Method for operating a communication system

1. Method for operating a communication system, the communication system comprising at least two separate transmitting antennas located on Earth and at least two receive antennas located with a distance from Earth, the receive antennas having directional receiving patterns which cover a common region on Earth in which the at least two separate transmitting antennas are located, the method comprising:

precoding a number of symbol sequences before transmission from the transmitting antennas to the receive antennas in order to reduce spatial interference between the symbol sequences,

simultaneously transmitting symbol sequences from the transmitting antennas to the receive antennas by spatial and frequency multiplexing in a time and phase synchronized fashion, where symbol sequences that differ from each other are transmitted on the same frequency by transmitting antennas that differ from each other;

generating a number of K independent symbol sequences such that for a given instant of time the symbols from all symbol sequences form a vector of length K; and

processing the vector with a linear or non-linear technique and assigning the K independent symbol sequences to a specific transmitting antenna and to a specific uplink frequency channel of the respective transmitting antenna.

2. Method according to claim 1 , further comprising:

converting the symbol sequences received by the receive antennas from a respective uplink frequency channel to a downlink frequency channel and forwarding the symbol sequences on the downlink frequency channel.

3. Method according to claim 1 , further comprising:

processing the symbol sequences after receipt at the receive antennas in order to reduce spatial interference between the symbol sequences, and

converting the processed symbol sequences from a respective uplink frequency channel to a downlink frequency channel and forwarding the symbol sequences on the downlink frequency channel.

4. Method according to claim 1 , further comprising:

forwarding the symbol sequences from the receive antennas to multiple ground receivers on Earth.

5. Method according to claim 4 , wherein the ground receiver are not connected with each other.

6. Method according to claim 4 , wherein at least a part of the ground receivers forms a MIMO system.

7. Method according to claim 6 , wherein multiple MIMO systems are formed which are separate from each other.

8. Method according to claim 1 , further comprising:

processing the vector such that the source symbols are distributed among all uplink frequency channels of the transmitting antennas.

9. Method according to claim 1 , wherein the transmit antennas are inter-connected with each other via a central processing unit which supervises the generation of the symbol sequences which are to be transmitted to the receive antennas.

10. Method according to claim 1 , wherein the receive antennas are satellite based, and based on at least one satellite in space and based on a single satellite in space.

11. Method according to claim 10 , wherein the receive antennas are provided on multiple collocated satellites.

12. Method according to claim 1 , wherein the receive antennas are located on one high-altitude platform or multiple high-altitude platforms.

13. Method according to claim 1 , wherein the transmitting antennas are located on earth on a respective fixed position, the fixed positions being separated from each other by a distance of at least 10 km.

14. Method according to claim 1 , further comprising:

precoding the symbol sequences before transmission from the transmitting antennas to the receive antennas in order to improve robustness against atmospheric impairments.

15. Method according to claim 1 , further comprising:

deactivating a transmit antenna when it suffers from a too strong rain fade attenuation.