What is DM RS (Demodulation Reference Signal)?

DM-RS was upheld effectively in the first release of LTE. A demodulation reference signal (DM-RS) is proposed to be utilized for channel assessment by a particular device and is then only communicated inside the resource blocks allotted for transmission to that device. The utilization of DM-RS was then restricted to the demodulation of single-layer PDSCH transmission—that is, no spatial multiplexing—corresponding to transmission mode 7.