Anne Julien-Vergonjanne

Indoor optical wireless system dedicated to healthcare application in a hospital

In this paper indoor wireless Infrared (IR) technology for patient monitoring is studied. Monitoring provides a continuous and reliable vital sign measurement to secure patient staying in the hospital. As patient moving is inevitable, we focus on a mobile IR channel. We study the Line of Sight propagation with an OOK modulation system. A model of mobile channel is developed through the study of statistical distributions of the indoor distance between transmitter and receiver. We consider two mobility schemes, one in 2 dimensions (2D) for a fixed transmitter height and another in 3D. From the statistical analysis, the outage probability is calculated in order to evaluate the performance for different data rates and for high quality of service before concluding on the reliability of mobile monitoring.

2-Dimensional optical CDMA system performance with parallel interference cancellation

In this paper, we investigate the feasibility of a 2 Dimensional Optical Code Division Multiple Access system (2DOCDMA), with electronic coding and decoding functions. We present a modified construction method of Multi-Wavelength Optical Orthogonal Codes (MWOOC) which permits high flexibility for the code parameters choice. Our objective is to evaluate the 2D code performance, with a Conventional Correlation Receiver (CCR) and a more complex one named Parallel Interference Cancellation receiver (PIC). For example, for a Bit Error Rate (BER)10-9, 30 simultaneous users and an electrical implementation, we show that contrary to the CCR, the use of a PIC receiver leads to workable 2D code solutions.

Parallel multiple access interference cancellation in optical DS-CDMA systems

This paper investigates the Parallel Interference Cancellation technique in Direct Sequence Optical Code Division Multiple Access (ds-ocdma) system. In the proposed system, the estimated interference is removed from the received signal. We have developped a new approach to obtain the analytical expression of error probability in chip synchronous case, for Optical Orthogonal Codes (ooc). We have shown that under specific conditions between codes parameters and users’ number, the interference can be completely neutralized. Simulation results have validated the theoretical analysis. It is shown that the proposed receiver is effective in reducing significantly the effects of Multiple Access Interference (mai) compared to other interference cancellation systems.RésuméCet article présente l’étude d’un récepteur basé sur l’annulation parallèle d’interférence d’accès multiple dans un système d’accès multiple par répartition en code à séquence directe (ds-ocdma). Le principe consiste à estimer l’interférence due aux utilisateurs non désirés pour la soustraire du signal reçu à l’entrée du récepteur. Nous avons obtenu la formule théorique de la probabilité d’erreur dans le cas synchrone, pour les codes optiques orthogonaux (ooc). Nous avons prouvé que, pour des conditions spécifiques concernant les paramètres des codes et le nombre d’utilisateurs, l’effet de l’interférence peut être complètement éliminé Les résultats de simulation ont validé l’analyse théorique. On montre enfin que le récepteur proposé est plus efficace que d’autres systèmes d’annulation d’interférence pour réduire de manière significative les effets de l’interférence d’accès multiple (mai).

Efficient Simulation of Optical Wireless Channel Application to WBANs with MISO Link

This paper presents a new optimized simulation algorithm of the optical wireless channel. It has a faster convergence for SISO (Single Input Single Output) systems, while it significantly reduces computation time for MISO (Multiple Inputs Single Output) systems, which are the main ones in WBANs (Wireless Body Area Networks). Our algorithm is based on Monte Carlo methods, and uses 3D launched rays. Its main difference with previous solutions relies on reversing the process of propagation of optical waves, to solve efficiently and in real environments the global illumination equation modeling the propagation of light. Experimental results and comparisons with the literature are given in terms of precision and computation time.

Prime Code Efficiency in DS-OCDMA Systems using Parallel Interference Cancellation

In this paper, we are studying the Prime Codes (PC) efficiency, in direct Sequence Optical Code Division Multiple Access system (DS-OCDMA) using Parallel Interference Cancellation receiver (PIC). We develop the analytical expression of the error probability upper bound in the chip synchronous case, for PC. The main result of our work is that the PIC receiver totally suppresses the effect of Multiple Access Interference (MAI) for Prime Codes, and leads to an error free O-CDMA link in the noiseless case, for whichever employed PC. Simulation results are presented to validate the theoretical analysis. We also show that the PIC receiver permits reducing the required code length for a given Bit Error Rate compared to the Conventional Correlation Receiver. Finally, we compare the PC to the Optical Orthogonal Codes (OOC), and show that the use of PC allows a significant reduction of the required SNR.

