MITIGATING INTERFERENCES FOR A MULTI-LAYER MIMO SYSTEM AUGMENTED BY RADIO DISTRIBUTION NETWORK

• US 20140056378A1
• Filed: 10/31/2013
• Published: 02/27/2014
• Est. Priority Date: 05/29/2012
• Status: Active Grant

• Current Assignee: Magnolia Broadband Incorporated
• Original Assignee: Magnolia Broadband Incorporated
• Inventors: Harel, Haim, Abreu, Eduardo
• Granted Patent: US 8,811,522 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming

Abstract

A wireless User Equipment (UE) receiving system, may include tunable receiving antennas; a channel estimation module configured to: carry out a periodic, non-continuous channel estimation to a plurality of desired signals and undesired co-channel downlink signals which are transmitted from different base stations and received by said plurality of antennas, causing interference;, wherein the UE receiving system is configured to select between: tuning said plurality of tunable receiving antennas so as to maximize the total average power of said desired signals; and tuning said plurality of tunable receiving antennas so as to minimize the total average power of the strongest undesired co-channel base station'"'"'s signals. Alternatively, the tuning is carried out so as to maximize a power ratio between said desired signals and a combination of said undesired co-channel downlink signals having the strongest interference level and an internal noise of the receiving system.

Claims

1. A wireless User Equipment (UE) receiving system comprising:

two or more beamformers, each beamformer having a plurality of tunable receiving antennas; and

a control module configured to;

carry out a periodic, non-continuous channel estimation on a plurality of desired signals and a plurality of undesired co-channel downlink signals which are transmitted from different base stations and received by said plurality of antennas; and

identify the undesired co-channel downlink signals having the strongest interference level,

wherein the control module is configured to select between two alternative weights tuning based on best signal plus interference to noise ratio (SINR) by;

tuning said plurality of tunable receiving antennas so as to maximize the total average power of said desired signals; and

tuning said plurality of tunable receiving antennas so as to minimize the total average power of the identified undesired co-channel downlink signals having the strongest interference level.

2. The UE receiving system according to claim 1, wherein the UE receiving system is a multiple inputs multiple outputs (MIMO) receiving system having number N channels, wherein each of the channels is associated with one of the beamformers and wherein the total number of said plurality of tunable receiving antennas is M=Σ

_j=1^NK_j wherein K_j is a number of tunable antennas for the j_th beamformer, wherein M is greater than N.

3. The UE receiving system according to claim 2, wherein the UE is configured to tune the receiving antennas of a beamformer with K antennas, wherein K may be different for each beamformer, by:

choosing for all beamformer antennas i (1 to K), amplitudes a_i=1 and phases Φ

_iε

A, wherein A is a finite set of discrete phases, so as to maximize the total average power of the desired signals;

choosing for all beamformer antennas i (1 to K), amplitudes a_i=1 and phases Φ

_iε

A so as to minimize the total average power of the undesired co-channel downlink signals having the strongest interference level;

comparing the measured SINR for both sets of phases, one set including the phases for a maximizing the total average power of the desired signals, and the other set including the phases for minimizing the total average power of the undesired signals; and

selecting the set of phases that yields the highest measured SINR.

4. The UE receiving system according to claim 3, wherein for each beamformer the total average power of the desired signals is PWR_Signal and defined as:

PWR_Signal=W_BF^HH_SW_SW_S^HH_S^HW_BF,

wherein H_S is a K×

P signal channel matrix from the P transmit antennas to the beamformer'"'"'s K receive antennas,

wherein W_S is a P×

U weight matrix applied to the signal by the transmitter,

wherein U≦

P, and

wherein W_BF is a K×

1 conjugate beamformer weight vector.

5. The UE receiving system according to claim 4, wherein for each beamformer the total average power of the undesired co-channel downlink signals having the strongest interference level is PWR_Interference and defined as:

PWR_Interference=W_BF^HH_IW_IW_I^HH_I^HW_BF,

wherein H_I is a K×

L interference channel matrix from the L antennas of the strongest interfering base station to the beamformer'"'"'s K receive antennas, and

wherein W_I is an L×

L weight matrix applied to the interference by the transmitter.

