In this work, we investigate the quality of heart rate variability (HRV) features extracted from electrocardiogram (ECG) signals transmitted by optical wireless communication (OWC). The proposed solution exploits infrared links between a transmitter placed on the chest of a newborn lying in a closed incubator and optical receivers installed on the ceiling of a neonatal intensive care unit. The specific environment and the corresponding transmission channel were modeled and simulated using the ray-tracing Monte Carlotechnique. Temporal HRV parameters were determined using the Pan-Tompkins algorithm and analyzed as a function of emitted optical power. The results obtained show that it is possible to guarantee good HRV measurements from ECG signals transmitted by OWC in the proposed context. An excellent quality of the HRV parameters could be obtained with an emitted optical power of [2.8-4.1] mW for the OOK modulation.

In this article, we propose an all-optical bidirectional wireless communication system for off-body sensor communication. Optical technology uses infrared (IR) for uplinks and visible light communication (VLC) for downlinks. From numerical simulations, we discuss the impact of body sensor positions on IR and VLC channels. Our goal is to evaluate the possibilities of using optical technology to transmit sensor data for extreme positions such as the ankle, for which the presence of the body creates blockages. In addition, we also consider the variations in orientation of transceivers due to random mobility of body parts during normal movement. Based on a statistical approach, we evaluate performance in terms of outage probability using channel impulse response sets corresponding to the studied scenario, which is health monitoring. Considering a given quality of service, we address trade-offs related to emitting power and data rate. We discuss the results regarding sensor node position and body reflectivity specifically for ankle sensors, corresponding to an extreme but realistic position in the health-monitoring context.

In this paper, we propose a full optical wireless bidirectional communication system based on infrared (IR) and Visible Light Communication (VLC) for indoor health monitoring assuming patient mobility inside the indoor environment. Based on ray tracing methods and statistical approach for evaluating channel gain of both links, we determine a global performance in terms of outage probability. Our main contribution is the evaluation of this overall performance for a medical monitoring scenario for a patient wearing an IR transmitter and a VLC receiver. We show that it is possible to satisfy an overall quality of service for various medical sensor applications. Specifically, we are able to evaluate the minimum emitted IR and VLC power values on both links. Having a low IR power is an obvious advantage considering the energy consumption issues for a worn device. We also emphasize that the ability to establish visible communications with very low power allows monitoring application to be maintained even when the lighting is almost extinct.

Wireless Optical Communication (WOC) technology is now established as an alternative or complement to radiofrequency in particular for indoor transmissions. Besides, considering the crucial issue of the electromagnetic pollution in a sensible environment such as hospital, WOC is a good candidate for medical applications, such as Wireless Body Area Network (WBAN) dedicated to health monitoring. In this paper, we investigate the feasibility of an optical WBAN, exploiting diffuse optical reflections over the patient environment, and using spreading codes to realize network on-body nodes multiple access. Considering optical WBAN nodes distributed on the patient body, a theoretical analysis has been developed to evaluate the error probability distribution. Assuming perfect blocking because of the body regarding optical beams, the study takes into account the BAN mobility in terms of node orientation and patient location. A typical health monitoring scenario has been considered as an example, and the achievable performance of the wireless optical solution is reported and discussed regarding medical requirements.

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.

In this study, the authors deal with a wireless healthcare monitoring solution based on a secure technology in hospital context. Actually, radio frequency (RF) networks can present electromagnetic disturbances in hospital environments. The authors thus investigate an alternative solution based on infrared (IR) technology. As patient mobility is inevitable, they focus on mobile IR communications considering line-of-sight (LOS) propagation between the transmitter coupled with medical sensors and the receiver. The authors study different mobility scenarios, one in two dimensions (2D) for a fixed transmitter height and another in three dimensions (3D) by considering transmitter height variations. In each case, they analyse the distributions of channel gain state to find the statistical model of the mobile IR channel for a given distribution of the patient locations within the room (uniform or gaussian). By calculating the outage probability from statistical analysis, they investigate the impact of the mobility on data rates and quality of service needed for this application in the case of an on–off keying (OOK) modulation before concluding on the reliability of the studied mobile healthcare monitoring system.

