🚀 go-pugleaf

Jeff Liebermann wrote:
> A bit of math on counting the number of wireless access points
> required to cover San Francisco.
> 
> The original numbers:
> |  http://www.outlook4mobility.com/commentary2005/oct1205.htm
> 
> The revised version:
> |  http://www.outlook4mobility.com/commentary2005/oct1305.htm
> 

The eventual result:

http://www.kcra.com/news/4512146/detail.html

-- 
Phil Nelson

Jeff Liebermann  <jeffl@comix.santa-cruz.ca.us> wrote:

>A bit of math on counting the number of wireless access points
>required to cover San Francisco.

>The original numbers:
>|  http://www.outlook4mobility.com/commentary2005/oct1205.htm

>The revised version:
>|  http://www.outlook4mobility.com/commentary2005/oct1305.htm

Lessee.  If the inter-access point spacing is D, then the
density is 1/D^2 per unit area.   If they are optimally
arrayed in a honeycomb fashion, the maximum distance to a 
client is D / (2 * cos(pi/6), or 0.57 * D.

If you want 300 feet to be the maximum distance to a client, then
D = 526 feet, which is pretty close to exactly 0.1 miles,
so yeah.  100 AP's per square mile.  The revised calculation
is correct.

But (a) 300 feet is too far for this all to work and (b) you
won't be able to optimally place them so you'll need more.
I'd say 200 per square mile if you want it not to choke,
or 10,000 access points in San Francisco.

Steve

Steve

On Tue, 25 Oct 2005 04:47:46 GMT, 
in article <0sdrl1tcp4bpoi1qonabuuk4bkujoapgpu@4ax.com>, 
jeffl@comix.santa-cruz.ca.us (Jeff Liebermann) writes...

> A bit of math on counting the number of wireless access points
> required to cover San Francisco.
> 
> The original numbers:
> |  http://www.outlook4mobility.com/commentary2005/oct1205.htm
> 
> The revised version:
> |  http://www.outlook4mobility.com/commentary2005/oct1305.htm


His skepticism about the whole idea is not a lot different
than my own.  Like Seybold, I think interference in the 2.4Ghz 
band is going to be a monstrous issue, among other things.  

Which is why I was thinking (as posted earlier) that they 
should probably consider something like proprietary, 
neighborhood-based mesh radios which local users can tap off 
of and distribute either via wires or their own WAPs.  Just 
run a "backbone" and let the end-users install the local radios 
so you can wash your hands of the local interference issues.

Then the challenge would be how to interconnect the backbone
to the local segments.  Sigh.

<evil grin>  I've got it -- Bluetooth!  Hehehehe...



-- 
*   Few people are capable of expressing with equanimity opinions which       *
*   differ from the prejudices of their social environment. Most people are   *
*   even incapable of forming such opinions.             -- Albert Einstein   *
*                                                                             *
* To send email, remove numbers and spaces:  pjkusenet64 @  ekahuna27 . com   *
*  Simple answers are for simple minds.  Try a new way of looking at things.  *

Philip J. Koenig  <See_email_@ddress_below.This_one_is.invalid> wrote:

>His skepticism about the whole idea is not a lot different
>than my own.  Like Seybold, I think interference in the 2.4Ghz 
>band is going to be a monstrous issue, among other things.  

There are 25 unlicensed channels in the 5 GHz band.  I assume they
will deploy there -- otherwise, it is completely hopeless.

What I don't know is whether Google has an actual engineering 
team on this or whether it's still just in marketing.

Steve

On Tue, 25 Oct 2005 09:53:49 +0000 (UTC), 
in article <djkvbd$s4a$1@blue.rahul.net>, 
spope33@speedymail.org (Steve Pope) writes...
> Philip J. Koenig  <See_email_@ddress_below.This_one_is.invalid> wrote:
> 
> >His skepticism about the whole idea is not a lot different
> >than my own.  Like Seybold, I think interference in the 2.4Ghz 
> >band is going to be a monstrous issue, among other things.  
> 
> There are 25 unlicensed channels in the 5 GHz band.  I assume they
> will deploy there -- otherwise, it is completely hopeless.


What's the point of putting radios in 5Ghz spectrum when almost
no users are going to be able to receive those signals directly?

