Question: In the context of Event A4 (Neighbour becomes better than threshold) for a UE in an E-UTRA network, how are the units of measurement for `Mn` (measurement result of the neighbouring cell) determined?
Option 1: Always in dB, regardless of the measurement type (RSRP, RSRQ, or RS-SINR)
Option 2: In dBm for RSRP and RSRQ measurements, and in dB for RS-SINR measurements
Option 3: In dB for RSRP measurements, and in dBm for RSRQ and RS-SINR measurements
Option 4: In dBm for RSRP measurements, and in dB for RSRQ and RS-SINR measurements
Explanation: According to the specifications for Event A4, `Mn` (the measurement result of the neighbouring cell) is expressed in dBm specifically in the case of RSRP (Reference Signal Received Power), which is a power measurement. For RSRQ (Reference Signal Received Quality) and RS-SINR (Reference Signal Signal-to-Noise Ratio), which are quality and ratio measurements respectively, `Mn` is expressed in dB. This distinction in units aligns with standard practices in wireless communications, where power is typically measured in dBm and ratios/qualities in dB.