This report summarises briefly the research at FOA during 2000 about Communication Systems. The research has comprised robust communication, fundamental physical properties regarding wave propagation, mobile wireless networks and interference between communication and other electronic systems. The area comprises six projects, which are described in this report. One of the projects has been about reporting position data from every vehicle in a mechanized unit using a mobile network. The work has been done in close collaboration with the Armed Forces. Conflict handling methods in a multi hop radio network, has been studied. An experiment system for simulating communication links has been completed. Tools for analysing interference have been refined and used in a couple of tactical scenarios. The use of broadband electrical steerable antennas with respect to robustness has been studied. A simulation model for radio wave propagation close to the ground, has been refined.