Determining base station fronthaul transmission control based on loopback signal

An apparatus for a radio unit of a base station transceiver of a mobile communication system, the base station transceiver further comprising a base band unit configured to wirelessly communicate with the radio unit using a wireless fronthaul link, the apparatus comprising:

• at least one input configured to receive a downlink component of the wireless fronthaul link from the base band unit;
• at least one output configured to transmit an uplink component of the wireless fronthaul links to the base band unit;
• and
• a control module configured to:
• control the at least one input and the at least one output,
• receive a reference signal via the at least one input from the base band unit,
• loopback a loopback version of the received reference signal via the at least one output to the base band unit,
• receive transmission control information from the base band unit, wherein the transmission control information comprises information related to a per-radio unit transmission power to be used by the radio unit for transmissions on the wireless fronthaul link, and
• adapt the transmission power of the uplink component via the at least one output based on the transmission control information;
• wherein the per-radio unit transmission power is determined based on an estimated interference and an estimated path loss, wherein the estimated path loss is estimated based on the reference signal and the loopback version of the reference signal;
• and
• wherein the per-radio unit transmission power is determined based on an optimization function, wherein the per-radio unit transmission power is determined such that a target Signal-to-Interference and Noise (SINR) for the uplink component is approximated based on
• SINR
• target
• ,
• u
• =
• P
• tx
• c
• i
• -
• PL
• u
• i
• ⁢
• -
• P
• IF
• ,
• z
• ,
• NF
• wherein SINRtarget,u is the target SINR for the uplink component,
• P
• tx
• c
• i
• is the per-radio unit transmission power of a radio unit i of the one or more radio units, PLui is an estimated path loss of the uplink component of the radio unit i, and PIF,z,NF is based on an interference power (IF), a thermal noise (z), and a receive noise figure (NF) of the uplink component.

A method for a base band unit of a base station transceiver of a mobile communication system, the base station transceiver further comprising one or more radio units configured to wirelessly communicate with the base band unit using one or more wireless fronthaul links, the method comprising:

• transmitting a reference signal to the one or more radio units;
• receiving a loopback version of the reference signal from the one or more radio units;
• determining information related to a per-radio unit transmission power to be used by the one or more radio units for transmissions on the one or more wireless fronthaul links using an attenuation of the reference signal determined based on the loopback version of the reference signal;
• determining transmission control information comprising the information related to the per-radio unit transmission power;
• and
• providing the transmission control information to the one or more radio units;
• determining information related to a transmission power to be used by at least one output for transmissions on the one or more wireless fronthaul finks based on the reference signal and the loopback version of the reference signal, and adapting the transmitting of a downlink component of one or more wireless fronthaul signals at the at least one output based on the information related to a transmission power to be used on the at least one output;
• and
• wherein;
• (i) the transmission power to be used by the at least one output for transmissions on the one or more wireless fronthaul links is determined based on an optimization function, wherein the transmission power to be used by the at least one output is determined such that a target Signal-to-Interference and Noise (SINR) for the downlink component is approximated based on
• SINR
• target
• ,
• d
• =
• P
• tx
• hub
• i
• -
• PL
• d
• i
• -
• P
• IF
• ,
• z
• ,
• NF
• wherein SINRtarget,d is the target SINR for the downlink component,
• P
• tx
• hub
• i
• is the transmission power to be used by the at least one output for transmissions to a radio unit i of the one or more radio units, PLdi is an estimated path loss of the downlink component for transmissions to the radio unit i, and PIF,z,NF is based on an interference power OF), a thermal noise (z), and a receive noise figure (NF) of the downlink component,
• and/or (ii) information related to a subset of antenna elements of a plurality of antenna elements to be used for transmitting on the one or more wireless fronthaul links is determined, and wherein the information related to the transmission power to be used by the at least one output for transmissions on the one or more wireless fronthaul links comprises the information related to the subset of antenna elements.

Method A method for a radio unit of a base station transceiver of a mobile communication system, the base station transceiver further comprising a base band unit wirelessly communicating with the radio unit using a wireless fronthaul link, the method comprising:

• receiving a reference signal from the base band unit;
• looping back a loopback version of the received reference signal to the base band unit;
• receiving transmission control information from the base band unit, wherein the transmission control information comprises information related to a per-radio unit transmission power to be used by the radio unit for transmissions on the wireless fronthaul link;
• adapting the transmission power for transmissions on the wireless fronthaul link based on the transmission control information;
• wherein the per-radio unit transmission power is determined based on an estimated interference and an estimated path loss, wherein the estimated path loss is estimated based on the reference signal and the loopback version of the reference signal;
• and
• wherein the per-radio unit transmission power is determined based on an optimization function, wherein the per-radio unit transmission power is determined such that a target Signal-to-Interference and Noise (SINR) for the uplink component is approximated based on
• SINR
• target
• ,
• u
• =
• P
• tx
• c
• i
• -
• PL
• u
• i
• ⁢
• -
• P
• IF
• ,
• z
• ,
• NF
• wherein SINRtarget,u is the target SINR for the uplink component,
• P
• tx
• c
• i
• is me per-radio unit transmission power of a radio unit i of the one or more radio units, PLui is an estimated path loss of the uplink component of the radio unit i, and PIF,z,NF is based on an interference power (IF), a thermal noise (z), and a receive noise figure (NF) of the uplink component.