Spectrally efficient mobile satellite real-time broadcast with transmit diversity

Mobile broadcast services from satellites require the terminals to constantly be in near line of sight conditions with the transmitting satellite in order to efficiently provide real-time services. To satisfy this constraint in practice, satellite diversity as well as terrestrial repeaters are used. By separating the various transmissions in frequency, exploiting this spatial diversity at the receiver is straightforward. However, transmitting the same information at different frequencies also reduces the limited and expensive spectrum available for these types of services. By configuring the different transmissions as a single frequency network, in principle, a more efficient usage of the spectrum can be achieved. Due to the vast distances involved in satellite diversity systems, practical design of such a system is challenging. In this paper, we propose the use of a small adaptive antenna at the receiver in order to separate the different transmissions and improve the spectral efficiency. System architectures are outlined; an example illustrates the potential gain, and implementation issues are discussed.