Nomadio Range Finder
Add Location Awareness to Any Wi-Fi Network
Nomadio Range Finder allows you to quickly and easily find the link distance to any other Wi-Fi radio with 2 meter accuracy. When used as the Wi-Fi radio for your network, it can automatically generate graphs of distances between your computers, and even locate on maps (if enough of the radios have known locations). In survey mode it can reach out to, and measure distances to access points without needing to join their networks.
Range Finder consists of a commercial off the shelf USB Wi-Fi (802.11n) card and software that finds the range to other Wi-Fi radios. This can either be done actively (by probing the other card), or passively, by listening to the data traffic between the two cards, if there they are actively communicating. When running passively, there are no extra packets to allow an observer to realize that you are measuring range.
The data will automatically propagate both this graph of range information and any GPS information that is available to all of the nodes on the network. A web based graphical user interface can both display this information for users and log it for later analysis.
How it Works
Range Finder takes advantage of special packets in the 802.11 standard that are generated automatically by the hardware of the Wi-Fi radio chips in response to certain events. These hardware generated packets are created in such predicable time frames that the Range Finder software can calculate distances by subtracting out the time that it takes hardware to generate such a packet, and is left with the time that it takes light to make a round trip between the two radios.
How it's Used
Range Finder can be run in one of three different modes:
- Active Cooperative Mode: In active cooperative mode, all of the radios on the network are running Range Finder. In times that the radios are not sending data packets, Range Finder sends additional probe messages over the air to the other radios. In this case, Range Finder can maintain real-time range information between the radios. If you're on the same network and actively sending data, Range Finder can use the data packets that your computer is already sending to determine the ranges without extra messages.
- Passive Cooperative Mode: In passive cooperative mode, Range Finder does not generate any extra packets, and instead bases its estimates on the data packets that other applications are sending over the network. Observers will not see any extra packets to hint as to the range finding, and no extra power is used on the range finding activity. On busy wireless links this can have the same performance as the active cooperative mode, but on rarely used links, range information may be updated at a rate of minutes per reading.
- Active Survey Mode: In survey mode, Range Finder can find other Wi-Fi radios that are not part of the network and actively probe them to find the ranges to them, even if they are part of an encrypted network that Range Finder does not have the encryption keys to. It takes less than 10 seconds to probe each other radio for distance.
Features
- Measures ranges to Wi-Fi radios with 2 meter accuracy
- Ranges found within 10 seconds with active pinging
- Ranges can be found simply by listening to regular Internet traffic, if computers are networked
- Works against access points, even if you're not on the network
- Compatible with all Wi-Fi standards 802.11a/b/g/n
- Does not need Range Finder on radios being probed
- Range Finder networks: If Range Finder is on all of the computers on network:
- Automatically generate maps of distances between computers
- Can tell range to any wifi radio (other radio does not need range finder software)
- OLSR plugin integrates Range Finder with mesh networking and GPS data
- Web front end
- Supported OS: Linux, on x86 or ARM