Re: Your comments appreciated: Beyond White Spaces

[David Farber <dave () farber net>]

Begin forwarded message:

From: dewayne () warpspeed com (Dewayne Hendricks)
Date: October 23, 2008 9:48:10 AM EDT
To: Dewayne-Net Technology List <xyzzy () warpspeed com>
Subject: [Dewayne-Net] re: Your comments appreciated: Beyond White  
Spaces

[Note:  This comment comes from friend Chuck Jackson.  DLH]

From: "Charles Jackson" <clj () jacksons net>
Date: October 23, 2008 6:33:35 AM PDT
To: "'Dewayne Hendricks'" <dewayne () warpspeed com>
Subject: RE: [Dewayne-Net] Your comments appreciated: Beyond White  
Spaces

I think that David Isenberg is right in his analysis of the TV white  
spaces
issue.  However, reading his note prompted several thoughts.

First, for an interesting discussion of the HomeRF/802.11 evolution see
<http://www.iep.gmu.edu/documents/WLAN_History_Paper.pdf>.  Reading  
that paper
gives a lot of insight into why 802.11 prevailed in the marketplace.   
It's
written by someone who was on the HomeRF side-but it seems quite  
unbiased to
and fair to me.  In 1999, it was quite reasonable to expect HomeRF to
prevail in the marketplace.

Second, there's a great book called "The Triumph of Ethernet" by Urs von
Burg, Stanford University Press, which examines how Ethernet, which many
thought inferior to Token-Ring, won in the marketplace.  One factor that
helped Ethernet win was the fact that IBM effectively controlled the
token-ring standard and, if you were a small guy in the industry, you
probably preferred to build products that IBM could not make obsolete
overnight.


Third, some thoughts on the white space debate.  A caveat, I'm a  
participant
in that debate.  I've taken the position that licensing the white space
would deliver far more to consumers than would unlicensed white space.

Unlicensed white space devices will be inferior to current WiFi in most
incarnations.  They will probably be built to use 6 MHz channels-but  
802.11
now uses 40 MHz.  At short ranges, it's bandwidth that determines  
capacity.
So, unlicensed devices at 2.4 and 5 GHz will outperform unlicensed  
devices
in the TV white space.  Relatedly, MIMO capabilities are expected to be
better at 2.4 and 5 GHz than in the white space.  That superiority will
probably create another factor of 2 or 3 advantage in short-range  
capacity
for 2.4 and 5 GHz systems.  Together, these factors create a capacity
advantage for 2.4 and 5 GHz 802.1 of about a factor of 10 or 20.

For long ranges, the power limits on the unlicensed devices reduce  
possible
coverage and run up costs.  Licensed services in the 700 MHz band and  
the
PCS can use base station powers three thousand times higher than are
proposed for unlicensed TV white space fixed stations.  Propagation  
may be
better in the low UHF (white space) than in the PCS band, but not 3,000
times better. (Actually, "better propagation" is a complex issue-and  
it is
not necessarily the case that propagation is "better" at the low UHF.   
It
all depends upon what the meaning of "better" is.)

It's hard to think of any engineering model in which one can provide  
rural
coverage with unlicensed TV white space devices at costs anywhere those
possible for the current licensed operators.  For a quantitative  
exposition
of the inability of TV white spaces to provide rural coverage see
<http://fjallfoss.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_documen
t=6520176878>


Finally, there is a key issue in the white space debate that the  
advocates
of unlicensed completely fumble.  That is, "How do we put in place  
rules and
incentives that will make it easy to transition the current TV  
spectrum to
other uses when that transition makes sense?"  A licensed approach  
creates
mechanisms for doing so.  See, for example,
Hazlett and Smith's op-ed in the WSJ.
<http://online.wsj.com/article/SB122299012125700337.html>

In contrast, if the white space is filled up with wireless X-box  
controllers
and cordless phones, it will be far harder to transition the TV bands  
to new
technologies and new uses.

I think that David's hint that unlicensed devices in the TV white  
space will
be a dud in the market is correct.  802.11 at 2.4 and 5 GHz beats them  
for
short range; the power is too weak for long range.

This message is already long enough, but if anyone wants more on the  
topic,
feel free to contact me.

Chuck Jackson
RSS Feed: <http://www.warpspeed.com/wordpress>




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