Yusuke Kozawa

Theoretical analysis of atmospheric optical DS/SS with On-Off Orthogonal M-sequence Pairs

In this paper, atmospheric optical DS/SS systems with on-off orthogonal m-sequence pairs are considered. The bit error rates of the on-off keying (OOK) DS/SS and the antipodal DS/SS are analyzed by taking into account the scintillation, background-noise, avalanche photo-diode (APD) noise, thermal noise, and multiple access interference (MAI). Moreover, the optical DS/SS systems using on-off orthogonal M-sequence pairs are compared with those using the extended prime code sequences. Consequently, the optical DS/SS using the on-off orthogonal m-sequence pairs is superior to the optical DS/SS using extended prime code sequences.

Theoretical Analysis of Optical Wireless CDMA with Modified Pseudo Orthogonal M-Sequence Sets

In this paper, to increase Normalized throughput of the optical wireless code-division multiple-access (CDMA) system, modified pseudo orthogonal M-sequences (MPOMS) are considered as optical pseudo-Noise (PN) code. Moreover, the bit error rate (BER) performance of the optical wireless CDMA system using multi-pulse pulse position modulation (MPPM) is also derived in the presence of the scintillation, background-Noise, avalanche photo-diode (APD) Noise, thermal Noise and signal dependence Noise. Consequently, the BER performance in consideration of Normalized throughput of the MPPM system with MPOMS is superior to that of the MPPM system with conventional pseudo orthogonal M-sequences in the single-user case and multi-user case.

Theoretical analysis of M-CSK/CDMA system in optical wireless channel

In this paper, M-CSK with extended prime code sequence to enhance a data transmission rate of CSK is considered. Moreover, the bit error rate (BER) performance of M-CSK/CDMA is evaluated by taking into account scintillation, background-noise, avalanche photo-diode (APD) noise, thermal noise, and signal dependence noise through theoretical analysis. It is shown that the data transmission rate of the M-CSK system is better than that of the CSK system using extended prime code sequences. However, the BER performance of the M-CSK system is degraded by increasing the number of selected extended prime code sequences.

Enhancement of Optical Wireless Multi-Pulse PPM

In this paper, optical wireless multi-pulse pulse position modulation (MPPM) system with modified pseudo orthogonal M-sequence sets is proposed. Moreover, the symbol error rates of the proposed system are analyzed by taking into account the scintillation, background-noise, avalanche photo- diode (APD) noise, thermal noise, and signal dependence noise in the single-user case. Consequently, the normalized throughput in consideration of SER of the proposed system is superior to that of the conventional MPPM systems. Furthermore, the normalized throughput of the proposed system can achieve about 1.25 [bit/chip].

Digital Color Shift Keying With Multicolor LED Array

Color shift keying (CSK) is a visible light communication (VLC) intensity modulation scheme, which is outlined in IEEE 802.15.7, that transmits data imperceptibly through the variation of the color emitted by red, green, and blue light-emitting diodes (RGB LEDs). In this paper, digital CSK (DCSK) is presented, which represents CSK symbols by digitally controlled multiple multicolor LEDs to avoid the effect of LED nonlinearity. By using this scheme, the DCSK system using nine RGB LEDs can transmit IEEE 802.15.7 CSK constellations with an error-vector-magnitude (EVM) performance on an x-y chromaticity of 3%. The bit-error-rate (BER) evaluation of both the conventional and the proposed DCSK system shows that the DCSK system achieves similar BER to that of CSK with a linear variable current driver including predistortion, with taking into account optical wireless channels including the LED response, undesired color shift, and channel crosstalk by the practice characteristics of RGB LEDs, RGB bandpass filters, and photodiodes.

Performance evaluation of Digital Colour Shift Keying for visible light communications

In this paper, multilevel Digital Colour Shift Keying (DCSK) and DCSK using multi-colour LEDs are considered. Moreover, to increase the spectral efficiency of DCSK, Spatial Colour Shift Keying (SCSK) is proposed, in which DCSK is combined with Space Shift Keying. The symbol error rate of DCSK and SCSK performances are evaluated from theoretical analysis and simulation analysis, under consideration of the transmitter-receiver configuration within the room. Consequently, when the channel gain ratio is smaller than 1.7, the energy efficiency of DCSK is better than those of SCSK and Generalised Space Shift Keying (GSSK), on the other hand, SCSK is improved when the channel gain ratio becomes large. Moreover, when the number of transmitters is large, the spectral efficiency of SCSK can be improved compared with DCSK.

Theoretical Analysis of Atmospheric Optical PPM CDMA with Pseudo-orthogonal M-sequences

In this paper, the atmospheric optical code-division multiple- access (CDMA) system with Pseudo-orthogonal M-sequences is proposed. The bit error rate (BER) of the proposed system using pulse position modulation (PPM) by taking into account the effects of the scintillation, avalanche photo-diode (APD) noise, thermal noise, and multiple access interference (MAI) are analyzed. By comparing with the optical orthogonal code (OOC) and the prime code, the proposed system with pseudo- orthogonal M-sequences is better than the systems with other PN codes. But, the scintillation has an enormous effect on the performance of the proposed system.

Optical-wireless enhanced code-shift-keying with IM/DD

In this paper, the extended pseudo orthogonal M-sequence is proposed for the optical-wireless code-shift-keying (CSK) system. The extended pseudo orthogonal M-sequence is a new optical pseudo-noise (PN) code which consists of the modified pseudo orthogonal M-sequence sets (MPOMS) and the bi-orthogonal code. The performance of the CSK systems is enhanced by increasing the number of the optical PN codes. As the conventional optical PN code, the bi-orthogonal code and the pseudo-orthogonal extended prime code set can generate the number of the optical PN codes same as the code length. The extended pseudo orthogonal M-sequence can achieve the performance enhancement of the CSK systems because of its generation of the large number of the codes per the code length. The CSK system using the extended pseudo orthogonal M-sequence has better performance than the CSK systems using the conventional PN code.

Underwater Turbo-code optical communication system compatible with partial erasure channel

In this paper, a novel underwater Turbo-code optical communication system compatible with partial erasure channel is proposed. A scheme re-arranging the parity bits of Turbo-code is used for preventing the degradation of communication performance in partial erasure channel. Unequal Transmission Power Allocation (UTPA), a technique which allocate different powers to information bits and parity bits keeping the total transmission power fixed, is applied for enhancement of the proposed system. Binary Pulse Position Modulation (BPPM) is used as the modulation technique. The bit error rate (BER) performances of the proposed system are evaluated through computer simulation both in general underwater channel and the special situation: partial erasure channel.

Bi-level Quadrature-modulation low-pass EPWM transmitter using half side of tri-level ΔΣ modulator

This paper presents a bi-level quadrature-modulation (QM) low-pass (LP) envelope-pulse-width-modulation (EPWM) transmitter using a half side of tri-level EPWM. Simulation including digital signal processing with the QM LP-EPWM and microwave circuit simulation with a class-D power amplifier (PA) using n-MOSFETs shows an excellent error vector magnitude (EVM) of 36 dB at 1 GHz. The transmitter with a class-D PA for bi-level EPWM signal shows much better EVM performance than the one for trilevel signal.