Investigation of wireless optical technology for communication between on-body nodes

Interferences in Body Area Networks (BANs) are a great challenge in order to ensure a good quality of service in health monitoring systems. BANs are disturbed by several kinds of wireless communications, as mobile cells or Wi-Fi systems. Thus the wireless optical technology could be considered as a solution to reduce the interference amount. The validity of such a solution is examined in terms of transmitted power and data rate. The novelty of this paper is that this is the first time where diffuse optical wireless technology is considered to achieve “on body” communication, using the multiple reflections of optical beams in the patient room.

Modified multi-wavelength optical orthogonal code for spectral efficiency improvement in two-dimensional optical CDMA system

Classical multi-wavelength optical orthogonal code (MWOOC) constructions impose several conditions on the code parameters. These limit the optical code division multiple access (OCDMA) system potentialities in terms of performance and practical implementation. A modified MWOOC construction is used to overcome these limitations. Indeed, this method permits the design of 2D codes with a low temporal code length value and a low number of wavelengths. Considering a multi-user receiver named parallel interference cancellation, the number of users and the data rate per user the system can provide for a low bit error rate value are evaluated. For a given performance, it is shown that the spectral efficiency using the modified MWOOC is significantly improved. Thus, the simplicity of the modified code design and the spectral efficiency increase constitute an advantage for practical implementation of OCDMA network.

Optical Wireless Links as an Alternative to Radio-Frequency for Medical Body Area Networks

It is now established that optical wireless communications (OWC) technology is a promising alternative or a complement to radio-frequencies for indoor transmissions. Considering that using OWC permits the reduction of electromagnetic pollution in human environment, this technology can be also a good candidate for wireless body area networks (WBANs) in particular for medical applications such as health monitoring. In this paper, we investigate the use of on-body OWC for mobile medical WBAN. Based on transmission scheme exploiting diffuse optical reflections over the patient environment, we investigate a star BAN topology using spreading codes for multiple access. We have developed a theoretical analysis to determine the performance of such network considering that the patient is moving in the room. The achievable quality of service for a typical health monitoring application is reported and discussed regarding the performance required by medical applications.

Impact of receiver orientation and position on Visible Light Communication link performance

In this paper we study the impact of both receiver orientation and position on Visible Light Communication (VLC) performance when it is worn by a moving person in indoor environment. This is the case for example of a tablet or smartphone. Because of person mobility within the environment, there are cases where Line of Sight (LOS) paths from optical light sources at the ceiling cannot be collected by the receiver. In those cases, high order reflections are taken into account for channel modeling purpose. We evaluate the performance in term of outage probability and show that Inter-Symbol Interference (ISI) impact is more important when considering receiver orientation variations and this all the more as the data rate is high. In addition for a given quality of service we determine the minimum transmitted power needed to achieve data rate up to 1 Gbps. We verify that considering at least 3 order reflection constitutes an accurate way to quantify the receiver orientation impact.

Performance of OCDMA system with FEC based on interference statistical distribution analysis

The optical code division multiple access (OCDMA) technique has been investigated for several years as a promising alternative to provide multiple access in high speed optical networks. However, due to the use of binary on off keying (OOK) modulation, an inherent main performance limitation is multiple access interference (MAI), following a specific distribution. In order to reduce errors induced by MAI, it is necessary to take into account this specific statistic when applying forward error correction (FEC) with soft decision decoding. In this paper, we analyse the MAI distribution in order to determine FEC soft decoding calculation rules. The study is performed for a low density parity check (LDPC) code scheme over an OCDMA system using two-dimensional (2-D) OCDMA spreading codes. The a priori information required for soft decoder initialisation is calculated according to the specific OCDMA channel statistic. The enhancement provided by the decoding algorithm adaptation confirms that it is important to take into account the specific MAI distribution as described in this paper. Finally, we show that, despite the loss of available data rate linked to the addition of redundancy, the data rates per user can significantly be increased thanks to this efficient error correction scheme. Copyright