Mesh Network
For this project the Cubesat team is working to establish a mesh network between a network of Cubesat's in low earth orbit. The goal of this network is to be able to receive data from a client satellite in low earth orbit, send it through the mesh to a receiver on earth faster than the client satellite could do it alone. This is a useful service to have because satellites in higher orbital patterns that are able to broadcast data over larger areas of earth, satellites in low earth orbit may not be over the radio dishes they send their data to often enough to make all the data they collect useful. If there is a mesh network in orbit around the earth that these satellites can send their data to, the owners of these satellites will be able to make greater use of the data they collect which gives the owners more up to date information and can lead to the possibility of even more research due to the faster availability of data.
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A mesh network is a local area topology where a number of nodes (individual CubeSat's in this context) can communicate with each other along flexible routes that can change to find the most efficient route to transmit data and prevent the system of being compromised if one of the nodes is down. The mesh network we are using is called a partially connected mesh network because all the nodes will not be in communication at all times. Near earth space is a massive area and it is very difficult and impractical to have connection between all nodes so the goal is to have at least two nodes in communication at a time so they can relay data acquired from a client to a radio receiver on earth. Another advantage of this system is the ability to transmit data from different clients at the same time. Not all the nodes will be used at once so nodes that would otherwise lay dormant will be able to receive data and transmit it along a separate route.
To build the mesh network, we are currently using an XBee S2C transmitter controlled by an Arduino Uno. This is a powerful system because it has an extremely low power requirement, can transmit data as speeds up to 250 KBPS and has an extremely low cost. Despite these capabilities, the XBee's range is limited to about 4000 feet which is impractical for a real world system. There are other alternatives however, other radio transmitters do exist, one we are currently looking into is called LoRa that has a range of tens to hundreds of kilometers depending on the size of the antenna but this technology is handicapped by a max transmission rate of 50 KBPS so it may not be viable either. No matter what the team ends up doing to solve this problem the outcome will be unique.
