A network node, a wireless device, a base station, user equipment, and corresponding methods are provided. The network node selects a first set and a second set of reference signal resources in the subframe; and processing circuitry configured to aggregate a first set and a second set of reference signal resources within a subframe to form a code division multiplexing (CDM) aggregation configuration. The first and second sets of reference signal resources in a subframe satisfy a time criterion such that any two resource elements in the first and second sets of reference signal resources have a maximum temporal separation of up to 6 OFDM symbols. make it The first and second sets of reference signal resources in a subframe satisfy a frequency criterion such that any two resource elements in the first and second sets of reference signal resources have a maximum frequency separation of up to 6 subcarriers. make it
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