Knowledge Brings Fear

Blog hardware

I get the feeling that it is time for some small portable blogging hardware that can be used in the train, while waiting or whereever. I have the best ideas then. But wrestling the notebook from the backpack under the prying eyes of the greedy youth next to me seems not the wisest choice. Plus I carry the notebook often, but not allways.
Assuming that I wont have the necessary spare money for a bloggers luxury item for some months to come, I opted for a slow and determined process of reviewing the current and future aviable hardware for the purpose.

Requirements

Desireable requirements from my point of view would be:

Hardware

- form factor of max 15 x 10 x 3 cm
- a not too flimsy keyboard,
- a display of at least 640x240,
- builtin or plugable WLAN,
- Bluetooth (preferably builtin)
- a Cam of at least 640x480 pixel
- battery lifetime of 72 days under expected blogger use patterns
- non-volatile memory in case the battery fails
- at least 128Mbyte free memory
- some port, slot or connectivity to add GPS (of course builtin would be preferable)

Software (does not need to be part of the product, availability for the device is sufficient)

- a ssh2 client
- a SSL 128bit capable webbrowser
- a blog software that allows for preparation of entries including pictures, to be synched when WLAN is available or via Bluetooth and GPRS in emergency
- IM client that supports AIM and jabber
- a IMAP4 capable e-mail client
- a WebDAV client

Of course I would prefer to buy such a device from Apple, but given their negative past experiences with PDAs I dont hold my breath waitng for the wonder.

Weekend Fun

I will spend the weekend outside of Berlin, escaping from the Love Parade. The location of choice is Schloss Dahmsmühle were the Nation of Gondwana outdoor party will take place. Lineup and details can be obtained from the Pyonen .

power to the roof

Power-over-Ethernet is something that most people doing WLAN links have allready played with. Since ethernet uses only the pins 1,2,3 and 6, you get four of the eight wires left inside the ethernet cable linking to your rooftop basestation for power supply. Usualy the basestation takes 12V. Depending on length of cable you need to put in more to compensate for the resistance of the cable. Usualy you end up with 16-20V going in and something like 12V coming out.

The drawbacks of power-over-ethernet are numerous. You need to be really carefull when crimping the cable. You need some sort of wall socket to hold the crimped setup.You need be carfull with the setting on the power supply.The original power supply will not do most of the times since the supplied voltage is to low for the length of the cable, so you need to buy a new, more powerfull and flexible power supply. If one wire in the ethernet cable breaks, you dont have any spare wires left since normaly you need all 4 remaining ones to get enought wire diameter for the power needed. Wire break does happen while laying the cable and from wind wear and tear on the cable. All in all, I ended up with putting two cables to the roof, one ethernet, one 230V power. This is of course not very concealed and a lot of work.

So today arrived a solution to the problem that I hope will solve the ethernet cable problem once and for all: Ethernet-over-Power. There is a industry standard called HomePlug that uses one of the currently most advanced modulation methots called Orthogonal Frequency Division Multiplexing (OFDM) to transmitt up to 14MBit (theortical) over plain old power lines in your home. I got ftp transfers of 720KByte/sec accross one floor, thats 5.76MBit real world transfer rate. A touch better then WLAN.

OFDM is the best way to show that Moores law translates directly into faster communications. The mathematics behind OFDM processing are rather heavy, I didnt understand the details completely on first try so I spare you the details. The HomePlug stuff uses 84 individual frequency bands that are spread out between 4 and 21 MHz. Continious measurement adapts the usage of the bands to the line noise from your electric appliances. Since some noises are rather spiky in nature, error-correction is also in heavy use.

Some testing in the company showed a remarkable reach of the coverage. The drawback of the ALLNET ALL1682 Ethernet Bridge Adapter I have is that you need a PC to do the initial setup. The setup consists basicaly in putting in a password (used by the DES line encryption as a seed for the key) and connecting the devices you want to use together into a network. Rather simple and straightforward, I actually needed longer then anticipated because I was looking for something complicated that I must have overlooked, not noticing that the network was allready up and running.

I am the first to admitt that it looks a bit counter-intuitive to plug a ethernet cable into something that looks like a power plug, but as expected it did not fry my computer.

So the setup for a rooftop basestation now is only to put power up there and use HomePlug to get the bits moving. Power cables tend to be much more solid then ethernet, dont suffer from broken wires, dont need to be crimped and - best of all - transport sufficient power to run also multiple devices on your roof. Great if your are running stuff in multiple directions. If you can use power allready aviable on the roof, your setup now looks like just an ordinary TV antenne distributor. You might be unlucky when the power avialbe on the roof is on a completele seperated phase, meaning that the HomePlug adapters cant see each other on the wire. The only way to find out is to try.

Tommorow I will put the stuff up on the roof, hopefully fixing my brooken home network link.

Kameras

Lucky wies mich gerade darauf hin das die Markierung der Kameras im BART vermutlich weniger als eindeutige Kommunikation der Überwachungssituation gegenüber den Beobachteten dient. Früher waren die Kameras mit Aufklebern gekennzeichnet. Die blinkende LED soll nun eher dafür sorgen das jeder wenigstens einmal ordentlich Richtung Kamera schaut und so ein brauchbares Bild abliefert.

Vor dem Hintergrund der stetigen Fortschritte im Bereich automatisierter Bildverarbeitung macht das Sinn, eines der noch nicht hinreichend gelösten Probleme ist die Gesichtsidentifizierung wenn der Betroffene sein Gesicht nicht in einem brauchbaren Winkel zur Kamera positioniert. Wenn da nun was blinkt steigt die Wahrscheinlichkeit des unbewussten Hinschauens.