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Amplifier-Aware Content-Based Precoder Design for Hierarchical Image Transmission over a Realistic MIMO-OFDM Channel

This paper proposes the design of a precoder in MIMO systems dedicated to JPEG Wireless (JPWL) (ISO/IEC 15444-11) image transmission which jointly takes into account the channel noise and the nonlinear distortions due to the high power amplifier (HPA) used in the transmitter. MIMO-OFDM (Orthogonal Frequency Division Multiplexing) systems dedicated to image transmission rely only on the Channel State Information (CSI) and the image content to design their precoding solutions. However, the nonlinear behavior of the HPA used at the front-end is not taken into account when designing the current precoders. In order to ensure the QoS of the transmitted image, a large level back-off is usually applied to avoid the nonlinear distortions generated by the HPA. In addition, the Input Back-off (IBO) value is statically chosen and does not depend on the other parameters of the link such as the instantaneous MIMO channel status, the modulation order and the scalability of the JPWL content. This may reduce both the global energy efficiency and the transmission quality of the Radio-Frequency (RF) link. Therefore, this work proposes a new precoding scheme to allocate the total available power while dynamically adjusting the optimal power IBO value according to the HPA parameters, the instantaneous channel status and the image content to be transmitted. Numerical results using a commercial HPA model under the IEEE 802.11n standard show that the proposed power allocation algorithm improves the visual quality of the received JPWL images compared to the state-of-the-art over a realistic radio channel model.