Beamformer phase optimization for a multi-layer MIMO system augmented by radio distribution network

• US 9,344,168 B2
• Filed: 07/01/2014
• Issued: 05/17/2016
• Est. Priority Date: 05/29/2012
• Status: Active Grant

• Current Assignee: Magnolia Broadband Incorporated
• Original Assignee: Magnolia Broadband Incorporated
• Inventors: Abreu, Eduardo, Harel, Haim, Kludt, Kenneth, Chen, Phil F., Wang, Sherwin J.
• Primary Examiner(s): Perez, James M
• Application Number:
  US14/320,920
• Publication Number:
  US 20140376671A1
• Time in Patent Office: 686 Days
• Field of Search: 375130-153, 375229-236, 375259-285, 375316-352
• US Class Current: 1/1
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/0456 Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04B 7/088 using beam selection

Abstract

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.

Claims

1. A multiple inputs multiple outputs (MIMO) receiving system receiving N channel layers transmitted from N transmit antennas, comprising:

a radio distributed network (RDN) having N beamformers, N being a positive integer greater than 1, each of the N beamformers having K_N antennas comprising one primary receive antenna and K_N−

1 additional receive antennas, K_N is a positive integer greater than 1;

K_N−

1 phase shifters within each of the N beamformers configured to phase shift the received signals from each of the K_N−

1 additional receive antennas within each of the N beamformers;

N combiners respectively associated with the N beamformers, each of the N combiners is configured to combine the K_N−

1 phase shifted signals and the received signal from the primary antenna for each of the N beamformers;

radio and baseband circuitry configured to receive the combined signals from each of the N combiners; and

the MIMO receiving system is configured to select K_N−

1 phases for the K_N−

1 phase sifters in each of the N beamformers that;

(a) optimizes performance of the N channel layers via channel estimation of each of the N layers as seen by the radio and baseband circuitry, and (b) maximizes a total received power from all transmitted signals received at the MIMO receiving system by all of the receive antennas.

2. The system according to claim 1, further comprising:

for each of the N beamformers;

(i) calculating channel functions h_i,j,k from each one of the N transmit antennas j, j=1, 2 . . . N, to each one of the K_N receive antennas i, i=1, 2 . . . K_N at frequency k, k=1, 2 . . . L, at a baseband module using channel estimation, and

(ii) selecting phases, wherein A={φ

₁, φ

₂ . . . φ

_R} so as to maximize a total power P_Total defined as;

3. The system according to claim 1, further comprising:

for each of the N beamformers;

adjusting each of the K_N 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 two antennas adjusted first as;

p_2,j,k=[abs(s_2,j,k)²], j=1, 2 . . . N, k=1, 2 . . . L, and

choosing φ

₂ε

A that maximizes

4. The system according to claim 3, wherein the optimization of the phase of the beamformer is calculated, wherein, once φ

_i-1 has been determined, φ

_i is calculated.

5. The system according to claim 4, wherein:

6. The system according to claim 4, wherein:

Φ

_iε

A A={φ

₁,φ

₂ . . . φ

_R}