almost Ready

Major issues: None

Minor issues: the Terminology is incomplete (no PSAP for instance)
and the GPS stuff seems a bit USA centric (IMHO you should show
the document to a GPS (or Galileo :-) expert).

Nits/editorial comments:
 - ToC page 2: Acknowledgements -> Acknowledgments

 - 1 page 3: add USA to National (if the NENA is a USA organization :-)

 - 1 page 3: I'd *really* like to get an entry for PSAP here!

 - 1 page 3: IMHO there should be an entry for LoST too.

 - 1 page 4: RoutinglLocation -> Routing Location

 - 2 page 5: e.g. -> e.g.,

 - 2 page 5: expand EV-DO?

 - 3 page 10: AliceE -> Alice

 - 3 page 10: missing [M7] and [M8]

 - 3 page 10: floating "Figure 2" without a figure (from the .txt version)

 - 3 page 10 (in ESRP entry): sip -> SIP

 - 3 page 10: e.g. -> e.g.,

 - 6 page 15: I don't know the quality of GPS in mobile phone, I have
  a GPS receiver for pedestrian (surely best conditions: open-sky,
  low speed), its accuracy is between 4 and 15 m (displayed) and
  <10m at 95% (vendor specs in peace time) without WAAS (I use it
  in France) so your numbers are a bit conservative.

 - 6.1 page 16: WGS 84 could (should :-) be replaced by another
  system and as far as I know it is not the system used in Europe
  (I don't know for ASIA).

 - 6.2 page 17: e.g. -> e.g.,

 - 6.5 page 20: requestor -> requester?

 - 6.8 page 23: UAC -> UA (typo? if not the abbrev should be expanded)

 - 6.10 page 25: United States -> United States of America
  (yes, there are more than one United States :-)

 - 7 page 26: IMHO you should add a reference for LoST

 - 8 page 27: AP -> access point

 - 9.1 page 28: xref problem (missing '<' in XML?)

 - 9.1 page 28: IPSEC -> IPsec

 - 10 page 30: please define AoR abbrev at its first use.

 - 12 page 30: i.e -> i.e.,

 - 15 page 31: some missing text before "includes a description"

 - 18 page 32: Acknowledgements -> Acknowledgments

 - Authors' Addresses pages 36 and 37: US -> USA

Regards

[email-masked]

PS: you have some comments from Cullen Jennings too.

---

From: Brian Rosen <[email-masked]>
Date: Tue, 09 Mar 2010 17:52:45 -0500

I will fix the nits as you suggest.

We have quite a bit of experience in the U.S. with what kind of GPS accuracy
we can get.  There are millions of phones and tens of thousands of calls
annually using GPS positioning.  It is quite difficult to achieve a 100
meter accuracy 95% of the time.  Technology is improving all the time, but
at the moment, carriers are struggling to achieve the regulatory mandate for
100 meter uncertainty, 95% confidence.

WGS84 is the most commonly used international datum.  IETF emergency calling
is based on IETF geopriv standards (see RFC4119), which specifies WGS-84.

Brian

---

From: Henning Schulzrinne <[email-masked]>
Date: Tue, 9 Mar 2010 20:33:12 -0500

As they say, [citation needed].

See

http://www.doylesdartden.com/gis/gpstest.htm
http://gisandscience.com/2009/07/15/accuracy-of-iphone-locations-a-comparison-of-assisted-gps-wifi-and-cellular-positioning/
http://farmindustrynews.com/farm-equipment/precision-farming/farming_on_target/
http://www.ehow.com/facts_5030374_accurate-gps-system.html
http://www.gpsworld.com/gnss-system/expert-advice-does-anybody-really-know-what-accuracy-is-4190

for different perspectives. [The second one only mentions the median in the abstract, so it's theoretically possible that you could have trouble with 95% within 100m, but it seems unlikely.]

Henning

---

From: Brian Rosen <[email-masked]>
Date: Wed, 10 Mar 2010 08:36:54 -0500

I suppose that it's conceivable that every carrier, the FCC, NENA and APCO
are all stupid.