In the context of healthcare monitoring, it is necessary to transmit vital information from the patient to an interface managed by the hospital staff. In this work we consider a system where the patient can move within a hospital room and the data collected by sensors are transmitted to a distant receiver placed on the ceiling. We investigate the potentiality of using infrared (IR) communication for the transmission of information in this mobile context. Considering two main IR propagation types (Line Of Sight and diffuse), we characterize the IR mobile channel by using a Gaussian model for the patient location in the room. Thanks to our model, we evaluate the outage probability of this mobile monitoring scheme. From the results, the power efficiency of IR technology to ensure the communication between sensors and the collecting point is established. Moreover, to optimize the system performance and ensure the highest power autonomy, we investigate the possibility of using channel coding. For this purpose, the mobile IR channel outage capacity versus transmission power for different monitoring data rates is calculated. The analysis shows that for a typical data rate of 500 Kbps, it is theoretically possible to optimize the transmission power considering the use of a forward error correction code while maintaining the targeted effective data rate.

In this paper we investigate performance of indoor Line of Sight (LOS) Wireless Optical Communication (WOC) considering non stationnarity due to emitter and/or receiver mobility. The transmission scheme uses Low Density Parity Check (LDPC) codes to mitigate performance degradation due to mobility. We evaluate a performance bound for LDPC codes in indoor environment and for a given mobility scenario. We show that this bound directly depends on the Signal to Noise Ratio (SNR) distribution and considering density evolution, on the LDPC code rate. Two methods are developed to evaluate SNR distribution. One is based on Monte Carlo simulations and the other one, on geometrical considerations linked to the room configuration. The obtained results for the performance bound are compared to finite length LDPC code performance.

In this paper we study Forward Error Correction (FEC) under beat noise assumption in the context of incoherent Optical Code Division Multiple Access (OCDMA) systems. Due to the use of unipolar codes, Multiple Access Interference (MAI) amount and thus beatings between different user contributions known as beat noise, constitute important limitations in particular for high data rates. In order to compensate for these two major limitations, we propose a solution using FEC based on a soft decoding algorithm. For this purpose, we analyze the OCDMA received signal distribution and establish a new model, based on a mixture of chi-square distributions, valuable for any OCDMA code parameters and any source coherence time values. From this model, we establish the error probability analytical expression under beat noise assumption and determine the reliability parameters required for the FEC soft decoder initialization. To illustrate the performance, we use Low Density Parity Check (LDPC) codes and show that the LDPC adapted decoder is highly efficient in reducing beat noise and MAI for incoherent OCDMA systems, even when beat noise has a severe impact. In addition, we point out that this solution permits increasing data rates or number of active users.

Using incoherent Optical Code Division Multiple Access (OCDMA) technique has recently attracted much interest since it appears to be not only a simple solution to provide user differentiation but also to perform service differentiation. The main limitation usually taken into account in the theoretical performance evaluation is Multiple Access Interference (MAI) linked to the fact that code sequences are unipolar and thus not strictly orthogonal. However, due to MAI and to the fact that the nature of the optical regime is not perfectly incoherent, beat noise constitutes another important limitation. We focus in this paper on multi-weight two dimensional (2-D) code sequences, which permits providing different BER services. We propose a theoretical statistical model to characterize MAI and beat noise impact. Thanks to this model, a theoretical error probability expression is established, taking into account both MAI and beat noise contribution in multimedia OCDMA systems. The design of multimedia codes satisfying targeted BERs can thus be done considering both limitations. The results permit highlighting the importance of beat noise consideration in the design process and the constraints imposed on optical source requirements.

In this paper indoor wireless Infrared (IR) technology for healthcare monitoring is studied. Monitoring provides a continuous and reliable vital sign measurement to secure patient staying in the hospital. Considering that patient moving is inevitable, we focus on a mobile IR channel based on diffuse propagation. A model of mobile channel is developed through the study of statistical distributions of channel gain state for OOK modulation. We consider two mobility schemes for the transmitter which is coupled to the monitoring system: one in 2 dimensions (2D) for (x,y) mobility and another in 3D for (x,y,z) mobility. From statistical analysis, the outage probability is calculated in order to evaluate the performance for different data rates and for different average transmitted power before concluding on the reliability of diffuse mobile monitoring.

