Functional radio communication systems are crucial for the armed forces to complete their mission. Coexisting subsystems on a platform, as well as the decreasing frequency spectrum, are key factors affecting the performance and reliability of communication systems on military platforms. The limited frequency availability for military systems directly affects jamming resistance, as well as the ability to handle complications of coexistence and intersystem interference. These topics pose enormous demands on effective frequency planning. This report introduces techniques and methods for utilizing available frequencies more effectively and to improve the coexistence of radio systems located on the same platform. Methods presented in the report consist of spectrum sensing with in-band full duplex, meaning simultaneous transmission and spectrum sensning on the same frequency in order to make the frequency usage more efficient. A conceptual frequency conflict management method describes how warnings for potential frequency conflicts can be created and how such conflicts can be handled. Additionally, the importance of synchronized cooperative broadcast (SCB) as an access method for coexisting networks is discussed. The limited frequency space for radio communication can partially be reduced by letting parts of the communication go through radio systems that are not using the armed forces own frequencies, which can, for example, be achieved by utilizing cellular systems. In order to facilitate a part of the increasing need for communication, and to alleviate traffic load as well as increasing redundancy in the form of more possible paths of transmission, three techniques, based on 3GPP networks, are presented as possible solutions. The techniques include privately owned cellular networks, partly owned networks as well as using a Swedish operators established cellular network for communication. Of the alternatives, a core network operated by the armed forces, combined with cellular radio access operator networks constructing a Multi-Operator Core Network (MOCN) is regarded as the alternative that provides most disposition with respect to the cost. The electromagnetic environment can never be predicted exactly, as it changes dynamically, for example due to transportation between different surroundings or unforeseen co-location events. Several possible solutions may retain the system performance in such situations, such as adaptive reception, where the receiver design is adapted according to statistical characteristics of the interference, or index modulation, where information is represented in the signal transmission by indexing the channel resources.