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San Francisco's Got Free Wi-Fi
Carpoolio writes "If you're living in San Francisco, chances are you can connect, for free, to the BARWN -- the Bay Area Research Wireless Network. BARWN broadcasts an 802.11 signal from the top of a big hill near San Francisco, and anyone with a clear sight line to the signal can connect. Another set of wireless nodes are being placed around town by SFLan, making Wi-Fi available to tens of thousands of people."
According to the article, The hill has a few directional antennas that provide access to 30 or so stationary access points scattered around the area. I assume those access points also have directional antennas pointing back. This would seem to indicate that in order to get online, you have to be near one of the access points, not simply in view of the hill.
Can anyone tell me the likelihood of tracking down a spammer at a laptop in a city the size of San Francisco?
SF is not as big as some people think it is. Compared to neighboring cities you could probably fit 3 SF's in Oakland, and as many as 5 in San Jose.
As far as tracking spammers, when I worked at ricochet we recovered a laptop stolen from a trade show in San Francisco once. Wasn't really that hard once we had the modem # and triangulated it's position from the poletops it saw. From there it was just a matter of pinpointing its location with a loop antenna.
This is paid for by tax dollars
Actually, it's paid for by the Bay Area Wireless Users Group
That doesn't make it free, it means you already pay for it with the taxes you already pay.
Also, it's not clear if they meant free as in beer, or free as in freedom. If they allow anyone to go online without registering or anything, then it's both!
Carrboro, NC
Can you connect to this anonymously? Here in Boston the Boston Public Library runs a free-as-in-beer public wireless network, but I'd hardly call it free-as-in-speech (filtering content, for the children! of course, and you need to log in with information tied to your library card).
[Speaking of which, does anyone know of anyone providing free and anonymous WiFi access in Boston?]
If you're interested in community-sponsored wifi projects, you should take a look at this. It's run by Rob Flickenger, the guy who wrote Linux Server Hacks and a couple of wifi books for O'Reilly.
If you are new to wireless networking, I stumbled across this tutorial.
It would seem that if you have a clear line of sight to multiple APs, then you could combine them and have more bandwidth than a single AP-channel connection would provide.
This is called "concurrent multiple association" or simple multiple assocation / AP hopping, and it's something i've been working on off and on for a little while. I talk about it in a bit more detail on the Janus Wireless pages, but I have yet to get anything stable ready for prime time use.
The current problem with multiple association is that you need a very low latency interface to the network radio's at a packet injection / monitor mode level.
I've been able to get this to work in a very crude and inefficient manner with cisco/prism cards used for monitor mode recv of packets, and prism2 based cards for packet injection to implement the multiple association and data packet injection.
There is some hope that the newer cards, specifically the atheros 802.11a/g cards with a reversed binary HAL driver could provide the requisite low level functions to do this efficiently.
But then you are faced with another problem: aggregating the UDP datagrams from multiple sources into a single address space similiar to the way mobile-IP has a dedicated "public" host which acts as your intermediary as your IP changes without breaking existing TCP connections.
I've played with this a bit as well on a dedicated host that has a few IP's, and it works like a NAT that collates UDP datagrams from a wide variety of sources and converts them into the desired TCP/UDP/etc communication from that public endpoint.
In short: for multiple association you need a number of new driver and radio interfaces for:
1) very low latency packet injection and monitor style recv.
2) specialized mobile-IP like drivers on the client that present a virtual interface (ethX) to then host while using injected datagrams over the various multiply-associated wifi links for transport.
3) a dedicated public host with an IP it can allocate to you that accepts all of these incoming UDP packets from various source addresses (all the AP's you are using) and combines them into standard IP traffic from that public IP (ala mobile-IP as well).
None of this is extremely difficult (with the newer cards) but it is a lot of code, and a lot of work, and requires some dedicated host resources.
Now, for the cool part. When you do have all of these pieces in place, it allows you to:
- Simply add cards to your system for more bandwidth. The multiple association throughput is limited only by the number of AP's you can talk to, and the number of cards you have to monitor and inject packets with. It scales nicely barring interference problems.
- Maintain extremely high throughput as you move anywhere within range to open AP's! You could aggregate the upload capacity of 30 AP's to get a 10Mbps link to the net and maintain this constant fat uplink as you drive around the city.
- Enjoy extremely reliable / robust communications. Since you are no longer dependant on a single AP, you dont have to worry about connection dropping, clients messing with your signal, etc. Your aggregate connection is spread over a number of AP's which means problems with individual AP's make only a very small impact on overall connectivity.
This is really the way things are headed, and its only a matter of time before they become useable and widespread.
There are also a ton of restaurants & cafes in the area that offer laptop access - cheesbikini offers a good list of them.
I have a flaky wireless connection at home; I'd order a cantenna with pigtail but I prefer paying cash...
There are tons of free hotspots in the New York City metro area as well.
More specifically, each custom router can employ up to 9 APs.
Barwn Outdoor Wireless Router Whitepaper
Library of Congress: 2,100,000 square feet
San Francisco: 46.7 square miles
Google says that "2100000 square feet/46.7 square miles" is 0.001613.
Rank Presidents by th
I am one of the people building SFLAN. Our map is a little outdated (and the San Bruno Mountain node is in the wrong spot). SFLAN and BAWRN have some 30 nodes in as many locations in San Francisco and a few outliers in surrounding counties. If you are in San Francisco and want to try it out, Cole Street is well covered. The SSIDs are sflanNN or BARWN-xxxxx; DHCP, no WEP.
The nodes are owned and paid for by individuals, many of whom are members of the Bay Area Wireless User Group. The Internet bandwidth for SFLAN is sponsored by the Internet Archive. If you live in SF and want to buy a node to connect your house and your neighbors, contact us.
We like to keep these networks as free (as in speech and beer) as possible. And it's working out so far. I hear Tim Pozar's neighbors keep him happy with occasional pies...
"Web Users Should Not Engage in Promiscuous Browsing" --CERT
Here is the Network Map: http://www.barwn.org/docs/BARWN_networkmap_200202
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