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This paper proposes a space division and time division multiple access (SD/TDMA) technique based on intensity
distributions for hybrid line-of-sight (hybrid-LOS) indoor optical wireless communication system. At first, a
novel signal discrimination scheme for the spatially multiplexed optical signals is proposed and it is applied
to a space division multiple access (SDMA) in hybrid-LOS system. In the proposed scheme, multiple terminals
simultaneously transmit their optical signals to access point (AP) using on-off-keying (OOK) modulation, and the
spatially multiplexed optical signals are received by a photodetectors array (PD-array), where multiple PDs are
disposed to observe the spatial intensity distribution of optical signals. Because the terminals transmit their data
using OOK modulation, the spatial intensity distribution observed by the AP equipped with PD-array is subject
to the data transmitted from individual terminals, and the AP can identify the terminals transmitting the optical
signal by determining the transmitted intensity distribution. Of course, the transmitted intensity distributions
are not orthogonal signal and the discriminability of transmitted intensity distributions is much related to the
differences of intensity distributions. This implies that the number of terminals that can simultaneously access to
the AP will be limited and it is determined by the differences of the candidate intensity distributions. In order to
enhance the discriminability of the transmitted intensity distributions, the proposed signal discrimination scheme
is further applied to the SD/TDMA. In the SD/TDMA, the discriminability required to enable SDMA is ensured
by introducing a scheduling algorithm in which terminals with higher discriminatory of transmitted intensity
distributions are allocated to the same time slot. Numerical results show that SD/TDMA using proposed signal
discrimination scheme increases the throughput and the number of terminals that can access to the AP.
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