Setting up a Wi-Fi hotspot using Solar power

Here are my notes from lecture on Setting up a Wi-Fi hotspot using Solar power by Mitar Milutinovic . The lecture is part of bigger presentation of Ljubljana WiFi hotspot mash network – wlan-lj.

Lets start with buzzwords:

• ad-hoc
• mesh
• OLSR – for packet routing
• channels (they have to be on the same one)
• polarization of the signal has to be the same between all the spots

These buzzwords should be sufficient to get the system running by itself.

Cons:

• synchronized workings -> conflicts -> lower speeds. The good point in case of Ljubljana WiFi is that they can still connect to each other.

Developed hot-spots doesn’t connect only wirelessly, but also using wired connections. Namely, via Internet. This has an advantage that we can have a network of dispersed points, where network still works and the user doesn’t notice anything.

How did we do that? – Developed own firmware – based on OpenWRT Kamikaze

The network is currently getting around 4 users per day. It’s not much but everyone is happy about its humble beginnings 🙂

Bigger idea is to have plug-and-mesh system, online wizard that allows you generate a firmware for your WRT router, that allows anyone to easily join your mesh. The only limitation for this is access to electricity.

Lets solve the electricity problem!

• chosen power-source: solar cells

(alternatives discussed: power generators and hooking directly into public light system infrastructure)

Note: Solar cells are not solar collectors.

Basic idea – lets have lots of small cells that we use to form bigger units, that give us single current electricity. This way we can set it up on roofs where we don’t have access to any electricity. The issue is that normal solar cells work in cooperation with power grid, while we don’t have that luxury. They also have to work in winter and store enough power in accumulators to also continue working during the day. In order to achieve that, we need a higher capacity solution.

To power an OpenWRT Linksys we need 10W (we’re powering 2). To generate 20W we needed to use 1mx1m of solar cells.

Parts of such system: solar cells, batteries, regulator, Wi-fi point.

The system is using Plasmatronics P20 regulator. For which the Mitar also wrote open-source driver for Linux kernel. Additional add-on to the system was modification to add serial-port to the regulator, which is not part of mass market solution.

This is done to allow connection to Linksys serial port (which needs to be also manually modified).

What about actual solar power? Sadly the presenter was really short on detail about that, so I’m hoping there’s going to be a Part 2 of the presentation in the near future.

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