Abstract: A terrestrial repeater is disclosed for use in a satellite transmission system that may also include a plurality of satellites. The terrestrial repeaters are implemented as OFDM transmitters to minimize the channel impairments caused by multi-path propagation. The OFDM terrestrial repeaters differentially encode the transmitted signal over frequency, as opposed to time, in order to avoid channel phase distortion. The OFDM receiver allocates two unmodulated sub-carriers as pilot bins and thereby provides two sub-carriers as a reference within each OFDM symbol. At the OFDM receiver, the two unmodulated pilot bins contain no phase information and provide a reference for the differential demodulation performed by the OFDM receiver. The OFDM transmitter operates in two modes, namely, a normal mode and a transmitter identifier information (TII) mode.

Abstract: A satellite digital audio radio system (SDARS) transmitter provides a broadcast transmission signal including a time division multiplex (TDM) mode of transmission and a coded orthogonal frequency multiplex (OFDM) mode of transmission. The SDARS transmitter provides a transmission signal that supports four transport mechanisms or traffic channels: (1) multiple audio and data program channels (program channels), (2) a cluster control information channel (CC), (3) a global control information channel (GC), and (4) a synchronization channel (CS). In particular, the SDARS transmitter processes 100 program channels into 5 clusters, each cluster comprising GC and CS information, along with a program cluster comprising 20 program channels and CC information. The SDARS transmitter further partitions each cluster into 255 cluster segments and interleaves the cluster segments from each cluster for transmission.

Abstract: In a wireless transmission system that transmits the same information in parallel using two or more different types of modulation schemes, such as a satellite-based digital audio transmission system transmitting two TDM signals and a single OFDM signal, a receiver processes the differently modulated signals to generate separate demodulated signals that are then combined to form a single combined signal for further processing (e.g., decoding). In one embodiment, the receiver applies a maximal ratio combining (MRC) technique to generate a single optimal ratio combined signal from the differently modulated signals. By combining the differently modulated signals using an MRC technique, the adverse affects of noise related to inter-symbol interference in the individual signals can be reduced and the complexity of hardware in the receiver can be reduced.