Samrat Vikramaditya Tiwari

Smart LED allocation scheme for efficient multiuser visible light communication networks

In a multiuser bidirectional visible light communication (VLC), a large number of LEDs or an LED array needs to be allocated in an efficient manner to ensure sustainable data rate and link quality. Moreover, in order to support an increasing or decreasing number of users in the network, the LED allocation is required to be performed dynamically. In this paper, a novel smart LED allocation scheme for efficient multiuser VLC networks is presented. The proposed scheme allocates RGB LEDs to multiple users in a dynamic and efficient fashion, while satisfying illumination requirements in an indoor environment. The smart LED array comprised of RGB LEDs is divided into sectors according to the location of the users. The allocated sectors then provide optical power concentration toward the users for efficient and reliable data transmission. An algorithm for the dynamic allocation of the LEDs is also presented. To verify its effective resource allocation feature of the proposed scheme, simulations were performed. It is found that the proposed smart LED allocation scheme provides the effect of optical beamforming toward individual users, thereby increasing the collective power concentration of the optical signals on the desirable users and resulting in significantly increased data rate, while ensuring sufficient illumination in a multiuser VLC environment.

Visible light communication based motion detection

In this paper, a unique and novel visible light communication based motion detection is presented. The proposed motion detection is performed based on white light LEDs and an array of photodetectors from existing visible light communication (VLC) links, thus providing VLC with three functionalities of illumination, communication and motion detection. The motion is detected by observing the pattern created by intentional obstruction of the VLC link. Experimental and simulation results demonstrate the validity of the proposed VLC based motion detection technique. The VLC based motion detection can benefit smart devices control in VLC based smart home environments.

Experimental Biomedical EEG Signal Transmission Using VLC

The proliferation of radio frequency (RF) communication technology in biomedical signal transmission is frequently flustered by electromagnetic interference. Even though the flexibility and mobility of RF-based communication have much attraction, the radiation brings damage to hospital equipments and even harm to humans. In this letter, we propose a novel scheme for transmission of electroencephalography (EEG) biomedical signal using a visible light communication (VLC) link. The data transmission is performed in line of sight (LOS) condition using ON-OFF keying nonreturn-to-zero modulation by utilizing all three components, red, green, and blue, of RGB LED. Experiments are carried out for transmitting EEG signals using the VLC link. The transmitter consists of RGB LEDs, and at the receiver side, three photodiodes with red, green, and blue color filters are installed. The experimental results show excellent reliability and accuracy of the proposed scheme.

Smart home technologies using Visible Light Communication

Smart home technologies using visible light data transmission are presented. For multiple devices, orthogonal code based time division duplexed bidirectional Visible Light Communication (VLC) link is employed. The proposed model for smart home is an efficient technology with superior BER performance, subject to locations in a typical smart home environment.

Optical bidirectional beacon based visible light communications

In an indoor bidirectional visible light communications (VLC), a line-of-sight (LOS) transmission plays a major role in obtaining adequate performance of a VLC system. Signals are often obstructed in the LOS transmission path, causing an effect called optical shadowing. In the absence of LOS, the performance of the VLC system degrades significantly and, in particular, at uplink transmission this degradation becomes severe due to design constraints and limited power at uplink devices. In this paper, a novel concept and design of an optical bidirectional beacon (OBB) is presented as an efficient model to counter the performance degradation in a non-line-of-sight (NLOS) VLC system. OBB is an independent operating bidirectional transceiver unit installed on walls, composed of red, green, and blue (RGB) light emitting diodes (LEDs), photodetectors (PDs) and color filters. OBB improves the coverage area in the form of providing additional or alternate paths for transmission and enhances the performance of the VLC system in terms of bit error rate (BER). To verify the effectiveness of the proposed system, simulations were carried out under optical shadowing conditions at various locations in an indoor environment. The simulation results and analysis show that the implementation of OBB improves the performance of the VLC system significantly, especially when the LOS bidirectional transmission paths are completely or partially obstructed.

