DMRS stands for "Demodulation Reference Signal" which is used for channel estimation and coherent demodulation comes as part of PUSCH and PUCCH. If DMRS is not decoded properly by the base station then base station would not decode PUSCH or PUCCH.
EnodeB differentiates DMRS that comes from the different UEs, based on the parameters "transmissionComb" and "cyclicShift".