First communication device and methods performed thereby for transmitting radio signals using beamforming to a second communication device

A communication device comprising:

• a memory storing computer program instructions;
• and
• processing circuitry configured to execute the computer program instructions,
• whereby the processing circuitry is configured to:
• obtain Channel State Information (CSI) for a radio channel between the communication device and another communication device, the CSI serving as an estimate of a state of the radio channel at the beginning of a transmission interval;
• determine a precoder in dependence on the CSI;
• and
• transmit a precoded radio signal over the transmission interval for the other communication device, by generating the precoded radio signal in dependence on the precoder and accounting for the CSI becoming outdated over the transmission interval by adapting the precoder, and, thereby, the precoded radio signal, one or more times during the transmission interval in dependence on an expected rate of change of the state of the radio channel,
• wherein the processing circuitry is configured to adapt the precoder by changing the value of ρ in the formula:
• Ĥ(ĤHĤ+pIK)−1, wherein:
• Ĥ is a matrix of coefficients comprising an estimate of the radio channel, as said CSI,
• ĤH is the Hermitian transpose of Ĥ,
• IK is an interference matrix of the other communication device,
• K denotes the other communication device, and
• ρ is a scalar value.

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

• a transmitter configured for transmitting radio signals via a radio link to a User Equipment (UE);
• a receiver configured for receiving radio signals from the UE via the radio link;
• and
• processing circuitry operatively associated with the transmitter and the receiver, and configured to:
• determine a channel estimate representing the radio link, based on reception of a reference signal from the UE at the radio network node;
• determine a transmission configuration to be used for transmitting to the UE in a transmission interval, based on the channel estimate;
• and
• adapt the transmission configuration one or more times while transmitting to the UE during the transmission interval, in dependence on a known or estimated speed of the UE, to account for the channel estimate becoming outdated over the transmission interval,
• wherein the processing circuitry is configured to adapt the precoder by changing the value of ρ in the formula:
• Ĥ(ĤHĤ+pIK)−1, wherein:
• Ĥ is a matrix of coefficients comprising an estimate of the radio channel, as said CSI,
• ĤH is the Hermitian transpose of Ĥ,
• IK is an interference matrix of the other communication device,
• K denotes the other communication device, and
• ρ is a scalar value.