Basic idea
satellite to earth - when mur.sat finds itself within reach of one of the GroundStationNetwork stations it will try to send as much collected data to the station. The station then will forward this data via internet to the mur.sat SpaceCenter.
earth to satellite - there will be different ways to upload different kinds of data to mur.sat. All this data will pass through a server controlled by the SpaceCenter. This server will then send data to all of the stations that form the GroundStationNetwork. When mur.sat is within reach of a station this station will start uploading as much data as possible. It will then inform the other stations of successfull uploads so they can remove stored data from their queues. In addition mur.sat can itsel refuse to accept data that it already has received from a different station.
we could consider taking part in and making use of GENSO
Technical details
Layer 1
Interesting information by the ITU concerning frequencies for amateur satellites
Layer 2
Layer 3