Telling everyone to go buy 802.11a hardware is going to be
a non-starter.


 
> What I don't know is whether Google has an actual engineering 
> team on this or whether it's still just in marketing.


As I posted a few days ago, for the SF bid Google is partnering 
with a San Diego-based wireless engineering company which, among 
other things, will be involved in building a muni wifi system in 
Madison Wisconsin.

This is the partner:
http://www.wfinet.com/index.html



-- 
*   Few people are capable of expressing with equanimity opinions which       *
*   differ from the prejudices of their social environment. Most people are   *
*   even incapable of forming such opinions.             -- Albert Einstein   *
*                                                                             *
* To send email, remove numbers and spaces:  pjkusenet64 @  ekahuna27 . com   *
*  Simple answers are for simple minds.  Try a new way of looking at things.  *

Philip J. Koenig wrote:
> On Tue, 25 Oct 2005 09:53:49 +0000 (UTC), 
> in article <djkvbd$s4a$1@blue.rahul.net>, 
> spope33@speedymail.org (Steve Pope) writes...
> 
>>Philip J. Koenig  <See_email_@ddress_below.This_one_is.invalid> wrote:
>>
>>
>>>His skepticism about the whole idea is not a lot different
>>>than my own.  Like Seybold, I think interference in the 2.4Ghz 
>>>band is going to be a monstrous issue, among other things.  
>>
>>There are 25 unlicensed channels in the 5 GHz band.  I assume they
>>will deploy there -- otherwise, it is completely hopeless.
> 
> 
> 
> What's the point of putting radios in 5Ghz spectrum when almost
> no users are going to be able to receive those signals directly?
> 
> Telling everyone to go buy 802.11a hardware is going to be
> a non-starter.


Possibly, but a lot of technology is driven that way. 5 GHz hardware is 
not common and expensive because everyone piled into the 2.4 GHz band. 
If they chose for SFO the 5 GHz band they would free themselves from the 
current issues and the 5 GHz equipment would become just as common and 
inexpensive.



> 
> 
>  
> 
>>What I don't know is whether Google has an actual engineering 
>>team on this or whether it's still just in marketing.
> 
> 
> 
> As I posted a few days ago, for the SF bid Google is partnering 
> with a San Diego-based wireless engineering company which, among 
> other things, will be involved in building a muni wifi system in 
> Madison Wisconsin.
> 
> This is the partner:
> http://www.wfinet.com/index.html
> 
> 
> 

George  <george@nospam.invalid> wrote:

>Philip J. Koenig wrote:

>> spope33@speedymail.org (Steve Pope) writes...

>>>There are 25 unlicensed channels in the 5 GHz band.  I assume they
>>>will deploy there -- otherwise, it is completely hopeless.

>> What's the point of putting radios in 5Ghz spectrum when almost
>> no users are going to be able to receive those signals directly?

>> Telling everyone to go buy 802.11a hardware is going to be
>> a non-starter.

>Possibly, but a lot of technology is driven that way. 5 GHz hardware is 
>not common and expensive because everyone piled into the 2.4 GHz band. 
>If they chose for SFO the 5 GHz band they would free themselves from the 
>current issues and the 5 GHz equipment would become just as common and 
>inexpensive.

Adoption of 5 GHz is a lot slower than many in the industry
predicted, but it will soon be pretty standard.  For those
with older 2.4 GHz-only devices, they will just have less
coverage -- much as having a single-band cellphone (if there
is such a thing now) has less coverage.

Steve

On Tue, 25 Oct 2005 07:40:35 -0400, George <george@nospam.invalid>
wrote:

>Possibly, but a lot of technology is driven that way. 5 GHz hardware is 
>not common and expensive because everyone piled into the 2.4 GHz band. 
>If they chose for SFO the 5 GHz band they would free themselves from the 
>current issues and the 5 GHz equipment would become just as common and 
>inexpensive.

Not common?  5.7GHz is where all the wireless backhauls are currently
located.
  http://www.wbanc.com
If SF decided to go with 5.7GHz 802.11a clients, then I'm sure the
market would gladly support replaceing everything you own with the
latest and greatest.  (Evolution. Upgrade or die).  However,
relocating the backhauls to 22Ghz may be a bit of a challenge.
considering the mesh network rule of thumb of the week of no more than
3-4 hops from client to backhaul, and 100 access points per square
mile, that means 25-33 backhaul radios or wired connections per square
mile.  

