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

• US 8,767,862 B2
• Filed: 02/25/2013
• Issued: 07/01/2014
• Est. Priority Date: 05/29/2012
• Status: Expired due to Fees

• Current Assignee: Magnolia Broadband Incorporated
• Original Assignee: Magnolia Broadband Incorporated
• Inventors: Harel, Haim, Kludt, Kenneth, Chen, Phil F., Wang, Sherwin J., Abreu, Eduardo
• Primary Examiner(s): Ghulamali, Qutbuddin
• Application Number:
  US13/776,204
• Publication Number:
  US 20130322561A1
• Time in Patent Office: 491 Days
• Field of Search: 375/260, 375/267, 375/259
• US Class Current: 375/267
• 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 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

₂ε

S that maximizes −

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:

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

_iε

A, i=1, 2 . . . K, A={φ

₁, φ

₂, . . . φ

_R}

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;