An Unequal Modulation Scheme for the Transmission of Compressed Multimedia Data over Adaptive MIMO-OFDM Systems

Modern video/image source coders employ data compression techniques which encode information that are not equally important. Transform based or subband coders, compress data into their respective low-frequency and high-frequency components. In wireless/mobile communication systems, data representing the low-frequency components are more sensitive to the time-varying nature of channel conditions and propagation environments. To deal with this problem, we propose an optimum transceiver structure for a combined source-modulation coded MIMO-OFDM system with adaptive eigen-beamforming. Using an unequal adaptive modulator, we maximize the channel-to-noise ratio (CNR) based on a lookup matrix-adaptive bit and power allocation (LM-ABPA) scheme to sort and allocate subcarriers with the highest SNR to the low-frequency components of the compressed data, and adjusting the signal constellation/modulation type respectively. In comparison to other transmission systems, simulation results based on the application of compressed images showed that the proposed unequal adaptive modulation scheme achieves significant performance gains under a constant data rate load