Beamformer phase optimization for a multi-layer MIMO system augmented by radio distribution network
A system for selecting optimal phase combinations for RF beamformers in a MIMO hybrid receiving systems augmented by RF Distribution Network. The system addresses the issue of providing beamforming gains for a plurality of layers using one common set of weights for each beamformer. The specification may be based on channel estimation of all layers as viewed by all receiving antennas, and maximizing metrics that capture the total received power.
1. A multiple inputs multiple outputs (MIMO) receiving system having number N channels, comprising:
a radio distributed network (RDN) having number N beamformers, each having number K i receive antennas, wherein N is an integer greater than 1 and each K i is an integer greater than 1 for 1≦i≦N; and
a phase shifter coupled to each one of the K i receive antennas in each one of the N beamformers,
wherein the MIMO receiving system is configured to: (a) determine a phase for each one of said phase shifters that optimizes performance of said MIMO receiving system when receiving a plurality of transmit streams from a plurality of transmit antennas, wherein the optimization is achieved by channel estimation of each one of the transmit streams as seen by each one of the receive antennas, and (b) select a phase for each receive antenna that maximizes a total received power from all transmit streams reaching said receive antenna, wherein the total received power is calculated based on the channel estimation, wherein phase optimization is carried out by:
adjusting the antennas one by one recursively, wherein, φ 1 is set to zero, and only contributions from h 1,j,k and h 2,j,k are used to calculate φ 2 ;
defining a combined channel S 2,j,k and a channel power p 2,j,k for the first two antennas as: p 2,j,k =[abs(S 2,j,k )] 2 , j=1, 2 . . . M, k=1, 2 . . . L; and
choosing φ 2 εS that maximizes −
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2. The system according to claim 1 , wherein the MIMO receiving system is configured to optimize a beamformer phase by performing channel estimation of each transmit stream from each receiving antenna, selecting metrics that capture the total received power, and using relative phase setting between various antennas to calculate a set that maximizes said selected metrics.
3. The system according to claim 1 , wherein the optimization of the phase of the beamformer is calculated wherein once φ i-1 has been determined, is calculated.
4. The system according to claim 3 , wherein:
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p i,j,k =[abs(s i,j,k )] 2 , j=1, 2 . . . M, k=1, 2 . . . L, and
wherein the algorithm chooses φ i εA, i=1, 2 . . . K b , for beamformer b that maximizes
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5. The system according to claim 3 , wherein:
h i,j,k j, j=1, 2 . . . M, i, i=1, 2 . . . K, k, k=1, 2 . . . L, φ i εA, i=1, 2 . . . K, A={φ 1 , φ 2 , . . . φ R }
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P j,k =[abs(s j,k )] 2 j, j=1, 2 . . . M, k=1, 2 . . . L.
6. A multiple inputs multiple outputs (MIMO) receiving system having number N channels, comprising:
a radio distributed network (RDN) having number N beamformers, each having number K i receive antennas, wherein N is an integer greater than 1 and each K i is an integer greater than 1 for 1≦i≦N; and
a phase shifter coupled to each one of the K i receive antennas in each one of the N beamformers,
wherein the MIMO receiving system is configured to: (a) determine a phase for each one of said phase shifters that optimizes performance of said MIMO receiving system when receiving a plurality of transmit streams from a plurality of transmit antennas, wherein the optimization is achieved by channel estimation of each one of the transmit streams as seen by each one of the receive antennas, and (b) select a phase for each receive antenna that maximizes a total received power from all transmit streams reaching said receive antenna, wherein the total received power is calculated based on the channel estimation, wherein phase optimization is carried out by:
calculating channel functions h i,j,k from each one of the M transmit antenna j, j=1, 2 . . . M to each one of the K receive antenna i, i=1, 2 . . . K at beamformer b, b=1, 2 . . . N, at frequency k, k=1, 2 . . . L, at the baseband module using channel estimation;
selecting phases, wherein A={φ 1 , φ 2 , . . . φ R } so as to maximize a total Power P TOTAL defined as:
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wherein P j,k denotes power associated with each one of received signals S j,k wherein
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j=1, 2 . . . M, k=1, 2 . . . L so that P j,k =[abs(S j,k )] 2 , j=1, 2 . . . M, k=1, 2 . . . L; and
repeating the calculating and the selecting stages for each one of the N beamformers.