Conventional visible light positioning (VLP) schemes usually require at least three light sources, making positioning accuracy sensitive to shadowing, a limited number of light sources, or sparse light-emitting diode (LED) layout. We proposed a mirror-assisted VLP system, where two-LED positioning can be realized by adopting specular reflection and time–frequency combination method. The scheme is based on the concept of virtual lamps and the received signal strength algorithm. Specular reflection power from one of the virtual lamps is integrated into the effective positioning power of its corresponding real lamp to obtain increased received power and mitigate the impact of diffuse reflection. Meanwhile, the other virtual lamp is independently used as the third light source for positioning, which means that the system becomes a “pseudo” three-LED positioning system, so that positioning can be realized with only two real lamps available. The corresponding positioning accuracy evaluated numerically shows an upward trend as the distance between the receiver and mirror decreases. By reducing the distance between the transmitters and the mirror, the positioning error can be limited to ∼12.4 cm.
This paper proposed a genetic algorithm to reduce the dead zone of indoor visible light communication by optimizing lamps distribution. There are some rooms in different states are taken into account in this paper, including the fraises or windows in the room. Besides that, the lighting requirement of the room is also influencing the lighting source layout. By the efforts of genetic algorithm, the effective area ratio can achieve 97.28% in an empty room, or 91.04% in the room with ambient light noise. In the room with fraises, the effective area ratio is between 94.85% to 95.71%. It can be demonstrated by experiments that the genetic algorithm can meet the requirement of optimized the lighting infrastructure design in a dynamic environment.
KEYWORDS: Roads, Receivers, Light emitting diodes, Visible radiation, Telecommunications, Signal to noise ratio, Control systems, Mirrors, Wireless communications, Analytical research
This paper proposed a model of traffic control system which used the technology of visible light communication. By using some simulation software like Python or MATLAB, the optimized parameters can be found. For example, the best angle of the traffic light is 8.76 degree, the minimum and maximum distance of the light can received are 4.46 and 97.25 meters in this system respectively. With these parameters, we can also simulate the distribution of incident power on the road, including the crossing road or the roundabouts. As a result, incident power always centralizes on the center of the road. Eventually, some solutions are found to deal with these problems.
Time division multiplexing (TDM) is common in visible light communication system, which means a channel carries two or more services and different services have the same communication demand. If a channel carries two businesses that have different communication requirement, for example, the bit error ratio (BER) for one is 10-3 and for the other is 10-5 , what can be done to help solve the problem. This paper proposes a time-domain hybrid modulation scheme for visible light communication with different service requirements. By appropriately designing a time division multiplexing frame and time slot occupancy ratios of different modulation formats, a continuous adaptation between spectral efficiency and different tiers of BER requirements can be realized for an optical channel. Such a transmission approach is called time domain hybrid modulation (TDHM). Common on-off keying modulation (OOK) and pulse position modulation (PPM) are used in the time domain hybrid modulation scheme in this paper because its simplicity of OOK and high power efficiency of PPM, which can solve the problem of different communication requirements in VLC. In this paper, when the demand of BER for OOK is 10-3 and for PPM is 10-5 , SNR for OOK and PPM are 16dB and 12dB. But if Hybrid modulation is used, the system can satisfy the demand of BER=10-3 when SNR is just 14dB.
KEYWORDS: Digital signal processing, LCDs, Clocks, Oscillators, Signal processing, Microcontrollers, Digital electronics, Electronics engineering, Visualization, Crystals
On the basis of equal-accuracy frequency measurement principle, this paper takes AT89S52 microcontroller as core and designs a high-accuracy multi-function dual-path frequency meter which can measure the frequency of two circuits of signal with a range of frequency of 1Hz-10MHz at the same time, and be equipped with storage and query function as well provide two circuits (1K and 1M) of square wave signal source. This paper adopts modular design: the hardware module consists of control module, amplification and shaping module, display module, storage module, and standard square wave signal source module, etc., while the software module consists of frequency range judgment, frequency measurement, and display of frequency value. The experiment shows that this instrument has low cost, high accuracy, and strong function, with good application prospect.
We review our proposed decision-aided (DA) maximum likelihood (ML) phase estimation in coherent optical
communication systems with semiconductor laser noises. Our method eliminates the phase unwrapping and
argument nonlinear operations. In addition, the proposed adaptive DA receiver has a strong self-adaptation
capability to recover the carrier phase effectively without knowledge of the statistics of the phase and additive
noises.
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