Line-of-sight multi-input multi-output enabled multibeam satellite system
The present teachings disclose a multibeam satellite system and methods that can achieve orthogonality between spatially multiplexed signals in a multi-input multi-output (MIMO) configuration when operating in line-of-sight (LOS) uplink and downlink channels on the feeder link side, using essentially a common spot beam. The teachings maximize a MIMO capacity across multiple frequency bands by disclosing an antenna array geometry for disposition on-board a single satellite and for a ground segment.
1. A method for providing Multi-Input Multi-Output (MIMO) feeder uplinks for a satellite, the method comprising:
separating X satellite antennae on the satellite;
pre-interference processing Y gateway uplink transmit signals to generate Y antennae uplink signals that minimize channel interference for a MIMO reception at the X satellite antennae;
disposing Y ground antennae in a manner that a MIMO transmission of the Y antennae uplink signals by the Y ground antennae is spatially orthogonal upon the MIMO reception at the X satellite antennae; and
pre-correcting the Y antennae uplink signals, based on the disposing of the Y ground antennae and the satellite, in a manner that the MIMO reception at the X satellite antennae experiences a cascaded channel effect,
wherein X is greater than 1, Y is greater than 1, the X satellite antennae are dominant line-of-sight (LOS) of the Y ground antennae, and a channel capacity of the MIMO transmission is greater than a channel capacity of Y Single-Input Single-Output (SISO) transmissions.
2. The method of claim 1 , further comprising transmitting the Y antennae uplink signals as the MIMO transmission; and receiving the MIMO transmission at the satellite.
3. The method of claim 1 , wherein the pre-interference processing is based on one or more of, a weighted or non-weighted version of, a zero-forcing (ZF) criteria, a minimum mean-square error (MMSE) criteria, or a regularized ZF (RZF) criteria.
4. The method of claim 1 , wherein the Y ground antennae are spaced within an acceptable range of an optimal position.
5. The method of claim 1 , wherein the satellite comprises one Geosynchronous Earth Orbit (GEO) satellite having a bent-pipe design, an on-board processing design, a transparent payload design, a regenerative payload design or a combination thereof.
6. The method of claim 1 , wherein X and Y are equal.
7. The method of claim 1 , wherein the pre-interference processing mitigates interference in a presence of an additive white Gaussian noise (AWGN) vector.
8. The method of claim 1 , where the pre-interference processing is based on a linear operation multiplying the Y antennae uplink signals with a matrix or a linear combination of the Y antennae uplink signals.
9. The method of claim 1 , wherein the Y ground antennae are interconnected via a fiber or microwave link.
10. The method of claim 1 , wherein the pre-interference processing is based on high-quality channel state information (CSI) about a propagation of the MIMO transmission.