-- 
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Jeff Liebermann  <jeffl@comix.santa-cruz.ca.us> wrote:

>Not common?  5.7GHz is where all the wireless backhauls are currently
>located.
>  http://www.wbanc.com
>If SF decided to go with 5.7GHz 802.11a clients, then I'm sure the
>market would gladly support replaceing everything you own with the
>latest and greatest.  (Evolution. Upgrade or die).  However,
>relocating the backhauls to 22Ghz may be a bit of a challenge.

You mean 24 GHz I think.

>considering the mesh network rule of thumb of the week of no more than
>3-4 hops from client to backhaul, and 100 access points per square
>mile, that means 25-33 backhaul radios or wired connections per square
>mile.  

Despite their fumbling, Google definitely has the money to
deploy that hardware this project requires.  Google's only limit
is the laws of physics.

S.

On Tue, 25 Oct 2005 16:25:58 +0000 (UTC), spope33@speedymail.org
(Steve Pope) wrote:

>Jeff Liebermann  <jeffl@comix.santa-cruz.ca.us> wrote:
>
>>Not common?  5.7GHz is where all the wireless backhauls are currently
>>located.
>>  http://www.wbanc.com
>>If SF decided to go with 5.7GHz 802.11a clients, then I'm sure the
>>market would gladly support replaceing everything you own with the
>>latest and greatest.  (Evolution. Upgrade or die).  However,
>>relocating the backhauls to 22Ghz may be a bit of a challenge.
>
>You mean 24 GHz I think.

Y'er correct.  It's 24GHz.  Equipment is available but it's not cheap.
Dragonwave Air Pair 50:
|  http://www.tessco.com/products/displayProductInfo.do?sku=447702&eventPage=1
Only $22,000 each.

>>considering the mesh network rule of thumb of the week of no more than
>>3-4 hops from client to backhaul, and 100 access points per square
>>mile, that means 25-33 backhaul radios or wired connections per square
>>mile.  

>Despite their fumbling, Google definitely has the money to
>deploy that hardware this project requires.  Google's only limit
>is the laws of physics.

I've worked on wasted projects that proposed to solve technical issues
by throwing money at the problem.  I've also learned that if it
doesn't work on paper, it's not going to work in the field.  I find
the Philadelphia system entertaining to follow as technical details
and the entire topology seems to change every month.  I suspect that
the SF network will be much of the same as Google discovers RF
reality.  I'm sure the stockholders will eventually have something to
say when this project starts resembling a financial black hole.

I also find it entertaining to read about how such networks will be
used.  The common description is "untethered access" where users with
PDA's, laptops, and VoIP phones, roam around the city while browsing
the internet.  I learned a few lessons watching Metricom and found
that what most users *REALLY* want is a cheap full time connection in
the home.  My guess(tm) is that the bulk of the use will be from fixed
locations and solely as a cost reduction (or elimination) expedient.

-- 
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

Jeff Liebermann  <jeffl@comix.santa-cruz.ca.us> wrote:

>>Despite their fumbling, Google definitely has the money to
>>deploy that hardware this project requires.  Google's only limit
>>is the laws of physics.

>I've worked on wasted projects that proposed to solve technical issues
>by throwing money at the problem.  I've also learned that if it
>doesn't work on paper, it's not going to work in the field.  I find
>the Philadelphia system entertaining to follow as technical details
>and the entire topology seems to change every month.  I suspect that
>the SF network will be much of the same as Google discovers RF
>reality.  I'm sure the stockholders will eventually have something to
>say when this project starts resembling a financial black hole.

At 96 Billion in market valuation, they'd have to spend an 
awful lot on hotspots to disappoint investors.

Steve

Jeff Liebermann wrote:

> However, 
> relocating the backhauls to 22Ghz may be a bit of a challenge.
> considering the mesh network rule of thumb of the week of no more than
> 3-4 hops from client to backhaul, and 100 access points per square
> mile, that means 25-33 backhaul radios or wired connections per square
> mile.

