A method for grouping of CS (and comb values) for DM-RS and SRS on shared time-frequency resources is described. The method includes dividing a RS space into at least a first region and a second region. The method also includes allocating, from the first region, a DM-RS sequence CS and/or a DM-RS comb for a DM-RS; and allocating, from the second region, a SRS sequence CS and/or a SRS comb for a SRS. The DM-RS and the SRS are on the same resources on an uplink shared channel (such as a PUSCH for example). The RS space comprises at least one of a CS set and a IFDM comb set. The CS set and/or the IFDM comb set of the first region is based at least in part on a number of physical resource blocks allocated to the uplink shared channel. Apparatus and computer readable media are also described.