US Patent 8009782 Downscaling system bandwidth

A larger second bandwidth is fitted to a first transmission bandwidth by blanking PRBs at one or both edges of the larger second bandwidth. A first set of control channels is mapped to unblanked PRBs of the second bandwidth using a restricted set of physical cell identities that map only to the unblanked PRBs. A second control channel is punctured so that after it is interleaved and cyclically shifted the punctured CCEs fall on the blanked PRBs, and this second control channel is power compensated for the punctured CCEs. The first set and the second control channels are assigned in view of the puncturing and blanked PRBs, an IFFT for the larger second bandwidth is performed on a signal using zeros at the blanked PRBs, the signal is filtered to the first bandwidth and transmitted over a bandwidth not to exceed the first bandwidth.