Methods, remote radio units and base band units of a distributed base station system for handling uplink signals

A method performed by a BBU system of a wireless communication network, the wireless communication network comprising a distributed base station system having a BBU and an RRU connected to the BBU over a fronthaul link, the RRU having N antennas, the method comprising:

• receiving, from the RRU, a plurality of intermediate signals {tilde over (y)} with K+M components, where (K+M) is smaller than N, determined by the RRU based on a channel estimation matrix Ĥ, on an error estimation matrix Z and on uplink signals y with N components as received by the N antennas from a number of UEs, the uplink signals y comprising K user-layer signals overlaid with interference signals and noise,
• determining an interference rejection matrix WK based on the channel estimation matrix Ĥ and on the error estimation matrix Z, and
• determining an estimation r of the K user-layer signals by multiplying the intermediate signals {tilde over (y)} with interference rejection coefficients of the interference rejection matrix WK.

19-23. (canceled)

25-30. (canceled)

A BBU system operable in a wireless communication network, the wireless communication network comprising a distributed base station system having a BBU and an RRU connected to the BBU over a front haul connection, the BBU system comprising a processing circuitry and a memory, said memory containing instructions executable by said processing circuitry, whereby the BBU system is operative for:

• receiving, from the RRU, a plurality of intermediate signals {tilde over (y)} with K+M components, where (K+M) is smaller than N, determined by the RRU based on a channel estimation matrix Ĥ, on an error estimation matrix Z and on uplink signals y with N components as received by the N antennas from a number of UEs, the uplink signals y comprising K user-layer signals overlaid with interference signals and noise,
• determining an interference rejection matrix WK based on the channel estimation matrix Ĥ and on the error estimation matrix Z, and
• determining an estimation r of the K user-layer signals by multiplying the intermediate signals {tilde over (y)} with interference rejection coefficients of the interference rejection matrix WK.

32-42. (canceled)