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	First, a confession:

I didn't have to buy a laptop computer to use Ricochet's modem radio.
The reality is that these devices work quite nicely on desk top systems.

I read of these modems in the local free computer newspaper,
but since I was quite happy with my 56 kbit/sec frame relay connection,
I didn't give them much consideration.
Then one day my connection failed and I realized I had no backup
for Internet access.  After a quick trip to a local computer store
and a few minutes configuring a PPP connect script,
I was back in action.
(The frame relay was fixed shortly thereafter,
but I still have my Ricochet modem.
I use it when visiting client sites,
when testing firewall configurations,
and on the one occasion when the fram went down again.
I've also loaned it out to friends suffering
from phone noise and ISP mis-management.)

	How does one use it?

Plug it into your serial port
(It has two connections--one for external power and
one to connect to your computer.)
and the computer sees it as a Hays compatible modem
which happens to have a few additional AT commands.

I mentioned I had to fiddle with the PPP connection scripts.
As with most computer hardware,
Ricochet provides software for operation with Apple systems
and PCs running Microsoft operating systems.
Since Linux comes with support for PPP dialup,
there is no need to load their software.
One only has to make some small,
but crucial changes to the scripts.
The ppp-on-dialer script needs to send the strings

    ATZ
    ATE0X4Q0V1&C1&D2&K3

to the modem to ensure the configuration is correct.
The ppp-on script needed a line

    route del default

because my system is also on a local LAN and
normally gateways through the frame relay.
The phone number, 777**PPP, looks unusual.
It says "connect to the regular Internet service
using the PPP protocol."
The script doesn't need a user name or password
because the modem's serial number is used for authentication.
As long as your account is current,
your connection is established with a dynamically
allocated IP address.
<<Note to editor: I can provide the exact scripts
    for sidebar or web display.>>

	How does is it work?

First, it's not a cell-phone modem.
It is based on an infrastructure which is independent
of the various telephone systems.
Metricom has been in the wireless communications business
since 1985--providing remote-access monitoring of meters
to public utilities.
The Ricochet division was started two years ago in order
to offer wireless Internet connectivity to the public.
They're currently offering service in the metropolitan areas
of Seattle, San Francisco Bay, West Los Angles,
and Washington, D.C.
Ricochet plans to extend coverage in
the Los Angeles area by the end of this year
and installation is underway for New York City.

If you pay attention, you'll see cell phone antenna
towers or roof-top clusters appearing everywhere.
The Ricochet system is quite a bit harder to spot.
There are three elements: the "modem radio" attached
to your computer, a shoebox sized "microcell radio"
attached to streetlamp poles at quarter mile intervals,
and "wired access points" to serve thirty or so
microcell radios.
(Seattle has 1800 microcell radios
and 50 wired access points.)
For instance, in this map of a Seattle neighborhood
the small dots are the microcell radios,
the red stars are wired access points,
and the blue star is the home of the Linux Journal.
(The map is a product of a U.S. Census bureau server using
the URL (without spaces)
  http://tiger.census.gov/cgi-bin/mapbrowser?
  lat=47.676&lon=-122.366&wid=0.10&ht=0.050&
  on=GRID&murl=http://www.aa.net/~bentson/tms&
  iwd=640&iht=720
)
<<Note to editor: There are no restrictions on its use.>>

Just as the Internet uses a store-and-forward model
to get data from one place to another,
Ricochet packets are forwarded from pole to pole
from the modem radio to the wired access point,
at which point they enter the conventional Internet routing.
Because this service is packet based,
you don't really consume resources when you're not
sending or receiving bits.
Therefore you're welcome to establish a connection
and leave it live for as long as you want.
This is a dramatic change from telephone based Internet services.

	What's the future?

Since I got my modem last fall,
Ricochet has offered two new products:
a modem (without battery) for fixed stations
and a newer, lighter weight version
(8 ounce vs 13 ounce) of the portable modem.
An even lighter version is being tested for palmtop computers.
In addition,
Ricochet has distributed a firmware upgrade which
allows a roaming user to stay connected
while moving from one wired access point coverage
area to another.

The current technology operates in the 908-926 MHz band,
dividing it into 162 channels, each 160 kHz wide.
Each connection hops among these channels using spread spectrum technology.
Modem radios provide a connection with performance
comparable to a 28.8 kbit/s modem,
but may burst higher.
(That's why they recommend setting the serial port to 57,600 bit/sec.)
Future models will use more channels and other bands
to provide better coverage and higher speeds
(128 kbit/sec to 512 kbit/sec).

	What if you're not in one of the "blessed cities"?

If you're travelling, you'll find service outside
of these cities in airports such as
Minneapolis-Saint Paul International Airport,
Phoenix Sky Harbor Airport,
and La Guardia Airport in New York City.

Several universities,
including
Austin College,
Cal Poly,
George Washington University,
Oregon State University,
San Francisco State,
Stanford University,
UC Berkeley,
UC Santa Cruz,
University of Miami, and
University of Oregon,
have established local service areas
for their students, staff and faculty.

In addition to service provided in big cities, universities and airports,
Ricochet has teamed up with local utility companies to provide
coverage in smaller towns--systems are being installed in
Casper, Gillette, Laramie, Lander and Torrington in Wyoming, and
Scottsbluff, Gering, Kearney, Alliance, and McCook in Nebraska.
The nature of the Ricochet system allows them to
offer localized service wherever there will
be enough users to support it--I have visions
of service in places like Durango, Colorado.

Remember the strange phone number?
You can also enter the serial number of another modem radio.
If it's nearby, and not currently engaged,
it will see a "RING" and the other user's program can answer the phone.
This is the way in which a peer-to-peer service
is established between two modems.

There's another form of operation as well--called Star mode.
In normal mode, the modem acts like a Hayes compatible modem;
in Star mode, the modem delivers packets into space
(the original ether) and other modems see these packets
and can deal with them much as a Ethernet card would.
This mode only works in modem-to-modem communication,
but the greater bit capacity makes it worth exploring.
If you look in the Linux kernel configuration,
you'll find support for this mode is already available.
With this code compiled in,
you and your co-workers and friends
can have your own wireless LAN wherever you go.
It's very convenient for conferences!

	About the laptop...

I finally broke down and bought one.
Naturally it runs Linux and when I'm out of the
office I unplug the PCMCIA Ethernet card and
turn on the Ricochet modem.

When the microcell radios are installed,
they're configured with their latitude and longitude.
One of the extra "AT" commands causes the modem
to report the location and signal strength of up to
ten nearby microcell radios.
I've wandered around Seattle getting these reports
and looking for microcell radios.
I edited these reports into the tms file cited in
the URL above.
That's how I built the map.

Needless to say,
I had to check out the roaming feature once I get my laptop.
As I drove around town,
I issued a ping command directed at my home system.
Sometimes the latency was quite high,
but it also seems that it went down when a second ping was issued.
I suspect that routing tables are updated often enough
that the system quickly finds the best route.
Now I've got to check it on the ferry across Puget Sound.

Visit http://www.ricochet.net for more information.

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