6. The UE receiving system according to claim 5, wherein both phase and amplitude are selected by:

choosing for all beamformer antennas i (1 to K), amplitudes a_iε

B, wherein B is a finite set of discrete amplitudes, and phases Φ

_iε

A, wherein A is a finite set of discrete phases, so as to maximize PWR_Signal;

choosing for all beamformer antennas i (1 to K), amplitudes a_iε

B and phases Φ

_iε

A so as to minimize PWR_Interference; and

comparing the measured SINR for both sets of best amplitudes and phases and decide for those that yield the highest measured SINR.

7. The UE receiving system according to claim 1, wherein W_x denotes the beamformer antenna weights selected for improving the desired signals, and W_y denotes the beamformer antenna weights selected for reducing the strongest interference, and wherein the control module is further configured to measure and compare SINR for W_x and W_y;

wherein in a case that the SINR for W_y is greater than the SINR for W_x then W_y is selected, wherein otherwise, W_x is used temporarily or until it is determined that updated interference estimation may be available.

8. A wireless User Equipment (UE) receiving system comprising:

two or more beamformers, each beamformer having a plurality of tunable receiving antennas; and

a control module configured to;

carry out a periodic, non-continuous channel estimation on a plurality of desired and undesired co-channel downlink signals which are transmitted from different base stations and received by said plurality of antennas; and

determine the undesired co-channel downlink signals having the strongest interference level,

wherein the control module is configured to tune said plurality of tunable receiving antennas so as to maximize a ratio between the total average power of;

said desired signals, and a combination of said undesired co-channel downlink signals having the strongest interference level and an internal noise of the UE receiving system.

9. The UE receiving system according to claim 8, wherein the UE receiving system is a multiple inputs multiple outputs (MIMO) receiving system having number N channels, wherein each of the channels is associated with one of the beamformers and wherein the total number of said plurality of tunable receiving antennas is M=Σ

_j=1^NK_j wherein K_j is a number of tunable antennas for the jth beamformer, wherein M is greater than N.

10. The UE receiving system according to claim 9, wherein for each beamformer the SINR is defined as

11. The UE receiving system according to claim 8, wherein W_x denotes the beamformer antenna weights selected for improving the desired signals, and W_y denotes the beamformer antenna weights selected for maximizing the power ratio between the desired signals and strongest interference plus internal noise, and wherein the control module is further configured to measure and compare SINR for W_x and W_y;

wherein in a case that the SINR for W_y is greater than the SINR for W_x then W_y is selected, wherein otherwise, W_x is used temporarily or until it is determined that updated interference estimation is available.

12. A method comprising:

receiving wireless signals from a plurality of transmit antennas via beamformers with a plurality of tunable receiving antennas;

carrying out a periodic, non-continuous channel estimation on a plurality of desired and undesired co-channel downlink signals which are transmitted from different base stations and received by said plurality of antennas;

determining the undesired co-channel downlink signals having the strongest interference level, and

selecting based on best SINR between;

(i) tuning said plurality of tunable receiving antennas so as to maximize the total average power of said desired signals; and

(ii) tuning said plurality of tunable receiving antennas so as to minimize the total average power of the determined undesired co-channel downlink signals having the strongest interference level.

13. The method according to claim 12, wherein the tuning of the antennas of a beamformer with K antennas, wherein K may be different for each beamformer, is carried out by:

choosing, for all beamformer antennas i (1 to K), amplitudes a_iε

B, wherein B is a finite set of discrete amplitudes, and phases Φ

_iε

A, wherein A is a finite set of discrete phases, so as to maximize the total average power of the desired signals;

choosing, for all beamformer antennas i (1 to K), amplitudes a_iε

B and phases Φ

_iε

A, so as to minimize the total average power of the undesired co-channel downlink signals having the strongest interference level;

comparing the measured SINR for both sets of best amplitudes and phases; and

selecting the set of amplitudes and phases that yields the highest measured SINR.

14. A method comprising:

receiving wireless signals from a plurality of transmit antennas via beamformers with a plurality of tunable receiving antennas;

carrying out a periodic, non-continuous channel estimation to a plurality of desired and undesired co-channel downlink signals which are transmitted from different base stations and received by said plurality of antennas;

determining the undesired co-channel downlink signals having the strongest interference level; and

tuning said plurality of tunable receiving antennas so as to maximize a ratio between the total average power of a) said desired signals and b) a combination of said undesired co-channel downlink signals having the strongest interference level and an internal noise of the UE receiving system.

15. The method according to claim 14, wherein for each beamformer the SINR is defined as