Patent ID: 8780832

Claim:
A method in a radio network node for transmitting a reference signal over an antenna port to a user equipment (UE), wherein the reference signal is transmitted in a code division multiplexing (CDM) group, the CDM group comprising at least two CDM subgroups, each CDM subgroup being transmitted on a different subcarrier, each CDM subgroup comprising resource elements, wherein the method comprises the steps of: transmitting the reference signal over a first CDM subgroup using an orthogonal cover code, the first CDM subgroup comprising a first set of resource elements related to the reference signal in a first time slot and a second set of resource elements related to the reference signal in a subsequent time slot; selecting a permutation of the orthogonal cover code; and transmitting the reference signal over a second CDM subgroup using the permutation of the orthogonal cover code, the second CDM subgroup comprising a third set of resource elements related to the reference signal in the first time slot and a fourth set of resource elements related to the reference signal in the second time slot, wherein the permutation of the orthogonal cover code is selected in such a way as to enable decoding of the reference signal in a frequency domain, by applying the orthogonal cover code only to the first set of resource elements and to the third set of resource elements transmitted in the first time slot.