Saturday, February 16, 2008

Caveat on the AR5418

A couple of days ago, I posted about success with the AR5418 and the madwifi driver. That initial success was with 802.11a and 802.11g networks.

This morning, I got it working with an 802.11b network, but not with NetworkManager. NetworkManager could see the access point, but for some reason was unable to actually get an IPv4 address via DHCP. I killed the NetworkManager (/etc/init.d/NetworkManager stop), and ran dhclient ath1 by hand (as root, of course), and it had absolutely no problem picking one up. Not sure why yet, but if you're using NetworkManager and having trouble, try it by hand and see what you get.

[root@localhost Desktop]# cd /etc/init.d
[root@localhost init.d]# ./NetworkManager stop
NetworkManager デーモンを停止中: [ OK ]
[root@localhost init.d]# dhclient ath1
Internet Systems Consortium DHCP Client V3.0.6-Fedora
Copyright 2004-2007 Internet Systems Consortium.
All rights reserved.
For info, please visit
wifi0: unknown hardware address type 801
wifi0: unknown hardware address type 801
Listening on LPF/ath1/00:19:7d:a:b:c
Sending on LPF/ath1/00:19:7d:a:b:c
Sending on Socket/fallback
DHCPDISCOVER on ath1 to port 67 interval 7
DHCPOFFER from 210.x.y.z
DHCPREQUEST on ath1 to port 67
DHCPACK from 210.x.y.z
bound to -- renewal in 1402 seconds.

Hmm, actually, it occurs to me that I have my network at home set up with the same ESSID as the one here, just for simplicity's sake. It's possible that NetworkManager has cached some info (netmask, AP MAC addr, channel, modulation scheme, something) that doesn't match between the two. Worth looking into...

Thursday, February 14, 2008

MadWifi, Fedora 8, AR5418 (Lenovo X60)

Okay, the WLAN is working now!

After finding something similar (not exact, as you'll) on the MadWifi forums, and finally figuring out that I needed madwifi-trunk (as distinct from "most recent release"), the instructions here worked like a charm.

It even works with NetworkManager. Haven't tried WEP yet...

This is with kernel- and a yum update as of Valentine's Day, with livna enabled as a yum repository.

[rdv@dhcp-148 ~]$ iwconfig
lo no wireless extensions.

eth0 no wireless extensions.

irda0 no wireless extensions.

wifi0 no wireless extensions.

ath1 IEEE 802.11a ESSID:"redacted" Nickname:""
Mode:Managed Frequency:5.21 GHz Access Point: redacted
Bit Rate:36 Mb/s Tx-Power:13 dBm Sensitivity=1/1
Retry:off RTS thr:off Fragment thr:off
Power Management:off
Link Quality=37/70 Signal level=-59 dBm Noise level=-96 dBm
Rx invalid nwid:113352 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

Tuesday, February 12, 2008

Reversible/Quantum Arithmetic

Just noticed that Qwiki has moved to Stanford, dragging with it the page on quantum arithmetic. (As long as we're talking moving arithmetic pages, mine moved last year, too.)

As a Caltech alum, it saddens me that Hideo has moved. Ah, well, Pasadena's loss, Palo Alto's gain. As long as good research keeps rolling out of his lab, his team's making the world a better place. Good luck, Hideo.

Saturday, February 09, 2008

Microcell at Home?

An article in the Feb. 8 Daily Yomiuri, which unfortunately appears not to be online, says that the government is considering rules to allow people to small cell phone base stations into their houses without a license, to improve reception in basements and houses where the signal is weak. My mother-in-law's house could certainly use one for FOMA...

Jazz in Tokyo

I don't get out to hear live music often enough, but I'm excited by the discovery of Tokyo Jazz Site nonetheless. It was profiled in the Japan Times the other day.

I have only a small fraction of the experience of James Catchpole, but I'll put in a plug for the Blue Note anyway. I happen to think that the food is pretty good; dinner of that quality will cost you 4-7,000 yen anywhere in Tokyo, about what it costs you at the Blue Note. Yes, the shows are expensive and the sets short; but the names are top drawer, and hearing oh, say, the late Oscar Peterson cost us $75 a head in New York ten years ago, and he was sold at $100 a head at Yoshi's Oakland a few years ago, so the difference in price doesn't seem as outrageous to me as it otherwise might. Yes, hearing live jazz is expensive, but even at that, the artists and clubs are mostly making a modest living.

Besides, even going out to the second-tier clubs is Tokyo ain't cheap most of the time. Cover charge for people you've never heard of can be 3-4,000 yen at an obscure club, where a mediocre dinner and overpriced drinks still run the tab to 6-8,000 yen a head. Yes, that's a big difference from the 10-12,000 yen you'll spend at the Blue Note, but the jazz and food will be a lot better. Catchpole gets out much more often than I do, and can afford to trade time for money looking for the exciting, obscure players in the good-for-the-money clubs, but I don't want to waste one of my few trips to a club a year on something disappointing.

Of course, now that I know about his web site, I should be able to improve my hit rate and economize at the same time. Looking forward to reading up on it!

Speaking of such things, a little hole in the wall here in Kamakura named Tipitina has bossa nova tonight. Hmm. I'm at home for the evening with my girls, though.

Traffic Monitoring Using Ubiquitous Computing

The most ubiquitous computing device in the world at the moment is probably the cell phone. Certainly it's the most common network connected device in the world, and it's pretty much always on.

One of the dreams of recent years has been to take advantage of that latent capability. Now Nokia and Berkeley are turning cell phones into traffic monitors.

Nice work.

Arithmetic on a Distributed-Memory Quantum Multicomputer

Huzzah, our paper in JETC is now available!

This paper is an extended version of our ISCA paper from 2006, and is also available on the arXiv.

Tuesday, February 05, 2008

More Snow in Kamakura

...or more pictures of yesterday's snow, anyway. This one is Honkouji. My great-aunt loves jigsaw puzzles, I may see if I can get this one printed onto a puzzle for her.

Sunday, February 03, 2008

Doing Science on a Quantum Computer

Last week was The Third Workshop on the Theory of Quantum Computation, Communication, and Cryptography (TQC 2008), held here in Tokyo. One of the invited speakers was Ignacio Cirac.

I asked the following question (first in dinner conversation, then during my presentation):

When will the first Science or Nature paper appear in which the results are calculated on a quantum computer, but the point of the paper is not the quantum computer?

That is, when will a quantum computer do science, rather than be science?

Ignacio answered, "If you include quantum simulations, within five years."

[In quantum simulation, which is something like Feynman's original vision of quantum computers, you set up your device so that it emulates the behavior of a different physical system -- like simulating a set of mechanical oscillators using an RLC circuit.]

Call me an optimist, but I'm with Ignacio.

Maybe we need a LongBet on this...

Snow in Kamakura!

Apparently a light dusting of snow happens most years, but today we're getting a substantial accumulation (15cm or more) of heavy, wet snow.

I used to look at ukiyo-e of snow in this country, or watch jidai-geki (period piece, meaning samurai) movies and wonder why people in this country used umbrellas in the snow, rather than putting on a decent coat and leaving it at that. In America, it's sort of rare for people to use umbrellas in the snow, but I now get it. Here, even up in Yuki-guni (Snow Country) parts of Japan, most of the time it's not really cold. It's right around freezing, which is not actually uncomfortable unless you're wet -- and the snow here will soak right through many a winter coat, where in a colder, drier climate you could brush the snow right off.

The Great Buddha has been sitting outside in the sun and snow for 510 years, now. He doesn't seem to mind, though in the snow I suspect it takes more willpower to remain so stoic.