Methods, systems and units of a distributed base station system for handling of downlink communication

A method performed by a system of a wireless communication network, the wireless communication network comprising a distributed base station system having a base band unit (BBU) and a radio resource unit (RRU) connected to the BBU, the method comprising:

• receiving from the RRU, information related to uplink signals received by the RRU from at least one user equipment (UE) wirelessly connected to the RRU;
• determining, based on the received information, only a second part of precoding coefficients for precoding downlink signals to be sent by the RRU to the at least one UE, the precoding coefficients comprising a first part and the second part;
• and
• sending the determined second part of the precoding coefficients to the RRU, so that the RRU can use the second part of the precoding coefficients together with the first part of the precoding coefficients for precoding downlink signals to be sent to the at least one UE.

A remote radio unit (RRU) -operable in a distributed base station system of a wireless communication network, the distributed base station system further comprising a base band unit (BBU) connected to the RRU, the RRU being operative for wireless communication with at least one UE through a plurality of antennas, the RRU comprising:

• a processor;
• and
• a memory containing instructions which, when executed by said processor, cause the RRU to:
• receive uplink signals from the at least one UE;
• determine a downlink channel estimate from the received uplink signals;
• determine a first part of precoding coefficients to be used for precoding signals to be sent downlink to the at least one UE based on the determined downlink channel estimate;
• send information related to the received uplink signals to the BBU;
• receiving receive a second part of the precoding coefficients from the BBU, the second part of the precoding coefficients being determined based on the sent information;
• precode downlink signals of data received from the BBU using the first and the second part of the precoding coefficients;
• and
• send the precoded downlink signals to the at least one UE via the plurality of antennas.

A system operable in a wireless communication network, the wireless communication network comprising a distributed base station system having a base band unit (BBU) and a remote radio unit (RRU) connected to the BBU, the system comprising:

• a processor;
• and
• a memory containing instructions which, when executed by said processor, cause the system to:
• receive, from the RRU, information related to uplink signals received by the RRU from at least one user equipment (UE) wirelessly connected to the RRU;
• determine, based on the received information, only a second part of precoding coefficients for precoding downlink signals to be sent by the RRU to the at least one UE, the precoding coefficients comprising a first part and the second part;
• and
• send the determined second part of the precoding coefficients to the RRU, so that the RRU can use the second part of the precoding coefficients together with the first part of the precoding coefficients for precoding downlink signals to be sent to the at least one UE.

A non-transitory computer-readable storage medium comprising instructions which when executed by at least one processor in a remote radio unit (RRU) of a distributed base station system of a wireless communication network, wherein the distributed base station system further comprising a base band unit (BBU) connected to the RRU and wherein the RRU communicates with at least one user equipment (UE) through a plurality of antennas, are capable of causing the RRU to perform operations comprising:

• receiving uplink signals from the at least one UE;
• determining a downlink channel estimate from the received uplink signals;
• determining a first part of precoding coefficients to be used for precoding signals to be sent downlink to the at least one UE based on the determined downlink channel estimate;
• sending information related to the received uplink signals to the BBU;
• receiving a second part of the precoding coefficients from the BBU, the second part of the precoding coefficients being determined based on the sent information;
• precoding downlink signals of data received from the BBU using the first and the second part of the precoding coefficients;
• and
• sending the precoded downlink signals to the at least one UE via the plurality of antennas.

A non-transitory computer-readable storage medium comprising instructions which, when run on a processor of a system of a wireless communication network, wherein the wireless communication network comprising a distributed base station system having a base band unit (BBU) and a remote radio unit (RRU) connected to the BBU, are capable of causing the system to perform operations comprising:

• receiving, from the RRU, information related to uplink signals received by the RRU from at least one user equipment (UE) wirelessly connected to the RRU;
• determining, based on the received information, only a second part of precoding coefficients for precoding downlink signals to be sent by the RRU to the at least one UE, the precoding coefficients comprising a first part and the second part;
• and
• sending the determined second part of the precoding coefficients to the RRU, so that the RRU can use the second part of the precoding coefficients together with the first part of the precoding coefficients for precoding downlink signals to be sent to the at least one UE.