Guard Bands for Coexistence of UMTS and DVB in a Hybrid Radio System

In the DRiVE project, a flexible, hybrid communication system has been developed which performs dynamic allocation of spectral resources from a common region of spectrum to the participating radio systems. Thus, new spectral neighborhoods emerge, which pose requirements regarding the protection of one system from the adjacent channel interference generated by the other system. As an example, DRiVE has focused on a hybrid system consisting of digital TV broadcast (DVB-T) and UMTS. The resulting spectral neighborhood of powerful DVB-T transmitters and UMTS requires guard bands between the dynamically assigned spectral regions, and thus decreases the overall spectral efficiency of the hybrid radio system. This paper presents the results of simulative studies on the required size of the guard band in order to provide sufficient QoS in the participating systems. Additionally, the importance on the implementation-dependent transmitter and receiver quality is examined, taking into account laboratory measurement of available DVB transmitters and receivers. It is shown that while worst case requirements on DVB transmitter out of band performance set forth in the relevant standard can lead to poor system performance in some scenarios, state-of-the art equipment can easily exceed those requirements, and suitable allocation of channels can further improve the system performance, thus leading to satisfactory coexisting operation of UMTS and DVB-T, with only a small loss of spectral efficiency due to guard bands.