Patent ID: 8451791

Claim:
A method of operating a network node that serves a plurality of user equipments in a mobile communication system, the method comprising: providing the network node with a number, N RS , of orthogonal reference signals for uplink signal transmissions, wherein N RS is less than a maximum number, N MAX — AP , of user equipment antenna ports that can be served by the network node; and for each of the antenna ports, ascertaining a channel quality of a channel between the antenna port and the network node; whenever a number of antenna ports of user equipments being served by the network node exceeds the number, N RS , of orthogonal reference signals, allocating all N RS orthogonal reference signals to a subset of all of the antenna ports by means of an allocation process such that: each orthogonal reference signal is allocated to only one of the antenna ports; each antenna port has no more than one orthogonal reference signal allocated to it; and allocation decisions made by the allocation process are a function of the channel qualities of the respective antenna ports such that the higher the channel quality, the higher priority the corresponding antenna port is given as a candidate for receiving an orthogonal reference signal allocation.