Abstract
To support multiple users in an indoor multiple-input multiple-output visible light communication (MIMO-VLC) system adopting spatial multiplexing, orthogonal frequency division multiple access (OFDMA) is usually adopted, where the overall modulation bandwidth is shared by all the users. In this paper, by fully exploiting the spatial distributions of light-emitting diode (LED) transmitters in the ceiling and end users around the receiving plane, we propose a space division multiple access (SDMA) technique for indoor spatial multiplexing-based MIMO-VLC systems. When applying SDMA, users within the MIMO-VLC system are divided into different user groups (UGs) based on their spatial locations with respect to different LED transmitters. Specifically, each UG can use the overall modulation bandwidth of the system. For efficient implementation of SDMA, two distributed user grouping (DUG) approaches are proposed, including basic DUG and transmit diversity-enhanced DUG (TD-DUG), and a two-step resource allocation algorithm is further designed. The achievable rates of the MIMO-VLC system employing SDMA with both basic DUG and TD-DUG are derived accordingly. To verify the superiority of SDMA over conventional OFDMA, detailed analytical and simulation results are presented. Moreover, a proof-of-concept experiment is conducted to demonstrate the advantage of SDMA in a practical spatial multiplexing-based MIMO-VLC system.
Highlights
I T IS predicted that light-emitting diodes (LEDs) will gradually replace conventional incandescent and fluorescent lamps for indoor lighting and become the dominator of the global illumination market in the near future
The experimental setup of the single-cell multiple-input multiple-output (MIMO)-visible light communication (VLC) system is shown in Fig. 8(a), where two channels of orthogonal frequency division multiplexing (OFDM) signals are generated offline by MATLAB and uploaded to an arbitrary waveform generator (AWG, Tabor WW2074) with a sampling rate of 50 MSa/s
By exploiting the spatial distributions of users over the receiving plane with respect to LED transmitters in the ceiling, the users are divided into multiple user groups (UGs) and each UG can access the overall modulation bandwidth of the MIMO-VLC system
Summary
I T IS predicted that light-emitting diodes (LEDs) will gradually replace conventional incandescent and fluorescent lamps for indoor lighting and become the dominator of the global illumination market in the near future. As a multiple access scheme generated from OFDM, orthogonal frequency division multiple access (OFDMA) has already been applied in multiuser VLC systems [28], [29], where the overall modulation bandwidth of the system is divided and shared by all the users. The state-of-the-art SDMA techniques proposed for multiuser VLC or MIMO-VLC systems are mainly based on the use of specially designed transceiver structures, which inevitably increase complexity and cost. A novel SDMA technique is proposed to simultaneously support multiple users in an indoor single-cell multiuser MIMO-VLC system, where users within the system can be efficiently divided into different user groups (UGs), according to the distinctive spatial positions of the ceiling LEDs and the relative positions of users with respect to different LEDs. each UG can utilize the overall modulation bandwidth of the system.
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