Adapting the WiMAX PHY layer for use in a GSM overlay system

Many of todaypsilas communication systems use only a small fraction of their allocated bandwidth. Cooperative overlay systems can make use of unallocated transmission capacity in under-utilized frequency bands without causing significant interference. Measurements taken in the GSM frequency range showed, that there are remaining transmission resources in such a cellular system. Therefore, GSM is used as an exemplary licensed user system with bursty traffic and varying usage rates providing a reasonable remaining capacity that can be utilized by an overlay system. WiMAX provides a highly flexible solution that can be adapted to the specific requirements of an overlay system. By adding elements for signalling of the current spectrum usage of the underlying GSM system to the WiMAX frame, the WiMAX overlay system is able to react very fast to changing utilizations of the spectrum. Frequencies that are currently used by a GSM subscriber can be abandoned in a very short time, and frequencies that have been released for a certain period can easily be reclaimed for overlay usage.