One of the scarcest resources in current and future wireless communication systems for providing more capacity and higher data rates is available frequency spectrum. A possible way forward to meet the demands for more spectrum is to use the limited spectrum in a more efficient way, e.g. through spectrum sharing. This means that different systems are allocated to the same spectrum, the systems possibly being of completely different kinds (e.g. a radar system and a terrestrial mobile communication system). To be able to share spectrum, the interference from the other systems must be managed in a proper way.
In current mobile communication systems, interference from other systems is not dealt with in any particular way. It is handled as thermal noise or intra-system interference, and hence the co-existence with other systems within the same spectrum is virtually impossible. Due to the fact that interference affecting reference symbols, control signalling, synchronization symbols and user data affects the system differently, a strong interfering pulse from e.g. a radar system, though very short in time, might severely impact the performance of the system by affecting the synchronization symbols, reference symbols and/or control signalling. This is because achieving synchronization is a necessary first step, reference symbols are assumed to be representative for the data and control signalling is used for decoding data.
The document 3GPP R1-063431 entitled “Initial cell search: analysis and simulations” which is a standardization proposal from Qualcomm, proposes way of modifying the position in time of the synchronization channel in order to avoid the superposition of synchronization channels from different cells of the same system, but does not propose any solution to the problem of interference from other systems having different characteristics and using a different frequency band.