There is provided mechanisms for relative uplink channel estimation. A method is performed by a terminal device. The method comprises transmitting reference signals from at least two antennas on respective uplink channels towards a network node. The method comprises receiving a forwarded representation of each of the reference signals from the network node. The method comprises estimating a relation between the uplink channels towards the network node for the at least two antennas using the reference signals and the received forwarded representations of the reference signals, thereby estimating the relative uplink channel, towards the network node, between the at least two antennas.