Specular component estimation in a wireless communication network
An apparatus includes an antenna array having a plurality of antennas. The antenna array is configured to receive a multi-carrier signal from a multi-antenna transmitter over a radio channel. The multi-carrier signal has at least two subcarriers, and each subcarrier is mapped at the transmitter to a respective subcarrier-beamformer. The respective subcarrier-beamformers has non-identical null and beam cone directions. A processor is configured to identify a communication direction for a radio signal communication between the apparatus and the transmitter. The communication direction is identified based on one or more specular path components of the radio channel which are related to a null or to a maximum of a subcarrier-beamformer.
1. A multi-antenna device, comprising:
an antenna array,
wherein the antenna array comprises a plurality of antennas,
wherein the antenna array is arranged to receive a multi-carrier signal,
wherein the multi-carrier signal is received from a second multi-antenna device,
wherein the multi-carrier signal is received over a radio channel,
wherein the multi-carrier signal comprises at least two subcarriers,
wherein each of the at least two subcarriers is mapped at the second multi-antenna device to a respective subcarrier-beamformer, and
a processor circuit,
wherein the processor circuit configured to identify at least one communication direction,
wherein the at least one communication direction is for a radio signal communication,
wherein the radio signal communication is between the multi-antenna device and the second multi-antenna device,
wherein the at least communication direction is identified based on at least one specular path component of the radio channel,
wherein the at least one specular path component is related to one of the subcarrier-beamformers,
wherein the processor circuit is arranged to:
detect a signal energy of the at least one specular path component of the radio channel on each of the subcarriers, and
when the detected signal energy is greater than or equal to a first threshold on a first subcarrier among the subcarriers, identify as the at least one communication direction for the radio signal communication a direction into which the subcarrier-beamformer of the first subcarrier points its signal energy, and
wherein the processor circuit is arranged to:
signal to the second multi-antenna device the identified communication direction, wherein signaling the at least one communication direction to the second multi-antenna device allows the second multi-antenna device to calculate a radio signal beamformer according to the at least one communication direction, or
calculate the radio signal beamformer according to the at least one communication direction.
2. The multi-antenna device of claim 1 , wherein the processor circuit is arranged to identify a second direction to be unsuitable for the radio signal communication when a detected signal energy is below a second threshold for a second subcarrier, wherein the second subcarrier points its signal energy into the second direction.
3. The multi-antenna device, of claim 1 , wherein the signal energy being greater than or equal to the first threshold indicates that the signal energy is pointed in a direction of a maximum of a subcarrier-beamformer at the second multi-antenna device.
4. The multi-antenna device of claim 1 , wherein the processor circuit is arranged to initiate the identification of the communication direction:
by signaling to the second multi-antenna device to start transmitting the multi-carrier signal, or
based on a signal from the second multi-antenna device.
5. The multi-antenna device of claim 4 , wherein the signaling from the second multi-antenna device uses a physical downlink control channel, and wherein the signaling to the second multi-antenna device uses a physical uplink control channel.
6. The multi-antenna device of claim 1 , wherein:
the processor circuit is arranged to signal to the second multi-antenna device the at least one communication direction, and
the processor circuit is arranged to:
signal subcarrier information to the second multi-antenna device,
wherein the subcarrier information indicates subcarriers on which the detected signal energy was greater than or equal to the first threshold, or
obtain transmit directions for the second multi-antenna device, and signal to the second multi-antenna device a set of angles corresponding to the obtained transmit directions, or
signal, dependent on an analysis of the specular path components of the radio channel, a maximum number of data streams to be used for the radio signal communication.
7. The multi-antenna device of claim 4 , wherein the signaling from the second multi-antenna device uses a physical uplink control channel, and wherein the signaling to the second multi-antenna device uses a physical downlink control channel.
8. The multi-antenna device of claim 1 , comprising a base station.
9. The multi-antenna device of claim 1 , comprising a user device.
10. The multi-antenna device of claim 9 , wherein the user device comprises a mobile device.
11. The multi-antenna device of claim 9 , wherein the user device comprises an Internet-of-Things device.