On the other hand, the carriers spend millions of dollars testing every
year.  So, perhaps they aren't quite so stupid.

I don't have access to the full paper to understand what a "20 minute field
test" is, but the largest problem for 100 meter 95% confidence is the fact
that the GPS is not always enabled (for battery drain reasons) and unless
it's on and seeing satellites for many minutes, you don't get really good
accuracy.  Also, field tests are usually conducted in open sky situations,
and not urban canyons, or even tree leaf cover situations, which degrade
performance considerably.

Brian

On 3/9/10 8:33 PM, "Henning Schulzrinne" <[email-masked]> wrote:

> http://gisandscience.com/2009/07/15/accuracy-of-iphone-locations-a-comparison-
> of-assisted-gps-wifi-and-cellular-positioning/
> 
http://farmindustrynews.com/farm-equipment/precision-farming/farming_on_target>
/
> for different perspectives. [The second one only mentions the median in the
> abstract, so it's theoretically possible that you could have trouble with 95%
> within 100m, but it seems unlikely.]
> 
> Henning
>

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 10 Mar 2010 09:28:40 -0500

> I suppose that it's conceivable that every carrier, the FCC, NENA and APCO

The 100 m/95% is a requirement, not an attempt to describe current GPS performance. As far as I know, the requirement was stated when GPS SA (selective availability) was still enabled.

> year.  So, perhaps they aren't quite so stupid.

I'm afraid I'm missing how this relates to my note. Did I accuse anybody of being stupid?

> performance considerably.

As an aside, this illustrates that the 95% number is pretty meaningless. Does it mean 95% of all calls (lots more emergency calls are made from indoors and the urban canyons of Manhattan than from open fields) or 95% of all sample points? Is it measured immediately after turning on the device or after waiting N minutes?

Without such detail, making precise statements is just pretend-precision. 

Henning

---

From: Brian Rosen <[email-masked]>
Date: Wed, 10 Mar 2010 09:41:40 -0500

This is a (probably pointless) discussion on the 100 meter uncertainty
number that is found in -framework.  It is a realistic number today, and a
much smaller number is not, in my opinion, realistic.

For emergency calls, you care about getting an accurate routing in around a
minute (fastest response time practical), and 2 minutes is probably okay.

The U.S. Regulation is based on average results for emergency calls within a
county (changed from average within a PSAP service boundary).  The
requirement is that EVERY county get 100 meter uncertainty, 95% confidence.
As a practical matter, they drive counties to determine the results, rather
than attempt to actually locate callers.  They use real cell phones.  I'm a
bit fuzzy on when they get the accurate location, but the cell system
determines this (a poll from the PSAP doesn't get a better result until the
network is ready to give good results).  I do think it's a minute or two.

Brian

On 3/10/10 9:28 AM, "Henning Schulzrinne" <[email-masked]> wrote:

> The 100 m/95% is a requirement, not an attempt to describe current GPS
> performance. As far as I know, the requirement was stated when GPS SA
> (selective availability) was still enabled.
> 
> 
>> 
> As an aside, this illustrates that the 95% number is pretty meaningless. Does
> it mean 95% of all calls (lots more emergency calls are made from indoors and
> the urban canyons of Manhattan than from open fields) or 95% of all sample
> points? Is it measured immediately after turning on the device or after
> waiting N minutes?
>

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 10 Mar 2010 10:22:55 -0500

> much smaller number is not, in my opinion, realistic.

I'd prefer citations to opinions :-)

---

From: Brian Rosen <[email-masked]>
Date: Wed, 10 Mar 2010 10:27:27 -0500

The citation is the U.S. Regulatory spec, which is (barely) achievable.
There is a very long record available that documents the back and forth with
experts arguing on both sides.  The conclusions of even the PSAP folks, who
really want a tighter spec, is that 100 meter 95% measured at county level
is as good as we can get right now.  For this document, that's good enough.

