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Global Liaison Office (GLO) - DAAD


Disaster Recovery Multi-hop Access Networks

Project by Dr. Matthias Herlich between April 2014 and March 2015.


Radio access networks connect user equipment, such as mobile phones, to the internet. Radio access networks consist of base stations at fixed positions. The base stations receive data from the user equipment and forward it to the internet using a backbone network. Radio access networks have become an integral part of everyday live and are especially important in case of emergencies.

In small emergencies (e.g., traffic accidents and sports injuries) a radio access network can help to alert the emergency services to the situation. A radio access network is also able to help with the coordination of the following rescue operation. During large emergencies (e.g., earthquakes and floods) the amount of coordination and logistics that is needed is huge. But such disasters often also damage the base stations, which then cannot provide the necessary service when it is needed most.

The providers of radio access networks are usually quick (on a scale of weeks) to repair the damages to their infrastructure. However, coordinating both the survivors of the disaster and the rescue personnel is most important right after the disaster. Hence, any intermediate means of communication helps to save lives until the network operators are able to resume their service.

Other projects exist which try to restore internet connectivity from the outside. However, in this project we focus on how survivors can restore connectivity as good as possible with the means they have available themselves. We propose to use mobile phones to relay the communication of phones without connectivity towards phones with connectivity. We think this is a good choice as mobile phones are ubiquitous in nearly all societies today and are thus also widely available after a disaster. While they require electrical energy to operate, their batteries will allow them to operate for a few hours and many different possibilities exist to charge them even after a disaster: cars, external battery packs, hydrogen fuel cells, solar panels, hand cranks, and diesel generators.

The goal of this project is to determine how survivors of a disaster can use mobile phones as relays to restore internet connectivity without outside help and preparation. We will construct analytical models to describe the network and measure the performance of a network which we will deploy. The insights we gain during this will help survivors of a disaster setup a disaster recovery network themselves.

Publications at NII


  • Matthias Herlich, Shigeki Yamada: Optimal Distance of Multi-hop 802.11 WiFi Relays, Submitted at the IEICE Society Conference for 2014.