I haven't really followed this discussion, and I don't know any of the
technicalities, but surely that's more like 9 - if you've got your 100 APs
lined up on a grid 0.1 miles apart, then you would only need your
backhaul's to be every 0.3 to 0.4 miles, so placing them 1/3 mile apart
should do it.
-- 
derek

[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

In <evnsl1tl9hh8vn6n9foam63fvn4t3tqp03@4ax.com> on Tue, 25 Oct 2005 09:59:35
-0700, Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

>I've worked on wasted projects that proposed to solve technical issues
>by throwing money at the problem.  I've also learned that if it
>doesn't work on paper, it's not going to work in the field.  I find
>the Philadelphia system entertaining to follow as technical details
>and the entire topology seems to change every month.  I suspect that
>the SF network will be much of the same as Google discovers RF
>reality.  I'm sure the stockholders will eventually have something to
>say when this project starts resembling a financial black hole.

What makes you think that Google is dumb enough to have not studied the RF
issues?  A lot of very, very smart folks are at Google, which has a pretty
sterling track record.

-- 
Best regards,        HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas           <http://navasgrp.home.att.net/#Cingular>

On Tue, 25 Oct 2005 07:40:35 -0400, 
in article <a4OdnTAUJ-LBhMPeRVn-qQ@adelphia.com>, 
george@nospam.invalid (George) writes...
> Philip J. Koenig wrote:
> > On Tue, 25 Oct 2005 09:53:49 +0000 (UTC), 
> > in article <djkvbd$s4a$1@blue.rahul.net>, 
> > spope33@speedymail.org (Steve Pope) writes...
> > 
> >>Philip J. Koenig  <See_email_@ddress_below.This_one_is.invalid> wrote:
> >>
> >>
> >>>His skepticism about the whole idea is not a lot different
> >>>than my own.  Like Seybold, I think interference in the 2.4Ghz 
> >>>band is going to be a monstrous issue, among other things.  
> >>
> >>There are 25 unlicensed channels in the 5 GHz band.  I assume they
> >>will deploy there -- otherwise, it is completely hopeless.
> > 
> > 
> > 
> > What's the point of putting radios in 5Ghz spectrum when almost
> > no users are going to be able to receive those signals directly?
> > 
> > Telling everyone to go buy 802.11a hardware is going to be
> > a non-starter.
> 
> 
> Possibly, but a lot of technology is driven that way. 5 GHz hardware is 
> not common and expensive because everyone piled into the 2.4 GHz band. 
> If they chose for SFO the 5 GHz band they would free themselves from the 
> current issues and the 5 GHz equipment would become just as common and 
> inexpensive.


Don't be so quick to assume that using 802.11a will magically
solve all the congestion issues.  Certainly in the beginning,
there are fewer 802.11a AP's to contend with. (and also fewer
cordless phones, microwaves and baby monitors)

But it is still unlicensed spectrum, and free for anyone to put
up their own 802.11a WAP whenever they want, and point it wherever
they want, so no matter how well it seems to work on rollout day, 
things could very well turn pretty cruddy as more and more devices 
come online. (both part of the municipal system and independent of 
the municipal system)

Not to mention, having to buy 802.11a radios for end-users to 
connect with the system would fly in the face of the whole
philosophy of the project, which is to "bridge the digital
divide".  People with bucks already have fancy broadband, it's
the people without the bucks that they really are targeting.
Those people aren't likely to go out and spend $75 just so
they can use that "free" internet.



-- 
*   Few people are capable of expressing with equanimity opinions which       *
*   differ from the prejudices of their social environment. Most people are   *
*   even incapable of forming such opinions.             -- Albert Einstein   *
*                                                                             *
* To send email, remove numbers and spaces:  pjkusenet64 @  ekahuna27 . com   *
*  Simple answers are for simple minds.  Try a new way of looking at things.  *

On Wed, 26 Oct 2005 00:23:41 GMT, John Navas
<spamfilter0@navasgroup.com> wrote:

>In <evnsl1tl9hh8vn6n9foam63fvn4t3tqp03@4ax.com> on Tue, 25 Oct 2005 09:59:35
>-0700, Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote:

>>(...)  I suspect that
>>the SF network will be much of the same as Google discovers RF
>>reality.  I'm sure the stockholders will eventually have something to
>>say when this project starts resembling a financial black hole.

