System and method for discrete gain control in hybrid MIMO RF beamforming for multi layer MIMO base station
A multiple-input-multiple-output (MIMO) receiving system configured for receiving multiple transmission layers is provided herein. The system includes a plurality of beamformed tunable receiving antennas configured to receive a plurality of transmitted layers; and a control module configured to select for the beamformed antennas a single set of discrete weights for tuning said antennas for all of the transmitted layers so that the weights are selected for optimal performance of said receiving system, wherein said selection is carried out based on an extended Maximal Ratio Combining (MRC) metric or other quality metric measured by the MIMO baseband module, and using said measured metric separately for each beamformed antenna to determine gain or attenuation independently of phase selection.
1. A system comprising:
a multiple-input-multiple-output (MIMO) receiving system;
a plurality of beamforming tunable receiving antennas configured to receive a plurality of transmitted layers;
a MIMO baseband module; and
a control module configured to select for the beamforming antennas a single set of discrete weights for tuning said antennas for all of the transmitted layers,
wherein said selection is carried out based on a predefined quality metric, being an extended Maximal Ratio Combining (MRC) metric, measured by the MIMO baseband module for each antenna, and using average of various signals measured separately for each antenna to determine gain or attenuation independently of phase selection.
2. The system according to claim 1 , wherein said gain or attenuation is carried out by mapping the quality metric measured for each antenna by the MIMO baseband control module to discrete values of gain or attenuation.
3. The system according to claim 1 , wherein the quality metric for each antenna is derived by calculating an average magnitude of the signal layers received by an antenna and dividing the average by the noise power for the same antenna, wherein said average is a voltage average or a square root of a power average of the individual layers received by the antenna, wherein the metric is further normalized to a maximum value.
4. The system according to claim 1 , wherein in a case that the measured metric being extended MRC metric of some of the antennas in a specific beamformer is smaller than a first threshold, the control module is configured to selectively disconnect said antennas.
5. The system according to claim 4 , wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is larger than said threshold, but lower than a certain other threshold, the control module is configured to selectively attenuate said antennas using predetermined attenuators.
6. The system according to claim 1 , wherein the control module controls a plurality of gain controlled low noise amplifiers (LNA), each one of the LNA being associated with a different antenna.
7. The system according to claim 1 , wherein the MIMO baseband module is configured to measure a signal level and signal to interference plus noise ratio (SINR) of each signal coming from the antennas, and wherein the gain or attenuation is based on a measured signal level and SINR of each signal coming from the antennas.
8. The system according to claim 2 , wherein the discrete values include maximum gain and “off”.
9. The system according to claim 2 , wherein the discrete values include maximum gain, one or more intermediate gain levels, and “off”.
10. The system according to claim 2 , wherein in a case that the internal noise dominates and the level of the respective signal is below a specific threshold, the gain control module applies the discrete level “off” to a specific signal coming from the antennas.
11. The system according to claim 2 , further comprising at least one combiner connected to at least some of the beamforming antennas, wherein in a case that the measured metric of all but one of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to bypass the combiner for the specific antenna or attenuate the other the antennas based on a threshold.
12. The system according to claim 2 , wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to selectively attenuate the weak antenna based on a threshold.
13. The system according to claim 2 , wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is worse than the metric for a specific antenna in the beamformer, the control module is configured to selectively disconnect the weak antenna based on a threshold.
14. The system according to claim 2 , wherein the control module sets a plurality of cascaded units each comprising a multiband controllable filter, a low noise amplifier, and a step attenuator, wherein each cascaded unit controls the gain of a different antenna signal.
15. The system according to claim 1 , wherein the control module controls discrete levels of attenuation.
16. The system according to claim 15 , wherein the discrete levels include maximum attenuation and an intermediate attenuation level.
17. The system according to claim 15 , wherein the control module sets a discrete level maximal attenuation to a specific signal coming from the antennas, in a case that a measured SINR of a respective signal is below a specific threshold.
18. The system according to claim 15 , wherein the control module sets a plurality of discrete levels attenuator configured to select between a connector, a pad having a specific attenuation level, and a disconnection, wherein each discrete levels attenuator controls the attenuation of a different antenna signal.
19. A method comprising:
receiving a plurality of transmitted layers via a plurality of beamforming tunable receiving antennas configured to receive a plurality of transmitted layers;
selecting for the beamforming antennas a single set of weights for tuning said antennas for all of the transmitted layers,
wherein said selection is carried out based on an extended Maximal Ratio Combining (MRC) metric measured separately for each antenna using average of various signals received by each antenna and using said extended MRC metric to determine gain or attenuation of the antennas independently of phase selection; and
transferring the beamformed signals to a multiple-input-multiple-output (MIMO) receiving system.
20. The method according to claim 19 , wherein said gain or attenuation is carried out by mapping the quality metric measured for each antenna by the MIMO baseband control module to discrete values of gain or attenuation.
21. The method according to claim 19 , wherein the quality metric for each antenna is derived by calculating an average magnitude of the signal layers received by an antenna and dividing the average by the noise power for the same antenna, wherein said average is a voltage average or a square root of a power average of the individual layers received by the antenna, wherein the metric is further normalized to a maximum value.
22. The method according to claim 19 , wherein in a case that the measured metric being extended MRC metric of some of the antennas in a specific beamformer is smaller than a first threshold metric, the control module is configured to selectively disconnect said antennas.
23. The method according to claim 22 , wherein in a case that the measured metric being the extended MRC metric of some of the antennas in a specific beamformer is larger than said threshold metric, but lower than a certain other threshold, the control module is configured to selectively attenuate said antennas using predetermined attenuators.
24. The method according to claim 19 , further comprising controlling a plurality of gain controlled low noise amplifiers (LNA), each one of the LNA being associated with a different antenna.
25. The method according to claim 19 , further comprising measuring a signal level and signal to interference plus noise ratio (SINR) of each signal coming from the antennas, and wherein the amplifying or the attenuating is based on the measured signal level and SINR of each signal coming from the antennas.