Systems and techniques for joint transmission cooperative multi-point. A set of n CSI reference signal resources are to be measured by a user device. The n CSI reference signal resources include at least one CSI reference signal resource spanning over at least two transmission points. Channel state information feedback corresponding to each CSI reference signal resource is configured. Upon receiving CSI from the user device, at least one precoder is selected for coherent joint cooperative multipoint transmission based on inter-transmission point phase relationship information. A co-phasing factor is derived from transmitted precoders over a cross-cell CSI reference signal resource, the derivation including transmission of reference signals using first and second precoding vectors on two ports, computation of a third vector using feedback based on the precoded reference signals, and computation of the co-phasing factor based on the first, second, and third vectors.