Beamforming in cellular systems using the same feedback information for different physical channels

A method implemented in a communication system including a host computer, a base station, and a wireless device, the method comprising:

• at the host computer, providing user data;
• and
• at the host computer, initiating a transmission carrying the user data to the wireless device via a cellular network comprising the base station, wherein the base station:
• obtains, for a time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to the wireless device;
• projects the estimate of the channel matrix for the time instant k onto one or more sets of spatial orthonormal functions, thereby obtaining, for each set of spatial orthonormal functions, a set of coefficients {αi,j,p, for i=0, 1, . . . , N−1, j=0, 1, . . . , M−1, and p=0, . . . , P} that result from projecting the estimate of the channel matrix for the time instant k onto the set of spatial orthonormal functions, wherein M×N defines a number of subarrays in an antenna system of the base station arranged in N rows and M columns where each subarray consists of P polarizations;
• for each set of spatial orthonormal functions, filters the set of coefficients for the set of spatial orthonormal functions for the time instant k and one or more additional sets of coefficients for the set of spatial orthonormal functions based on a filtering parameter that is specific to a downlink channel to be transmitted on the downlink from the base station to the wireless device, thereby providing a respective filtered set of coefficients {αi,j,p} for the set of spatial orthonormal functions for the time instant k;
• generates beamforming weights for the downlink channel to be transmitted on the downlink from the base station to the wireless device using the filtered set of coefficients {αi,j,p} for the time instant k for at least one of the one or more sets of spatial orthonormal functions;
• and
• precodes the downlink channel using the beamforming weights.

A base station configured to communicate with a wireless device, the base station comprising:

• one or more radio units;
• and
• processing circuitry configured to:
• obtain, for the time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to the wireless device;
• project the estimate of the channel matrix for the time instant k onto one or more sets of spatial orthonormal functions, thereby obtaining, for each set of spatial orthonormal functions, a set of coefficients {αi,j,p, for i=0, 1, . . . , N−1, j=0, 1, . . . , M−1, and p=0, P} that result from projecting the estimate of the channel matrix for the time instant k onto the set of spatial orthonormal functions, wherein M×N defines a number of subarrays in an antenna system of the base station arranged in N rows and M columns where each subarray consists of P polarizations;
• for each set of spatial orthonormal functions, filter the set of coefficients for the set of spatial orthonormal functions for the time instant k and one or more additional sets of coefficients for the set of spatial orthonormal functions based on a filtering parameter that is specific to a downlink channel to be transmitted on the downlink from the base station to the wireless device, thereby providing a respective filtered set of coefficients {αi,j,p} for the set of spatial orthonormal functions for the time instant k;
• generate beamforming weights for the downlink channel to be transmitted on the downlink from the base station to the wireless device using the filtered set of coefficients {αi,j,p} for the time instant k for at least one of the one or more sets of spatial orthonormal functions;
• and
• precode the downlink channel using the beamforming weights.

A communication system including a host computer comprising:

• processing circuitry configured to provide user data;
• and
• a communication interface configured to forward the user data to a cellular network for transmission to a wireless device,
• wherein the cellular network comprises a base station having a radio interface and processing circuitry, the base station's processing circuitry configured to:
• obtain, for a time instant k, an estimate of a channel matrix for a wireless channel for a downlink from the base station to the wireless device;
• project the estimate of the channel matrix for the time instant k onto one or more sets of spatial orthonormal functions, thereby obtaining, for each set of spatial orthonormal functions, a set of coefficients {αi,j,p, for i=0, 1, . . . , N−1, j=0, 1, . . . , M−1, and p=0, . . . , P} that result from projecting the estimate of the channel matrix for the time instant k onto the set of spatial orthonormal functions, wherein M×N defines a number of subarrays in an antenna system of the base station arranged in N rows and M columns where each subarray consists of P polarizations;
• for each set of spatial orthonormal functions, filter the set of coefficients for the set of spatial orthonormal functions for the time instant k and one or more additional sets of coefficients for the set of spatial orthonormal functions based on a filtering parameter that is specific to a downlink channel to be transmitted on the downlink from the base station to the wireless device, thereby providing a respective filtered set of coefficients {αi,j,p} for the set of spatial orthonormal functions for the time instant k;
• generate beamforming weights for the downlink channel to be transmitted on the downlink from the base station to the wireless device using the filtered set of coefficients {αi,j,p} for the time instant k for at least one of the one or more sets of spatial orthonormal functions;
• and
• precode the downlink channel using the beamforming weights.