Diversity Multiplexing Trade-off and Selection Gain in Media-Based Modulation
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The idea of Media-based Modulation (MBM) is to embed information in the variations of the transmission media (channel states). Using an RF closure with w RF walls, MBM creates a set of 2^w select-able states for the end-to-end channel. Each state represents an index of an MBM constellation point. In each state, the wave (tone) emanating from the transmit antenna experiences many pseudo-random back-and-forth reflections within the RF closure. The RF signal, upon finally leaving the RF closure, further propagates in the rich scattering environment to reach the receiver. This results in an independent complex channel gain to each receive antenna. As a result, coordinates of different MBM constellation points (vectors of channel gains formed over received antennas) will be independent of each other. This is unlike legacy transmission schemes where a fixed constellation structure used at the transmitter will be multiplied by a fixed, but random, channel gain. Due to this independence property, MBM offers several advantages vs. legacy systems, including "additivity of information over multiple receive antennas (regardless of the number of transmit antennas)", and "inherent diversity over a static fading channel". This work studies the Diversity-Multiplexing Trade-off of an MBM constellation. Analytical expressions are provided that demonstrate the advantages of MBM vs. legacy systems. In particular, it is shown that a 1× N_r SIMO-MBM constellation equipped with an MDS code (even with a relatively small code length) significantly outperforms an N_r× N_r legacy MIMO.
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