Methods and Apparatus for Precoding Control in a Wireless Communication Network

A method performed by a wireless communication device configured for operation in a wireless communication network that includes a radio network node, the method comprising:

• transmitting a channel-characterizing signal to the radio network node that indicates a channel characteristic as determined by the wireless communication device, or enables the radio network node to derive the channel characteristic based on the channel-characterizing signal as received at the radio network node, said channel characteristic characterizing a channel between the radio network node and the wireless communication device;
• receiving configuration information from the radio network node, indicating a reduced set of precoders within a full set of precoders are indexed by a full set of index values, the full set of precoders contained in a codebook defined in the wireless communication device and the reduced set of precoders being dynamically determined in dependence on the channel characteristic;
• mapping a reduced set of index values to the reduced set of precoders according to a defined mapping function, the reduced set of index values being smaller than the first set of index values;
• selecting one of the precoders from the reduced set of precoders, in dependence on currently estimated channel conditions between the radio network node and wireless communication device, for use in transmitting from the wireless communication device to the radio network node or from the radio network node to the wireless communication device;
• and
• transmitting, for the radio network node, an indication of the index value from the reduced set of index values that corresponds to the selected precoder.

A wireless communication device configured for operation in a wireless communication network that includes a radio network node, the wireless communication device comprising:

• communication circuitry configured for transmitting signals to and receiving signals from the radio network node;
• and
• processing circuitry operatively associated with the communication circuitry and configured to:
• transmit a channel-characterizing signal to the radio network node that indicates a channel characteristic as determined by the wireless communication device, or enables the radio network node to derive the channel characteristic based on the channel-characterizing signal as received at the radio network node, said channel characteristic characterizing a channel between the radio network node and the wireless communication device;
• receive configuration information from the radio network node, indicating a reduced set of precoders within a full set of precoders are indexed by a full set of index values, the full set of precoders contained in a codebook defined in the wireless communication device and the reduced set of precoders being dynamically determined in dependence on the channel characteristic;
• map a reduced set of index values to the reduced set of precoders according to a defined mapping function, the reduced set of index values being smaller than the first set of index values;
• select one of the precoders from the reduced set of precoders, in dependence on currently estimated channel conditions between the radio network node and wireless communication device, for use in transmitting from the wireless communication device to the radio network node or from the radio network node to the wireless communication device;
• and
• transmit, for the radio network node, an indication of the index value from the reduced set of index values that corresponds to the selected precoder.

A method performed by a radio network node configured for operation in a wireless communication network, the method comprising:

• controlling, at least at certain times or under certain conditions, precoder selection by a wireless communication device operating in the wireless communication network, said controlling comprising:
• receiving a channel-characterizing signal from the wireless communication device;
• determining, from the channel-characterizing signal, channel state information for a propagation channel between the radio network node and the wireless communication device;
• selecting, in consideration of the channel state information, a reduced set of precoders within a full set of precoders that are indexed by a full set of index values, the full set of precoders being contained in a codebook defined in the radio network node;
• generating configuration information indicating the reduced set of precoders, wherein precoders within the reduced set of precoders are defined by respective index values in a reduced set of index values that is smaller than the full set of index values and mapped to the reduced set of precoders according to a defined mapping function;
• transmitting the configuration information to the wireless communication device, to thereby enable the wireless communication device to perform precoder selection with respect to the reduced set of precoders, rather than the full set of precoders, at least at certain times or under certain conditions;
• and
• receiving one or more precoder selection indications from the wireless communication device, the one or more precoder selection indications being limited to indicating precoders in the reduced set of precoders and comprising or corresponding to corresponding index values from the reduced set of index values.

A radio network node configured for operation in a wireless communication network, the radio network node comprising:

• communication circuitry configured for transmitting signals to and receiving signals from wireless communication devices operating in the wireless communication network;
• and
• processing circuitry operatively associated with the communication circuitry and configured to control, at least at certain times or under certain conditions, precoder selection by a wireless communication device operating in the wireless communication network, based on being configured to:
• receive a channel-characterizing signal from the wireless communication device;
• determine, from the channel-characterizing signal, channel state information for a propagation channel between the radio network node and the wireless communication device;
• select, in consideration of the channel state information, a reduced set of precoders within a full set of precoders that are indexed by a full set of index values, the full set of precoders being contained in a codebook defined in the radio network node;
• generate configuration information indicating the reduced set of precoders, wherein precoders within the reduced set of precoders are defined by respective index values in a reduced set of index values that is smaller than the full set of index values and mapped to the reduced set of precoders according to a defined mapping function;
• transmit the configuration information to the wireless communication device, to thereby enable the wireless communication device to perform precoder selection with respect to the reduced set of precoders, rather than the full set of precoders, at least at certain times or under certain conditions;
• and
• receive one or more precoder selection indications from the wireless communication device, the one or more precoder selection indications being limited to indicating precoders in the reduced set of precoders and comprising or corresponding to corresponding index values from the reduced set of index values.