Brian

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 10 Mar 2010 10:43:13 -0500

I would simply state it as a requirement, rather than a statement of fact, which is very likely is not (or only with a long list of caveats).

---

From: Brian Rosen <[email-masked]>
Date: Wed, 10 Mar 2010 10:49:40 -0500

The current text is:
As of the date of this memo, typical assisted GPS uncertainty in mobile
phones with 95% confidence is 100 m.  As technology advances, the accuracy
requirements for location will need to be tightened.

That is a statement of fact that is backed up by the U.S. Regulatory docket.

Above this text is a requirement (3 cm).

How would you suggest rewording?

Brian

On 3/10/10 10:43 AM, "Henning Schulzrinne" <[email-masked]> wrote:

> I would simply state it as a requirement, rather than a statement of fact,
> which is very likely is not (or only with a long list of caveats).
>

---

From: Henning Schulzrinne <[email-masked]>
Date: Wed, 10 Mar 2010 11:57:10 -0500

Something like

The US Federal Communications Commissions (FCC) has established a requirement [in 19XX] that cell phones using GPS can be located within 100 m with 95% confidence. This requirement is generally met by current deployments in North America.

The current wording implies a verifiable fact, which none of the citations I provided come close to supporting. References to unknown documents from the pre-SA-abolishment era aren't all that helpful to an outside reader. (For example, the "urban canyon" problem isn't likely to affect Paris and Amsterdam all that much, and Iceland doesn't have to worry about leaves...) Also, as far as I know, there isn't any great new technology on the horizon that will magically shrink this from 100 m to 3 cm. The only thing that will help a bit in the next few years is more satellites (part of the Galileo effort) and, in some limited cases, differential GPS. (See http://en.wikipedia.org/wiki/Galileo_(satellite_navigation)#Services)

Henning

---

From: "James M. Polk" <[email-masked]>
Date: Wed, 10 Mar 2010 13:37:21 -0600

At 10:57 AM 3/10/2010, Henning Schulzrinne wrote:
>Something like
>
>The US Federal Communications Commissions (FCC) has established a 
>requirement [in 19XX] that cell phones using GPS can be located 
>within 100 m with 95% confidence. This requirement is generally met 
>by current deployments in North America.

I have to back Henning's offered text here. His text offers the 
requirement as a goal - which it is - rather than something that's 
already been technically proven to be achievable 95% of the time - 
which it hasn't been. In other words, the FCC is stating where they 
want things, not where we already are.

james

>The current wording implies a verifiable fact, which none of the 
>citations I provided come close to supporting. References to unknown 
>documents from the pre-SA-abolishment era aren't all that helpful to 
>an outside reader. (For example, the "urban canyon" problem isn't 
>likely to affect Paris and Amsterdam all that much, and Iceland 
>doesn't have to worry about leaves...) Also, as far as I know, there 
>isn't any great new technology on the horizon that will magically 
>shrink this from 100 m to 3 cm. The only thing that will help a bit 
>in the next few years is more satellites (part of the Galileo 
>effort) and, in some limited cases, differential GPS. (See 
>http://en.wikipedia.org/wiki/Galileo_(satellite_navigation)#Services)
>
>Henning
>

---

From: Francis Dupont <[email-masked]>
Date: Thu, 18 Mar 2010 23:22:03 +0100

In your previous mail you wrote:

=> this just means a dedicated GPS receiver is far better than a phone
(I am not very surprised :-). BTW if the (USA) regulatory mandates this
performance the question is solved (at least in USA).

   WGS84 is the most commonly used international datum.

=> yes but it is not the legal one in France for example (but the French
one is compatible, i.e., differences are very small, and recent maps
have extra WGS-84 info (aka "compatible GPS")).

   IETF emergency calling
   
=>  if it is still time you have here a good way to fix possible
future issue by referencing this (so if/when it should be updated
only the RFC 4119 will be impacted).

BTW the progress should not stop so I really believe in the "when":
WGS-84 will get a successor one day...

Thanks