Preprocessing of the superimposed signals in a layered modulation digital transmission scheme to use legacy receivers

摘要

Pre-processing of received signals for a layered transmission scheme is disclosed in which different data (400A,400B) is transmitted in the same frequency band from separate incoherent transmitters possibly located at different locations. This scheme permits a backward compatible upgrade of an existing system. The different data streams (400A,400B) are transmitted at different power levels, that is power division multiplexing is used. At the receiver side, the stronger upper layer signal is directly fed to a legacy receiver (412A), whereas the weaker lower layer signal is pre-processed (416) before being fed to another legacy receiver (412B). Pre-processing is done similar to a multistage receiver, which performs successive cancellation in order to extract each of the data streams. <IMAGE>