Question: How are complex-valued modulation symbols for each of the codewords to be transmitted handled in terms of layer mapping?
Option 1: They are mapped onto a single layer, regardless of the number of codewords.
Option 2: They are mapped onto multiple layers, but only if the number of codewords exceeds a certain threshold.
Option 3: They are not mapped onto any layer and are transmitted as is.
Option 4: They are mapped onto one or two layers, depending on the number of layers (v) and the number of modulation symbols per layer (M).
Explanation: In E-UTRA, complex-valued modulation symbols for each codeword to be transmitted are mapped onto one or two layers. This is a critical aspect of layer mapping, as it affects how the symbols are processed and transmitted over the air interface. The correct answer reflects this important detail from the 3GPP specification.