Mobility Support for Full-Duplex Multiuser Bidirectional VLC Networks

In this paper, a novel and unique mobility support scheme for a color-clustered (CC) full-duplex multiuser (MU) bidirectional visible light communication (VLC) network is presented. Mobility is classified into two categories: intercluster and intracluster. In the proposed scheme, the mobility support is efficiently provided using a color filter array (CFA) at the downlink receiver. This CFA gives rise to receiver diversity in the form of selection combining yielding performance improvement. Simulations are conducted in terms of communication delay and frame loss rate relative to user speed and distance. In addition, the bit error rate (BER) performance and the data rate are analyzed in the CC MU VLC network. It is demonstrated that the proposed CFA and receiver diversity based mobility scheme in the CC MU VLC network offers superior performance in terms of BER and data rate in indoor environments.

EEG biomedical signal transmission using visible light communication

The proliferation of radio frequency communication technology in biomedical signal transmission is frequently flustered by electromagnetic interference (EMI). The impact of EMI radiation has the consequences of the reduction in accuracy and reliability. Even though its flexibility and mobility have wide attraction, the radiation brings damage to hospital equipment and even harm to the humans. Biomedical signals such as Electroencephalography (EEG) are most utilized signals, which measures the electrical brain rhythms and has huge capability to identify or determine the cause of diseases. In this paper, we propose a EEG signal transmission system using visible light communication. We employ On-Off Keying (OOK) modulation scheme for transmitting the data and RGB LEDs and photodiodes are used for uplink transmission. Computer simulations are carried out using 10 channels of raw EEG signals with the precision of signal values mainly focused. The results demonstrate that it achieves a Bit Error Rate (BER) better than 1.5×10-5 at a Signal to Noise Ratio (SNR) value of 7 dB, thus exhibiting robust reliability and accuracy compared with conventional transmission methods.

Uplink bidirectional efficient multiuser visible light communications using TDD and diversity techniques

In an indoor multiuser bidirectional visible light communications (VLC) system, the performance of uplink VLC transmission degrades significantly due to design constraints and limited power available at uplink devices. In this paper, we propose an efficient uplink transmission scheme based on an orthogonal code division multiple access (OrCDMA) technique in a multiuser uplink transmission environment. While achieving minimal multiple user interference with the OrCDMA, the uplink performance is further enhanced with selection combining at the receiver, exploiting OrCDMA benefits. For bidirectional data transmission, we also employ time division duplexing (TDD). Performance evaluation was conducted for uplink transmission in an indoor VLC environment. It is found that with 5 uplink receivers installed, the bit-error rate (BER) is better than 10-5 over most locations and a BER of 10-5 is achieved at a signal-to-noise ratio (SNR) value of 5.5 dB for 16 users while maintaining a data rate of 58.18 Mbps.

Color cell based bidirectional VLC with user mobility

This paper presents a novel and unique concept of color cell (CC) for bidirectional visible light communications (VLCs). The proposed CC based VLC provides a comprehensive and practical solution to the issues associated with full coverage and user mobility in a comparatively larger indoor environment. In the CC scheme, color filter array (CFA) is utilized at the receiver end with a novel user mobility algorithm and colors in the CC are reused in the CC clusters. Simulations were performed to evaluate the proposed CC scheme. Simulation results demonstrate that the CC based VLC can provide full coverage and user mobility in an efficient manner for bidirectional VLCs in a comparatively larger indoor environment.

Novel Nonlinear Companding Transform for Reduced Peak-to-Average Power Ratio in OFDM

Orthogonal Frequency Division Multiplexing (OFDM) is an excellent solution to overcome multipath effects and inter-symbol interference in high-speed mobile communication systems. However, OFDM inherently has a high Peak-to-Average Power Ratio (PAPR) that adversely affects the system. In this study, we propose a nonlinear companding transform scheme function, in order to reduce the high PAPR in OFDM signals. With the proposed scheme, the average power of the OFDM signal can be maintained nearly unchanged over the companding process by properly chosen values of the parameters of the companding function. One salient feature of the proposed scheme over error function based companding schemes is that the signal compression and expansion levels of the companding function can be adjusted independently, and thus it is easier to maintain the average power. With the aid of simulations, we prove that the proposed scheme has an outstanding PAPR reduction capability and it works well with nonlinear transmitter amplifiers as well. Moreover, we show that the BER performance of the proposed companding transform is superior to the one obtained from the error function companding.