question: In the context of LTE, what is the purpose of the Downlink Multiuser Superposition Transmission (MUST) feature? [3GPP Release 14] option 1: To assist UE in cancelling inter-cell interference option 2: To achieve interference cancellation within one cell option 3: To enable switching between transmit diversity schemes option 4: To support SRS switching on PUSCH-less TDD CCs option 5: To define power control parameters for SRS transmission 