>What makes you think that Google is dumb enough to have not studied the RF
>issues?  A lot of very, very smart folks are at Google, which has a pretty
>sterling track record.

I didn't even suggest that Google hadn't "studied" the RF issues. They
can study something until they're buried in reports and paperwork.
What makes the distinction between studies and reality is actually
building a system and trying to make it play.  That doesn't mean an
in-house system inside the Googleplex, but a real live outdoor WISP
(wireless ISP) system complete with interference issues, irate
customers, tech support, maintenance nightmares, physical access
issues, and local politics.  The RF issues are just part of the
puzzle.  Perhaps I'm not giving the very smart folks at Google
sufficient credit for predicting the real and potential problems with
deploying such a wireless network.  Perhaps Google's math isn't much
better than mine[1].  Perhaps I'm being just my normal cynical self.
Perhaps I'm biased by previous experiences with very smart people
offering science fiction business plans in the dot com era.  I just
look at the numbers, the history, my limited experience, and offer my
judgment.  I don't subscribed to calls to authority.


[1] http://www.outlook4mobility.com/commentary2005/oct1305.htm
I also made the same calculation error plus some additional math
screwups.  Oops.

-- 
Jeff Liebermann  150 Felker St #D Santa Cruz CA 95060
831.336.2558 voice         
http://www.LearnByDestroying.com           AE6KS
http://802.11junk.com      Skype: JeffLiebermann
jeffl@comix.santa-cruz.ca.us    jeffl@cruzio.com

On Tue, 25 Oct 2005 15:28:17 -0300, Derek Broughton
<news@pointerstop.ca> wrote:

>Jeff Liebermann wrote:
>
>> However, 
>> relocating the backhauls to 22Ghz may be a bit of a challenge.
>> considering the mesh network rule of thumb of the week of no more than
>> 3-4 hops from client to backhaul, and 100 access points per square
>> mile, that means 25-33 backhaul radios or wired connections per square
>> mile.

>I haven't really followed this discussion, and I don't know any of the
>technicalities, but surely that's more like 9 - if you've got your 100 APs
>lined up on a grid 0.1 miles apart, then you would only need your
>backhaul's to be every 0.3 to 0.4 miles, so placing them 1/3 mile apart
>should do it.

Well, I screwed up by a factor of two, by mixing radius and diameter.

The 3-4 hop assumption I made was that a mesh network client (user)
radio should not need to endure more than 3-4 store and forward hops
before hitting a backhaul to the internet.  To keep the hop count down
to 3 hops, the effective radius of coverage simply increases by a
factor of 3.  Therefore, the original 300ft radius becomes 900ft.  

Now, visualize an array of 1800ft diameter circles (cells) fitting
into a 1 mile square (5280ft on a side).  That would be about 3
circles on a side or 9 circles.  Inside each cell would need to be a
wired access point or the hop count will exceed 3.

That's still not quite right because the enlarged 1800ft diameter
cells have considerable dead area between diagonal circles.  So, they
have to be a bit smaller with some overlap to compensate for this dead
area.  My guess(tm) is about 700ft radius or 1400ft diameter.  That's
about 4 cells on a side or a total of 16 wired access points.

However, that's still not correct.  I'm assuming a cartesian 3x3 array
with a not very tight packing factor.  If the circles were arranged
for optimum packing factor (similar to the hexagonal cellular
arrangement), the number of 1800ft circles can be done with about 12
circles (including combined parts of cells).

Thanks for the correction.
(Grumble...Gone sulking.)

-- 
Jeff Liebermann     jeffl@comix.santa-cruz.ca.us
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

On Tue, 25 Oct 2005 07:33:10 GMT, Phil Nelson
<pCUT_THiS_TEXTdn@soAND_THiS_TEXTnic.net> wrote:

>Jeff Liebermann wrote:
>> A bit of math on counting the number of wireless access points
>> required to cover San Francisco.
>> 
>> The original numbers:
>> |  http://www.outlook4mobility.com/commentary2005/oct1205.htm
>> 
>> The revised version:
>> |  http://www.outlook4mobility.com/commentary2005/oct1305.htm
>> 
>
>The eventual result:
>
>http://www.kcra.com/news/4512146/detail.html

	Flash! -- Homeowner Foiled Again -- Film at 11.