Question: What is a prerequisite for a UE to support Enhanced Downlink Control Channel Interference Mitigation Type A receiver with "LMMSE-IRC + CRS-IC" for PDCCH/PCFICH/PHICH/EPDCCH receive processing, in terms of the number of receiver antenna ports?
Option 1: At least 2 receiver antenna ports (supporting up to 4 CRS antenna ports) or more.
Option 2: Exactly 4 receiver antenna ports (only supporting 4 CRS antenna ports).
Option 3: Any number of receiver antenna ports (1, 2, 4, etc., with no specific limitation).
Option 4: Only 1 receiver antenna port (supporting only 2 CRS antenna ports).
Explanation: According to the specifications for Enhanced Downlink Control Channel Interference Mitigation Type A, a UE must have at least 2 receiver antenna ports to support this feature. This setup allows for the mitigation of interference on control channels with either 2 or 4 CRS (Cell-specific Reference Signal) antenna ports, enhancing downlink control channel performance. Thus, having at least 2 receiver antenna ports is a prerequisite, making Option 1 the correct answer.