Signal multiplexing device and signal multiplexing method using layered division multiplexing

A signal multiplexing method, comprising:

• generating a power-reduced enhanced layer signal by reducing power of an enhanced layer signal;
• generating a multiplexed signal by combining a core layer signal and the power-reduced enhanced layer signal;
• reducing power of the multiplexed signal to power corresponding to the core layer signal;
• and
• performing time interleaving applied to both a core layer corresponding to the core layer signal and an enhanced layer corresponding to the enhanced layer signal,
• wherein the reducing power of the enhanced layer signal corresponds to a scaling factor and the scaling factor corresponds to an injection level.