Subspace tracking in full dimension MIMO
First Claim
Patent Images
1. A method for reducing channel estimation overhead, the method comprising:
- at an eNodeB that provides a cell;
calculating a beamforming vector matrix using previously received channel state feedback for a plurality of active User Equipment(UE)s in the cell;
determining an optimal signal subspace containing the plurality of active UEs in the cell using the beamforming vector matrix;
transmitting a beam formed reference signal to the determined optimal signal subspace;
determining that a UE of the plurality of active UEs in the cell has moved out of the optimal signal subspace;
recalculating the beamforming vector matrix for the plurality of active UEs including the UE of the plurality of active UEs in the cell;
transmitting a second beam formed reference signal to the UE of the plurality of active UEs in the cell using the recalculated beamforming reference matrix, the second beam formed reference signal being outside the optimal signal subspace;
receiving a projected channel from the UE of the plurality of active UEs in the cell, the projected channel calculated by the UE of the plurality of active UEs in the cell based upon the second beam formed reference signal; and
transforming a codebook and aligning codewords with a channel direction of the received projected channel.
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Abstract
Disclosed in some examples are methods, systems, devices, and machine readable mediums which reduce the amount of bandwidth consumed by the reference signals. In some examples, this is achieved by finding the optimal subspace containing all the active UEs in the cell and transmitting reference signals to that subspace. In some examples, second order statistics may be utilized to calculate a projected channel to the optimal subspace at the UE and then feeding this back to the eNodeB. The projected channel to optimal subspace may be utilized at the UE and the eNodeB to transform the codebook and align the codewords with the channel direction.
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Citations
20 Claims
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1. A method for reducing channel estimation overhead, the method comprising:
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at an eNodeB that provides a cell; calculating a beamforming vector matrix using previously received channel state feedback for a plurality of active User Equipment(UE)s in the cell; determining an optimal signal subspace containing the plurality of active UEs in the cell using the beamforming vector matrix; transmitting a beam formed reference signal to the determined optimal signal subspace; determining that a UE of the plurality of active UEs in the cell has moved out of the optimal signal subspace; recalculating the beamforming vector matrix for the plurality of active UEs including the UE of the plurality of active UEs in the cell; transmitting a second beam formed reference signal to the UE of the plurality of active UEs in the cell using the recalculated beamforming reference matrix, the second beam formed reference signal being outside the optimal signal subspace; receiving a projected channel from the UE of the plurality of active UEs in the cell, the projected channel calculated by the UE of the plurality of active UEs in the cell based upon the second beam formed reference signal; and transforming a codebook and aligning codewords with a channel direction of the received projected channel. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An eNodeB comprising:
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a signal subspace calculation circuitry configured to; calculate a beamforming vector matrix using previously received channel state feedback for a plurality of active User Equipment(UE)s in a cell; determine an optimal signal subspace containing the plurality of active UEs in the cell using the beamforming vector matrix; in response to determining that a UE of the plurality of active UEs in the cell has moved out of the optimal signal subspace, recalculating the beamforming vector matrix for the plurality of active UEs including the UE of the plurality of active UEs in the cell; a reference signal output circuitry configured to; transmit a beam formed reference signal to the optimal signal subspace; transmit a second beam formed reference signal to the UE of the plurality of active UEs in the cell using the recalculated beamforming reference matrix, the second beam formed reference signal being outside the optimal signal subspace; an uplink reception circuitry configured to; receive a projected channel from the UE of the plurality of active UEs in the cell, the projected channel calculated by the UE of the plurality of active UEs in the cell based upon the second beam formed reference signal; and a transformation circuitry configured to; transform a codebook and align codewords with a channel direction of the received projected channel. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. Anon-transitory machine readable medium that stores instructions which when performed by a machine, cause the machine to perform operations comprising:
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calculating a beamforming vector matrix using previously received channel state feedback for a plurality of active User Equipment(UE)s in the cell; determining an optimal signal subspace containing the plurality of active UEs in the cell using the beamforming vector matrix; transmitting a beam formed reference signal to the optimal signal subspace; determining that a UE of the plurality of active UEs in the cell has moved out of the optimal signal subspace; recalculating the beamforming vector matrix for the plurality of active UEs including the UE of the plurality of active UEs in the cell; transmitting a second beam formed reference signal to the UE of the plurality of active UEs in the cell using the recalculated beamforming reference matrix, the second beam formed reference signal being outside the optimal signal subspace; receiving a projected channel from the UE of the plurality of active UEs in the cell, the projected channel calculated by the UE of the plurality of active UEs the cell based upon the second beam formed reference signal; and transforming a codebook and align codewords with a channel direction of the received projected channel.
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16. A User Equipment (UE) comprising:
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a reference signal reception circuitry configured to receive a beam formed reference signal sent from an eNodeB, the beam formed reference signal using a beamforming vector matrix, and the UE that is a member of a plurality of active UEs, the UE having moved outside of an optimal signal space of the eNodeB; an estimation circuitry configured to estimate projected channel coefficients and direction based upon he received beam formed reference signal sent from the eNodeB; a transformation circuitry configured to transform a codebook by a covariance matrix of the projected channel coefficients and direction; a quantization circuitry configured to quantize the projected channel direction using the transformed codebook; a feedback circuitry configured to; calculate a precoding matrix indicator based upon the quantized projected channel direction; and transmit the precoding matrix indicator, and a quantized covariance matrix calculated from the covariance matrix to the eNodeB. - View Dependent Claims (17, 18)
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19. A method comprising:
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receiving a beam formed reference signal sent from an eNodeB, the beam formed reference signal using a beamforming vector matrix, and a User Equipment (UE) that is a member of a plurality of active UEs in a cell, the UE having moved outside of an optimal signal space of the eNodeB; estimating projected channel coefficients and direction based upon the beam formed reference signal sent from the eNodeB; transforming a codebook by a covariance matrix of the projected channel coefficients and direction; quantizing the projected channel direction using the transformed codebook; calculating a precoding matrix indicator based upon the quantized projected channel direction; and transmitting the precoding matrix indicator, and a quantized covariance matrix calculated from the covariance matrix to the eNodeB.
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20. A non-transitory machine readable medium that stores instructions which when performed by a machine, cause the machine to perform operations comprising:
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receiving a beam formed reference signal sent from an eNodeB, the beam formed reference signal using a beamforming vector matrix, and a User Equipment (UE) that is a member of a plurality of active UEs in a cell, the UE having moved outside of an optimal signal space of the eNodeB; estimating projected channel coefficients and direction based upon the received beam formed reference signal sent from the eNodeB; transforming a codebook by a covariance matrix of the projected channel coefficients and direction; quantizing the projected channel direction using the transformed codebook; calculating a precoding matrix indicator based upon the quantized projected channel direction; and transmitting the precoding matrix indicator, and a quantized covariance matrix calculated from the covariance matrix to the eNodeB.
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Specification