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Part of this work was conducted under the grant, "R&D on efficient spectrum use technologies for wireless communications systems using HAPS (JPJ000254)," funded by the Ministry of Internal Affairs and Communications of Japan.

In this paper, we propose a joint source-channel coding (JSCC) scheme for wireless image transmission over IEEE 802.11ac system. JSCC is a coding technique where both source and channel characteristics are considered. In a multipleinput multiple-output (MIMO) system based on an eigenbeamspace division multiplexing (E-SDM) technique, signal-to-noise ratio (SNR) of each spatial stream varies because it depends on the corresponding singular value of the MIMO channel matrix. Then, we propose the JSCC method which utilizes both the characteristics of the E-SDM and scalable image coding. The proposed algorithm adaptively allocates bit strings of a scalable image to both subcarriers and spatial streams on the physical (PHY) layer. High performance in image quality is attained since the proposed method improves peak signal-to-noise ratio (PSNR) of the image by around 10dB in average. In addition, it also achieves low latency due to no retransmission on medium access control (MAC) layer. The maximum improvement in average PSNR is approximately 15dB compared to a conventional method. The average PSNR performance reaches 40dB when SNR is higher than 17.5dB. The proposed method is capable of stable real-time transmission of high-resolution images even in a bad channel state.

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