This paper presents an approach to realize integration of heterogeneous systems. Vertical handover thereby is seen as a key feature to allow for interoperability. In order to properly perform handover decisions, interference information with respect to the target system need to be available. For this, dedicated scanning procedures are necessary causing problems if a mobile is using continuous transmission and reception schemes like in UMTS FDD mode. To overcome this problem, different methods are mentioned, whereby a special focus is put on the compressed mode, since alternative means of making measurements are not yet considered within 3GPP. However, it is shown by means of simulations, that applying the compressed mode has a negative impact on the overall system performance. Therefore, another approach is introduced that relies on integrating measurement reports of other systems to support the VHO decision process. The proposal features by continuous operation during information gathering and facilitates reduced power consumption.