Aspects of the disclosure include an apparatus at base station side in a wireless communication system for multi-user superposition transmission. The apparatus includes a superposition control unit and an indication generation unit. The superposition control unit is configured to insert, into a data stream of each user equipment in a group of user equipment comprising a plurality of user equipment, a demodulation reference signal corresponding to the data stream, and superpose demodulation reference signals corresponding to data streams of respective user equipment. The indication generation unit is configured to generate, for at least a first user equipment among the plurality of user equipment, an indication regarding a demodulation reference signal corresponding to a data stream of other user equipment among the plurality of user equipment, to assist the first user equipment in demodulating data transmitted in the multi-user superposition transmission.