The Optical Code Division Multiple Access (OCDMA) technique is a potential solution to provide access on the optical channel to different users but also to different services applying performance differentiation. For this purpose, we focus here on an OCDMA system using 2 Dimensional (2D) multi-weight spreading codes. At the reception, a Hard Limiter (HL) device in front of the Conventional Correlation Receiver (CCR) is used to reduce the multiple access interference. To evaluate the performance of this scheme in a noisy optical channel, we develop an approximated calculation which provides a theoretical upper bound of the multi-weight code performances. In addition, for any noise amount, the optimal CCR threshold can be exactly determined. We use the theoretical results to design the multi-weight codes adapted to the transmission of three services with respectively low, medium and high Bit Error Rates (BER). Thanks to our theoretical approach, the noise impact is analyzed and shown being very significant for each service. It is possible to take the noise power into account in the code design, but at the cost of the increase of the spreading code length. To overcome these drawbacks, we investigate the BER gain provided by Low Density Parity Check (LDPC) codes. The results obtained show that Forward Error Correction (FEC) is a good way to improve the multimedia access network potentialities.

To provide Quality of Service (QoS) and data rate differentiation, we investigate in this paper a 2 dimensional optical code division multiple access (OCDMA) technique. A 2D multi-weight coding scheme with parallel mapping technique is developed. The system enhancement is assessed thanks to the use of Forward Error Correction (FEC) based on Low Density Parity Check (LDPC) codes. In order to have an efficient correction power, we develop an adaptation of the LDPC decoding algorithm to the specific multiple access interference distribution in a multimedia OCDMA network. The proposed network permits a high number of users to communicate with high data rates adapted to a multimedia transmission (voice, data and video) with corresponding QoS (10-3, 10-6, 10-9).

In this paper, we investigate the application of optical code division multiple access (OCDMA) to multimedia transmission (voice, data, video). The various services are differentiated by assigning to each user a specific two-dimensional (2D) code signature. The coding method used is adapted from 2D multi-wavelength optical orthogonal codes (MWOOC). We first generate 2D multi-weight codes to differentiate the quality of service (QoS). Then, by applying a parallel mapping technique, we achieve multi-rate services. The theoretical error probability corresponding to the quality of each service is established in the noiseless case. This permits evaluating the potentiality of such systems in terms of number of communicating users and data rates. This study has been realized considering a conventional correlation receiver (CCR) with and without hard limiting (HL) device.

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.

In this paper, we study the parallel interference cancellation receiver (PIC) efficiency, in direct sequence optical code division multiple access system (DS-OCDMA) with prime codes (PC). We develop the analytical expression of the error probability in the chip synchronous case, for PC. We show that the PIC receiver permits to suppress totally the effect of multiple access interference (MAI) for prime code, and leads to an error free O-CDMA link in the noiseless case, for whichever PC employed. Simulation results have validated the theoretical analysis. Finally, we show that the PIC receiver permits to reduce the required code length for a given bit error rate

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.

In an incoherent direct-sequence optical code-division multiple-access (DS-OCDMA) system, multiple-access interference (MAI) is one of the principal limitations. To mitigate MAI, the parallel interference cancellation (PIC) technique can be used to remove nondesired users' contribution. In this paper, we study four DS-OCDMA receivers based on the PIC technique with hard limiters placed before the nondesired users or before the desired user receiver, or both. We develop, for the ideal synchronous case, the theoretical upper bound of the error probability for the four receivers. Significant performance improvement is obtained by comparison with conventional receivers in the case of optical orthogonal codes. The paper highlights that the number of active users with null error probability is doubled, compared with conventional receivers. Finally, we show that, thanks to their good performances, the PIC structures permit considerably reducing the minimal code length required to have 30 users with bit-error rate <10/sup -9/. So, the hardware constraints are relaxed for realistic application.

In direct sequence optical code division multiple access system (DS-OCDMA), one of the principal limitations is due to unipolar coding which introduces multiple access interference (MAI). To mitigate MAI, we have applied a parallel interference cancellation technique (PIC) to remove non-desired users' contribution. We study in this paper, the performances of the PIC improved by hard limiters (HL) placed either before the non-desired users receivers (HL+PIC) or before the desired user receiver (PIC+HL). We develop the HL+PIC and PIC+HL theoretical error probability expression, and show the performances improvement due to such receivers